Home | 2009 | July

Monthly Archives: July 2009

Chameleon Color Change: Camouflage and Advertising at the Same Time?

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!


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.


Tortoise Diets: Mediterranean Species and Russian (Horsfield’s) Tortoises

Hello, Frank Indiviglio here. Judging from recent questions posted on this blog, there is a great deal of conflicting information available as regards the feeding of tortoise. The Greek or spur-thighed (Testudo graeca), marginated (T. marginata) and Hermann’s (T. hermanni) tortoises, collectively referred to as Mediterranean tortoises, and the popular Russian or Horsfield’s tortoise (T. horsfieldi) require a vastly different diet than do desert or rainforest adapted species.

While there is some flexibility as concerns diet, there are some general rules that should be followed. The following protocol has worked well for me in zoos and at home, and will hopefully help you in caring for these responsive and interesting reptiles.

Protein and Natural Foods

Mediterranean and Russian tortoises have evolved to process a diet that is high in fiber and calcium and low in protein and fat. In the wild, they feed almost exclusively on grasses, herbaceous plants and flowers, with fruit only sporadically available.

In captivity, high protein foods such as beans and dog/cat food should be strictly avoided. Fruit is not necessary, although a few berries can be given as a weekly treat during the summer.

Native Plants

In the warmer months, I use native grasses, weeds and flowers for 75-85% of the diet, with such accounting for nearly 100% of some specimens housed in outdoor zoo exhibits. In addition to wild grasses, the following are some native and introduced plants that can be offered to tortoises:

Honeysuckle (Lonicera periclymenum)

Dandelion (Taraxacum spp.)

Hawkweeds (Pictis spp.)

Clovers (Trifolium spp.)

Cat’s ears (Hypochoeris spp.)

Mallows (Malva spp.)

Sedums (Sedum spp.)

Chickweed (Stelaria media)

Hedge mustard (Sisymbrium sp.)

Bramble (Rubus fruticosus)

Plantains (Plantago spp.)

Please see the article on Toxic Plants referenced below for a list of species that may be potentially harmful to tortoises.


The balance of the diet is comprised of seasonally available greens (stems and leaves) such as kale, endive, Swiss chard and romaine. Other produce can be added as available, but avoid spinach and iceberg lettuce and use bok choy sparingly. Small amounts of yam and carrot are provided once weekly.

Commercial Diets

Zoo Med’s Grassland Tortoise Diet  is specifically formulated for Russian and Mediterranean tortoises, and can comprise up to 50% of the diet in winter or summer.

Winter Diet

During the winter, the diet of tortoises under my care typically consists of 70-75% commercially available greens and 25-30% Zoo Med Grassland Tortoise Diet. Grated yams and carrot can be offered once weekly as a treat. Some native plants freeze well, and can be stored for winter use.


I add Reptocal and Repti Calcium with D3 to all meals provided to growing tortoises, and 3x weekly for adults. A cuttlebone is always available as well .

Water should always be available, or the tortoises can be soaked on alternate days, during which time they will drink heavily.

Light and Heat

Russian and other tortoises will not be able to properly metabolize calcium or digest other nutrients unless provided with a warm basking site and high levels of UVB (I suggest either the Zoo Med 10.0 or a mercury vapor bulb).

Further Reading

For more information on tortoise care, toxic plants and growing food for reptiles, please see The Russian Tortoise, Reptile Gardens  and Toxic Plants .

Please write in with your questions and comments. Thanks, until next time, Frank Indiviglio.

Testudo image referenced from Wikipedia and originally posted by B kimmel.

Distinguishing the African Clawed Frog from the Dwarf Clawed Frog

For as long as I can recall, distinguishing between young African clawed frogs (Xenopus laevis) and adult dwarf clawed frogs (Hymenochirus boettgeri or H. curtipes) has been problematical for many frog keepers (and pet store employees!). The question is more than academic, because both are exceedingly common and popular in the pet trade, and their care differs radically.

Distinguishing the Species

Both are members of the frog family Pipidae, a group of 32 species of aquatic, tongue-less and thoroughly engaging creatures. Included the Pipidae is the bizarre, back-brooding Surinam toad (Pipa pipa) and its 5 relatives.

The two can be easily distinguished by closely examining the front feet. If the fingers are webbed, then the frog is a dwarf clawed frog. If they are not webbed, then it is a baby African clawed frog. Both have webbed feet.

There are subtle differences as well – dwarf frogs are even more flattened in shape than their larger cousins, and have somewhat pointed (as opposed the African clawed frog’s rounded) heads.

Lifestyle and Care Differences

African clawed frogs are boisterous, hardy beasts that eat most anything, prepared foods included, and are easily trained to feed from the hand. Captive longevity approaches 30 years.

Dwarf clawed frogs are live food specialists. Tiny and slow moving, they incessantly search the substrate for worms and other invertebrates, and do best in warm, densely-planted aquariums. A breeding group makes for an enchanting display.

Frogs and Fish?

Unfortunately, both are often sold as “oddities” for tropical fish aquariums. This situation rarely works out…African clawed frogs consume all but the largest of fishes, and dwarf frogs are inevitably out-competed for food and perish in short order.

There are major differences in the care of both species, which I’ll cover in detail in the future. Until then, please write in with your questions and comments. Thanks, Frank Indiviglio.

Further Reading

I’ve long been fascinated by aquatic frogs, and have bred a number of species. Please see my article African Clawed Frog Behavior  for some unusual observations upon which I’m seeking the comments of other frog enthusiasts.

Both frogs can be bred in captivity, and their tadpoles have a most unusual feeding strategy. For more information and a video clip, please see Suction Feeding in H. boettgeri.

Dwarf Clawed Frog Image referenced from Wikipedia and originally posted by Mwatro

Collecting Live Food for Amphibians and Reptiles: Pitfall Traps

Prehistoric cave paintings show that the pitfall trap, a simple covered or uncovered hole designed to capture animals, came into being very early in our evolution as a species.  Indeed, they are still used by hunters and field researchers today.  Pitfall traps also provide pet keepers with a simple, effective means of collecting live food for reptiles, amphibians, tarantulas, scorpions, mantids and other terrarium animals.

Building and Baiting the Trap

To create a pitfall trap, simple bury a can or jar flush with the ground and cover it with a board that is slightly elevated by small stones.  This will keep rain out while allowing invertebrates to enter.

An amazing assortment of creatures will simply stumble into such a trap, but you can increase its effectiveness by adding bait. A bit of ripe fruit, molasses, honey and some tropical fish flakes will lure all sorts of insects, sow bugs and other invertebrates (snails and slugs are especially fond of beer).  Be sure to keep some dead leaves or paper towels in the trap as well, to provide places for your catch to hide and keep away from one another.

Boards or other cover spread about an area, which can be easily turned and checked, will also attract a variety of insects. Spraying the area with a hose during dry weather will attract increased numbers of invertebrates to these shelters.


Always use caution when examining your catch, as potentially dangerous spiders, scorpions, hornets and other such creatures may be present.  Have a good field guide on hand if you are unfamiliar with local species, and use feeding tongs to remove animals from the trap.

Native Beetles in the Terrarium

If your interests extend to native invertebrates, your trap will likely provide you with some pleasant surprises.

One of my favorite and rather frequent catches is the caterpillar hunter (Calosoma scrutator), a widespread beetle that feeds upon caterpillars and other soft-bodied insects (a relative, the forest caterpillar hunter, was imported to the USA from Europe in 1905 to battle gypsy moths).  Next time I’ll write a bit more about the natural history and captive care of these colorful, interesting, but largely over-looked beetles.

Further Reading

I have long relied heavily upon wild-caught invertebrates as food for animals in both zoo and my own collections.  In the past I have written about collecting leaf litter and arboreal insects, as well as devices such as termite traps and the Zoo Med Bug Napper.  Please see the following articles for more information:

Collecting Leaf Litter Invertebrates

Collecting Live Food: an Entomologist’s Technique

Building a Termite Trap

Collecting Live Insects for Birds


Image referenced from Wikipedia and orignally posted by

Salamanders Used as Fishing Bait Linked to Amphibian Disease Epidemics – Part 2

As mentioned in Part I of this article, tiger salamander larvae (Ambystoma tigrinum), run through with a hook while alive, are still used as fishing bait in some parts of the USA.  Last time we learned about the bait trade’s role in spreading a Chitrid fungus that is decimating amphibian populations worldwide, and in hastening the extinction of endangered tiger salamanders through hybridization.

Endangered but Legally Exploited

Despite the aforementioned environmental nightmares, the bait trade in tiger salamanders remains largely unregulated, resulting in infected animals being shipped from state to state.  This practice hastens the spread of already fast-moving pathogens and of non-native salamanders, as surveys have revealed that most people and bait shops release unused larvae into local waterways.

The situation is rendered all the more bizarre by the fact that these largest of all terrestrial salamanders are critically endangered in many areas.  In fact, several subspecies, including the Eastern tiger salamander (Ambystoma tigrinum tigrinum), are protected by individual states as endangered species!

Other Threats

Tiger SalamanderTiger salamanders also face serious threats from habitat loss, pollution and the introduction of game fish to breeding ponds.  Their use of two distinct habitats – aquatic and terrestrial – renders them especially vulnerable.

Protection, when offered, is often ineffective.  In New York State, for example, 75 feet of land around breeding ponds is closed to development – but research has shown that few if any adults live within that radius!

Tiger Salamanders in Captivity

Tiger salamanders make interesting and unusually responsive captives. Longevities exceed 30 years, but captive reproduction is still somewhat problematical.  They certainly deserve more attention from hobbyists …please write in for further information.

American Bullfrogs

American bullfrogs (Rana/Lithobates catesbeianus) have also recently been implicated in spreading amphibian diseases (New Scientist: May, 2009).  Researchers monitoring food markets in NYC and California discovered that 8% of the frogs being offered for sale carried ranavirus and nearly 70% were infected with Chytrid!

Further Reading

You can learn about the natural history of the eastern tiger salamander, and the steps being taken by the NYS DEC to prevent its extinction, at


The Organization Amphibian Ark has taken a leading role in Chytrid research.  Read about how this fungus has caused amphibian extinctions, and predictions for the future of the epidemic, at http://www.amphibianark.org/chytrid.htm.

Image referenced from Wikipedia and originally posted by Tigershrike.

Scroll To Top