A brief survey of the cays of` Arrecife Alacran, a F4e::ican atoll F. R.

A brief survey of the cays of` Arrecife Alacran, a F4e::ican atoll F. R.

A b r i e f survey of t h e cays of' A r r e c i f e Alacran,
a F4e::ican a t o l l
'OY
F. R. F o s b e r ~
Issued by
THX PACIFIC SCIENCE BOAED
1Yational Academy of Sciences--iVational Research Council
I~Jashington, D. C.
Deceiilber 15, 1962
A b r i e f survey of the cays of Arrecife Alacran,
a Mexican a t o l l
F. R. Fosberg
I t has long seemed desirable t o make comparisons of a t o l l s , a t o l l l i k e reefs, and islands between the three d i f f e r e n t oceans where such
phenomena occur. A t a l k by J. T. Conover, Jr. before an AAAS Section G
audience i n 1960 on h i s investigations on Arrecife Alacran, Yucatan,
indicated some f e a t u r e s of the r e e f s t h a t seemed v a s t l y d i f f e r e n t from
any I had observed on the P a c i f i c Atolls. On h i s i n v i t a t i o n I made a short
v i s i t too Alacran during h i s second v i s i t there, i n J u l y 1961. This t r i p
w a s made possible by a grant of f'unds from the Office of Naval Research
t h r o u a the Pacific Science Board. Eight days were spent on the Reef, during
which it was possible t o v i s i t a l l s i x o f the cays.
My sincere thanks a r e extended t o M r . Charles Hoskin and D r . Conover,
i n charge, respectively, of the University of Texas and the University of
Rhode Island-Duke University p a r t i e s t h a t were working on Alacran (and
t o Sr. Cabanas, lighthouse keeper on lacr ran), f o r t h e i r kind h o s p i t a l i t y
and invaluable assistance i n enabling me t o v i s i t the cays, a s well a s f o r
f r e e l y sharing t h e i r knowledge of the Reef, making i t possible t o develop
some f a m i l i a r i t y with it, i n s p i t e of the shortness of the time I spent
there. I can only hope t h a t our discussions were a s stimulating t o them
a s they were t o me. A b r i e f notice of t h e i r investigations, a s well a s
those of Professor P. Bonet, and h i s associates, may be found i n A t o l l
Research Bulletin 84.
U n t i l recently, Alacran was one of t h e l e a s t known of a t o l l s , a l though it was described a s e a r l y a s 1699 by William Dampier, the English
privateer-writer, i n whose work is found some of the e a r l i e s t c a r e f u l l y
recorded f i e l d n a t u r a l history. Descriptions were again made by Alexander
Agassiz i n 1888, and by C. F. Millspaugh, i n 1916. During the l a s t few
years much investigation has been accomplished (see ARB 84), but r a t h e r
l i t t l e of it has been published a s yet. I n terms, a t l e a s t , of observations
i n manuscript, Alacran has now become one of the b e s t Imown of a t o l l s . It
has even joined the s e l e c t compaay of a t o l l s t h a t have been investigated
i n depth by core d r i l l i n g .
Arrecife Alacran has been described and a small-scale map of it
published by Kornicker and associates (1959), and some of t h e fauna l i s t e d
from t h e i r c o l l e c t i o n s made i n 1959. Also a d e t a i l e d study of the r e e f s
and e s p e c i a l l y of the r o l e s of the various r e e f organisms has j u s t been
published by Kornicker and Boyd (1962). The emphasis o f both these papers
. i s mainly on the r e e f s and the marine aspects. The map shows Alacran a s
an i n t r i c a t e network of reefs, roughly oval i n shape, with an arcuate,
p r a c t i c a l l y uninterrupted windward r e e f . Accumulated boulders on t h i s
break t h e water surface a t low t i d e . The cays o r i s l e t s a r e on the Leeward
side, mostly toward the north and south ends of t h i s reef, and together
they do not aggregate more than 0.5 sq. km i n area.
The l a r g e s t cay i s Perez, with t h e lighthouse and weather s t a t i o n .
Southeast of t h i s a r e Pajaros and Chica, near t h e south end of t h e r e e f .
About a t h i r d of t h e way up t h e west s i d e i s Desertora ( ~ l l i s o nCay) and
a t t h e north end t h e Desterrada ( ~ t o w a n a )cays, u n t i l r e c e n t l y one i s l e t
which a storm c u t i n two by removing t h e middle p a r t , leaving t h e two ends
separate.
Physiography
The cays a r e a l l very low, probably nowhere more than between 3 and
4 m, mostly much lower than t h i s . On each cay, dune r i d g e s and beach r i d g e s
account f o r a l l l a n d above a general l e v e l between 1 and 2 m. No boulder
r i d g e s were seen, nor any g r a v e l above pebble-gravel s i z e , except f o r Wle
p i l e s of Strombus s h e l l s mentioned below. A very few s c a t t e r e d boulders,
50 cm o r more i n l a r g e s t dimension occur. These a r e mostly compact, f i n e grained limestone, b u t one o r two a r e p e g n a t i t e . I n a l l p r o b a b i l i t y these
were brought t o Alacran a s b a l l a s t . Large b r a i n c o r a l s a r e abundant on
t h e r e e f s , b u t s u r p r i s i n g l y few a r e thrown up on land, where actualJy none
of any l a r g e s i z e were seen. A s p e c i a l search ~ r a smade f o r beach rock and
emerged r e e f conglomerate b u t no consolidated rock of any s o r t w a s seen,
and it i s thought t h a t none e x i s t s on any of t h e cays. Loose lime-sand
and " f i n g e r gravel" of broken Acropora c e r v i c o r n i s a r e t h e most common
m a t e r i a l s . The sand, i n p l a c e s where b i r d s a r e e s p e c i a l l y abundant, i s of
a da.rk yellowish brown color, elsewhere white t o p a l e gray-brown. Most of
it would correspond e i t h e r t o t h e Shioya S o i l S e r i e s of t h e P a c i f i c i s l a n d s
o r t o what has been termed Unaltered Sand and Gravel i n t h e Mmshall
I s l a n d s ( ~ o s b e r g1959)
.
The following p r o f i l e was encountered i n a p i t , dug f o r t h e purpose
on Perez I s l e t j u s t n o r t h of t h e lighthouse buildings, about 90 paces f'rom
t h e seaward beach, 68 paces from t h e lagoon beach, on ground very g e n t l y
sloping from a dune r i d g e toward the lagoon, i n a small opening i n open
Suriana scrub, t h i c k l y populated by sooty t e r n s :
0-2 cm:
loose dry sand mixed with Suriana l i t t e r .
2-3 cm:
somewhat caked sand.
3-10 cm: f i n e sand, t h i n l y and i r r e g u l a r l y bedded l i g h t and dark
gray-brown
10-35 cm: medium-fine sand, i r r e g u l a r l y mottled p a l e brown and yellow
brown, f i r s t t r a c e s of moisture v i s i b l e a t about 25 cm,
Suriana r o o t s common i n t h i s layer; they a r e up t o 1 cm t h i c k .
35-65 cm: coarser p a l e sand with f i n e r o o t s s c a t t e r e d through it.
65-105 cm: coarse sharp very p a l e sand.
105-140 cm : coarse sharp white sand with s c a t t e r e d , r a t h e r r o t t e n
c o r a l fragments.
idater l e v e l , a t 12:10 p.m., 133 cm, at 3:30 p.m., 133 cm, a t 6:00 p.m.,
150 cm.
The water i n t h i s p i t t a s t e d q u i t e s a l t y . R sample, analyzed by S.
Rettig, of t h e U. S. Geological Survey, showed C 1 15,500 ppm., NO2 1,420
ppm. , a s PO4, 1 . 2 ppm. , HC03 437 ppm., pH 7.1, and s p e c i f i c conductance
a t 25 C 41,700 micromhos The high n i t r a t e content i s doubtless from t h e
excrement of s e a b i r d s .
.
.
Along t h e beaches on s e v e r a l of t h e cays, e s p e c i a l l y Perez, Chica
and Pajaros, a r e conspicuous r i d g e s o r h i l l o c k s a s much as 1 o r 1.5 m
high of t h e l a r g e s h e l l s of Strombus gigas. These s h e l l s a r e thrown t h e r e
by fishermen a f t e r they have removed the animals t o use a s b a i t . Each s h e l l
has a hole broken i n the smaller whorls. Another curious f e a t u r e i s t h e
frequent occurrence of what appear t o be l e a f l e s s skeletons of a somewhat
thorny i r r e g u l a r l y branched shrub with a woody enlargement a t the base.
These a r e washed-up skeletons of l a r g e gorgonians commonly c a l l e d sea-whips
t h a t a r e very common on t h e r e e f s . Purple sea-fans, a l s o common i n the
beach s e d h e n t s , are likewise abundant components of t h e r e e f community.
Climate
Records kept by t h e Mexican government weather s t a t i o n on Alacran
between Januazy 1959 and t h e time of my v i s i t , were made a v a i l a b l e through
t h e courtesy of t h e personnel oT t h e s t a t i o n , t o whom I am very g r a t e f u l ;
these show s e v e r a l i n t e r e s t i n g f e a t u r e s , though t h e period covered i s f a r
too s h o r t f o r adequate g e n e r a l i z a t i o n . Time was only a v a i l a b l e t o study
and copy c e r t a i n f e a t u r e s of t h e s e records, so wind d i r e c t i o n and r a i n f a l l
d i s t r i b u t i o n were chosen a s having the most influence on o t h e r f e a t u r e s
studied, namely physiography and vegetation. Data on wind s t r e n g t h have
been compiled from t h e same s e t of records by J. T. Conover, and kindly
made a v a i l a b l e t o me.
The records of wind d i r e c t i o n t h a t a r e generalized i n t h e accompanying graphs were made t h r e e times daily? The b a r s on the graphs simply
represent t h e t o t a l number of observations of wind from each d i r e c t i o n ,
t h e bottom b a r i n d i c a t i n g observations recorded a s calm. It is c l e a r t h a t
t h e r e i s a p r e v a i l i n g wind from t h e e a s t , commonly ranging t o northeast
o r southeast, r a r e l y t o north o r even northwest. The only m o n t b t h a t were
notable exceptions, during t h e 2* years of record, were November 1959,
when t h e preponderant d i r e c t i o n was north with only a moderate e a s t e r l y
component, and September 1960, when t h e winds were f a i r l y w e l l d i s t r i b u t e d
a s t o d i r e c t i o n . From A p r i l through August, tile s o u t h e r l y t o westerly
components a r e n e g l i g i b l e and during t h e r e s t of t h e year almost so. The
d a t a assembled by Conover (unpublished) i n d i c a t e t h a t wind exceeds 20
h o t s on h a l f o r more of the days i n 8 months of t h e year.
The r a i n f a l l regime i n d i c a t e d by t h e s t a t i o n records i s so remarka b l e t h a t it seems necessary t o present t h e a c t u a l figures: generalized
only t o t h e e x t e n t of adding together t h e amounts shosrn by t h r e e d a i l y
observations i n t o d a i l y t o t a l s . .The t h r e e enormously high f i g u r e s , 999 mm
on each day, on Sept. 11, 1359, Dec. 26, 1960, and Jan. 9, 1961, each
r e p r e s e n t s i n g l e readings of t h e gauge ( 1 meter), thus being the record
f o r 1 2 hours o r l e s s . I t was s a i d t h a t on each of 'these occasions t h e
gauge overflowed i n a storm, so t h e record should be more than- a meter f o r
each of these readings. A s the regime i n d i c a t e d by these records is so
unusual t h a t it may possibly n o t be accepted by c l i m a t o l o g i s t s , it w i l l
n o t be discussed here, o t h e r than t o say t h a t t h e sparseness of the veget a t i o n , its poverty i n species, and the extremely xeromorphic c h a r a c t e r
of t h e p l a n t s seem g e n e r a l l y c o n s i s t e n t with extreme drought.
I n t h e s o i l p i t dug on Perez I s l e t , t h e f i r s t t r a c e s of moisture
were encountered a t about 25 cm, t h e sand became wet at 105 cm, and t h e
water was s a l t y . According t o t h e record t h e r e had been no r a i n f o r 20
days, then o n l y 3 mm, and before t h a t none f o r 105 days.
* Graphs
and r a i n f a l l f i g u r e s w i l l be found a t end of Bulletin.
Vegetation
The vegetation of Alacran has been described i n some d e t a i l by Bonet
and Rzedowski ( i n p r e s s ) , whose observations agree i n most r e s p e c t s with
mine. Therefore only a summary need be given here. The vegetation i s all
of an extremely pioneer character, i s composed of few species and shows
a s t r o n g tendency t o form r e c o m i z a b l e communities, a s w e l l a s a tendency
toward almost pure stands of s i n g l e s p e c i e s , Mowhere i s t h e dynamic nature
of vegetation b e t t e r shotm. 7Jhile on t h e b a s i s of such a b r i e f survey a
d e t a i l e d successional p a t t e r n could not be worked out, c e r t a i n dynamic
r e l a t i o n s h i p s may be indicated.
E a r l y records of t h e vegetation of Alacran m e meager, incleed.
William Dampier, who v i s i t e d t h e a t o l l i n 1675, says i n t h e account of
h i s voyage (1931 ed., p. 143) "The Alacranes a r e 5 o r 6 low sandy I s l a n d s . .
On some t h e r e a r e a few low bushes of Burton-wood, b u t they a r e mostly
barren and sandy, bearing nothing b u t only a l i t t l e Chicken-weed; n e i t h e r
have t h e y any f r e s h water."
Doubtless by "~urton-woodl'hemeans Conocarpus (button wood), now
almost lacking on Alacran. What "chicken-weed" might be i s not so c l e a r ,
though p o s s i b l y it may be Portulaca oleracea.
T. Smith (1838, pp. 804-805) i s perhaps t h e next t o mention t h e
vegetation of Alacran. He says t h a t "these sand bores soon g e t covered
with grass, samphire, and various kinds of herbs. 'I The g r a s s was doubtless
Sporobolus v i r g i n i c u s and t h e samphire must have been Sesuviwn. The l a c k
of any mention of shrubs suggests t h a t between W p i e r ' s v i s i t i n 1675,
and 1838 t h e a t o l l may have been swept by a storm of unusual violence and
t h e v e g e t a t i o n removed. However, t h e West I n d i a P i l o t (p. 371) says t h a t
t h e t h r e e cays a t the southeast extreme of t h e r e e f were "clothed with
g r a s s and brushwood." This is most l i l i e l y based on a r e p o r t by T. Smith
o r by Captain Barnett who surveyed Alacran i n the 1840 s Marion (1884)
says t h a t i n 1865, on Perez t h e r e was n o t a t r e e , only s h o r t g r a s s and
sea-fennel ( f e n o u i l marin) and one hut.
.
I n 1899 C, F, Millspaugh v i s i t e d Alacran on t h e Utowana Ex-pedition
and prepared a d e t a i l e d d e s c r i p t i o n and maps of t h e vegetation of most
i s l e t s (Millspaugh 1916). The i s l e t s were p r i n c i p a l l y covered by Sesuvium,
with considerable a r e a s of Sporobolus, and a s c a t t e r i n g of o t h e r herbs
and shrubs.
Since Millspaugh's v i s i t profound changes have occurred. It was
evident t o Millspaugh t h a t the vegetation of t h e cays was a l l of an e a r l y
pioneer c h a r a c t e r and he regarded most of it a s no more than 57 years old,
as, according t o him, Pajaros and Chica had been described i n 1842 a s
"bare sand s p i t s devoid of vegetation" and Perez and Allison ( ~ e s e r t o r a )
a s having "grass and samphire only. " Although he nowhere says so i n so
many words, Millspaugh apparently regarded t h e youthfulness of t h e vegeta t i o n a s i n d i c a t i n g t h a t t h e i s l e t s , themselves, were very young, as he
s a i d "The discovery, on these i s l e t s , of t h r e e species new t o science,
with t h e proof t h a t they have evolved within t h e known and d e f i n i t e
period of 57 years, i s a f a c t impressive as it i s important." The species
.
he r e f e r r e d t o were Calrile a l a c r a n e n s i s Millsp. (apparently a form of
C-. l a n c e o l a t a though t h e taxonomy of Cakile s t i l l leaves much t o be
desired),hhs
a l a c r a n e n s i s ~ i l l s ~ ~ of
o trh emv a r i a b l e T, c i s t o i d e s ) and Cenchrus i n s u l a r i s Scribn. ( C p i l o s u s H.B.K. ) A l l of these
seem t o be merely forms o r synonyms of more widely d i s t r i b u t e d , previously
described species.
.
.
-
There is, of course, no way of proving t h a t t h e i s l e t s of Alacran
e i t h e r a r e o r a r e not of such r e c e n t o r i g i n . It does seem probable t h a t
i n 1838 and 1842 t h e r e was l i t t l e vegetation. Whether t h i s was a p r i m i t i v e
condition i s questionable i n view of t h e statements of Dampier and Smith
(1838), and since t h e violence of storms i n the region i s such t h a t
complete denudation of t h e islets i s e a s i l y possible and m y have taken
place not long before t h e v i s i t of t h e B r i t i s h survey p a r t y i n t h e 1840's.
In any event, t h e r e p o r t of nothing b u t grass (Sporobolus) and samphire
( ~ e s u v i u m )on Perez and Desertora and nothing a t a l l on Pajaros and Chica
i n m r o v i d e s an important reference p o i n t f o r estimating t h e r a t e of
colonization of bare sand cays by p l a n t s and of t h e development of t h e i r
vegetation.
The p o s s i b i l i t y t h a t between 1675 and 1838 t h e woody vegetation may
have been e n t i r e l y destroyed by s e a l e r s ~ d i owould have used it f o r f i r e wood i n t r y i n g o u t s e a l o i l cannot be ignored. However, constant use of
Suriana f o r firewood by t h e i n h a b i t a n t s of Perez I s l e t since t h e lighthouse was e s t a b l i s h e d over 40 years ago has not prevented t h i s shrub from
becoming t h e dominant vegetation on t h e i s l e t . Also, on the s i m i l a r Pedro
Cays, south of Jamaica, annual c l e a r i n g of woody vegetation t o f a c i l i t a t e
egg gathering, has not, i n many years, eliminated t h i s vegetation. The
woody p l a n t s concerned s p r o u t r e a d i l y from t h e r o o t crowns, and these
crowns a r e not e a s i l y p u l l e d o u t by such ordinary means a s would l i k e l y
be employed by firewood g a t h e r e r s .
The d i s c e r n i b l e p l a n t communities o r vegetation types a r e l i s t e d
below and b r i e f l y characterized; t h e i r r e l a t i o n s with substratum v a r i a t i o n s , something of t h e i r p a t t e r n s of arrangement, and h i s t o r i c a l changes,
where known, a r e discussed. It i s hard t o be sure t h a t some of t h e primary
pioneer communities l i s t e d a r e n o t j u s t f o r t u i t o u s aggregations of p l a n t s
with no significance, except where a d e f i n i t e r e l a t i o n with substratum o r
topographic v a r i a t i o n s i s d i s c e r n i b l e . A d e t a i l e d map of these c o r n u n i t i e s
would be d e s i r a b l e , b u t time t o make such maps a t a l l c a r e f u l l y was not
a v a i l a b l e . The arrangement followed i s a r r i v e d a t purely subjectively,
s t a r t i n g with t h e most extreme pioneer s i t u a t i o n s and ending with t h e
most advanced vegetation, i n a successional sense. It should not, however, be assumed t h a t t h e r e i s any r e g u l a r o r l i n e a r successional s e r i e s
of communities intended. To e s t a b l i s h a c t u a l dynamic r e l a t i o n s h i p s between
these communities would take long and d e t a i l e d study, with repeated v i s i t s
over a period of years.
1. C y p r u s colonies. Occasionally, on g r a v e l bars, a t t h e tops of
beaches, and more r a r e l y on ' i n t e r i o r sand f l a t s , a r e small groups of
u s u a l l y widely sepaxated t u f t s of t h e spreading culras and r a t h e r harsh
leaves of Cyperus p l a n i f o l i u s . That t h i s i s a primary community is shotm
by stands of t i n y seedlings on otherwise bare a r e a s . Locally, as on t h e
sand f l a t a t t h e top of t h e beach a t t h e north end of Perez, dead t u f t s
of t h i s sedge were seen. No apparent reason f o r t h e dead condition was
noted, b u t perhaps with t h e extreme drought prevalent here, only s l i g h t
d i f f e r e n c e s i n p o r o s i t y may r e s u l t i n desiccation of t h e r o o t s . Colonies
of Cy-perus a r e now much more widely d i s t r i b u t e d than indicated by Millspaugh, who mapped it only from t h e south end of Perez, where it i s s t i l l
present.
2. A t r i p l e x colonies. A t t h e tops of beaches of f i n e g r a v e l and sand,
and on sand f l a t s i n the i n t e r i o r of i s l e t s a r e small r a t h e r open patches
of Atyiplex pentandra, a gray-green bushy herb, c l e a r l y t o l e r a n t , a s a r e
most of i t s congeners ( g e n e r a l l y c a l l e d salt-bush), of high s a l t concent r a t i o n s . It seems a b i t more widely d i s t r i b u t e d than i n d i c a t e d by Millspaugh, being abundant on Desertora (Allison) I s l e t , where he does n o t
show it.
-
3. Euphorbia mesembrianthemifolia dwarf scrub. One of t h e most wide
spread vegetation types i s an open dwarf scrub of Euphorbia mesembrianthemifolia, with various, u s u a l l y minor, admixtures of o t h e r p l a n t s , e s p e c i a l l y such herbs a s Cenchrus, Portulaca, Calcile, and, occasionally, Atriplex.
The substratum i s usually small gravel o r a mixture of sand and gravel,
high enough t o be w e l l drained. I n places t h e Euphorbia i s l a r g e l y dead
o r i n poor condition, but mixed with dead o r dying p l a n t s a r e occasional
healthy green ones. Millspaugh shows t h i s type t o be more confined t o t h e
p e r i p h e r i e s of t h e i s l e t s than it is now, though it i s s t i l l more commonl y found t h e r e . There seems t o be no i n d i c a t i o n t h a t t h i s community follows
o r r e p l a c e s any o t h e r , and it has every appearance of a primary community
t h a t would, i n an undisturbed s i t u a t i o n , be r e a d i l y replaced by Suriana,
o r possibly even by Sesuvium o r Sporobolus.
4. Portulaca oleracea stands. Locally, on sand and g r a v e l f l a t s ,
both a t t h e tops of beaches and i n t h e i n t e r i o r s of i s l e t s , a r e open, more
o r l e s s pure, stands of Portulaca oleracea. 'This f l e s h y herb forms depressed c i r c u l a r m a t s , each made up of one p l a n t , up t o 25 o r even 30 t o 40 cm
across. There i s no apparent difference between the s i t u a t i o n s occupied
by Portulaca and those of t h e Euphorbia described above. This i s c e r t a i n l y a primary community, probably very s h o r t - l i v e d . Millspaugh records only
a few i n d i v i d u a l s of Portulaca s c a t t e r e d among Sesuvium (and Sporobolus).
It is much more abundant now.
5. Cakile stands. On beaches, beach ridges, and sand f l a t s j u s t back
of beaches a r e occasional a r e a s of sparse stands of Cakile lanceolata, a
somewhat f l e s h y annual. Almost a l l mature p l a n t s vere dead, b u t shedding
mature f r u i t s i n J u l y . A few were green and flowering, and l o c a l l y small
seedlings were abundant. This a l s o seems t o be a primary pioneer communit y , confined t o s u b s t r a t a of sand o r g r a v e l l y sand.
6. Open Tournefortia. scrub. On Desterrada I s l e t and on t h e northwest
p a r t of Perez, a l s o on a small sand lobe on t h e e a s t s i d e of Perez, i s a
community l a r g e l y made up of low round dome-like bushes of Tournefortia
gnaphalodes, with some admixture of Euphorbi3 Cenclirus, Portulaca, and
Cakile. This community occupies sandy t e r r a c e s , dune ridges, and dune
f i e l d s , and, a t l e a s t on Perez I s l e t , seems t o i n d i c a t e land t h a t has
r e c e n t l y been added t o the i s l e t by deposition of sand. It is n o t u n l i k e l y
t h a t t h e r e l a t i o n with dunes may be t h e reverse of vhat might be expected,
-
t h a t is, t h a t the dunes r e s u l t from the accumulation of sand by the Tourn e f o r t i a p l a n t s which a c t a s sand t r a p s . These bushes a r e commonly growing up through a low mound of sand of about the same shape as the bush,
with t h e stems o r i g i n a t i n g a t t h e o r i g i n a l ground l e v e l beneath the mound.
Examination of Perez I s l e t from t h e top of the lighthouse shows t h a t t h e
former outline of t h e i s l e t , t h a t shown on Millspaugh's map, i s l a r g e l y
preserved by the present area of Suriana scrub ( s e e below) and the areas
occupied by Tournefortia scrub appear t o have been added subsequently, a s
they a r e c l e a r l y outside t h e periphery of the i s l e t as mapped by M i l l s paugh. Ground examination of t h i s a r e a shows some indication of invasion
by Suriana, suggesting t h a t Suriana w i l l eventually replace the Tournefort i a . On Desterrada I s l e t s , t h i s i s t h e p r i n c i p a l community, except i n
peripheral s i t u a t i o n s . Much of the a r e a i s an i r r e g u l a r f i e l d of low
dunes l a r g e l y occupied by Tournefortia.
7. Sesuvium mat. On most of t h e i s l e t s a r e areas, usually not very
extensive, covered by closed mats of p r o s t r a t e , f l e s h y Sesuvium p o r t u l a castrum. These areas a r e mostly low and very s a l i n e , sometimes a c t u a l l y
s r e t m i g l i t i d e . This vegetation type was, a t the time of Millspaugh ' s
v i s i t , by f a r t h e most prevalent, covering the l a r g e r p a r t of a l l the
i s l e t s he mapped. Other p l a n t s indicated by him as growing i n t h e areas
mapped as Sesuvium suggest invasion. However, i n most places the closed
Sesuvium community i s replaced by open types, so some other f a c t o r than
invasion and ordinary succession must be involved, as a succession from a
closed t o en open vegetation would be most unusual. The f a c t t h a t t h e
a r e a s concerned a r e now occupied by l a r g e b i r d populations may be of
significance. Another f a c t may be added here. On Desertora (Allison) I s l e t ,
some areas of Sesuvium mat a r e i n a very unhealthy condition, and some
a r e completely dead, b u t with t h e dead p l a n t s mostly s t i l l there and
i n t a c t . These a r e a s a r e i n some cases occupied by nesting f r i g a t e b i r d s ,
b u t the n e s t s a r e f a i r l y widely spaced. No other reason f o r t h i s condition
suggests i t s e l f , since there seems t o be no topographic o r other d i f f e r ences between these areas and those where the Sesuvium is healthy and
flourishing. On Perez I s l e t the former extensive Sesuvium area i s now
completely occupied by open Suriana scrub i s the s i t e of an enormous sooty
t e r n rookery.
-
8. Avicennia swamps. On Pajaros and Perez i s l e t s a r e very small
salt-water ponds, c u t off from t h e sea by sand s p i t s , i n which Avicennia
germinans forms t i n y mangrove swamps. The shrubs a r e a t most s e v e r a l
meters t a l l , mostly much smaller, and very young ones and seedlings a r e
p l e n t i f u l . No other species grow with them, and no such swamps were i n d i c a t e d by Millspaugh, who d i d not f i n d Avicennia a t a l l . These swamps, though
very small, a r e s o conspicuous t h a t they could not have been missed by
e a r l i e r i n v e s t i g a t o r s i f they had been present. The l o c a l people s a i d t h a t
they brought the p l a n t s from t h e swamp on Pajaros I s l o t t o t h e pond on
Perez, b u t gave no indication of t h e o r i g i n of those on Pajaros. I n a l l
p r o b a b i l i t y a s i n g l e p l a n t l e t was washed ashore on Pajaros while t h e pond
was s t i l l p a r t l y open, o r may have been washed i n t o t h e pond on a high
wave, i n very recent times, since Millspaugh's v i s i t , giving r i s e t o t h i s
vegetation.
9. Tribulus f l a t s . I n t h e i n t e r i o r of t h e Pajaros and Desertora
i s l e t s , which serve as rookeries f o r l a r g e numbers of blue-faced boobies,
on r a t h e r h a d packed sand, i s a s p a r s e very depressed vegetation of l a r g e
very open mats of Tribulus c i s t o i d e s , with l o c a l l y , s c a t t e r e d small mats
of Portulaca. This occupies a r e a s i n d i c a t e d on Millspaugh's map a s Sesuv i m . Its presence i s doubtless i n some >ray r e l a t e d t o t h e b i r d s .
10. Sporobolus v i r g i n i c u s sod. On Pajaros, Chica, and Desertora a r e
a r e a s covered by a closed s t a n d of harsh, wiry s a l t - g r a s s , Sporobolus
v i r g i n i c u s . This i s g e n e r a l l y f a i r l y l u x u r i a n t where p r e s e n t a t a l l ,
u s u a l l y 20-30 cm t a l l . Nothing was seen t o be invading it. However, i t s
a r e a i s now much smaller than i n d i c a t e d by Millspaugh, and it i s a l t o g e t h e r
lacking on Perez I s l e t , where he showed a l a r g e a r e a on t h e south end and
smaller patches i n t h e c e n t e r . Mow t h e s e places a r e e n t i r e l y covered by
Suriana scrub. This, however, i s open, and how it supplanted t h e dense
g r a s s sod so completely i s not c l e a r .
11. Suriana scrub. The dominant vegetation on most of Perez I s l e t
i s an open scrub about 1.5 t o 2 m t a l l of Suriana
- maritima. The densely
branched, b r i g h t green bushes a r e widely enough spaced t h a t i n most places
it i s easy t o walk a t w i l l among them. The sand between them i s a b s o l u t e l y
bare of vegetation. Innumerable sooty t e r n s , a d u l t s and f e a t h e r e d o u t
young, occupy t h e spaces between t h e p l a n t s and r o o s t i n l a r g e numbers on
t h e bushes themselves. I n 1899, according t o Millspaugh's map, Suriana
formed a narrow f r i n g e along t h e seaward s i d e of t h e i s l e t , somewhat a s
it does now on some of t h e o t h e r i s l e t s . The p o s i t i o n of t h i s f r i n g e i s
marked now by a sand ridge covered by Suriana, t h a t s e p a r a t e s t h e Suriana
scrub from open sand and g r a v e l f l a t s apparently added t o t h e i s l e t s i n c e
1899 and c h a r a c t e r i z e d by o t h e r vegetatibn. The- c u r i w s f a c t t h a t an open
Suriana scrub B a s replaced two types of closed herbaceous vegetation has
been alluded t o above. It i s apparent t h a t , whatever t h e mechanism, Suriana i s able t o replace a l l t h e o t h e r n a t u r a l vegetation types except
p o s s i b l y t h e Opuntia. The ground occupied i s mostly sand.
12. Opuntia scrub. Millspaugh i n d i c a t e s a s i n g l e small patch of what
he c a l l s Opuntia toona, o r 0. tuna, growing on a small p i l e of c o r a l heads
north of t h e c e n t e r of ~ e r e zI s l e t . Now t h e r e a r e two patches, much l a r g e r
than i n d i c a t e d by Millspaugh, one i s approximately t h e same place, one
south of t h e lighthouse; t h e r e i s a l s o one patch on t h e south end of Des e r t o r a I s l e t . The p l a n t s seem t o be Opuntia d i l l e n i i r a t h e r than 0. tuna.
These fleshy, l e a f l e s s , very spiny p l a n t s form a s o l i d s t a n d a b o u t 1 m o r
l e s s tall, and seem c l e a r l y t o be spreading a t t h e expense of t h e Suriana.
I f l e f t t o themselves they may e v e n t u a l l y occupy t h e e n t i r e i s l e t . The
patch on Desertora i s a b i t l e s s s o l i d , and i s t h e s i t e of a considerable
number of F r i g a t e b i r d n e s t s . The presence of t h e b i r d s seem t o have a
bad e f f e c t on t h e Opuntia. How t h e b i r d s go about s t a r t i n g a n e s t I n such
an unpleasant s i t u a t i o n i s not c l e a r , b u t t h e n e s t s a r e dense and s u b s t a n t i a l enough s o t h a t t h e young b i r d s a r e n o t bothered by t h e s p i n e s so
long as they s t a y i n t h e n e s t .
13. Casuarina groves. Around the lighthouse on Perez, and extending
a s h o r t distance t o t h e north and south of it, Casuarina e q u i s e t i f o l i a
t r e e s have been planted, and have reached a considerable s i z e , perhaps
10 meters. Smaller numbers of Cordia subcordata and Coccoloba uvifera
shrubs have a l s o been planted and seem t o t h r i v e . None of them, however,
a r e reproducing themselves t o any e x t e n t by seed, and t h i s vegetation
type seems t o be dependent f o r i t s spread, i f not f o r i t s persistence,
on human intervention. The t r e e s a r e f a i r l y widely spaced and the
intervening spaces a r e occupied b y t h e Suriana scrub t h a t covers most of
t h e r e s t of the i s l e t . Numbers of f r i g a t e b i r d s use f o r r o o s t s soEe of
the Casuarina t r e e s t h a t a r e a l i t t l e distance from t h e houses around
the lighthouse.
Vascular Flora
The t a b u l a r arrangement of t h e p l a n t species gives an i d e a of the
f l o r i s t i c changes t h a t have taken place, with perhaps more r e l i a b i l i t y
than such f i g u r e s u s u a l l y have, s i n c e t h e Millspaugh survey was a
c a r e f u l one, a s lras t h a t by Bonet. It i s seen t h a t species have disappeared
a s w e l l a s become e s t a b l i s h e d . Water, b i r d s , and people a r e t h e p r i n c i p a l
agencies of d i s p e r s a l , and most of t h e p l a n t s a r e Ire11 adapted t o
u t i l i z e one o r more of these means. Why some species have disappeared
i s n o t so r e a d i l y apparent. Some may have been crowded o u t a s succession
progressed. Others, such a s Scaevola, may never have been p r e s e n t i n
s u f f i c i e n t numbers t o preclude t h e i r disappearance because of a c c i d e n t a l
elimination of one o r t ~ r op l a n t s . Storms may a l s o have swept c e r t a i n
species away. F i n a l l y , some may n o t have been a b l e t o endure the e x t r a ordinary droughts t h a t seem c h a r a c t e r i s t i c of t h i s i s l a n d .
In t h e f o l l o ~ r i n t~a:b l e s , E stands f o r records e a r l i e r than M i l l s paugh's; M f o r Millspaugh;B, Bonet; F, Fosberg; C . W., Conover, and
;Jelch. 1 i n d i c a t e s t h a t only
s i n g l e i n d i v i d u a l was seen on an i s l e t ,
X, more than one.
Perez
W and ED a r e West Desterrada and E a s t Desterrada
Desertora
Pajaros
Chica
WD EiYA
L i s t of Flowering Plants
The following l i s t includes a l l the species known t o e x i s t on
Alacran i n JLiy 1961, l i s t e d under the names believed t o be correct, with
c i t a t i o n s of specimens seen by me. My own c o l l e c t i o n s have not yet been
d i s t r i b u t e d t o herbaria, nor have those of Vi. Bruce Welch. A number of
the names used d i f f e r from those used f o r the same species by M i l l s paugh ( 1900a, 1900b, 1916)
f i e r e Millspaugh ' s names a r e regarded a s
synonyms of those used here, they a r e l i s t e d a s such, under the correct
names. IJhere they a r e considered a s misidentifications, they are
r e f e r r e d t o i n the coments, so a s not t o confuse the reader. An a s t e r i s k (") precedes the names 6f planted species.
.
Diplanthera m i g h t i i ( ~ s c h). Asch.
Perez, F 41873.
Submerged marine aquatic, l o c a l l y common i n shallotr areas i n lagoon
and around i s l e t s , forming a sod alone o r with Thalassia.
Syringodium
- f i l i f o r m e KWz.
manatarum Asch. )
Submerged marine aquatic with t e r e t e leaves, l o c a l i n Thalassia sod
near i s l e t s .
Thalassia testudinarum Koen. e t Sims
Perez, F 41872.
Submerged marine aquatic, abundant generally i n shallow water on
sandy bottoms, forming a dense sod trhich i s the predominant
marine vegetation on l a r g e p a r t s of the r e e f .
Cenchrus gracillimus Mash
Desertora, F 41929.
Common l o c a l l y along lagoon beach ridge and somewhat inland.
only s l i g h t l y from C.
- pauciflorus.
Differs
Cenchrus pauciflorus Benth.
Desterrada, F 41919.
Occasional on low sand dunes. This may be the p l a n t reported by
Millspaugh (1900) a s C . t r i b u l o i d e s L. and (1916) a s C. carolinianus Walt. b u t it could a s well have been the preced&g.
It
now seems t o have disappeared completely from Perez I s l e t , where
Millspaugh's c o l l e c t i o n was made.
Cenchrus pilosus H.B.K.
.
.
.
( ~ e n c h r u salacranensis Millsp )
Pajaros, ~ n e r r a d a F, 41914; Desertora, F 41930.
Local on sand f l a t s and dunes.
Sporobolus virginicua L.
Chica, F 41905; Pajaros, F 41901; Desertora, F 41926.
Forming dense sod on sand f l a t s . I n Millspaugh's time t h i s species
covered much l a r g e r areas than now. On Perez I s l e t , where it
then formed a l a r g e p u t of the vegetation it has disappeared
completely.
Cyperus p l a n i f o l i u s L.C.Rich.
( ~ y p e r u sbrunneus Sw.; C erus brizaeus Vahl; Cyperus o t t o n i s Boeclcl.)
Perez, F m e l c h *
i
Pajaros, F 41095
Occasional and l o c a l on sand f l a t s and a t tops of beaches.
e r i n u m sp.
Perez, F 41891.
Planted around dwellings; not s u f f i c i e n t l y developed f o r i d e n t i f i c a - asiaticum L.
tion, but probably C.
-xCasuaxina e q u i s e t i f o l i a L.
Perez, F 41876.
Planted i n considerable numbers around lighthouse and i n c e n t r a l
p a r t s of Perez I s l e t , where they have reached a considerable
s i z e but do not seem t o e s t a b l i s h themselves spontaneously from
seed.
e o c c o l o b a uvifera L.
Perez, F 41878.
Planted near lighthouse.
Atriplex pentandra (Jacq. ) Standl.
( ~ t rlie x c r i s t a t a H. & B. ex Willd. )
Perez, F 1870, 41871 Welch i n 1961; Desertora, F 41924.
Local, a s s c a t t e r e d individuals, more usually open patches, i n sandy
and gravelly places.
9-7,
-
Sesuvium portulacastrum ( L. ) L.
Perez, F 41874, idelch i n 1961; Pajaros, F 41903; Chica, 41908;
Desertora, F2
-5.
Abundant l o c a l l y , forming mats, sometimes very large ones, i n low
s a l i n e places; on Desertora i n some areas these mats a r e dead
or apparently dying.
Portulaca oleracea L.
Perez, F 41867, Welch i n 1961; Pajaros, F 41902; Chica, F 41909,
41912; D e s t K d a , F 41917; h s e r t o r a , F 41922.
Common t o abundant generally i n open areas; a form with flowers very
l a r g e f o r t h i s species.
Cakile l a n c e o l a t a ( ~ i l l d). Schulz
.
( ~ a k i l ea l a c r a n e n s i s Millsp. ; C edentula var. alacranensis (Millsp. )
Schulz; C. ae u a l i s L 1 ~ e r T C_.
; l a n c e o l a t a var. alacranensis
(Mi1lsp.J *S
~ e r e z ,F 41864 41868; Pajaros, F 41900; Chica F 41910; Desterrada,
F e ~ e s e r t ~ i Fa 41932.
,
Common on upper p a r t s of beaches, beach ridges, and on other open
sandy o r g r a v e l l y areas; o& m a t e r i a l i s a l l of var. alac&ensis,
with g r e a t l y swollen d i s t a l segments t o t h e f r u i t s , b u t
Millspaugh (1900a, b ) reported var. lanceolata, f i r s t a s C.
maritima Scop., then as C. a e q u a l i s LIHer. This has narrowed
merely t e r e t e d i s t a l segments. The d e t a i l e d taxonomy of these
forms i s not y e t i n a s a t i s f a c t o r y condition, so the whole
complex i s here r e f e r r e d t o C_. l a n c e o l a t a .
Suriana maritima L.
Perez, F 41875, Velch i n 1961; Pajaros, F 41898; Chica, F 41906;
Desertora, F
-28.
Locally forming an open scrub, e s p e c i a l l y on Perez I s l e t , where it
dominates most of t h e undisturbed p a r t of t h e i s l a n d .
Tribulus c i s t o i d e s L.
( Tribulus a l a c r a n e n s i s Millsp. )
Pajaros, F 41898; ~ e s t e r r a d a , F 41916; Desertora, F 41923.
Common on open f l a t s of hard ground, e s p e c i a l l y where boobies a r e
nesting. The Alacran p l a n t s a r e of a small-flowered form, b u t
s i n c e forms with such small flowers may be seen l o c a l l y i n
o t h e r p a r t s of t h e world, and since t h e species i s a v a r i a b l e
p a n t r o p i c a l one, it does not seem advisable t o maintain t h i s
l o c a l papulation a s a d i s t i n c t species. I f a c a r e f u l study of
t h e v a r i a t i o n of
c i s t o i d e s were made, t h e r e ~ ? o u l ddoubtlees
be a number of v a r i e t i e s distinguished.
x.
Euphorbia mesembria;nthemifolia Jacq.
( ~ h m a e sce buxifolia, (Lam. ) Small; Eu horbia b u x i f o l i a Lam. )
Perez, F 1862, 41865; Pajaros, F 41 99, Chica F 41911; Desterrada,
F 41915; Desertora F 41931.
__Yr
8e-
Conocarpus e r e c t a L.
Perez, F 41893.
There seems t o be only one bush of t h i s s p e c i e s remaining here, a.
depauperate specimen with small l e a v e s t h a t s o resembles t h e
dominant Suriana t h a t it was missed ' e n t i r e l y u n t i l Professor
F. Bonet c a l l e d my a t t e n t i o n t o it.' Several a r e shown i n t h e
same l o c a l i t y on Millspaugh's map.
*Nopalea. c o c h i n e l l i f e r a (L. ) Salm-Dyck
Perez, F 41879.
Planted, b u t only one o r two individuals, n e a r dwellings.
Opuntia d i l l e n i i ( ~ e- ~
r a w l e )r Haw.
Perez, F 41892, Welch i n 1961; seen a l s o on Desertora.
Forming dense patches, b u t very l o c a l ; r e p o r t e d by Millspaugh
-. (1900a, 1916) a s 0
tuna (L. ) M i l l .
K o r d i a sebestena L.
Perez, F 41877.
A number of t r e e s of v a r i o u s s i z e s p l a n t e d n e a r t h e l i g h t h o u s e and
dwellings, abundantly flowering b u t almost completely l e a f l e s s
i n July.
T o w n e f o r t i a gnaphalodes ( L. ) R. B r
.
F 41907; Desterrada F 41918; Desertora, F 41927.
Abundant i n sandy a r e a s on Perez and Desterrada I s l e t s , very r a r e on
Desertora, P a j a r o s and Chica, only one t i n y s e e d l i n g seen on
t h e l a t t e r i s l e t . Millspaugh found one p l a n t on Pajaros and
none on Desertora o r Chica. Because of t h e f l o a t i n g mechanism
on t h e f r u i t s , t h i s s p e c i e s and i t s Indo-Pacific counterpart,
T. argentea, a r e o f t e n segregated a s a s e p a r a t e genus, c a l l e d
e i t h e r Messerschmidia o r Mallotonia, depending on whether o r
n o t t h e S i b e r i a n Messerschmidia s i b i r i c a i s regarded a s a l s o
i n t h e same genus.
P
Avicennia germinans ( L. ) L.
Pa jaros, F 41904.
~ e r e z~41866;
,
Locally abundant around tl-ro small ponds, s a i d t o have been brought t o
Perez from Pajaros; undoubtedly absent from both i s l e t s a t t h e
time of Millspaugh ' s v i s i t .
I n a d d i t i o n t o t h e 24 s p e c i e s l i s t e d above, t h e following were
growing i n enclosures p r o t e c t e d from t h e wind and spray, as w e l l as from
chickens, by bamboo fences :
*setcrkasea purpurea Boom ( F 41886)
Whenopodium ambrosioides L'-887)
*Portulaca grandif l o r a Hook. )(-F
x-Jatropha ( ~ n i d o s c o l u)s urens L. ( F 41882)
q e r m i n a l i a catappa L. ( ~ 4 1 8 8 3 )
*Mentha s-picata L. ( F 4 1 8 8 4 )
'ACapsicum annuum L. ~
~ 41889, 8two forms)
,
+Solanurn lycoper s i c u m r 4 1 m
*Sesamum indicum L. (F 4 1 8 . r
I t is p r a c t i c a l l y c e r t a i n t h a t none of t h e s e would survive exposure t o
s a l t and d r o u g h t on Alacran without s p e c i a l p r o t e c t i o n and watering.
P l a n t s p r e v i o u s l y r e p o r t e d from Alacran by Millspaugh, b u t a p p a r e n t l y
n o t found t h e r e a t p r e s e n t , a r e Boerhavia r e e n s L., Philoxerus verrnicularis ( L. ) R. Br Scaevola p l u m i e ~ .r e p o r t e d a s S. l o b e i i a M u r r . ) ,
and F l a v e r i a l i n e a r i s Lag.
.,
f-
T e r r e s t r i a l Vertebrates
J u l y i s a poor month t o see a l a r g e v a r i e t y of b i r d s on Alacran,
though a . f e w species a r e present i n l a r g e numbers and s e v e r a l n e s t a t
t h i s season o r j u s t before. I n a l l , only 1 3 species of b i r d s were seen
during a v i s i t of over a week. These a l l seemed t o be r e s i d e n t b i r d s .
Doubtless a much longer l i s t could be observed during migration seasons.
The following b i r d s and r e p t i l e s were a l l seen during the f i r s t
week i n J u l y 1961. A f e ~ rof t h e species had been recorded e a r l i e r by
Kornicker and a s s o c i a t e s (1959)~ and s e v e r a l by Dampier (1699). Birds a r e
a l s o l i s t e d by Kennedy (1917) and Paynter (1953, 1955) b u t t h e i r records
w i l l not be discussed here. The two marmnal records a r e included a s they
may represent t h e e n t i r e mama1 fauna i n pre-lighthouse days.
Mammals
Rattus sp.
"large r a t s "
Dampier (1699, 1931 ed. p. 143) records " l a r g e r a t s , which a r e i n
g r e a t p l e n t y . " No rats were seen i n 1961 on any of t h e i s l e t s . They may
have been eliminated by the dogs and c a t s of the lighthouse s t a f f , b u t
t h i s does n o t seem l i k e l y . Other evidence suggests t h a t a severe storm
may have swept the i s l e t s , e l i m i n a t i n g t h e vegetation, subsequent t o
Dampier's v i s i t . The r a t s may w e l l have been eliminated a l s o .
Monachus t r o p i c a l i s ( ~ r a . ~ )
West Indian Seal, West Indian Pionk Seal
Alacran was formerly an important h a b i t a t of t h i s t r o p i c a l s e a l .
Dampier (1. c . , pp. 145-146) speaks of t h e abundance of s e a l s on Alacran
and gives an account of an expedition from Jamaica t o prepare s e a l o i l .
I n r e c e n t years, no s e a l s have been seen on t h e a t o l l , and it i s f e a r e d
t h a t these i n t e r e s t i n g c r e a t u r e s may now be e x t i n c t . Raymond Gilmore
made a search f o r them over t h e i r former range a f e ~ ryears ago but f a i l e d
t o f i n d any. However, he t o l d Gordon Gunter (1954) t h a t t h e y had been
r e p o r t e d l y seen on Alacran a s l a t e a s 1948.
Sula d a c t y l a t r a
-
Lesson
Blue -faced booby
Two vere seen f l y i n g by Perez I s l e t on f i r s t day, b u t none were
n e s t i n g o r even r o o s t i n g on Perez. On J u l y 4, 8 o r 10 were seen on Chica
I s l e t , mostly with downy t o p a r t l y feathered out young, one p a r e n t s t a y i n g with each b i r d . Two of the young seemed nevly hatched, s c a r c e l y even
domy y e t . One b i r d had trjo eggs. One hundred o r more were seen on
Pajaros I s l e t , mostly with young i n various stages from newly hatched t o
almost grown. Two were seen with eggs, one v i t h one, and one with two. An
enormous number were seen on Desertora I s l e t , from t h e lagoon; l a t e r many
hundreds were examined on the ground, with eggs and young i n a l l s t a g e s .
Nests were about 2 m a p a r t .
From Dampier ' s account (1699, 1931 ed., pp. 143-144) boobies must
have been more numerous i n 1675 than now, though t h e i r behavior and t h e
f a c t t h a t they occupy d e f i n i t e t e r r i t o r i e s on t h e i s l e t s have n o t changed.
Sula leucogaster
-
(~oddaert)
Brown booby
Six vere seen f l y i n g north of Desertora i n forenoon of J u l y 5. I n
afternoon, 50-60 were i n a i r over Desertora Cay. I t i s not c l e a r where
they l i v e . One Tias seen on t h e ground on Cesertora on J u l y 6.
Fregata magnificens Mathem
Frigate bird
Hundreds of t h e s e g r e a t b i r d s r o o s t on t h e Casuarina t r e e s on Perez
I s l e t d u ~ i n gt h e daytime. On J u l y 5, a l a r g e number were on t h e ground
and on some o l d p i l i n g s off t h e lagoon beach of Desertora I s l e t . Many
were n e s t i n g on t h e ground t h e r e ; t h e n e s t s a r e very low mounds of t ~ r i g s ,
i n t h i n , dead, o r half dead Sesuvium mats. The young were f u l l y f e a t h e r e d
o u t b u t not y e t f l y i n g . Many dead young f r i g a t e b i r d s were seen. About
75 n e s t s were i n a cactus patch near t h e southeast corner of t h e cay.
Campier ( 1 . c., p. 144) gives an excel-lent account of "Men-of -\Jar ~ i r d s "on Alacran, r e p o r t i n g them i n g r e a t numbers and recording t h e i r
h a b i t of piracy, robbing t h e boobies both young and old, of t h e i r
a l r e a d y swallowed f i s h . Possibly t h i s i s t h e e a r l i e s t account of t h i s
phenomenon.
F l o r i d a caerulea L.!
L i t t l e blue heron
A small dark heron, seen on one of t h e lagoon b a r s toward t h e souhh
end of Perez I s l e t , may have been t h i s s p e c i e s . Its behavior resembled
s a c r a ) on P a c i f i c c o r a l i s l a n d s .
t h a 5 of t h e r e e f heron (Cemigretta
Arenaria i n t e r p r e s L.
Ruddy turnstone
A small f l o c k of t u r n s t o n e s were cbserved on Perez I s l e t , 5 b i r d s
on Chica, and 2 on Desertora, running and f l y i n g along t h e beaches, t h e i r
h a b i t s much t h e same a s on P a c i f i c a t o l l b e a c n e s .
Castrophorus semipalmatus Ginelin
Willet
One was seen on tile lagoon beach of Pajaros and another on t h e
lagoon beach a t East Desterrada I s l e t .
Larus a t r i c i l l a L.
Laughing g u l l
On J u l y 4, 20-30 were seen on Chica I s l e t . A small n e s t , of
b i a mesembrianthemifolia, i n a mat of Portulaca oleracea, about
across and containing a d u l l gray egg with i r r e g u l a r blackish-brown spots,
probably belonged t o a p a i r of these, a s t h e y f l e v around making much noise
when it was approached.
One g u l l was seen on Pajaros I s l e t , s e v e r a l were with a f l o c k of
r o y a l t e r n s on E a s t Cesterrada, and s e v e r a l were f l y i n g over Desertora
Islet.
Thalasseus maximus ( Boddaert )
Roya.1 t e r n
One was seen f l y i n g near Perez I s l e t , none were r e s t i n g o r n e s t i n g
t h e r e . On J u l y 4, 20 o r 25 were seen s i t t i n g on a small sand horn on Chica
I s l e t . On J u l y 5, a number were over t h e lagoon n o r t h of Desertora I s l e t ,
a l l f l y i n g toward Desterrada. An enormous flock, of perhaps s e v e r a l
thousand b i r d s , were s i t t i n g on t h e salld on a low beach r i d g e on t h e n o r t h
e a s t s i d e of E a s t Desterrada, p r o t e s t i n g when scared up, mostly n o t ~ m n t i n g
t o l e a v e . Eleven l a r g e gray eggs with b l a c k spots, i n s l i g h t depressions
i n sand on t h e berrn a t t h e t o p of t h e seaward beach, probably belonged
t o some of t h e s e b i r d s , as they made a tremendous commotion when the eggs
were approached.
'
Sterna hirundo L.
Common t e r n
A considerable number of l i g h t backed t e r n s with black b i l l s , , which
must have been t h i s s p e c i e s , were seen on E a s t Desterrada, mixed with t h e
l a r g e f l o c k of r o y a l t e r n s described above.
S t e r n a f u s c a t a L.
Sooty t e r n
An enormous colony of t h e s e g r a c e f u l b i r d s occupies t h e g r e a t e r
p a r t of Perez I s l e t o u t s i d e t h e p o r t i o n immediately around t h e lighthouse
and weather s t a t i o n b u i l d i n g s . Almost f u l l grown young, f u l l y f e a t h e r e d
o u t b u t n o t q u i t e a b l e t o Tly, were seen i n g r e a t numbers. These young
had dark b r e a s t s , p a l e gray a n a l p a r t s , black b a c l s b a r r e d riith buff t o
white on f e a t h e r t i p s . Vhen a person >ralked through t h e a r e a t h e s e young
b i r d s scrambled f r a n t i c a l l y t o g e t away through and under t h e bushes, and
clouds of a d u l t s f l e w up. ' h e sooty t e r n s r e s t i n hundreds on t h e -Suriana
.bushes, b u t i n t e n s of thousands on t h e ground between them. One egg was
seen on t h e s8nd on a seavard s p a r s e l y vegetated sand t e r r a c e near t h e
south end of t h e i s l e t . A t n i g h t t h e sooty t e r m viere s t i l l r o o s t i n g on
t h e ground and i n t h e Surian? bushes, making l e s s noise than during t h e
day. A s t r o n g l i g h t s c a r e s -them up b u t they f l y with much l e s s sureness
than i n daytime. On J u l y 3, clouds blew over and a very few drops of r a i n
f e l l , n o t enough t o be r e g i s t e r e d by t h e r a i n gauges. This occasioned a
t e r r i f i c clamor among t h e sooty t e r n s , f a r more than t h e normal l e v e l of
noise, and g r e a t numbers 03 t h e b i r d s l e f t t h e ground and flew around i n
g r e a t confusion and excitement. Some immature b i r d s , with varying amounts
of gray on under p a r t s , were seen f l y i n g over t h e lagoon n o r t h of Perez
I s l e t and a d u l t s were comon i n t h e a i r around Perez. None were o b s e r v e d .
on t h e ground anywhere except on Perez I s l e t . People r e s i d e n t on Perez
s8y t h e t e r n s leave t h e i s l a n d i n September a.nd r e t u r n i n February.
The "Egg-Birds" recorded by Dampier (1. c., pp.143-144) were probably
s o o t y t e r n s . He says: "The Egg-Birds, t h o ' they a r e many, y e t being b u t
s m a l l take up l i t t l e room t o t h e rest. Yet i11 t h a t l i t t l e p a r t which they
i n h a b i t they a r e s o l e Masters, and n o t d i s t v r b e d by t h e i r ~ e i g h b o u r s . "
This does n o t correspond riel1 with t h e p r e s e n t s i t u a t i o n , where t h e s o o t y
t e r n s a r e "sole masters" of almost t h e e n t i r e Perez I s l e t and f a r more
numerous than any o t h e r b i r d on t h e a t o l l . The d i f f e r e n c e may of course
be due t o a d i f f e r e n c e i n season, as Dampier was t h e r e i n t h e f a l l ,
probably October
.
Sterna anatheta Scopoli
Bridled t e r n
Many of t h e s e were seen on J u l y 5 i n a mixed f l o c k with black t e r n s
s i t t i n g on t h e e a s t s p i t of 1,iTest Desterrada I s l e t .
Chlidonias n i g r a ( L . )
Black t e r n
Many were seen i n a mixed f l o c k with b r i d l e d t e r n s s i t t i n g on t h e
e a s t sand s p i t of ?Jest Desterrada I s l e t .
Anous s t o l i d u s L.?
Common noddy?
Many noddies were seen on Perez I s l e t , apparently t h e common noddy
b u t r a t h e r l i g h t colored (compared t o P a c i f i c b i r d s ) , n e s t i n g i n Suriana
bushes (some i n ~ a s u a r i n a ) .The n e s t s were of Suriana twigs, very bulky
and poorly formed, b u t some f u l l y 1 meter t a l l and standing on t h e ground.
some-of t h e nests.were ornamented by a s many a s 25-30 bivalve s h e l l halves,
most had none. This seems t o be a m a t t e r of i n d i v i d u a l t a s t e on t h e p a r t
of t h e b i r d s . A few had eggs o r newly hatched young, while some had f u l l y
f e a t h e r e d o u t young. The l a r g e n e s t s a r e i n s t r i k i n g c o n t r a s t t o t h e small
flimsy c o l l e c t i o n s of twigs t h a t serve as n e s t s f o r t h e common noddy of
t h e P a c i f i c , a s seen i n he Northern Marshalls. 'Il~enoddies on Perez
mingle f r e e l y with t h e sooty t e r n s i n t h e same a r e a . TJeither noddies nor
t h e i r n e s t s were seen on the o t h e r i s l e t s .
Reptiles
b!!buya
mabuya ( Lacepede )
Skinl;
This l i z a r d i s apparently r a r e , as it was only seen twice, both
times on Perez I s l e t . A mature specimen was c o l l e c t e d on a c o r a l g r a v e l
r i d g e j u s t back of t h e beach on t h e n o r t h end of t h e i s l e t . It was ident i f i e d by Drs.Doris Cochran and Walter Brown, and i s deposited i n t h e
U. S. National Museum. A small specimen of what i s probably t h e same
s p e c i e s was found i n a b u i l d i n g near the lighthouse by Professor F. Bonet.
M r . Hoskin s t a t e d t h a t he had seen these l i z a r d s occasionally during
h i s e a r l i e r v i s i t s t o Alacran.
Chelone mydas (L. )
Green t u r t l e
Two egg p i t s were seen on a sand lobe on south end of Perez I s l e t ,
a number of o t h e r s on t h e v e s t sand r i d g e of Pajaros near t h e n o r t h end,
and s e v e r a l more on Desertora along t h e seaward t e r r a c e back of t h e
beach. Six g r e a t t u r t l e s had been captured and were on t h e i r backs i n a
shed on West Desterrada I s l e t on J u l y 5 .
T e r r e s t r i a l invertebrates: Insects
The following l i s t of i n s e c t i d e n t i f i c a t i o n s was furnished by the
U. S. National Museum.
Formic idae
Paratrechina l o n g i c o rn i s ( ~ a t r), d e t M. R. Smith
.
.
Coccinellidae
Naemia s e r i a t a (Melch), d e t . E. A. Chapin
Tenebr ionidae
Blapstinus sp., d e t . T. J. Spilman
Curculionidae
Dryotribuc mimeticus Horn
F i r s t record? rom Xexico, Yucatan, d e t . R. E. Warner
Tethinidae
Bhicnoessa sp.
Muscidae
?Lispocephala sp.
Sarcophagidae
Tricharaea fernoralis (Schin. ), d e t . C. W. Sabrosky
Iiippoboscidze
O l f e r s i a s p i n i f e r a (Leach), d e t . A. Stone
Pentatomidae
Murgantia h i s t r i o n i c a ( ~ a h n )
Microporus obliquus Uhler
Lygae
idae
. .
Exptochiomera sp.?
Rysius sp., d e t . R. C . Froeschner
Myrmeleontidae
Psammoleon c f . b i s t i c t u s ( ~ a g),. d e t . 0. S. F l i n t
Coccoidea
Phenacoccus sp., on c u l t i v a t e d pot p l a n t . Det. H. Morrison
Acrididae
Trimerotropis p a l l i d i p e n n i s Bum.
Blattidae
P e r i p l a n e t a americana ( L )
Panchlora sp.
Gryllidae
Cycloptilumsp., d e t . A. B. Gilrney
The c o l l e c t i o n a l s o included Histeridae, Sarcophagidae, ?"nysanura
and s p i d e r s which were n o t i d e n t i f i e d .
Comparison between Alacran and Pokak A t o l l s
One of t h e p r i n c i p a l purposes of v i s i t i n g Alacran was t o compare it
with t h e P a c i f i c a t o l l s with which I am f a m i l i a r . I-t was soon evident
t h a t t h e P a c i f i c a t o l l i n my experience most comparable with Alacran i s
Polrak ( ~ a o n g)i, t h e northernmost of t h e Marshall Archipelago ( ~ o s b e r g
1955, 1956, 1957). They a r e both completely i n the t r a d e wind b e l t , n o t
exposed t o doldrum influence t o any s i g n i f i c a n t e x t e n t . Alacran i s a t
22O30 ' N l a t i t u d e , Pokalr l k O35 'I?. Both a r e dry, though adequate r a i n f a l l
records a r e not a v a i l a b l e f o r comparison.
Detailed l i s t s of species a r e n o t a v a i l a b l e e i t h e r except f o r vasc u l a r p l a n t s and l a n d v e r t e b r a t e s , and t h e b i r d l i s t s cannot be compared
p r o f i t a b l y because they were c o l l e c t e d a t d i f f e r e n t seasons. Itor a r e
analyses, e i t h e r chemical o r mechanical, of the s o i l s and sediments a v a i l able f o r Alacran. It rmuld perhaps be p r o f i t a b l e t o have some made f o r
comparison with those on hand from Pokalr and o t h e r Marshall I s l a n d s . It
would be of g r e a t i n t e r e s t t o study t h e Polrak marine b i o t a t o determine
the r o l e of the various species i n t h e r e e f community, a s Kornicker and
Boyd (1962) have r e c e n t l y done f o r t h a t of Alacran.
The follotring t a b u l a r comparison i s mostly of very general f e a t u r e s .
Some of these a r e s i n g l e items, o t h e r s may be regarded a s i n t e g r a t i o n s of
many components. The l i s t m y only be regarded a s a s t a r t toward a d e f i n i t i v e comparison, b u t may be i n d i c a t i v e of the degree of s i m i l a r i t y o r
dissimilarity.
-21 POKAK
Reef and lagoon f e a t u r e s
Orientation north-south
Same
Total length, 25 lm
T o t a l length, 18 km
Tota.1 width, 13 km
Total width, 8 krn
Maximum depth of lagoon, 23 m
Maximum depth of lagoon, 1 5 m
Lagoon open on a l a r g e p a r t of
leeward s i d e
Lagoon closed except f o r a
t i n y leeward channel
Lagoon l e v e l changing with t i d e s
Lagoon l e v e l almost constant
Xndward reef crescenl; -shaped
Same
Algal ridge none
Algal ridge well developed
Niggerheads none
Niggerheads abundant
Reef platform sandy, evident only
on windward side, where it i s
covered by an incomplete pavement
of slabby boulders, an accumulat i o n of these on the windward
edge exposed a t lowest t i d e s
Reef platform flat, a completely
consolidated a l g a l pavement,
probably a planation surface
enamelled by calcareous r e d algae
Outer slope of leeward reef
gradual, shelving
Outer slope of leeward r e e f
abrupt, s t e e p
Lagoon r e e f s abundant, forming
a network extending through
most of t h e lagoon
Lagoon r e e f s few, mostly
p a r a l l e l t o main r e e f , concentric
t o it
Alcyonarians abundant on r e e f s
Alcyonarians r a r e o r absent
Calcareous r e d algae n o t making
up a l a r g e proportion of r e e f
community
Calcareous r e d algae abundant
POKAK
Islets
I s l e t s a l l on leeward s i d e of a t o l l ,
well d i s t r i b u t e d from end t o end
I s l e t s a l l on southeast quadrant,
on windward s i d e
I s l e t s with no e v i d e n t reef-rock
platform
Reef -rock platform prominent,
mostly somewhat under 2 m abom
mean low t i d e , few humps t o 3 m
o r more
No consolidated rock on i s l e t s ,
neither reef -rock nor beachrock
Reef -rock and beachrock abundant
Sediments on i s l e t s mostly sand
and small gravel
Sediments from sand t o boulders,
mostly coarse
Boulder r i d g e s none, l o ~ rsand
beach r i d g e s and dune r i d g e s
general
Boulder r i d g e s on most windward
coasts, l o c a l l y on lagoon s i d e ,
sand r i d g e s and dune ridges only
very l o c a l
Large boulders on i s l e t s none
(except a few from b a l l a s t )
Large boulders on i s l e t s common
Ground water s a l i n e
Same
Vegetation
Thalassia beds abundant on sandy
bottoms
Thalassia
or o t h e r sea-grasses
--
Algal c r u s t s on sand none except
where wet by s a l t water
Algal c r u s t s general on dry open
sand
Algal d i s c o l o r a t i o n of dry c o r a l
rocks almost none
Algal d i s c o l o r a t i o n of dry c o r a l
rocks general and conspicuous
Native vegetation low, semi-arid
i n aspect, maximum h e i g h t about
2.5 m.
Same, b u t maximum height
P r i n c i p a l n a t i v e vegetation types:
1. Open scrub of Suriana; 2. open
scrub of Tournefortia; 3. Nangrove
s~mnp; 4. open dwarf scrub of
Euphorbia; 5. closed Sporoboius
sod; 6. Sesuvium
- mat
P r i n c i p a l n a t i v e vegetation types:
1. Open scrub f o r e s t of Tournef o r t i a ; 2. closed scrub f o r e s t of
Pisonia; 3. closed scrub of Scaev
m . open scrub of >-Sida- 5.
shrub-savanna of Lepturus with
Sida; 6. Lepturus bunch grass.
-
absent
5-7 m
POKAK
Land Biota
Birds ( r e s i d e n t )
6 terns
1 gull
2 boobies
1frigate bird
1 heron
2 shore b i r d s
( occasionally r e s i d e n t )
Mammals
1 r a t (formerly)
1 s e a l (formerly
Birds ( r e s i d e n t )
7 terns
3 boobies
2 tropic birds
1frigate bird
1 heron
4 shore b i r d s
(occasionally resident )
1 shearwater
Mammals
1 rat
Reptiles
1lizard
1turtle
Reptiles
1lizard
Vascular p l a n t s
19 n a t i v e species
3 introduced species e s t a b l i s h e d
2 o t h e r s perhaps able t o p e r s i s t
without p r o t e c t i o n
Vascular p l a n t s
9 n a t i v e species
Mo exotics- (coconut was
introduced b u t d i d n o t l i v e )
Perusal of t h i s t a b l e shows t h a t , except f o r f e a t u r e s t h a t c h a r a c t e r i z e a l l a t o l l s , and trhich a r e not included, t h e d i f f e r e n c e s between
these t ~ aot o l l s a r e perhaps more important than the s i m i l a r i t i e s . If
Alacran were compared ?,rith a t o l l s i n w e t t e r climate b e l t s , t h e d i f f e r e n c e s
would be eve? more impressive. However, Alacran i s only one of t h e
Caribbean a t o l l s , and no g e n e r a l i z a t i o n i s p o s s i b l e u n t i l a s u b s t a n t i a l
sampling of o t h e r s have been compared with P a c i f i c a t o l l s i n s i m i l a r
c l i m a t i c s i t u a t i o n s . Also comparisons of much more d e t a i l e d and exact
f e a t u r e s a r e needed.
Bibliography
Bonet, F. and Rzedowski, J.
Vegetacion de l a s i s l a s d e l Arrecife Alacranes, Yucat'an ( ~ e x i c o )
( i n press)
.
Dampier, W.
M r . Dampier's voyages t o t h e Bay of Campeachy, i n : Voyages and
d e s c r i p t i o n s 2 ( 2 ) : 1-132, 1699.
----------
[Panzer, M. N., ed.]
Voyages and d i s c o v e r i e s .
1-311, London, 1931 ( r e p r i n t of 1729 e d i t i o n of t h e above work).
Fosberg, I?. R.
S o i l s of t h e Northern Marshall A t o l l s , with s p e c i a l reference t o the
Jemo s e r i e s .
s o i l Science 78: 99-107, 1954.
---------Northern Marshall Expedition--Narrative.
A t o l l Res. Bull. 38: 1-36, 1955.
----------
General geography, and o t h e r chapters, i n : ~ W l i t a r ygeography of t h e
Northern Marshalls i - x i , 1-320, 1956.
----------
.
Lonely Pokak
Living hrilderness 62: 1-4, 1957.
Great B r i t a i n , Hydrographic Off i c e
The West India P i l o t . Vol. 1
1-528, London, 1861.
... compiled by
Captain E. Barnett, R.N.
Gunter, G.
Mammals of t h e Gulf of Mexico, in: Galstoff, P. S., ed., Gulf of
Mexico, i t s o r i g i n , waters, and marine l i f e .
U. S. F i s h V i l d l i f e Serv., Fishery Bull. 55(89): 541-551, 1954.
Kennedy, J. N.
A little-known b i r d colony i n t h e Gulf of Mexi'co.
I b i s X, 5: 41-43, 1917.
Cann, R., and Hoskin, C. M.
Kornicker, L. S., Bonet, I?.,
Alacran Reef, Campeche Bank, Mexico.
Pub. I n s t . Marine S c i . 6: 1-22, 1959.
Kornicker, L. S., and Boyd, D. W.
Shallow-water geology and environments of Alacran Reef complex,
Campeche Bank, Mexico.
Bull. Am. Assoc. P e t r o l . Geol. 46(5): 640-673, 1962.
Marion,
Excursion a m "Ies Alacrans.
Bull. Soc. Acad. Brest 11, 9 : 5-21, 1884.
Millspaugh, C . G.
Plantae utowanae. P a r t I --Catalogue of t h e species.
FieldColumbianIvlus. Pub. 43, Bot. Ser. 2 ( 1 ) : 1-110, 1900a.
Plantae utowanae. P a r t IA--Reconsideration of t h e Cyperaceae.
~ 50,
~ Bot.
.
Ser. 2 ( 2 ) : 111-135, 1900b.
F i e l d Columbian M ~Pub.
Vegetation of Alacran Reef.
F i e l d Mus. Nat. I-Iist. Pub. 187, Bot. Ser. 2 ( 1 1 ) : 421-431, 1916.
Paynter, R. A . , Jr.
Autumnal migrants on the Campeche Bank.
Auk 70: 338-349, 1953.
---------The arnithogeography of t h e Yucat6.n Peninsula.
Peabody Mus. Nat. H i s t . Yale Univ. Bull. 9: 1-347, 1955.
SCmith], T.
Description of Alacran, and Cay Arenas, i n t h e Gulf of Mexico.
Nautical Magazine 7 : 804 -805, 1838.
The following paper, d e l i m i t i n g marine p l a n t communities i n the
v i c i n i t y of Perez I s l e t has j u s t come t o our a t t e n t i o n :
Huerta, M. L.
Flora marina de 10s alrededores de l a i s l a Perez, Arrecife Alacraiies,
sonda de Campeche, Mexico.
Ann. Escuela Nac. C i . Biol. 10: 10-22, 1961.
W I N D GRAPHS
-
1
-N
NNE
NE
ENE
I
ESE
SE
SSE
N
NNE
NE
ENE
s-
--
11
-N
NNE
NE
ENE
E
ESE
SE
SSE
s-
ESE
SE
SSE
S
SSW
WSW
W
WNW
NW
NNW
Colm
FEBRUARY 1959
1 12 13 14 15 1617 1 8 1 9 1101ll ~1211311411511611711811912012112212924125126~
SSW I
SW
wsw
wWNW
NW
NNW
MARCH 1959
ESE
SE
SSE
APRIL 1959
- -
FNF
ESE
SSE
OCTOBER 1959
-
s-
MAY 1959
ESE
SE
SSE I
S
SSW
SW
WSW I
W
I
WNW
NW
NNW I
Colm
ssw
SW I
WSW I
wWNW
.....
NW
NNW
Colm
ENE
ESE
SE
SSE
NOVEMBER 1959
-
s-
JUNE 1959
I 1 121 3141 5 16 17 18 1 9 110111 112113114115116117118119I2M2I122123124125124
N
I
NNE
NE
ENE
E
ESE
SE
SSE
5
1
SSW I
SW
WSW I
W
WNW I
NW
NNW
Calm I
-
--
NNNE I
L l 1 2 ] 3 1 4 ] 5 16 1 7 1 8 1 9 l l O l l l 112113114115116117l18II9I2U2I12212312425126~
-
SSW
SW
wsw I
wWNW 1
NW
NN W
Calm
1 1 1213141516171819~10111112113114115116117118II9I2~21122123124125126~
-
--
-
s-
E SE
SE
SSE
S
ss W
sW
wsw
W
WN W
NW
NNW I
-
-
SEPTEMBER 1959
NNNE
NE
ENE
1 1 12 13 1 4 1 5 1 6 1 7 1819 110111 li2113114115116117118II9I20I2I122123124125124
NNNE
ESE
SE
SSE
5
1
SSW
SW
wsw
W
WNW
NW
NNW I
Calm
I1 12 13 14 15 16 17 18 19 110111 1121131141151161171181l91~21
1221231241251261
-
-
-
AUGUST 1959
[ 1121 3 1 4 1 5 1 6 1718 19110111 112113114115116117118Il9l20l2I122123124125126~
N
I
NNE
NE -ENE
121314 15 1617 1819110111 11211311411511611711811912d21l22123124125126j
-
JULY 1959
1121 3 1 4 1 5 1 6 17 181 9110111 112113l141151161171181191201211221231241251261
-
SSW
SW
WSW I
W
I
WNW
.. .... I
NW
NNW
N
NNE
1
112113114115l16l17118119120(211P123l2425I26I
ESE
SE
SSE
S
SSW I
SW
wsw I
wWNW
NW
NNW
Colm I
NNNE
NE
ENE
-
JANUARY 1959
1 12 13 14 1516 17 181 9 110111
SSW
SW
WSW
wWNW
NW
NNW
-
DECEMBER 1959
1 1 1213 1415 16 17 1819110111 1121131141151161171181191201211221231241251261
N
NNE
NE
ENE
ESE
SE
SSE I
S
I
SSW
SW I
wsw
W
I
WNW
NW
NNW
Calm
WIND GRAPHS
1
N
NNE
NE
ENE
JANUARY 1960
1 I 2 13 141 5 161 7 18 1911011111211311411511611711811912U21
122123124125126(
-
ESE
SE
SSE
s
NNF
. .NE
ENE
ESE
SE
SSE
ssw
FEBRUARY 1960
-
s-
ES E
SE
SSE I
sSSW
SW I
wsw
W
W W
NW
NNW
Calm I
--
MARCH 1960
1 2 1 3 1 4 1 5 1617 18191101111121131141151161171IB11912MZl1221231242512612712~
-
-
ESE
SE
SSE
-
s-
ssw
SW
Ww
W
WNW
NW I
NNW
NNNE
NE
ENE 7
EESE
SE
SSE
5SSW
SW
wsw
W
I
WNW
NW I
.
NNW
Calm
APRIL 1960
-
N I
..
ENE
NOVEMBER 1960
MAY 1960
[ I 1 2 1 3 1 4 1 5 1 6 1 7 1819110111112113114115[16117118119120121122123124125126~
ESE
SE
SSE I
S
SSW
SW I
WSW
W
WNW I
NW
NNW
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW I
NNW
1 1 12 1 3 1 4 1 5 1 6 1 7 1819110111112113114115116117118119120121L21231242512612712~
N
I
NNE
NE
ENE
-E
ESE I
SE I
SSE I
q
SSW
SW
wsw
W
WNW I
NW
NNW
-
JUNE 1960
I1 12131415161718191101II 112113114115116117l181191~21122123124125I26127I28~
NNNE
NE
ENE
-
ESE
SE
SSE I
S
ssw
SW
wsw I
W
I
WNW
NW
NNW I
SSW
sw
wsw
W
WNW
NW
NNW
Calm I
-
OCTOBER 1960
I 1 12 13 141 5 16 17 18 19 110111 112113114115116117lIBI19120121j22123124125126127l2B~
NNNE
NE
ENE
ESE
SE I
SSE I
NNNE
NE
ENE
SEPTEMBER 1960
1 1 1213 1415 16 171819110111 1121131141151161171181191201211221231241251261271~
I1 12 131415 161718 19llOll111211311411511611711811912a2112~23124125126127128I29I
NNE
AUGUST 1960
1112131415161718191101111121131141151161171181191~
I
N
NNE
NE
ENE
SSW
SW
wsw
W
I
WNW
NW
NNW
Calm I
N
NNE
NE
EhE
-
121314 1516171819110111 1 1 2 1 1 3 1 1 4 1 1 5 1 1 6 1 1 7 1 1 8 1 1 9 1 2 d 2 I 1 2 U 2 ~ ~
ESE I
SE 7
SSE I
11
--
wsw
W
I
WNW I
NW
NNW I
calm
-
-N
NNE
NE
ENE
--
s-
SSW I
sW
wsw
wWNW
NW
NNW
Calm I
u
-
JULY 1960
I1 12 13 141 5 1617 18 191101111121131141151161171181191~1211221231241251261271~
N--
-
NNE I
NE
ENE
ESE
SE I
SSE I
s-
-
SSW I
SW
WSW
W
WNW
NWNNW
DECEMBER 1960
W I N D GRAPHS
JANUARY 1961
I I 1 2 13 14 15 16 17 18 19 110111 112113114115116117118119Ih)l21 122123124125126127128]
Y
4E
JE
JC
E
,E
iE
jE
S
,W
M
-
NNE
NE
ENE
ESE
SE
SSE
s
FEBRUARY 1961
11 12 13 14 15 161 7 1.819 110111 112113114 11511611711811912012l122123124[25126127(i131
-N
N
NNF
NE
ENE
-F
SE
SSE
h
I
r.
h
M-
--
MARCH 1961
IE
1E
-
S
SSW
SW
wsw
W
WNW
NW
NNW
mlm I
I I I 2 I 3 14 1 5 1 6 17 18 L9 110111 112 113114115 116117I18119120121122123124125126127l28l
N
MAY 1961
I 1 12 13 14 15 16 17 18 19 11011 1 112113 114115116117118119120121122123124125126127128I29I3013I132133134135136~
..,.L
-a
-
ssw
SW
wsw
W
WNW I
NW
NNW
Calm
W
I
w
W
W
W
Irn I
5
-
APRIL 1961
-
JUNE 1961
( 1 12 13 1 4 1 5 16 17 181 9 I I O l l l 112113114115l16117[18l19120121122123124125126127128I29IMI3I~
N
I
NNE
NE
ENE
ESE
SE
SSE
S
ssw
SW
wsw
W
WNW
NW
NNW
Calm
I
-
Daily Rainfall (in millimeters )
Jan.
20
0
0
0
21
8
0
18
0
0
0
0
0
0
0
0
0
0
0
0
0
7
0
0
1
0
0
0
Feb
.
0
0
0
0
0
1
0
0
0
. -0
1
0
0
0
0
0
0
0
0
0
20
0
0
0
0
0
0
4
5
0
0
* The
gauge overflowed
Mar.
5
0
0
0
0
8
0
2
0
0
0
0
0
0
0
0
0
0
5
0
0
0
0
0
0
0
0
0
0
0
0
Apr
0
0
0
0
0
0
0
0
0
0
0
2
1
0
0
0
4
0
0
0
0
0
0
0
0
0
0
0
0
0
.
.
June
Aug
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
16
0
18
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Sept
.
0
0
'
0
0
0
0
0
0
0
6
999*
0
0
0
2
0
0
Oct.
0
0
0
0
0
9
0
0
9
0
1
0
0
0
0
0
0
Dec
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3
0
0
0
0
9
0
0
0
0
0
0
7
3
4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
22
5
0
0
8
.o
20
0
0
0
0
1
0
.
Nov.
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
5
0
0
0
0
0
0
0
0
h i l y r a i n f a l l ( i n millimeters)
Jan.
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
* The
Feb
.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
gauge overflowed.
Max.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Apr
.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
40
0
0
0
June
0
0
0
0
0
0
0
0
0
0
0
0
4
0
0
0
0
0
2
0
0
0
0
0
0
0
0
0
0
0
Jay
Aug
.
Sept
0
0
8
0
0
0
0
0
0
0
0
0
0
3
0
0
0
6
0
0
0
0
1
0
0
0
21
28
0
7
.
Oct.
1
0
0
0
1
0
0
0
25
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
19
Mov
.
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
20
0
0
0
0
0
0
0
0
Dec
.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
6
0
0
2
0
0
0
0
0
0
0
999*
0
0
0
0
0
Daily Rainfall ( i n milirneters)
Jan.
0
0
0
0
0
0
0
0
999*
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Feb
.
0
0
1
0
0
0
9
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
29
0
0
0
3
0
0
* The
gauge overflowed
Max.
Apr
.
June
J
~
Y