That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

In direct contrast to popularly-held theories, researchers at Australia’s University of Melbourne believe that the need to rapidly signal other chameleons, and not the need to hide from predators, has driven the evolution of the amazing color-changing abilities possessed by these lizards.  In a sense, the primary function of color change is to render the animals more conspicuous – the opposite of being well-camouflaged!

Camouflage

However, the need to camouflage still exerts an influence.  By being able to affect color changes in a mere fraction of a second, the lizards lessen the chance that predators will notice them.

Earlier research at the University of Melbourne has also revealed that at least 1 species does endeavor to “match” the background upon which in rests.  In fact, Smith’s dwarf chameleon actually alters the degree of color change it exhibits in response to the type of predator it faces (please see article below).

Other Possibilities: My Experience

I have noticed that, unlike most animals that display (male birds, for example, often sing for hours on end, even if when other birds are not visible), chameleons only flash messages when in the presence of possible rivals or mates.  This would also seem to limit their exposure to predators.

Chameleons also display an incredible range of subtle color variations, most not visible to the human eye which, I believe, also assists in “getting their message across” as quickly as possible.

Further Reading

To learn more about new research regarding color change and predator avoidance, please see my article Chameleons and Camouflage.

Southeast Asia’s bizarre tentacled snake (Erpeton tentaculatum) is a long-time favorite of mine and I’ve kept and bred a great many in zoo collections over the years.  Despite watching them intently for so long, I’ve never quite been able to figure out how they manage to so effectively catch fast-moving fishes while striking out in a direction that seems designed to insure that they miss the intended target.

A Unique Escape Strategy

Recently published (Vanderbilt University, Tennessee: June, 2009) research has provided the answer.  Many fishes, it seems, utilize an escape maneuver known as the C-Start.  Upon sensing danger, the body contorts into a “C” shape, the tail is flicked and the fish, in a millisecond, darts away.

Exploiting the Defensive Maneuver

Tentacled snakes, anchored to submerged objects by their tails and resembling water-logged roots, lie in wait for passing fishes.  The snake always holds itself in a very distinctive “J” shaped position.  As a fish approaches, the snake “feints” with its body by sending a ripple of water towards the fish.  This incites the C-Start reaction and propels the fish directly toward the snake’s jaws.

Once initiated, the C-Start maneuver cannot be altered, so the hapless fish is doomed.  The snake’s “J” position allows it to strike not at the fish but rather where the fish will be once it flees.  What’s more, the strike nearly always catches the fish in the head region, assisting the snake in swallowing its slippery prey.

Further Reading

To learn more about the natural history and captive care of tentacled snakes, please see my article The Tentacled Snake, an Unusual Pet Serpent .

A Control Program Backfires
Please see Part I of this article for background information. With introduced green iguanas (Iguana iguana) driving endangered burrowing owls from their nests and raccoons (Procyon lotor) devouring sea turtle eggs, the Florida Department of Environmental Protection initiated control measures. At a preserve in Dania Beach, an intensive trapping and collection campaign greatly reduced the numbers of both species, but an unexpected consequence of these efforts soon became apparent.Within a year of the raccoon numbers being brought under control, iguana populations skyrocketed. In one area of the park, researchers counted 626 iguanas per square kilometer (0.4 square miles)…an unprecedented density for any lizard species!

It seemed that raccoon predation had been a very effective control on iguana numbers. Although hawks, gray foxes, night herons, alligators and other animals prey upon iguanas, only raccoons take eggs, hatchlings and sub-adults in significant numbers.

Iguanas…Here to Stay?
Young iguanas are now especially common at the site, pointing towards an even greater population increase in the future. Hand-collection, although possible, is a daunting task, so biologists are looking into alternate control measures. Meanwhile, spurred by ample food and little competition, lizards as young as 2 years of age are laying eggs.

In Belize, black rats effectively control one green iguana population by taking nearly every egg laid. However, Florida’s parks already have enough problems without black rats…in fact, their notorious cousin, the Norway rat, is already a resident of many!

Further Reading
It was my good fortune to work with green iguanas in a natural, if somewhat unusual (i.e. treeless) habitat. Please see my article, The Green Iguana on the Venezuelan Llanos  for the story.

To learn more about the challenges and rewards of keeping these impressive lizards, please check out our care guide, Green Iguanas.

Snakes are well known for their abilities to survive long fasts – up to 2 years in some cases – without ill effect.  Working with ball pythons, diamondback rattlesnakes and various rat snakes, researchers at the University of Arkansas have recently shown that fasting snakes slow their metabolisms by up to 80%, and yet continue to grow even when food is withheld for 6 months.

Ball Pythons, the Champion Fasters

The reduced rate of metabolism may explain why many snakes lose little weight when fasting.  Keyed by circadian rhythms (“internal clocks”), ball pythons are notoriously worrisome to pet keepers in this regard.  Most refuse food for long periods of time each year, yet remain in good condition…in fact, the longest-lived captive snake is believed to be a ball python that attained approximately 51 years of age at the Philadelphia Zoo.

Growing Without Eating

The fact that fasting snakes continue to grow suggests that large size confers important survival advantages.  If it did not, precious fat reserves would not be allocated to growth during food emergencies.

Evidence from Zoo Animals – the Gharial

Other reptiles and amphibians seem possessed of similar abilities, although confirmation is lacking.  Fish-eating crocodilians known as Indian gharials (Gavialis gangeticus) are one example.  A group of 8 at the Bronx Zoo ceased feeding in tune with the cool season in their native Pakistan each year for the nearly 20 years that they were under my care.  They fasted for 3 months, but continued to move about and bask, and lost little of their 400-600 pound bulk during that time.

Other Reptile Pets

Bearded dragons and temperate zone reptiles, such as box and Eastern painted turtles, often stop feeding during the winter, even if kept warm.  Bearded dragons usually become largely inactive, but turtles often move about normally.  Despite this apparent use of energy, they lose little if any weight.

Interestingly, at least for turtles, individuals born in captivity usually remain active during the winter if kept warm, while wild-caught specimens typically go off feed for 2-6 months.

Know Your Pets’ Needs

Providing your pet with proper care and a healthful diet is vital if it is to survive seasonal fasts.  Be sure to research the species that you keep carefully.  Please consult our reptile and amphibian care books, and don’t hesitate to write in with any questions you may have.

Further Reading

To learn more about hibernation and fasting periods, please see my article Hibernation in Bearded Dragons and other Reptiles and Amphibians.

Writing in the current issue of the journal Animal Behavior, researchers from the University of Grenada report that female Mexican lance-headed rattlesnakes frequently consume infertile eggs and non-living young after giving birth.  This is said to be the first documented case of cannibalism among rattlesnakes (please see below for my observations, however).  Interestingly, with a sole exception, the females did not consume young that were born alive, even though these remain inactive for several hours after birth, and appear (to us, at least!) to be dead.

Rattlesnakes bear live young, and females use up a great deal of energy and body mass during gestation (they do not feed while gravid).  It is theorized that consuming those young which are dead upon birth helps them to recover their strength.

Rattlesnake Cannibalism in another Species

While working with the comprehensive rattlesnake collection at NYC’s Staten Island Zoo, I had the opportunity to participate in breeding efforts for a number of species.  Most births occurred at night and were not filmed, so I cannot say if females of other species ever consumed non-living young.  However, newly born Neo-tropical rattlesnakes (Crotalus durissus) did consume litter-mates on two occasions.

Hog Fat and other Unusual Snake Foods

Contrary to popular belief, many snakes consume non-living prey (i.e. carrion) in the wild.  The most unusual incident I recall was a note published in the journal Herpetologica…a water moccasin (Agkistrodon piscivorous) was observed stripping fat from a road-killed feral hog!

Of the snakes I have worked with in the field and captivity, moccasins, indigo snakes, black racers and anacondas stand out as taking the widest variety of prey species, and each engages in cannibalism.  One particularly large moccasin I cared for consumed a northern water snake that shared its exhibit (not my idea – I had moved on by then!!).  I’m sure the same occurs in the wild, in areas where moccasins and various water snakes co-exist.

A Collection for Rattlesnake Aficionados

I had the wonderful opportunity of participating in the renovation of the Staten Island Zoo’s reptile house, former stomping ground of legendary snakeman Carl Kauffeld (known to all snake keepers as the author of Snakes, the Keeper and the Kept and Snakes and Snake Hunting).

As in former times, the zoo now boasts an impressive rattlesnake collection…please visit if you have the opportunity.  Pictured here are a few exhibits that I set up for the opening – Neo-tropical rattlesnakes, banded rock rattlesnakes and desert Massasaugas.

Further Reading

Lance-headed rattlesnake photos and natural history information are posted at:

http://www.ratelslangen.nl/gallery/Crotalus_polystictus_Mexican_lance-headed/