Another Visiting Bullfrog

Female Bullfrog in the front yard

A couple of weeks ago, on July 4, 2022, I came across a big female Bullfrog sitting out in the yard. I was doing my morning chicken-chores, and there she was. Sitting there like some sort of garden gnome.

Another view of the Bullfrog

I thought the timing on this incident was interesting. On July 19th, 2019 (almost exactly three years ago), I found another female Bullfrog that was wandering through the yard.

We don’t have the kind of yard that one would ordinarily think of as Bullfrog habitat. It’s mostly dry here. We’re surrounded by irrigated hay fields and increasingly small fragments of Pinyon-Juniper-Sagebrush.  There are a couple of bodies of water within a few hundred yards of us, though - a water treatment plant with standing water, and a creek that’s mostly irrigation runoff, that sort of thing. To get to our yard, though, a frog needs to traverse some pretty un-froglike habitat.

Both times I’ve found wandering Bullfrogs in the yard,  we’d had a Summer monsoon rain a day or two previously.  And both times I’ve found Bullfrogs in the yard, they have been females. Was that pure chance, or could these wandering Bullfrogs be part of the normal biology of the frogs?

I looked into this a little more. In 2003, JD Austin and his associates examined various aspects of the natural history of Bullfrogs and predicted that the frogs would exhibit a ‘female-biased dispersal’. They confirmed this idea via genetic tests (that I really didn’t understand).

In any case…I’m thinking that my wandering female Bullfrogs may be part of the normal dispersal of the frogs from the core Bullfrog breeding areas.

Kind of neat, to have been in a place long enough to start to notice these patterns.

Sources:

Austin, J. D., Dávila, J. A., Lougheed, S. C., & Boag, P. T. (2003). Genetic evidence for female-biased dispersal in the bullfrog, Rana catesbeiana (Ranidae). Molecular Ecology, 12(11), 3165–3172. doi:10.1046/j.1365-294x.2003.01948.x