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

Today’s update, while concerning an animal not suited as a pet (the American Alligator, Alligator mississippiensis) will I’m sure will be of interest to all who keep or study reptiles.  Scientists from the Savannah River Ecology Lab, working with alligators in Louisiana’s Rockefeller Wildlife Refuge, were surprised to find a high degree of mate fidelity in their study population.

Remaining Faithful Despite Choices

Writing in the October, 2009 issue of Molecular Ecology, the researchers explained that 70% of the female alligators they studied over a 10 year period mated with the same male each year.  This is the first time such behavior has been documented in any Crocodilian, and is rendered even more interesting by the fact that the refuge supports a very dense population of alligators, and females freely move through the territories of a great many males.

A Look Back in Time

Crocodilians are the sole surviving reptiles classified as Archosaurs, a group that includes the dinosaurs and which gave rise to the birds (some taxonomists argue that alligators are closely related to birds, and should be removed from the Class Reptilia).  It is hoped that this newly discovered alligator mating behavior will reveal something about the mating strategies of dinosaurs and the ancestors of modern day birds.

Working With Crocodilians

Crocodilians make poor pets, but, as you see from the accompanying photos, they can be exciting to work with in zoos (please be in touch if you’re considering a career in herpetology).

A pair of Cuban crocodiles (Crocodylus rhombifer) under my care at the Bronx Zoo produced young together over a period spanning 40 years (the photo shows some of the “little ones” rushing to a meal) – but, unlike the Louisiana gators, they were housed together, without others of their kind, and so had little choice!

Further Reading

To read about how other research with alligators is granting us a peek at how dinosaurs may have lived, please see this piece.

Most turtles become quite responsive to their owners (especially near feeding time!), and a great many show impressive abilities to learn and adjust to new situations. In my experience, however, few approach the wood turtle (Glyptemys insculpta, formerly Clemmys,) in these areas.

Testing Turtles

Herpetologists and experienced turtle enthusiasts consider the wood turtle to be among the most intelligent of the turtles – in lab tests, they consistently scoring higher than other species on maze and reward-association tests. In my experience, captives exhibit a degree of curiosity and problem-solving abilities not evident in other turtles.

“Thinking” before Acting?

While all turtles soon come to associate their owners with food, wood turtles rarely rush about “begging” each time one approaches their enclosure, as do other species. Instead, they most often look intently at their benefactor – deciding, it seems, if it would be “worthwhile to beg”. A group I worked with would always regard me carefully as I passed, but only scrambled for position if I carried their food trays.

These turtles were housed in a 6-foot-long cattle trough, tilted on one end to form a pool. When I drained the enclosure, they invariably gathered near the drain to snatch leftover food carried there. Turtles that missed a morsel of food would peer down the drain for some time, often changing angles to get a better view. Again, they seemed to “consider” the situation – not wasting effort trying to retrieve a food item that was unreachable.

Turtles Tricking Earthworms

Earthworms, a favorite food, are lured to the surface by stomping the front feet and the plastron against the ground. It is believed that earthworms interpret the vibrations as rain, or that the vibrations stress the worms and force them upward – hammering a piece of wood into the ground often has the same result. This is the only turtle known to employ such a technique.

While this behavior may be instinctive and does not necessarily indicate intelligence, one has to wonder why other turtles do not do so. It would be interesting to discover if all wood turtles do this, or if a degree of learning is indeed involved.

I’ll cover wood turtle care in the future. Please write in with your questions and comments. Thanks, until next time, Frank Indiviglio.

Further Reading

An interesting field report on how habitat development affect wood turtles is posted at http://www.woodturtle.com/Saumure%20and%20Bider%201998.pdf.

To read more about reptile intelligence, please see my article Learning: Observations of Zoo Animals (Lizards).

Scorpion venom has recently undergone an image upgrade…once feared, these little-studied toxins are now yielding valuable medicines. Researchers at China’s Wuhan University have recently (August, 2009) discovered 9 new types of peptides and proteins in the venom of Scorpiops jendeki, a scorpion native to southwestern China.

Current Research

Although considered only mildly toxic, S. jendeki’s venom is quite complex, containing at least 19 different proteins. Scientists believe that these molecules may be useful in synthesizing new drugs. Newly discovered molecules, which may attack cells in novel ways, are always looked upon with great interest by medical researchers working with incurable diseases and drug-resistant microbes.

Role for a Deadly Scorpion

In recent years, even the much-maligned “death stalker” or Israeli yellow scorpion (Leiurus quinquestriatus) is being treated with new respect in the lab – an irradiated version of a protein in its venom shows great promise in the treatment of brain cancer.

Further Reading

You can read more about current research involving scorpion venom and brain cancer at http://www.nano.org.uk/news/april2009/latest1847.htm.

I remember well my shock when the news concerning temperature dependant sex determination (TDSD) among reptiles first broke.  Imagine…a turtle or crocodile egg can develop as either a male or female, depending upon the incubation temperature!  Well, it now seems that at least one species of lizard, the three-lined skink (Bassiana duperreyi), complicates matters even further.

Egg Size and Sex

Writing in the June, 2009 issue of Current Biology, University of Sydney biologists have revealed that large skink eggs develop into females, while small eggs become males.  Furthermore, removing yolk from a large egg resulted in a male hatchling, despite the fact that female genes were present; adding yolk to a small egg over-rode the effect of the male genes already in the egg, producing instead a female.

Temperature and Sex

Extreme nest temperatures, it seems, can also affect the hatchlings’ sex, regardless of its genetic makeup, resulting in xx chromosome males (males are usually xy) and xy females (females are typically xx).

Survival and Conservation Implications

The question that begs answering, of course, is why has this lizard evolved such a unique and complicated reproductive strategy?  Researchers are now looking into its ecology to determine the answer.

Understanding such matters has greatly assisted those working to conserve reptiles and amphibians.  Knowing the parameters of TDSD has allowed us to pick and choose the sexes of highly endangered species being bred in zoos, so that a favorable sex ratio can be maintained.

Of course, there were some problems early on.  I was working with green sea turtle head-start programs in Costa Rica when TDSD first came to light.  The organization I was with had been gathering sea turtle eggs for 30 years, incubating them, and then releasing the young when they had grown past the vulnerable stage.  Great in theory…but by using a single incubation temperature, we may have produced only female green turtles for the entire 3 decades!

Further Reading

You can read more about the natural history of the three-lined skink and its relatives at http://www.jcvi.org/reptiles/species.php?genus=Bassiana&species=duperreyi.

Small, shrimp-like marine crustaceans known as krill have long featured prominently in the diets of aquarium fishes.  I’d like to relate here some personal experiences that point to their value as food for turtles, tadpoles, newts and salamanders.

Krill as Turtle Food

Some years ago a herpetologist of my acquaintance, noting that krill were quite high protein and calcium, decided to use this food as a major part of the diet of a group of Blanding’s turtles (Emydoidea blandingii) that had hatched in his collection.  The diet he used, simple by current standards, was comprised of 50% freeze-dried krill and 50% Reptomin Food Sticks.  The turtles matured into beautiful, healthy adults with hard, well-formed shells…not always an easy task in captivity.  I later successfully repeated the experiment with a clutch of Eastern painted turtles (Chrysemys picta).

Amphibians

The diet fed to tadpoles greatly influences their survival rate during the stressful period when they transform into frogs.  I have found that species typically considered to be herbivorous, such as bullfrog and spring peeper tadpoles, actually fare much better when protein such as krill is included in their diets.  Newts, amphiumas, axolotls and African clawed frogs relish krill as well.

Useful Products

We carry a wide variety of freeze dried and frozen krill of various sizes at ThatFishPlace/ThatPetPlace.  You will also find krill and shrimp in Reptomin Select-A-Food, Suprema Food Sticks and Gammarus Shrimp Supplement and in Zoo Med Can O’ Shrimp.

The World’s Most Abundant Animal?

The Antarctic krill, Euphausia superba, may be the planet’s most numerous species…550 million tons of them are swimming in the southern Pacific Ocean at any one time (our own biomass tops out at a mere 110 million tons).  Krill form nearly 100% of the diet of certain seals, whales, birds, shrimp, squid and fishes.

Further Reading

To learn more about using freshwater shrimps, please see my article Zoo Med Canned Freshwater Shrimp.

Krill image referenced from Wikipedia and originally posted by Saperaud

Blandings Turtle image referenced from Wikipedia and originally posted by Raphael Carter.