By Prathipa Anandarajan
Animals have evolved to choose their mates, with females generally the pickier sex due to their greater investment in gametes and (in mammals) offspring care. Females typically prefer males with traits that will enhance offspring fitness, assessing potential mates’ genetic quality, health and ability to provide resources from physical attributes (e.g. body condition) and courtship displays (e.g. vocalizations). Stressed males are therefore often unattractive to females. However, in captivity, stress is common in animals housed sub-optimally (e.g. in small, barren cages), which could explain why in rats, mink, and even drosophila, raising males in higher quality conditions enhances their success with females. We therefore tested the hypothesis that housing quality affects male attractiveness in mice (Mus musculus), predicting that females will treat males from conventional small cages as lower-quality, preferentially courting with males from well-resourced ‘enriched’ conditions, known to enhance welfare.
To test this, pairs of DBA male litter-mates were differentially-raised from weaning until 12 weeks of age. Twelve oestrous DBA female sister pairs (also 12 weeks old) were then each presented with a brother pair, in a T-maze mate choice test lasting 30 minutes. Ultrasonic recording confirmed that male-female interactions were sexual: all trials involved courtship singing. Behaviour was videoed, and videos were analysed blind to mouse housing. Results showed that females spent on average 1.5 times longer near well-resourced males than their conventionally-caged brothers (F1,20 = 12.653, p = 0.002), and sniffing them for nearly twice as long (F1,20 = 20.290, p = 0.002). Thus, as predicted, well-resourced males were more attractive. We will now investigate which housing-sensitive traits (e.g. body size/song quality/others) are influential. Overall, our results suggest that improving welfare could help improve the success of conservation breeding programmes including giant pandas, black-footed ferrets and other species with poor reproductive performance in captivity.
