An instance of Anolis sagrei eggs remaining viable after an

Herpetology Notes, volume 6: 167-169 (2013) (published online on 20 April 2013)
An instance of Anolis sagrei eggs remaining viable after an extended
exposure to excessively wet conditions
Gerrut Norval 1*, and Jean-Jay Mao 2
Anolis sagrei (Duméril & Bibron, 1837), is an exotic
invasive lizard species in Taiwan (Norval et al., 2002;
Chang, 2007). The reproductive cycle of A. sagrei
in Taiwan is long and cyclic (Norval, Goldberg and
Mao, 2012), and is very similar to that of conspecific
populations in Belize (Sexton and Brown, 1977),
Cuba (Rodriguez Schettino, 1999), Jamaica (Licht and
Gorman, 1970), Florida (Lee et al., 1989), and Hawaii
(Goldberg et al., 2002). As with populations in Belize
(Sexton and Brown, 1977), Cuba (Rodriguez Schettino,
1999), and Florida (Lee et al., 1989), in Taiwan the
most active reproduction period coincides with the wet
season.
On June 22, 2012, at ca. 10:30, two eggs were found
in a hole (hole A), which was covered by two roof tiles.
The hole was located at the edge of a basketball court,
in a small park in Santzepu, Sheishan District, Chiayi
County, Taiwan (23º25’43”N, 120º28’28”E; datum:
WGS84) (Fig.1). The interior of the hole was very wet,
and the eggs appeared swollen. When attempts were
made to move one of the eggs, it burst open, and a fully
developed female A. sagrei hatchling emerged. At this
point it started to rain, so no further observations were
made, and after a few photographs were taken, the roof
tiles were placed back again over the hole. On June 25
we returned to the locality to inspect the remaining egg.
An additional egg was found in a similar hole (hole B),
located 3.8 m from hole A (Fig.2), and which also was
covered with roof tiles. Both holes were subsequently
inspected every two to three days to determine the
conditions of the eggs. On July 4 we found that the first
egg (hole A) had hatched, while the second egg (hole B)
was found hatched on July 13.
: Applied Behavioural Ecology & Ecosystem Research Unit,
Department of Environmental Sciences, UNISA, Private
Bag X6, Florida, 1710, Republic of South Africa, (e-mail:
[email protected]).
2
: Department of Forestry & Natural Resources, National Ilan
University. No. 1, Sec. 1, Shen-Lung Rd., Ilan, 260, Taiwan,
R.O.C.
* corresponding author
Even though the oviposition sites were covered, and
thus protected from rain directly falling into them, the
roof tiles could not prevent water from flowing into
them. Since the whole area surrounding the holes is
covered by concrete (i.e. not water permeable), it is very
likely that at times of heavy rain in the 14-day period
before the first observations were made (Fig.3), large
amounts of water flowed into the holes.
To confirm the potential flooding of the floor in the
holes during heavy rains, on July 20, two vials (length
= 75 mm; diameter = 10 mm) were inserted into the
soil, at a depth of ca. 65 mm (i.e. the opening of the
vial was ca. 10 mm above the soil surface), along the
center of the section of each hole where the eggs were
found. The vials were placed in such a manner that in
each hole, one vial was at the lowest point and the other
at the highest. In the afternoons and evenings of July
21 and 22, the rainfall in the area was 50.5 mm and
1
Figure 1. A birds’ eye view of hole A, on June 22, 2012 (top).
Note the un-hatched egg (single arrow), the remains of the
hatched egg just below it, and the hatchling (double arrow).
And a close-up (below) of the hatchling, un-hatched egg,
and the remains of the hatched egg (photographed by Gerrut
Norval).
168
Gerrut Norval & Jean-Jay Mao
Figure 2. The positioning of the holes and the surrounding environment (top), and a bird’s eye view of the holes (center), indicating
the positioning of the eggs (yellow arrows). And close-up views off the eggs (bottom) (photographed by Gerrut Norval).
28.5 mm respectively. When the vials were inspected in
the morning of the July 23, we found that all the vials
were filled with water and some silt. This confirmed that
the inflow of water into the holes was substantial, and
that the floor experienced flooding to a certain extent.
Sexton, Veith and Phillips (1979) described the shell
of A. limifrons and A. sagrei eggs and water absorption
through them, and explained that when water gains
exceed losses, the egg will swell. This would explain
the swelled state of the eggs on the day of the first
observation described herein. Recent studies by Reedy,
Zaragoza and Warner (2012) and Warner et al., (2012)
found that A. sagrei females prefer nest sites with a
relatively high humidity, and that hatchlings from these
nests tend to be healthier than those from drier nests.
Losos, Schoener and Spiller (2003) determined that
Figure 3. The daily rainfall as reported by the Taiwanese Central Weather Bureau for Chiayi County for the period May 01 to July
12, 2012 (http://www.cwb.gov.tw/V6e/index.htm).
An instance of Anolis sagrei eggs remaining viable after an extended exposure
the eggs of A. sagrei can remain viable even when
submerged in seawater for up to 6 hours. However,
since seawater is more saline than the content of the
eggs, it can be expected that the eggs would lose water
under such conditions, and would thus not swell (Losos
J.B., personal communication). It is very likely that at
times, the eggs described herein were also submerged,
although by freshwater and for an unknown duration.
Evidence of this is the eggs, which are usually buried
in a moist substrate (Sanger et al., 2008), but in our
observations were exposed because the soil that covered
them was washed away. Such flooding would also mean
that the incubation environments described herein,
at times exceeded the maximum treatment of 75%
humidity, used by Reedy, Zaragoza and Warner (2012).
Also, since the incubation period of A. sagrei eggs is
about one month (Losos, Schoener and Spiller, 2003;
Norval, Goldberg and Mao, 2012), it can be deduced
that the eggs described herein were at different stages
of development when they were exposed to the various
degrees and durations of excessively wet conditions.
The observations described herein therefore
demonstrate that the eggs of A. sagrei, at different stages
of development, can remain viable when exposed (for a
few hours) to excessively wet conditions. It also reveals
that unless washed away or damaged, the eggs of A.
sagrei can remain viable during the high rainfall (often
as a result of typhoons) season in Taiwan.
Acknowledgements. The authors would like to express their
gratitude to Shao-Chang Huang for obtaining some of the
references, and Jonathan Losos and Amber Wright for their
comments and suggestions.
169
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Accepted by Zoltán T. Nagy; managing editor: Philipp Wagner