What a surprise it was to see behaviour I had seen in frogs around 1959 described in the news media a couple of weeks ago. And what a delight when I looked up the original paper that the same behaviour had first been recorded by Ronald Henry Maxwell Savage (1900-1985) (see my earlier articles here and here) in 1934.
The recent paper which attracted media attention reiterated Savage’s observations on female Common Frogs, Rana temporaria. In to order to escape amplexus, which can sometimes, or often, involve more than one male in the female-grabbing frenzy of what the authors term ‘explosive’ breeders, the female uses a numbers of tactics. Grunting (thought to be ‘I have already laid my eggs so you are wasting your time’ signal is one such tactic. Others are rolling sideways and playing dead for sufficiently long for the males to lose interest. Different tactics were employed by female frogs of different size. Larger ones mainly grunted and rolled; smaller ones did the same but were more likely to appear dead.
Amplexus of a single female with a number of males is known to be a dangerous activity for the female which can lead to drowning. So keen are the males that even goldfish in the same pond may not escape the clutches of a male frog.
These tactics of mate avoidance can be interpreted in two ways. First, they enable a female to select a mate, perhaps on the basis of who can kick away their rivals. Second, the female while having arrived at the breeding pond may not be physiologically ready to ovulate and lay eggs, and having males hanging on for longer than necessary may be a dangerous encumbrance. In other words, on a particular occasion, are females ridding themselves of particular males or all males.
I saw and heard all the tactics described in Common Frogs I was keeping around 1959. For some reason I cannot now remember I had them in a large container in my grandfather’s greenhouse. I recall there was only one female with about four males. After all the mating ball activity, things settled down with just one male in amplexus. The female did not lay her eggs until about a week later which always led me to suppose that there was some physiological process occurring leading to ovulation. By contrast in our garden pond (until it was ruined by local vandals) I have seen females join males and lay their eggs during the first night of amplexus.
Dittrich C, Rödel M-O. 2023. Drop dead! Female mate avoidance in an explosively breeding frog . Royal Society Open Science 10, 230742 DOI: 10.1098/rsos.230742
Savage RM. 1934. The breeding behaviour of the common frog, Rana temporaria temporaria Linn., and of the common toad, Bufo bufo bufo Linn. Proceedings of the Zoological Society of London 104, 55-70.