Costs Of Too Much Sex: Declines In Performance For An Australian Carnivorous Marsupial Across Their Intensive Mating Season

The northern quoll (Dasyurus hallucatus) is a medium-sized (approx. 1 kg) predatory marsupial previously common across the entire top-end of Australia. It is the largest known semelparous mammal in the world, which means mating is highly synchronous, males live for only one year, and males undergo total die-offs soon after the mating season. Such population-wide male die-offs are most likely due to the physiological stress of procuring copulations and the intense fighting among males. Given the importance of procuring mates in such a short period (approx. 2 weeks), the ability for males to win fights and cover long distances to find reproductively mature females is presumably of critical importance. In contrast, females live for two to three years and their die-off occurs after the young are weaned - which is around four months after the mating season. In this study, we explored how eight different dimensions of whole-animal performance varied across the intensive mating period for male and female northern quolls within a 125ha area on Groote Eylandt in remote northern Australia. We assessed the running acceleration, sprint speed, jumping power, biting force, manoeuvrability, motor control, gripping strength and endurance for individual quoll across the mating season. We expected the performance of males of high quality to be high throughout the breeding season while those of poor quality to rapidly decrease across the mating period. In contrast, we expected changes in the performance of females to be dependent on their age, with older females experiencing rapid declines due to the intensive attention from males within the population.