I couldn’t quite believe my ears. At the junction where the Virginia Street Extension (the dirt road) meets Marina Boulevard, next to the big wild blackberry bush, I heard what sounded like the croaking of frogs. Puddles of rainwater, almost small ponds, offered frog habitat. However, try as I might, I could not see the creatures whose voices I had heard. That’s probably because I was looking in the daytime.
Edwin Wu, however, the Cal molecular biology student who spotted the extremely rare Common Poorwill bird in November (“Rare and Unique,” Nov. 23 2021), pursued the frogs in this area at night, and scored big. He saw and flash-photographed two of these frogs (photo of one above). They are Sierran Treefrogs.
The name is a bit misleading. Although on rare occasions they’ve been seen up a tree, they’re almost entirely ground dwellers. At the time Edwin photographed them, they were a brownish-grey color. When they move into a grassy habitat, they can change their body color to green in a matter of minutes.
Unlike birds, which generally breed in warmer months, these frogs start their breeding season in November and continue into early spring. Males compete for sex with the females, as in many other species. But the actual copulation is a bit unusual. The male mounts the female as she is laying eggs. But he doesn’t enter her, as with mammals, and he doesn’t touch his reproductive organ to hers, as birds do. Instead he spreads his sperm over her eggs as they come out. This fertilizes them externally, much of the time, and then they turn into tadpoles which in time develop into frogs.
The frog is a California native also found in nearby regions. But its sound has become the stereotype of frog vocalizations. Listen. Almost every Hollywood movie with frogs in it will use this sound, even if the location is far outside this frog’s range.
More about Sierran Treefrog: Californiaherps.com