A Survey of Amphibians, Reptiles and Insects Suitable for Maintenance in Outdoor Ponds – Part I, The American Bullfrog, Rana catesbeiana (Lithobates catesbeianus)

Albino BullfrogsAn outdoor pond or other such habitat will expose you to facets of your pets’ behaviors that are difficult if not impossible to observe in indoor terrariums. I am a great fan of naturalistic, outdoor enclosures and from time to time will write about some of the many creatures that will thrive in them.

Surprising Colonizers
In most cases, the animals within our terrariums have been put there on purpose. However, if you establish an un-fenced outdoor pond, you may be in for a few pleasant surprises, even in densely populated areas.
Surprisingly, creatures that seem incapable of moving great distances, such as frogs, salamanders, snakes and turtles, are actually quite adept at sensing the presence of new water sources and traveling to them.

Especially skilled in this regard are bullfrogs, leopard frogs, pickerel frogs, grey tree frogs, American toads, water snakes and snapping turtles. There is an incredible amount of pressure on young animals (in the form of territorial and hungry adults) to leave their natal homes, so it makes sense that they would be equipped with keen abilities to find new habitats. So surprising is the arrival of frogs at isolated ponds that, in earlier times, people believed they rained down from the sky or were spontaneously generated from the mud!

An Impressive Pond Resident
The American bullfrog, Rana catesbeianus, is the largest North American frog and a truly spectacular addition to the garden pond. Bullfrogs do not like to be crowded – most backyard ponds will support but 1 male and 1 or 2 females. Bullfrogs have large appetites and have been known to consume small birds, bats and mice, and especially favor smaller frogs (related or otherwise!) If you move about slowly and cautiously when the frogs are out sunning, they will soon accept your presence and will reward your patience by swallowing earthworms or crickets tossed nearby.

Introducing Bullfrogs to Your Pond
If you decide to add bullfrogs to an unenclosed pond, be sure to start with tadpoles – frogs introduced to a strange area will nearly always leave, apparently in search of their original homes. Tadpoles that mature in your pond will be quite content to stay nearby.

Bullfrog Tadpoles
The large tadpoles may take up to 2 years to mature. The tadpoles will eat whatever algae and dead insects they may find. However, they require a good deal of food for proper development, and should be given supplementary green vegetables that have be soaked for a few minutes in hot water (this breaks down the tough cell walls, which are indigestible) and held below water by rocks . Vegetables such as romaine, kale and dandelion are necessary foods when fish are about, as fish will out-compete the tadpoles for food items such as flakes and algae tablets.

Frogs in Winter
Green Frog in my backyard pondAlthough bullfrogs and other temperate species can be over-wintered in the pond, it is safer to bring them indoors. They should be kept in a large aquarium with a good deal of cover in the form of floating plastic plants and enough water in which to submerged themselves, along with a smooth rock or piece of wood on which to rest. If kept at temperatures of 50 F or so (i.e. in a basement, if available), they will be fairly calm and will require but 1 weekly feeding. The Green Frog, Rana clamitans, and Leopard Frog, Rana pipiens, can be kept in small groups in outdoor ponds, as they are far less territorial than their larger cousin.

The accompanying photo shows 2 female albino American Bullfrogs. Albino bullfrogs are striking additions to the outdoor pond, but will quickly be captured by predators if the pond is unenclosed. The animals pictured here are yearlings, and have a good deal of growing left to do.

Please write in about your own experiences with housing herps outdoors. Thanks, until next time, Frank.

Observations on Cyclical Activity Patterns in Amphibians and Reptiles and a Request for Information

Wood FrogIn the course of my work with captive amphibians and reptiles I have often noted that the activity patterns of some seemed strictly controlled from within, while others were quite flexible.  This varied from species to species, and sometimes among individuals within the same species.

We know that most if not all species, ourselves included, are influenced by what might be described as an “internal clock”.  A number of processes, including daily activity patterns (termed circadian rhythms) are affected.  My own observations involved both daily and seasonal activities of a number of species.

Snapping TurtleAt one point I was caring for exhibits housing white-lipped treefrogs, Litoria infrafrenata and Wallace’s treefrogs, Rhacophorus nigropalmatus at the Bronx Zoo.  Both species are largely nocturnal.  On nights when zoo-sponsored special events resulted in the exhibit lights being kept on later than usual, each reacted differently.  The white-lipped treefrogs became active at 6 PM, the time when the lights would have been turned off on most days (as did, incidentally, the hoards of mice that occupied the building!).  The Wallace’s treefrogs, however, did not begin their evening activities until the lights were actually turned off, some 3-4 hours later than usual.

Similar examples abound – wild caught temperate species, such as Eastern painted turtles (Chrysemys picta) usually refuse to eat during the winter months, despite being kept warm.  However, the captive born offspring of such a turtle will generally feed throughout the year.

Wild-caught reptiles and amphibians hailing from temperate climates, such as the wood frog, fire salamander and snapping turtle viewed here, may become lethargic and go off feed in winter even if kept at their usually preferred temperatures.

Indian gharials (Gavialis gangeticus) under my care at the Bronx Zoo, hatched in their native northern India, refused to feed during their homeland’s cold season, despite having been shipped to NYC at less than 1 year of age.  The habit persisted for the 15 years or so that I was in contact with them.  Interestingly, they lost barely any weight during their 3 month long fast, even thought they were kept warm and remained active.

I would be most interested to hear about your own experiences in these matters, and will be sure to include your thoughts in future articles.  Thanks, until next time, Frank.

The abstract of an interesting article on temperature cycles in green iguanas is posted at:

Zoo Med’s Canned Freshwater Shrimp – an important new food reptile, amphibian, fish and invertebrate pets

Can o ShrimpAs I noted in an earlier article (Canned Insects and Other Invertebrates, July 1, 2008), several companies are now marketing canned grasshoppers, snails, silkworms and other invertebrates.  I believe these to be an important means of providing dietary variety to a wide range of captive reptiles and amphibians.

I have recently been experimenting with the canned shrimp offered by Zoo Med.  What caught my interest was the fact that the shrimp used, Macrobrachium nipponense, are a freshwater species.  Freshwater shrimp are an important and often dominant part of the diets of a great many aquatic animals, and their nutritional value varies greatly from that of both insects and fish – yet they are difficult for the average pet owner to procure. 

Of course, it is great fun to collect and breed freshwater shrimp, but how many of us actually have the chance to do this?  Generally, we are left to use pieces of marine shrimp (usually pre-cleaned and thus missing nutritionally valuable internal organs) purchased at food markets, or frozen/freeze dried marine species marketed for the tropical fish trade.  While such are useful, they are far from ideal, as there are a number of health issues involved in the long term feeding of marine species to freshwater pets.

The shrimp used by Zoo Med are small, whole animals.  Feeding them to a large turtle would be impractical, but they are ideal for innumerable smaller creatures.  I have found them to be readily accepted by a wide variety of creatures, including aquatic frogs (African clawed, dwarf African clawed), newts (eastern, marbled, ribbed), aquatic salamanders (sirens, axolotls) and turtles (spotted, painted, snapping, musk, mud).

Tropical fish of all kinds also relish these shrimp, as do US natives such as Banded Sunfish and Tadpole Madtoms.  I have also fed them to other freshwater invertebrates, such as Bamboo Shrimp, African Filter-feeding Shrimp, Crayfish and Caddisfly Larvae.

I am excited by the possibilities offered by this product – perhaps the nutrition contained in them holds the key to maintaining delicate aquatic amphibians and other creatures that now fare poorly in captivity. 

Please write in and let me know your own experiences with this and similar foods.  Thanks, until next time, Frank.

North America’s Colorful, Venomous Lizard – The Gila Monster, Heloderma suspectum

Gila MonsterOverview
Every so often I like to cover a species that, while not recommended as a pet, is well worth a closer look.  One such lizard that I have had the good fortune of working with is endemic to North America, the strikingly-marked Gila Monster.

Note: Gila Monsters are bred in captivity and sometimes appear for sale in the pet trade.  Please do not let your interest in these admittedly fascinating creatures lead you to purchase one.  They are venomous, and, despite recurring rumors to the contrary, have caused human fatalities.  Gilas are considered by many to be somewhat docile and slow moving.  Having long cared for them as a zoo herpetologist, I can assure you that this is not so.  They are often inactive, but can bite with amazing speed – and, in contrast to many snakes, there is no preparatory coil or other movement to warn of their intentions. If anything, their generally calm demeanor can lull one into a sense of false security – indeed, Gila bites are among those most frequently suffered (and covered up!) by zoo keepers.  Observe them in public collections and the wild, but please leave captive care to zoos.

Physical Description
This stoutly built creature is the USA’s heaviest native lizard, outweighed only by Florida’s introduced Green Iguanas and Nile Monitors. 

The scales, underlain by boney plates known as osteoderms, are bead-like in appearance.  The body is marked in widely varying patterns of pink, black yellow and orange blotches.   The blunt tail serves as a food-storage vessel – during lean times it may lose 20% or more of its mass.  Adult size ranges from 9 to 24 inches.

Two subspecies, the Reticulate Gila Monster and the Banded, are recognized.  They are found in western, central and southern Arizona and adjacent New Mexico, southwestern Utah through Nevada and from southwestern California to Sinaloa in northern Mexico.

Although typically thought of as a desert-dwelling species, Gila Monsters do not live in overly dry, central desert areas.  Rather, they frequent arid desert fringes and habitats that are referred to as “succulent or vegetated deserts” – areas that usually support a heavy growth of succulent plants, cacti, grasses and shrubs.  They may also be found in semi-arid plains and rocky foothills, lightly wooded thickets and about farms, usually near streams, springs or other sources of moisture.  Gilas sometimes enter oak forests and in Sinaloa, Mexico, inhabit the lower slopes of mountains and nearby beaches. 

Gilas may forage above-ground but are otherwise largely fossorial.  They occupy burrows dug by gophers and other mammals or those of their own making, abandoned woodrat nests and cavities below large rocks.

Despite the arid climate prevalent in their range, Gila Monsters favor areas of high humidity and spend the vast majority of their time in fairly moist underground retreats.  When kept in dry zoo exhibits, Gilas will soak in water bowls for hours on end.

Gila Monsters are diurnal in the springtime but become largely nocturnal as summer progresses.  During the hottest parts of the year they generally appear above ground only after rains.

Status in the Wild
Gila Monster populations are declining due to habitat loss and, in some cases, collection for the pet trade.  They are protected by law in all states within their range, are listed on CITES Appendix II and classified as Near Threatened by the IUCN.

Gilas feed on slow-moving animals – most commonly young mammals still in the nest, i.e. ground squirrels, kangaroo rats, pocket gophers, rabbits and cactus mice.  They also take the eggs and chicks of doves, quail and other ground-nesting birds, lizards and their eggs, tortoise eggs, locusts and other large insects and carrion.

These lizards are well-adapted to a harsh environment in which food is often scarce.  They gorge when food is available, consuming up to 50% of their bodyweight, and in some areas eat but 3-4 large meals annually.

Mating occurs in April and June, with 3-12 eggs being laid from July through August.  The eggs are buried in the sand, usually in a location exposed to full sun.  The eggs do not hatch until the following May – 10 months after being laid.  This long incubation period is a function of seasonality within the Gila’s range…artificially incubated eggs have hatched in as few as 30 days.

Captive longevity exceeds 28 years; unknown in the wild.

Lizard Venoms
The Beaded Lizard, H. horridum, 4 subspecies of which dwell in Mexico and Guatemala, is a close relative of the Gila and the only other member of the family Helodermatidae.  These 2 species were, until recently, considered to be the only venomous lizards (please see below).  In contrast to venomous snakes, the venom glands of Gila Monsters and Beaded Lizards are in the lower jaw and the teeth are grooved rather than hollow.  Venom flows into the mouth through ducts that open between the teeth and gums.  In order to insure the venom’s introduction into a prey animal or enemy, both lizards retain a firm grasp when biting. 

In 2005, researchers at Australia’s Melbourne University discovered that the Bearded Dragon, Pagona vitticeps, produces a mild venom (other Agamids are being studied).  Several monitor lizards, including the Komodo Dragon, Varanus komodoensis and the Lace Monitors V. varius, were also found to produce venoms of varying strengths.  Studies of Lace Monitor venom have revealed that it causes the lizard’s prey to rapidly loss consciousness by affecting the blood’s pressure and clotting ability.  This venom is likely the source of the strong reaction, previously attributed to oral bacteria, that is often associated with bites inflicted by monitor lizards upon people.

A synthetic version of a chemical found in the saliva of the Gila Monster is the basis of an important medication used to treat Diabetes Type II.

The species name, suspectum, was coined in 1869 by renowned herpetologist and paleontologist Edward Drinker Cope – upon noting the Gila’s grooved teeth, he “suspected” that it was venomous!  The genus name, Gila, is taken from the Gila River Basin in Arizona.
Thanks, please write in with any Gila Monster related observations or questions.  Until next time, Frank.

You can read more about the Gila Monster and the reptiles and amphibians that share its habitat at the web site of the Arizona Sonora Desert Museum:

Image referenced from Wikipedia Commons at http://en.wikipedia.org/wiki/Image:Gila_monster2.JPG and posted by Blueag9

Cicadas – An End of Summer Treat for Pet Reptiles, Amphibians and Invertebrates

As summer winds down, resourceful herp keepers are presented with a unique opportunity to treat their pets to a novel food item – providing, at the same time, a source of important nutritional variety. The waning days of summer bring with them the annual die-off of untold millions of large, juicy insects – the annual and periodical cicadas.

More than 100 of the world’s 2,000+ cicada species make their home in North America, and they are widely distributed. I still hear them regularly in the heart of Manhattan, and various species are quite common in and near other large cities as well. Most have a life cycle of 2-8 years, but 7 species in the eastern USA have a 13 or 17 year cycle and a number reach adulthood in 1 year.

The entire cicada population of a given area expires within a short period, usually at the end of August or in early September in the northeastern USA. This yearly event provides a bonanza (up to 1.5 million periodical cicadas may emerge from a single acre of soil!) of nutritious food for a wide range of creatures – deer mice, wood turtles, box turtles, skunks, flying squirrels, black bears and a host of others have been observed gorging on cicadas. Even adult copperhead snakes, not normally thought of as insect eaters, partake of the feast.

If you are alert at the right time, you may find hundreds of these normally arboreal songsters, spent and cicadaabout to die, on the ground. Your medium and larger sized reptile, amphibian and invertebrate pets will consume them with gusto, and you can freeze the excess for future use. Cicadas occur on every continent except Antarctica, and pets both native and exotic – American bullfrogs, African mud turtles, red-kneed tarantulas – unfailingly attack them with gusto. You can also collect the nymphs as they emerge from the ground in early summer – this usually occurs at night, and often within as short period of time as 1-7 days.

Dietary variety is an important key to keeping your pets healthy and in breeding condition. Those of us who keep insectivorous herps and invertebrates often face limited food choices. The annual cicada die-off may provide a relatively easy way for some of us to remedy that situation.

One word of caution: I have noticed that populations of annual cicadas near NYC have seemingly declined drastically in recent years. A colleague suggested that the insecticides sprayed to control mosquitoes bearing West Nile Virus may be the culprit. I tend to agree – cicadas, with their largely arboreal lifestyles, are easy targets for insecticides sprayed from airplanes (far easier targets than mosquito larvae, which seem as common as ever). I have not run into secondary poisoning problems when feeding cicadas to captive animals, but suggest that you do not collect in areas that have been commercially sprayed.

Please pass along your own ideas re alternate food sources for insectivorous pets. Thanks, until next time, Frank.

Image attributed to wikipedia: http://www.cirrusimage.com/homoptera_cicada_T_linnei.htm

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