3.8

Dendrobatids
The Poison Dart Frogs

Cope, 1865

Order:  Anuran
Supergroup: Dendrobatoidea
Family: Dendrobatidae

Beautiful but Deadly…
This title was taken from a section of a book in the old Life Nature Library collection called South America.  It is where at around age 8 I first saw images of poison dart frogs, and I was completely mesmerized.  Neighborhood frogs, toads, lizards and various “critters” from our local pet store (where I spent nearly every free moment) I had collected; however, even as an artistic kid with a vivid imagination I could never have conjured up what I was seeing.  I knew then that if I ever had the opportunity to own and raise these animals I would.

Dendrobatids (superfamily Dendrobatoidea), commonly and collectively known as “poison dart frogs” are small, diurnal frogs endemic to the tropical and subtropical rainforests of Central and South America.  Most Dendrobatids have aposematic coloring.  That is, their brilliant colors warn potential predators that attempting to make a meal of them could be lethal.  Long known for the alkaloid-based poison excreted through glands in their skin, which can paralyze or kill potential predators (or careless humans), the Dendrobatid family of frogs includes some of the earth’s most brilliantly colored animals, which in some cases, harbor some of the most toxic compounds known to modern science.

To date there are more than 250 species of Dendrobatids.  Explorations continue to reveal new species and morphs/locales, most of which are included in the following genera:

Adelphobates (Zimmermann and Zimmermann, 1988)
Ameerga  (Bauer, 1988)
Andinobates  (Brown and Twomey, et al., 2011)
Colostethinae  (Cope, 1866)
Dendrobates  (Wagler, 1830)
Epidobates  (Myers, 1987)
Excidobates  (Twomey and Brown, 2008)
Hyloxalus  (Jimenez de la Espada, 1867)
Minyobates  (Myers, 1987)
Oophaga  (Bauer, 1984)
Phyllobates  (Dumeril and Bibron, 1841)
Ranatomeya  (Bauer, 1988)

The alkaloids that are the poison dart frogs’ primary defense are derived from their diet of various alkaloid-laden insects.  While these insects themselves may contain trace amounts of the toxins (whether self-manufactured, diet-derived or a combination of both is not clear), their potency may be negligible.  However, once consumed by these frogs the toxins from the insects are metabolized by the various species in ways render them lethal to predators.

There are three species of poison dart frogs, all in the genus Phyllobates, that can easily kill humans and larger mammals.  P. terribilis, as its name might suggest, is at the top of the list.  P. bicolor and P. aurotaenia, depending on the study come 2nd and 3rd or tie for 2nd.   The alkaloidal steroids, called batrachotoxins, excreted by these frogs are among the most lethal in the animal kingdom.  The indigenous Emberá and Cofán people of Colombia use all three of these frogs to poison their darts for hunting.  When P. terribilis is used, the darts are poisoned by rubbing the tips across the skin of a live animal causing it no harm.  That is all that is needed to make a weapon that will remain deadly for three years or more!  The process is a different when P. bicolor and P. aurotaenia are used.  In order to extract adequate amounts poison these frogs are impaled and sometimes held over a flame.  This causes the distressed frogs to foam, producing the necessary amounts of poison required for hunting.

It is important to note that the most lethal elements of the dart frog’s poison come from its natural diet in the wild.  This diet has not been replicated for captive specimens by neither institutions nor hobbyists.  In captivity, wild caught specimens decrease in potency over time, while captive-bred specimens never acquire the deadly alkaloids.  That said, it is known that if agitated other chemicals can be excreted which can cause irritation and/or illness, as is the case with many amphibians.  Care should always be taken if and when handling these frogs is necessary.

Dendrobatids are essentially terrestrial frogs, although some climb more than others and do so for various reasons, which I address as it relates to the species on this site.   All are diurnal, foraging throughout the daylight hours for insects.  Relative to their sizes Dendrobatids are microphagus, preying upon very small insects, such as mites, ants, tiny beetles and grubs, and other micro-fauna.  Members of certain genera, such as Phyllobates and Ameerga can take larger prey; however, compared to other anurans their prey is still relatively small.

In general, Dendrobatids require warm daytime temperatures at between 72-82 degrees, nighttime temperatures low to about 60 degrees, and humidity should be kept between 80 and 100%.  Some species can tolerate or may actually prefer conditions outside of these parameters, and this too I will address on this site where relevant.

Under suitable conditions Dendrobatids will breed in captivity, demonstrating highly evolved parental behaviors.  All will lay their eggs terrestrially and transport hatched tadpoles to a water source for metamorphosis.  With some species parental involvement ends there while with others further more complex behaviors are demonstrated.  In species of the genus Ranatomeya, for example, it is typically the male that will transport tadpoles individually to small pools of water, and will periodically call the female to each location to feed them unfertilized eggs as a supplement to what they will forage from their environments.  Because these tadpoles are omnivorous, they are considered to be “non-obligate egg-feeders”.  In species of the genus Oophaga, it is the female that transports the tadpoles, and their diet will consist soley of the  unfertilized nutritive eggs that she feeds them.  These are “obligate egg-feeders”.   In fact Oophaga, translated from Greek, means egg-eater.  In both cases, the egg-feeding behavior continues until the tadpole develops front legs, at which time it will derive nourishment through the absorption of its tail.  When the the tail is fully or near fully absorbed, the young metamorph will emerge and begin to forage for insects.

Many institutional and commercial breeders, as well as hobbyists remove the eggs of all but the obligates and hand-rear them.  There are some valid reasons for doing this.  One is to try to manage the survival rate, leaving less to chance.  This can be practical for the especially rare or difficult to breed frogs.   Another more common reason is to increase production.  Typically, frogs in breeding condition will readily deposit another clutch of eggs if one that they are caring for is removed.   If this practice is not managed it can lead to over-breeding, which can affect the overall health and lifespan of the frogs.  Given proper care, Dendrobatids can live for more than 15 years maintaining their fecundity throughout their lives.

There is another consequence for removing Dendrobatid eggs from their parents.  Over time, the highly-evolved breeding behaviors that this family of frogs are known for can be lost.  Anecdotally, this seems to occur over generations.  I will speculate here and suggest interfering with a parental contact phenomenon called “imprinting”, that would occur during the tadpole transporting stage can over time render inactive the gene that affects the hormones that compel these frogs to express their complex breeding behaviors.  This results in frogs lacking the instincts and innate capability to care for their egg clutches or tadpoles.  I have witnessed the following:

  • Frogs that lay eggs and turn around and eat them.
  • Frogs that never transport hatched tadpoles to water sources
  • Frogs that eat their own tadpoles as they hatch.

Continued, generational human intervention during breeding is what these frogs all had in common.  They were all removed as eggs and hand-reared, as were their parents, as were their parents’ parents, etc.  Essentially, this had gone on for generations.  This is behavior that, for obvious reasons, cannot be passed on to even a single generation in the wild.  This is why I typically do not pull eggs.   My intention is to ensure that the animals in my care live as naturally and realistically as possible given the  constraints of their man-made environments.

There will be more on Imprinting in an upcoming post that I will call  Inheritance.

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