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Amphibians and Reptiles 
Declining at La Selva, Costa Rica

Amphibians stand at the forefront of a
global biodiversity crisis. More than one-
third of amphibian species are globally
threatened, and over 120 species proba-
bly have become extinct since 1980.
Most alarmingly, many rapid declines
and extinctions are occurring in pristine
sites lacking obvious adverse effects of
human activities. The causes of these
“enigmatic” declines remain highly con-
tested. Still, lack of long-term data on
amphibian populations severely limits
our understanding of the distribution of
amphibian declines, and therefore the
ultimate causes of these declines.
WHITFIELD ET AL. (2007. Proceedings of
the National Academy of Sciences (USA)
104: 8352–8356) identified a systematic
community-wide decline in populations
of terrestrial amphibians at La Selva
Biological Station, a protected old-
growth lowland rainforest in lower
Central America. The authors used data
collected over 35 years to show that pop-
ulation densities of all species of terres-
trial amphibians had declined by 75%
since 1970, and they demonstrated iden-
tical trends for all species of common
reptiles. The trends are neither consistent
with recent emergence of chytridiomyco-
sis nor the climate-linked epidemic
hypothesis, two leading putative causes
of enigmatic amphibian declines.
Instead, the data suggest that declines are
due to climate-driven reductions in the
quantity of standing leaf litter, a critical
microhabitat for amphibians and reptiles
in this assemblage. These results raise fur-
ther concerns about the global persist-
ence of amphibian populations by iden-
tifying widespread declines in species and

habitats that are not currently recognized
as susceptible to such risks.

Herpetofauna of 
Longleaf Pine Savannas

MEANS (2006. Chapter 6. Vertebate
Faunal Diversity in Longleaf Pine
Savannas. Pp. 155–213 in S. Jose, E.
Jokela, and D. Miller (eds.), Longleaf
Pine Ecosystems: Ecology, Management,
and Restoration. Springer, New York)
thoroughly reviewed the vertebrates
(including 9 salamanders, 26 frogs, 29
snakes, 14 lizards, 1 amphisbaenian, and
10 turtles) that are characteristic species
residing in longleaf pine savannas. The
author discusses at length each of the spe-
cialists (species whose geographic limits
are confined within or closely associated
with the limits of longleaf pine, and
which live in the longleaf pine commu-
nity itself ) and then the importance of
temporary ponds, dead trees (snags,
fallen logs), stumpholes or tree bases, fire,
problems associated with pine plantation
silviculture, habitat fragmentation, and
declining species.

Large Snakes in 
North-Central Florida

Little is known concerning home range
and activity of large terrestrial snakes.
During the course of an inventory of a
large biological preserve in north-central
Florida, DODD AND BARICHIVICH

(2007. Florida Scientist 70: 83–94)
tracked five snakes (Eastern Indigo
Snakes, Drymarchon couperi, and
Coachwhips, Masticophis flagellum) for
periods of 49–322 days. A single Eastern
Indigo Snake had a home range of
100–185 ha, depending on estimator,

whereas the Coachwhips used smaller
home ranges that varied individually and
by season. The authors provided infor-
mation on ecdysis, feeding activity, and
retreat sites for the five tracked individu-
als, which includes the first such data on
free-ranging Coachwhips. Gopher
Tortoise and small mammal burrows
were important retreat sites for both
species, particularly during ecdysis. Both
species frequented upland habitats, with
Coachwhips using longleaf pine and
xeric oak sandhills and former pastures,
and the Eastern Indigo Snake preferring
upland mixed pine and hardwoods.
Although sample sizes are small, these
results, coupled with data on the move-
ments of other upland species, suggest
that large terrestrial snakes require sub-
stantial amounts of contiguous habitat in
order to maintain populations.

Movements and Home Ranges 
of Otago Skinks

Otago Skinks (Oligosoma otagense) are
among New Zealand’s largest and rarest
lizards. GERMANO (2007. Journal of
Herpetology 41: 179–186) examined
movements and home ranges using

196 IGUANA  •  VOLUME 14, NUMBER 3  •  SEPTEMBER 2007 CONSERVATION RESEARCH REPORTS

C O N S E R V A T I O N  R E S E A R C H  R E P O R T S

Eastern Indigo Snakes (Drymarchon couperi)
in Florida had a home range of 100–185 ha
and preferred upland mixed pine and hard-
woods.

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Otago Skinks (Oligosoma otagense) are among
New Zealand’s largest and rarest lizards.
These individuals, bearing radio-transmitters,
were part of a study to determine movements
and home ranges.

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Declines in populations of amphibians and
reptiles, such as the Speckled Racer (Drymobius
margaritiferus), at La Selva, Costa Rica, have
been attributed to climate-driven reductions in
the quantity of standing leaf litter.

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The Florida Worm Lizard (Rhineura flori-
dana) is probably the most unusual of the 54
reptilian species known to occur in longleaf
pine savannas.

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radio-telemetry at the Redbank Reserve
near Macraes Flat, Central Otago. She
tracked 13 skinks from December
2003–April 2004 for 26–111 days.
Neither distances moved nor frequencies
of movements differed significantly
between males and females. Home range

estimates (using the 100% minimum
convex polygon method) ranged from
200–5,400 m2, with male home ranges
significantly larger than those of females,
and those of non-gravid females signifi-
cantly larger than those of gravid females.
Home range overlap was substantive and

interactions between individuals
occurred frequently. Capturing animals
increased frequency of movements, espe-
cially on days immediately following cap-
ture. Data generated by this study will be
incorporated into a management plan for
the species.

IGUANA  •  VOLUME 14, NUMBER 3  •  SEPTEMBER 2007 197NATURAL HISTORY RESEARCH REPORTS

Desert Tortoise 
Hibernation

NUSSEAR ET AL. (2007. Copeia 2007:
378–386) examined the onset, duration,
and termination of hibernation in Desert
Tortoises (Gopherus agassizii) over several
years at multiple sites in the northeastern
part of their geographic range in Utah,
Arizona, and Nevada, and recorded the
temperatures experienced by tortoises
during winter hibernation. The timing of
hibernation by Desert Tortoises differed
among sites and years. Environmental
cues acting over the short-term did not
appear to influence the timing of the
hibernation period. Different individual
tortoises entered hibernation over as
many as 44 days in the fall and emerged
from hibernation over as many as 49
days in the spring. This range of variation
in the timing of hibernation indicated a
weak influence at best of exogenous cues
hypothesized to trigger and terminate
hibernation. Regional trends do appear,
as hibernation tended to begin earlier
and continue longer at sites that were
higher in elevation and generally cooler.
The emergence date was generally more
similar among study sites than the date of
onset. While the climate and the subse-

quent timing of hibernation differed
among sites, the average temperatures
experienced by tortoises while hibernat-
ing differed by only about five degrees
from the coldest to the warmest site.

Feeding Ecology of 
Rattleless Rattlesnakes

Crotalus catalinensis is a rattleless rat-
tlesnake endemic to Santa Catalina
Island, in the Gulf of California, Mexico.
Some authorities have hypothesized that
the lack of a rattle in this species is a
stealth adaptation for hunting birds in
vegetation. AVILA-VILLEGAS ET AL.
(2007. Copeia 2007: 80–84) provided

detailed data on the diet of these snakes
from samples obtained during nine trips
to the island in 2002–2004. Over two-
thirds (70%) of the diet was composed of
the Santa Catalina Deer Mouse
(Peromyscus slevini). The remaining prey
were lizards (Dipsosaurus catalinensis, Uta
squamata, and Sceloporus lineatulus). The
diet shifted ontogenetically, and feeding
activity was greater during the dry sea-
son. The diet of this species is only a
small subset of the diet of its supposed
closest relative, C. ruber, probably as a

result of limited prey diversity on the
island. The lack of birds in the diet
argues against the hypothesis relating the
lack of a rattle with a stealth hunting
technique for birds in vegetation.
However, because P. slevini is partially
arboreal, the lack of a rattle might be an
adaptation for stealth hunting for mice in
vegetation.

Habitat Affects 
Predator Attack Frequencies

Predators use characteristics such as pat-
tern and shape in forming search images
of prey, thereby influencing the evolution
of prey morphology. In lizards, sit-and-
wait foraging species are thought to have
body shapes that enhance their ability to
remain cryptic to predators. Structurally
complex habitats provide more opportu-
nities for prey to avoid detection, thus
predator foraging efficiency is predicted
to be higher in structurally simple habi-
tats. SHEPARD (2007. Herpetologica 63:
193–202) used clay lizard models to test
whether predation varies among lizards
with different body shapes and whether
predation varies among habitats in the
Brazilian Cerrado with different struc-
tural characteristics. Predator attack fre-
quency was highest in the most struc-
turally complex habitat, but the
probability of being attacked was higher
in more open microhabitats. Attack fre-
quencies did not differ significantly
among the four lizard model shapes.
Lizards and birds were the main attackers
of models, and attacks were primarily
directed toward the models’ heads.
Results demonstrated that predator-prey
interactions are largely influenced by the
environmental context and scale, and
that body shape alone does not efficiently
promote crypsis.

N A T U R A L  H I S T O R Y  R E S E A R C H  R E P O R T S

Local climate affected timing of hibernation,
but average temperatures experienced by
hibernating Desert Tortoises (Gopherus agas-
sizii) differed very little.

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Rattleless Santa Catalina Island Rattlesnakes
(Crotalus catalinensis) feed primarily on mice
and lizards, arguing against the hypothesis
that the lack of a rattle facilitates stealthy
hunting for birds in vegetation.

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