A green-and-black poison frog (Dendrobates auratus) allows me to get a closer look at its asymmetrical mask — a fleeting moment before it continues along with its perpetual hopping. This species of poison frog is one of my favorites in the neotropics. Among the leaf litter they appear to be glowing faintly from the green light filtering down from the canopy. If it wasn’t for their habit of constantly hopping away, the majority of them might go unnoticed. Every individual has a unique arrangement of almost fluorescent green blotches running along the entire body. In Costa Rica they have a prominent V-shaped mask, all the more striking when contrasted with its jet black body. In some individuals the green stripes wrapping around the body create a concentric effect (a black circle enclosing a green circle enclosing a black dot) which I’ve most commonly seen on the throat and belly.
Just as in many poison frogs in the Dendrobatidae, D. auratus shows considerable variation in color pattern, though not to the same extent as others such as the strawberry poison frog (Oophaga pumilio) and the mimic poison frog (Ranitomeya imitator… one of the most beautiful frogs on the planet!). In the Osa peninsula D. auratus generally has more black coloration, while in other areas the green stripes bleed out more, giving the frog a splotched appearance with the majority of the frog being blue-green. But the diversity doesn’t stop there! Other morphs in Panama can be almost entirely black with small green dots, cream-white and black, pale orange with undulating black patterns, or metallic silver and green.
The black-and-green poison frog is diurnal and mostly terrestrial, feeding on small arthropods and insects. Because of their shy and cryptic nature, I’ve never managed to happen upon one feeding on ants or termites, though I have witnessed several interesting behaviors in Oophaga pumilio including male-male combat. The toxicity of many poison frogs results from uptaking alkaloids from their diet, and D. auratus is no exception. For this reason poison frogs can lose their toxicity in captivity when on a different diet.
Males of this species exhibit brood care where they transport larvae (hatching in the leaf litter) to tree holes or depressions, some relatively high off the ground. Since males invest parental care, polygyny imposes a direct fitness cost; it would be unwise for a male to invest the energy in brood care if they were not his own offspring. Through experiments males have been observed to care for any clutch residing in his territory (whether or not it is actually his own clutch), while cannibalizing clutches when occupying a new location in search of a mate. This simple cognitive decision likely proves to be an effective measure for preventing misdirected brood care. Males often deposit more than a single egg in a tree hollow, and increased tadpole density may decrease viability of larvae. In addition, males mating with multiple females would be required to allocate parental care between clutches, so females likely also face a fitness cost in polygynous matings. To reduce this effect, females exhibit mate-guarding by remaining near a male and preventing other females from mating.
Macro shot above: photographed during the day with flash after a few jumps (almost but not quite in situ)— these guys are always on the move!
Photo below: A different individual photographed in situ at night, with flash.