In a previous post ("Frog Sex is a Strange Affair") I discussed the shenanigans that mountain yellow-legged frogs engage in during the breeding season. During a recent trip into the backcountry to survey frog populations, I was reminded of the peculiar sexual behaviors that these frogs display in the fall when frogs are obviously not breeding. With the arrival of shorter days and cooling water temperatures in late-August and September frogs start engaging behaviors normally associated with breeding, including calling and amplexus (above photo was taken two days ago). Seeing frogs engaging in these behaviors in the fall is rather odd since actual breeding is still nine months away. So, what are these frogs doing?My guess is that they are "practicing" for the breeding season that will occur next spring. This guess is based on the fact that most of the individuals showing these behaviors appear to be small males. Their small size suggests that they may have just attained sexual maturity and therefore have not yet participated in a breeding season. If true, it would be valuable to be able to "practice" calling and amplexing before next spring's breeding season. The individuals I watched a few days ago who were trying to amplex other frogs were certainly clumsy in their efforts. For example, the male shown in the above photo has placed his forearms in front of the forearms of the other frog instead of behind them. I watched this pair for several minutes, and it seemed that the amplexing individual needed all the practice he could get - what a bumbler!
With the return of ice and snow just a month or so away, the frogs may be using this short window in the fall to practice their breeding skills and thereby improve their chances of mating successfully in the spring.
I wonder if other amphibian species show similar pre-breeding behaviors....
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