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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.


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.

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.


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

The Skinks (Family Scincidae) – An Overview of the Largest Lizard Family

Prehensile-Tailed SkinkIntroduction
The family Scincidae, the skinks, contains over 1,200 species – more than any other family of lizards.  Skinks range throughout the Eastern and Western Hemispheres, reaching their greatest diversity in Southeast Asia, Australia and Africa.  Among its members we find some of our most common pet reptiles and least-known lizards.  The following information is meant to introduce you to their wonderful diversity of forms and lifestyles.

The Unusual Giant
The group’s largest member, the Prehensile-Tailed Skink, Corucia zebrata, reaches 28 inches in length and is unique in a number of ways – it is entirely arboreal, has a prehensile tail, is limited in range to the Solomon and surrounding islands, feeds on leaves, gives birth to 1 (rarely 2) large offspring after a gestation period of 8-9 months, and seems to have a complex social structure that includes parental care of the young.

Lifestyle and Diet
Typical skinks are elongated in form with small legs and shiny scales.  Most are secretive and, although often diurnal (active by day), spend a good deal of time below rocks, logs or leaf litter.  Legs are absent or reduced in many species, including the various African and Middle Eastern “Sandfish” (Shenops and other genera) which seem to swim as they wriggle through shifting sand dunes.  Most skinks are insectivorous, but many also take fruit, carrion and small mammals, birds, reptiles and amphibians.  Several consume vegetation exclusively.

Skink Reproduction
Almost half of the known species bear live young, and a number of these have evolved a primitive placenta.  Many oviparous (egg-laying) skinks guard their eggs, and there is evidence that females may move the egg clutch in response to disturbances.

A Few That Break the Mold
Quite a few skink species depart from the group’s typical body plan and lifestyle.  New Guinea’s Fojia Skink, Fojia bumui, for example, has plate-like scales down the center of the back and granular scales along the sides.  It clings to vertical rock surfaces along streams, dives after small invertebrates that swim by, and climbs into bushes to sleep on large, sturdy leaves.  The genus Egernia contains at least 23 species that live in extended family groups and exhibit complex social behavior.  There are also aquatic, arboreal and fossorial skinks, some of which have scale-covered, sightless eyes.

Carl Kauffeld and New York City’s Lizards
While growing up in NYC, I was pleased to learn that New York State is home to 2 skink species – the Five-Lined Skink, Eumeces fasciatus and the Coal Skink, E. anthracinus. They are, in fact, the state’s only native lizards – Staten Island’s Eastern Fence Lizards were introduced there by none other than the Staten Island Zoo’s famed reptile man, Carl Kauffeld (to provide a source of food for lizard-eating snakes) and the Italian Wall Lizard of the Bronx, Queens and Nassau County is a pet trade escapee (I have observed free-living Wall Lizards for some time now…more on them to come).


Further background information on skinks, with links to individual species, is available at:

Research Notes – Hourglass Treefrogs (Dendropsophus ebraccatum) can choose either land or water as egg deposition sites

Frogs are full of surprises when it comes to reproduction – there are species that incubate eggs below the skin of their backs and in the vocal sacs, while others carry them wrapped about their rear legs or construct foam nests on land.  But in May of this year Boston University biologists working in Panama uncovered what may well be the oddest reproductive strategy of all – a frog that actively chooses to lay its eggs on either land or in water, depending upon the threats presented by each habitat.  To date this is the only example of an egg that can hatch in either environment, and these frogs are the only vertebrates known to show such reproductive flexibility.

When breeding near shaded ponds, hourglass frogs lay their eggs on tree leaves overhanging the water (the tadpoles drop into the water upon hatching), thus avoiding fish and other aquatic predators.  However, when utilizing ponds exposed to the sun, the majority of the frogs lay their eggs directly in the water, lest they dry out before hatching.

The “decision” is not governed genetically, because the same female frog will choose different egg laying sites when placed in a shaded or un-shaded pond.

Amphibians were the first group of vertebrates to evolve some independence from water.  Biologists are now studying the hourglass frog to determine if its unique egg-laying flexibility might shed light on the evolution of terrestrial amphibian eggs.


You can read more about the hourglass treefrog and its relatives at:


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