Skip to main content

Birds of a feather flock together!

Register for press mailing list

Please note that only people who register using our registration form receive our press releases.

Press release,

This also applies for the European common frog (Rana temporaria) where mating of individuals of similar size is more likely than it would be by chance. In a recently published study, Carolin Dittrich, Mark-Oliver Rödel (both Museum für Naturkunde Berlin) and colleagues, show that the mate choice of one of Europe´s most common frog species is much more complex than previously thought. The scientists found that breeding pairs of frogs are more likely to form if they have a similar body size. Aside from mate choice behavior and male-male competition, size dependent temporal migration patterns cause these assortative mating. Larger males and females reach breeding ponds earlier in the season and are thus more likely to meet.

In the two research areas near Braunschweig and the Franconian Steigerwald, scientist of the Museum für Naturkunde Berlin have been able to detect a positive size-assortment of frog pairs over several years, that is, larger females mated with larger males. One of the causes of size-assortment was that larger animals, males and females, migrate earlier to the reproduction sites. Additionally, mate choice behaviour and competition among males seems to have an influence on the size-assortment. The researchers have shown that the smaller males grab the females faster (and are probably less choosy), thereby increasing their chance of getting a mate. The big males have an advantage when they are in direct competition with other males, that is, they are more likely to win fights to get access to a female. Finally, the scientists have investigated whether the size-assortment results in a higher number of offspring, because in frogs fertilization outside of the body is common and the distance of the cloacae of both partners to each other can influence the fertilization success. However, it could be shown in the experiments that this had no influence on the fertilization success. Nevertheless, as the size of the females is strongly correlated with their fertility, large females have a higher number of eggs; males should prefer larger females to increase their potential number of progeny. “Overal”, says Carolin Dittrich, PhD student at the Museum für Naturkunde Berlin and first author of the study, “we were able to show that mate choice in one of Europe's most common frog species is much more complex than previously thought.”

Published in: Dittrich et al. (2018) Temporal migration patterns and mating tactics influence size-assortative mating in Rana temporaria. Behavioral Ecology, doi: 10.1093/beheco/arx188.

Keywords