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

Central and South American frogs of the family Dendrobatidae secrete virulent skin toxins (histrionicotoxins, batrachotoxins and others) when disturbed.  Many people believe that the toxins of many species of Poison Frogs, known also as “Poison Arrow Frogs” and “Dart Poison Frogs”, were once used to coat darts and arrows used in hunting and warfare.  Actually, this is not the case – but the actual facts are no less interesting.

Origin of Frog Toxins

Poison Frog toxins are derived from the diet, being concentrated and synthesized from chemicals within the ants and millipedes (and possibly other invertebrates) upon which the frogs feed.  Wild-caught frogs gradually lose their protective toxins after a time in captivity… captive-born Poison Frogs do not develop toxic skin secretions unless they are fed the appropriate types of invertebrates.

Some years ago, I was fortunate enough to be at the National Aquarium in Boston when the origin of Poison Frog toxins was being investigated.  In one experiment, Green and Black Poison Frogs (Dendrobates auratus) that had lost their skin toxicity were liberated in the aquarium’s huge rainforest exhibit.  When recaptured some time later, the frogs had regained their potent skin toxins.  Studies showed that the source of these toxins were invertebrates that had been transported to the exhibit in soil and on tropical plants.

Toxin Use in Hunting

The use of frog toxins on hunting darts was first reported in the literature in 1823, by British naval captain C. Cochrane.  He reported that certain forest-dwelling people collected Golden Poison Frogs (Phyllobates terribilis) and confined and fed the frogs until toxins were needed.  The frogs were pierced with a stick in order to induce the secretion of the toxins, which appeared as white froth on the skin.

Up to 50 darts could be treated with the secretions from a single frog, and the darts were reported to retain their potency for at least 1 year.  A jaguar shot with a poison-coated dart was said to die within 4-5 minutes, and monkeys and smaller animals were killed instantly.

Darts, and not arrows, were utilized for hunting…toxin use on arrows shot from bows has never been observed.

Toxins were used in this manner by the Mucushi, Chaco and, possibly, other groups of people.

Toxins and Warfare

It comes as a surprise to many folks that frog toxins have never been documented as being used in wars or against human enemies.

Frog Species Utilized

The skin secretions of only 3 species of frog have been identified as being used as dart coatings.  These frogs are not, as often believed, the familiar Dendrobates species, but rather belong to the related genus Phyllobates.  Frogs belonging to this genus are less commonly seen in the pet trade than Dendrobates, although one, the Golden Poison Frog (P. terribilis), is fairly well-established in captivity.

Medicines from Frog Skin

The skin toxins of a great many frogs, related and unrelated to the Dendrobatids, are highly complex and are being studied with a view towards developing medications that may be useful in oncology and infectious disease research.  A compound derived from the secretions of the Phantasmal Poison Frog (Epipedobates tricolor) shows great promise as a pain medication…it is more effective than morphine, non-addictive and non-sedating.

Further Reading

You can read more about studies on the medicinal value of frog toxins here.

Golden Poison Frog image referenced from wikipedia and originally posted by Wilfried Berns

In Part I of this article I talked a bit about collecting (or trying to collect!) the Huntsman Spider, Heteropoda venatoria, in a most unlikely setting.  Usually purchased as a “curiosity”, the Huntsman often surprises its new owners with a range of interesting behaviors – if you thought that spider pets were limited to tarantulas, please consider this fascinating alternative!

Caution: Although Huntsman Spiders are not considered to be dangerously venomous, they are fast and aggressive, and will not hesitate to bite.  We know little about spider venom, and the possibility of an allergic reaction must be considered (central nervous system reactions have been reported on rare occasions)….please do not touch any spider with bare hands.

Natural History

The Huntsman Spider likely originated in southern India and Sri Lanka, but is now well-established in warm regions worldwide (including Florida).  They frequently enter buildings, where they sometimes welcomed for their roach-catching abilities.

The alternate name, Giant Crab Spider, took hold because these spiders hold the first 2 pairs of legs spread-out like a crab on guard.   Huntsman Spiders build no webs, but rather run down their prey, and are quite ravenous.  I’ve observed youngsters being dragged about by roaches three times their size, and adults sometimes catch lizards and small bats.

Huntsman Spiders are entirely arboreal and adapted to living upon flat surfaces, such as walls and tree trunks, as opposed to branches.

Huntsman Terrariums

In captivity, they take readily to cork bark  and will climb terrarium glass as well.  Position cork bark slabs near the glass, so that the spiders will remain visible when using the reverse side of the bark as a shelter.

While arboreal tarantulas (i.e. Pink-toed Tarantulas, Avicularia spp.) do well in standard aquariums turned on end to provide additional height, I hesitate to recommend such for Huntsman Spiders – opening the screen cover leaves a wide area available for escape.  I much prefer a “tall or high style” aquarium, with the cover is on top.  Alternatively, a Faunarium turned on its end might work, as the access door is small and should limit escapes.

Heat and Humidity

Huntsman Spiders favor warm, humid habitats, and should be maintained at 77-85 F and provided daily misting and a moisture-retaining substrate.

Diet

Huntsmans take nearly any insect prey available, but particularly favor roaches.  Wild caught moths, katydids, beetles and grasshoppers should also be provided whenever possible.

Breeding

Male Huntsman Spiders are smaller and thinner than females, and their carapace bears darker markings.  When ready to breed, males cease feeding and develop noticeably swollen pedipalps (leg-like structures bearing sperm packets).  They wander about in search of females to mate with (and, usually, to be consumed by!). I’ve had breeding males escape with their lives, but none have survived for long afterwards.

The female carries her uniquely flattened egg case below her body.  The young stay on her for a short time, and then disperse.  If you are raising this species, be sure to cover the terrarium’s screening with an extra layer of mosquito netting, lest the hatchlings escape – a colony established in the home is not to everyone’s liking!

Further Reading

Huntsman and other spiders produce a range of sounds.  An interesting article on this topic, which includes photos of males in breeding condition, is posted here.

A video showing this species’ speed and hunting style is posted

Huntsman Spider image referenced from wikipedia and originally posted by Ed g2s and Saperaud

As a boy, my favorite exotic animal collecting site was, of all places, the loading dock of the local A&P Supermarket.  Raymond Ditmars and other famous city-born naturalists had taken this route, and so I followed.  The store was not far from the Bronx’s Hunts Point Market, where trucks from all over delivered fresh produce. Hidden within the produce crates were the creatures I sought – tree frogs, spiders, lizards, insects and such (I once narrowly missed a Mouse Opossum).  All large spiders were called “Banana Spiders”…one, the Giant Crab or Huntsman Spider (Heteropoda venatoria), appeared on occasion but was always too fast for me.  I became obsessed with this beast, whose leg span approached 6 inches, but, try as I might, I remained crab spider-less.

Meeting Both a Long-Lost Spider and Entomologist

It was to be over 15 years before I next crossed paths with the Huntsman Spider – this time in a Bronx Zoo building (JungleWorld) in which I worked as an animal keeper.  A huge population, having arrived with tropical plants, was established, and I was ecstatic (my mammal-keeping co-workers were far less impressed!).

The spiders were faster than I remembered (and I was slower!)…those I captured had mainly fallen into places from which they could not escape.  They proved surprisingly easy to breed and, once set up in our exhibit area, were very popular with our visitors.

I took a specimen to the American Museum of Natural History, where it was identified as Heteropoda venatoria.  Amazingly, the woman who identified the spider for me was famed invertebrate specialist Alice Gray…while speaking, we discovered that it was she who had answered my mantis rearing questions when I called the museum as a boy, 25 years earlier!

Captive Care

These impressive spiders occasionally appear on the price lists of Florida-based reptile dealers, and they are quite inexpensive.  If a few guidelines are followed, they make fascinating, active terrarium inhabitants, and breed readily.  Once their amazing speed in hunting is seen in action, even die-hard tarantula fans cannot resist them!

I’ll cover the natural history and captive care of Huntsman Spiders in Part II of this article.

Further Reading

An interesting article on this spider’s life cycle is posted at on the website of the Cambridge Entomological Society.

Male Huntsman Spider image referenced from wikipedia and originally posted by B. Navez

Like most reptile keepers, I have often marveled at the efficiency of snake digestive systems.  I attributed their abilities to break down bone to “powerful digestive enzymes”, but recent research has shown that, at least for Burmese Pythons (Python molurus), a far more complex and amazing process is at work.

Digesting Large Vertebrates

I’ve observed some quite large snake feasts – a Red Foot Tortoise and a 60 pound deer taken by Green Anacondas (the tortoise was an unfortunate exhibit mate; the deer fell to an anaconda at my study site in Venezuela) and 40 pound pigs regularly fed to Reticulated and Burmese Pythons under my care at the Bronx Zoo, for example.

A few shell scutes, hoofs, some bone fragments and fur where all that passed in the feces of these snakes – the rest being digested.  How do they do it?

Bone-Digesting Cells

Research at the Louis Pasteur and Indiana Universities has revealed that, after feeding, the digestive systems of Burmese Pythons undergo a dramatic transformation.  New cells are produced and worn-out cells die and are eliminated in preparation for the work at hand.

Studies of the small intestine have uncovered a new type of cell, previously unknown to science.  These cells are responsible for degrading bone and releasing its components into the snake’s bloodstream.  This process promotes efficient calcium absorption, and may be the reason that most captive snakes do not require a UVB source if fed a diet comprised of whole rats, mice and other vertebrates.

Warm-Blooded Snakes?  Not Quite, but…

We’ve known for some time now that Burmese Pythons break the “cold-blooded” rule when digesting their meals.  While most snakes must seek out a hot basking spot in order to maximize digestion, Burmese Pythons can actually raise their internal temperatures without an external heat source! 

Further Reading

Please see Big Snake Meals for some examples of how large (and unusual) snake prey can be.

To read about recent research concerning another unusual snake feeding adaptation, please see How Snakes Grow despite Food Deprivation.

An account of the original research showing that pythons can raise their body temperatures may be found in this Journal of Herpetology article.

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.