What’s Hoppenin’
It has been quite a while since we last updated everyone about how the frogs are doing. To review, in August 2006, we received 82 mountain yellow-legged frog Rana muscosa tadpoles. These animals were salvaged from a streambed that was drying up in Southern California’s San Jacinto Mountains. Fires, drought, disease, nonnative species, and water pollution have all but wiped out the frogs in Southern California. They remain in only three mountain ranges, surviving in only eight populations. It is estimated that fewer than 250 of these beautiful frogs are left in Southern California.

The tadpoles were brought to our lab at the San Diego Zoo’s Beckman Center for Conservation Research and separated into 2 50-gallon (227-liter) tanks. From there, the real work began. Water must be monitored daily as water quality is the single most important factor in raising tadpoles. Because tadpoles produce so much ammonia, water changes were made daily. Within a few months, some of the tadpoles, which were collected in seven different areas along the stream, began to sprout legs. We had to quickly build rearing tanks as we knew that the tadpoles would be morphing into froglets at various stages and sometimes in large groups. They did just that! Fed on a diet of different vegetables, algae, and fish foods, the tadpoles soon began to morph into little frogs. Once their tails started to disappear and all four limbs were functioning, the froglets were moved into one of eight rearing tanks.

Jump to today, February 22, 2008. I just finished a water change on the remaining three tadpoles. We have one rearing tank left for these tadpoles. Now I have the task of cleaning up after seven large tanks of hungry frogs. I am proud to say that three of the tanks contain adult frogs already, while the other tanks contain frogs that are well on their way to adulthood. The adults are just starting to be warmed up from their winter cool-down (when breeding many reptiles and amphibians, a cool season is given to emulate winter) and already animals are starting to call and some have even be seen in amplexus (amplexus is the amphibian love hold in which the male grasps hold of the female to fertilize the eggs as they leave the female’s body). No eggs have been seen yet, but we don’t mind them practicing to make it perfect!

We have also just finished a meeting with our conservations partners (U.S. Geological Survey, U.S. Fish and Wildlife Service, California Department of Fish and Game, and the U.S. Forest Service) to develop a strategy for frog reintroductions. Our plan will be to keep the frogs in captivity at the San Diego Zoo and other zoos, and all offspring will be returned to the wild and monitored over time. Stay tuned: things are going to start hopping in the frog lab and hopefully in the wild!!

Jeff Lemm is a research coordinator for the San Diego Zoo’s Applied Animal Ecology Division.

Here’s more information about the mountain yellow-legged frog recovery program…

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