Not many people have seen a toad the size of a small rabbit. And yet there are four right here in Golden Gate Park – in the Borneo level of the Academy’s rainforest exhibit to be exact. Borneo river toads (Phrynoidis juxtaspera), a.k.a giant river toads, are notable for their large size, and predators would be wise to steer clear: these toads secrete a highly toxic, milky poison from their warts when threatened or injured.
Sharing the toads’ space, usually found wrapped around a branch at the top of the tank, are two red-tailed green rat snakes, and a mangrove snake. The mangrove snake (Boiga dendrophila) is mildly venomous and an excellent nighttime hunter. Its vertical, cat-like pupils open wider than round pupils, allowing in extra light in the dark. Red-tailed green rat snakes (Gonyosoma oxycephala), despite their colorful name, are not always green, nor are their tails always red. Case in point, the two female snakes on display at the Academy look very different from one another—one is green with a gray tail and the other is all gray with a greenish head (below, at right), and neither tail could be described as “red.”
Aquatic biologists at the Academy first began breeding Asian horned frogs (Megophrys nasuta) in captivity one year ago, and have now successfully raised over a dozen tadpoles into young frogs. Even after a year, around 40 of the frogs are still tadpoles, but more metamorphose every week, and seem to be in excellent health. The young frogs and tadpoles are being raised behind the scenes in the aquarium’s amphibian holding room.
Very few zoos and aquariums have been able to breed this species successfully, so our biologists have been learning as they go. One of the discoveries they made was that the size of an egg clutch can actually be as large as 1,400 eggs – a figure much higher than the popular literature suggested.
Native to the rainforest floors of Indonesia, Malaysia and Singapore, these frogs are not currently threatened in the wild, but are vulnerable to habitat destruction and exploitation by the pet trade industry. At the Academy, several adult Asian horned frogs can be seen on the Borneo level of the rainforest exhibit, blending into their leafy surroundings.
Photos: (c) Brian Freiermuth/California Academy of Sciences
Left: The much smaller male holds on to the large female in amplexus, the typical grasping behavior many frogs engage in prior to egg laying and fertilization.
Center: Tadpoles have upward turned mouths that allow them to filter feed at the water’s surface.
Right: A newly metamorphosed froglet still has some tail left, but already has tiny projections over the eyes like its adult counterparts.