Gray`s Spiny-tailed Iguana - Florida Museum of Natural History

322 NATURAL HISTORY NOTES
Fig. 1. Ctenosaura hemilopha drifting on log in the Sea of Cortez,
Mexico.
most rainfall occurs during late-summer tropical storms. The isolated occurrence of this iguana on the Baja California peninsula
presumably results from dispersal over land originating from the
Mexican mainland (Smith 1972. Great Basin Nat. 32:104–111) or
from human introductions (Stebbins 2003, op. cit.). Here we describe a rare observation of a long distance dispersal phenomenon and natural mechanism for dispersal over water.
On 28 September 2012 tropical storm Norman moved northerly over the Sea of Cortez with reports of heavy rain and flooding
in La Paz and other coastal towns. While boating on 2 October
in the Sea of Cortez between La Paz and Cerralvo Island we observed extensive debris carried by coastal floodwaters and wind.
Tree trunks, large branches, and smaller woody debris were observed. The debris field appeared to be moving from the La Paz
area toward Cerralvo Island and the open waters of the Sea of
Cortez. On the same day an adult Ctenosaura hemilopha was
found floating on driftwood between La Paz and the northern tip
of Cerralvo Island (Fig. 1). The lizard was approximately 7 km W
of the island and 40 km E of La Paz (24 km E of the nearest shore).
The driftwood log was approximately 90 cm in length and the
size of the iguana was estimated at 22 cm SVL. The iguana was
captured and appeared to be in good health. It was later released
in the village of La Ventana, south of La Paz, Baja California Sur.
Evidently the stranded iguana, caught in flood waters, floated
on debris for 24–40 km or more from the La Paz area and for a
period of up to four days (i.e., from the time the storm began
to the time observed in open water). It is plausible that this lizard could have continued to drift at a rate of 5–10 km/day and
reached Cerralvo Island within 1–2 days. Our observation documents a natural dispersal event rarely seen, and indicates that
peninsular individuals of this species may still be colonizing the
island today.
We thank Pangaro Yoni, La Ventana, Baja California Sur, Mexico.
DAVID G. COOK, Sonoma County Water Agency, 404 Aviation Blvd,
Santa Rosa, California 95403, USA (e-mail: [email protected]); DENNIS
HAUSSLER, 1666 Maryland Street, Redwood City, California 94061, USA.
CTENOSAURA SIMILIS (Gray’s Spiny-tailed Iguana). NONNATIVE DIET. Ctenosaura similis is native to Central America,
occurring from Mexico through to Panama (Traveset 1990. Am.
Midl. Nat. 123:402–404), and has been introduced to several Caribbean islands, and Florida, USA (Kraus 2009. Alien Reptiles and
Amphibians: A Scientific Compendium and Analysis. Springer,
[Dordrecht, Netherlands], 563 pp.; Krysko et al. 2003. Florida Sci.
66:74-79). This species exhibits an ontogenetic diet shift, where
juveniles are primarily carnivorous and adults are primarily herbivorous (Hirth 1963. Ecology 44:613–615; Krysko et al. 2009.
Fig. 1. Ctenosaura similis eating Canavalia rosea flowers at Crandon
Park beach.
Florida Sci. 72:48–58; Rand et al. 1990. J. Herpetol. 24:211–214).
Diet has been documented for some introduced populations
in southern Florida, particularly those on Gasparilla Island,
Charlotte and Lee counties, and Key Biscayne, Miami-Dade Co.
(Krysko et al. 2009, op. cit., Krysko et al. 2010. Herpetol. Cons.
Biol. 5:132–142). Herein, we augment previously documented
diet of C. similis on Key Biscayne.
On 14 September 2012 between 1205–1220 h, a single adult
female Ctenosaura similis was observed in beach coastal habitat feeding on flowers of the native Baybean, Canavalia rosea
(Fabaceae), at Crandon Park, Key Biscayne (25.706°N, 80.153°W,
WGS84; elev. <1 m). The iguana periodically foraged through a
large area (ca. 20 m x 20 m) of Baybean and ate 21 individual
flowers; no other parts of the plant were eaten. This is the first
documentation of C. similis consuming Canavalia rosea (Krysko
et al. 2009, op. cit.; Krysko et al. 2010, op. cit.). Florida currently
has the largest number of non-native herpetofaunal species in
the world, and the impact of native/non-native interactions on
ecosystem functioning remain poorly understood (Krysko et al.
2011. Zootaxa 3028:1–64). The potential impacts of this feeding
behavior on local plant survivability are not known and should
be considered important in future monitoring. No sympatric
reptile species were observed throughout the duration of the
feeding behavior.
JAMES T. STROUD, Department of Biological Sciences, Florida International University, 11200 SW 8th St, Miami, Florida 33199, USA (e-mail:
[email protected]); KENNETH L. KRYSKO, Division of Herpetology, Florida Museum of Natural History, Dickinson Hall, University of Florida,
Gainesville, Florida 32611, USA (e-mail: [email protected]).
DIPSOSAURUS DORSALIS (Desert Iguana). REPRODUCTION
BAJA CALIFORNIA SUR. Dipsosaurus dorsalis ranges from
southern Nevada to the tip of Baja California (Stebbins 2003. A
Field Guide to Western Reptiles and Amphibians. Houghton Mifflin Co., Boston, Massachusetts. 533 pp.). Detailed information
on D. dorsalis reproduction in southern California was reported
by Mayhew (1971. Herpetologica 27:57–77). Previous information on reproduction of D. dorsalis in Baja California Sur was
reported by Asplund (1967. Amer. Midl. Nat. 77:462–475) and
Grismer (2002. Amphibians and Reptiles of Baja California Including its Pacific Islands and the Islands in the Sea of Cortés.
Univ. Calif. Press, Berkeley. 399 pp.). The purpose of this note is
Herpetological Review 44(2), 2013