Siring success in kangaroos: size matters for those in the right place at the right time

In polygynous species, male reproductive success is predicted to be monopolized by a few dominant males. This prediction is often not supported, suggesting that ecological and alternative mating tactics influence siring success. The spatiotemporal distribution of individuals and the number of males competing for each receptive female are often overlooked, because they are difficult to monitor in wild animals. We examined how spatial overlap of female-male pairs, the time spent by a male on the breeding site, number of competitors and morphological traits influence siring probability in eastern grey kangaroos (Macropus giganteus). We compared home range overlap for 12,208 dam-male pairs and 295 known dam-sire pairs to define local competitive groups and to estimate every male’s opportunity to sire the young of each female. We compared models considering morphological traits relative to the entire population or to local competitive groups. Including local competition improved model perfor...