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endures a wet season, with a dry season that extends roughly from
December through February. Our fieldwork was performed well
into the dry season, so the lakes and rivers in the area were
essentially at their lowest levels. As a result, some of the areas we
worked in were not covered with water but were extremely muddy.
On 27 January 2000, two team members located an adult, female
E. murinus
(TL = 4.76 m) inside a hollowed out, fallen tree in the
exposed muddy bed of Laguna Grande. The specimen was located
at 1300h during which the air temperature was 34°C, temperature
inside the tree was 27°C, and the snake's external body temperature
was 29°C. We believe this
E. murinus
took shelter in the log to
avoid the high daytime temperatures associated with the dry season
and to wait for the lake's water level to rise during the ensuing wet
season. Attempts to remove the
E. murinus
from its lair failed,
though it did eventually come out on its own and partially buried
itself in the mud, under the root system of the upturned tree. Efforts
were made to expose and extricate the
E. murinus
by pulling off
sections of the tree's root structure. As this occurred, the specimen
started to burrow, almost vertically at times, into the soft mud to
escape capture (Fig. 1.). We estimate that the anterior portion of
this
E. murinus
reached a depth of ca. 60 cm. The more team
members worked to uncover this specimen, the more it burrowed
into the mud, until eventually ca. 1.5-2.0 m of its body was buried.
As we continued to pull pieces of the root system away and dig
out some of the mud, it became clear that the
E. murinus
was not
able to breathe, as there were no air pockets in the mud. This
became particularly evident when we saw water seeping out from
the hole where the
E. murinus
had burrowed.
Eventually we retrieved the specimen (Fig. 2), though it took an
appreciable amount of time and effort. We estimate that this
E.
murinus
suspended respiration for a period of ca. 40-45 min. This
is particularly interesting because the specimen was struggling
against the efforts of its captors, which we feel would have resulted
in an increased metabolic rate and subsequent tissue oxygen
demand. Under these conditions, some reptiles are known to resort
to anaerobic metabolism (Bennett and Dawson 1976.
In
C. Gans
and W. R. Dawson [eds.], Biology of the Reptilia, Vol. 5,
Physiology A, pp. 27-223), and it seems probable that
E. murinus
utilized anaerobiosis while it was submerged in the mud.
Furthermore, the
E. murinus
was nearly exhausted from its struggle
(i.e., the specimen exhibited no aggression or resistance to handling
once captured), which has been reported to be a symptom of reptiles
that have utilized anaerobic metabolism (Bennett 1982.
In
C. Gans
and F. H. Pough [eds.], Biology of the Reptilia, Vol. 13, Physiology
D, pp 155-199. Academic Press, London, UK).
Following capture, we allowed the
E. murinus
to rest for a short
period, and then various measurements were made and its general
health was assessed (e.g., body weight, presence of ectoparasites
and injuries, etc.). When data collection was complete, the
specimen was released.
Because
E. murinus
is a species highly adapted to a semi-aquatic
existence, it is reasonable to conclude that the ability to suspend
respiration for extended periods of time or use anaerobic
metabolism would give
E. murinus
an advantage in both predatory
and threat-avoidance activities. Since the actual anaerobic capacity
of large reptiles is not well understood, well-documented field
observations can be an important step in the study of this
physiological process.
FIG. 2.
Female
E. marinas
after being extricated from mud into which
it had burrowed. The specimen was exhausted after the struggle and offered
no resistance. (Photo by Jean-Thomas Bujard)
We
thank the members of the expedition team for their help and
support with regard to the capture and study of the specimen. Bill
Cacciolfi (New World Expeditions, Springboro, Ohio), Rudolph
Runge (RungeTV, Cologne, Germany), Rudolf Bermel
(Mediguard, Bonn, Germany) and Continental Airlines are
acknowledged for providing financial and/or other support. Thanks
to Jane Strimple, Ritt Enderson, Bill Cacciolfi, and Jean-Thomas
Bujard for reviewing the manuscript, and to Frederick Frye for his
input on reptile metabolism.
Submitted by PETER D. STRIMPLE,1028 Pine Creek Circle
NE, Palm Bay, Florida 32905, USA (e-mail: pstrimple@cfl.tr.com,
and
LUTZ DIRKSEN,
Museum A. Koenig, Adenauerallee 160,
53113 Bonn, Germany (e-mail: ldirksen@t-online.de).
EUNECTES MURINUS
(Green Anaconda).
JUVENILE
PREDATION.
Larger-sized reptiles tend to suffer little from
predation, whereas juveniles typically are more exposed to
predators and suffer higher mortality rates in their first years. This
observation is typical among female green anacondas (Rivas 1999.
Ph.D. dissertation. Univ. Tennessee, Knoxville, 287 pp.). However,
smaller adult males risk predation by spectacled caimans
(Caiman
crocodilus;
Rivas et al. 1999. Herpetol. Rev. 30:101) and by larger
female anacondas (Rivas and Owens 2000. Herpetol. Rev. 31:45-
46). In this contribution we document predation on juveniles of
different sizes. These observations were made in the Venezuelan
Hams, Distrito Mufloz, Apure State (7°30'N, 69
0
18'W).
Herpetological Review 32(2), 2001
107
On 25 April 1995 we observed a female anaconda (187 cm TL;
3.25 kg) being harassed by a crab-eating fox
(Cerdocyon thous).
The snake was on dry land and had adopted a defensive position.
The fox repeatedly tried to grab it, but jerked back each time as
the snake snapped defensively. We interrupted the interaction and
caught the snake, which had numerous ticks (evidence of having
been on dry land for a while). If we had not interrupted the fox,
the snake probably would have been eaten because she may have
become exhausted in a short time and, not having any water nearby,
was not likely to have escaped.
On 15 January 1996 we saw a tegu lizard (Tupinambis teguixin)
carrying a neonate-size anaconda in its mouth. The snake did not
have any bite marks or external evidence of having been killed by
the tegu, so it was not possible for us to assess whether the tegu
killed it or had found it dead. However, because tegus are generalist
foragers and often forage near the water, they are likely predators
of neonates.
We implanted transmitters in four neonate green anacondas to
study habitat use on 9 January 1996. Two of them were found
dead on 12 February. We found one of the transmitters at the bottom
of a tree that held an active nest of crested caracaras (Polyborus
plancus:
Falconidae). The other transmitter was found among some
bushes with the antenna chewed up, but with no other hint regarding
identity of the predator. The other two animals were alive at the
end of the three-month-long follow-up, but no information on their
later survival is available.
The animals reported in this contribution as preying on juvenile
anacondas are fairly common in the llanos. This suggests that risk
of predation may be an important selection pressure leading to
fast growth in juveniles.
We thank The World Conservation Society, The National
Geographic Society, and The Wildlife Conservation Society Field
Veterinary Program for logistic support. We thank COVEGAN
for allowing us to work on their land. We also thank W. Karesh, J.
Thorbjarnarson, C. Molina, and M. Munoz for help in the field
work.
Submitted by JESUS A. RIVAS, RENEE Y. OWENS,
Venezuela Nature Tours, 17126 Jamul, California 91935, USA,
and PAUL CALLE, Wildlife Conservation Society, Wildlife
Conservation Park, 2300 Southern Boulevard, Bronx, New York
10460-1099, USA.
MASTICOPHIS FLAGELLUM
(Western Coachwhip).
DIET.
Masticophis flagellum is known to feed on a large variety of food
items including insects, lizards, snakes, small turtles, birds, and
small mammals (Guidry 1953. Herpetologica 9:49-56; Hamilton
and Pollack 1956. Ecology 37:519-526; Collins 1974. Univ. Kan-
sas Publ. Mus. Natur. Hist. Publ. Ed. Ser. 1:1-283). Here we re-
port two food items found in the stomach of a M. flagellum. On 17
April 1999 at 2230 h, an adult male
M. flagellum (1186 mm total
length, 217 g) was found DOR on US 385 twenty-two miles south
of Fort Stockton in Pecos Co., Texas, USA. The stomach of the
snake was fully distended indicating recently-eaten prey. An adult
Cnemidophorus marmoratus (289.1 mm total length, 23.7 g) was
palped from the snake. A grasshopper (Orthoptera) was also found
in the stomach of the snake. To our knowledge, this is the first
report of
C. marmoratus
in the diet of
M. flagellum.
All three speci-
mens were preserved and placed at the University of Texas at Ar-
lington Collection of Vertebrates
(M.
flagellum
UTA-R46048,
C.
marmoratus
UTA-R46049).
We thank Ardell Mitchell, Winston Card, and Carl J. Franklin
for their helpful comments on this manuscript, and the staff of the
Dallas Zoo Department of Herpetology for their support.
Submitted by
RICHARD D. REAMS
and
BRIAN AUCONE,
Dallas Zoo, Department of Herpetology, Dallas, Texas 75203,
USA; e-mail (RDR): Hylareams@aol.com
.
NERODIA FASCIATA
(Southern Water Snake).
REPRODUCTION.
Nerodia fasciata
normally reproduces from
June through August with a typical litter size ranging from 9 to 50
(Wright and Wright 1957. Handbook of Snakes of the United States.
Comstock, Ithaca, New York. 1105 pp.), but averaging near 15
(Tennant 1997. A Field Guide to Snakes of Florida. Gulf Pub. Co.,
Houston, Texas. 257 pp.). Herein we report on reproduction in
two female
N. fasciata
that exhibited a phenology and fecundity
consistent with these values.
On 9 July 1998 at 2240 h, an adult female N. fasciata
(710 mm
SVL, 220 mm tail length) was found on a floating mat of vegetation
near the bank of an artificial pond at White Oak Plantation, Nassau
Co., Florida, USA (Sec. 43, T4N, R26E). The observation occurred
following the second major rain event of the summer. The female
was placed in a cloth bag, and retained overnight for measurements.
The following day, we discovered that the female had expelled 34
neonates into the cloth bag. Thirteen individuals from this litter
were found dead and subsequently were deposited in the Florida
Museum of Natural History (UF116347-59). SVL for live young
(mean ± SD, 163.5 ± 5.1 mm) and dead young (165.0 ± 3.3 mm)
did not differ (t-test, t = 0.93, P = 0.36). Pooled measurements for
all offspring were as follows: SVL 164.1 ± 4.5 mm (range 149.0-
172.0 mm); tail length 65.4 ± 3.6 mm (59.0-72.0 mm); mass 5.3 ±
0.5 g (4.2-6.1 g). Although the initial mass of the female was not
taken, its post-partum weight was 485.0 g. Live neonates and the
adult female were later released at the capture location.
On 22 July at 1235 h, a second female was observed expelling
offspring onto the muddy substrate along the shoreline of a small
pond at White Oak Plantation; a significant rainfall event also
occurred prior to this observation. Temperatures recorded at the
time of the observation were 28.4°C substrate, 30.6°C water, and
31.3°C air at 2 m in the shade. Although the adult escaped, five
neonates were captured for measurements. Measurements of the
young were as follows: SVL 168.6± 2.7 mm (range 166-173 mm);
tail length 59.2 ± 1.5 mm (57-61 mm); mass 4.7 ± 0.2 g (4.5-4.9
g). The captured neonates were released at the capture location
except for one, which we deposited in the Florida Museum of
Natural History (UF116360).
We gratefully acknowledge the entire staff of White Oak
Conservation Center for funding and use of on-site facilities, Pat
Ryder for expertise, and Kenneth L. Krysko and Steve A. Johnson
for constructive comments.
Submitted by
CHRISTOPHER O'BRIEN, RICHARD D.
OWEN,
and RICHARD FRANZ,
Florida Museum of Natural
History, University of Florida, Gainesville, Florida 32611, USA;
e-mail (CO): mailcob@ufl.edu
.
108
Herpetological Review 32(2), 2001
