No abstract

The sugar glider Petaurus breviceps is generally considered to be a polygynous, group-nesting species. However, recent captive studies have indicated that dominance hierarchies and shared codominance amongst males formed when males were housed in multiple-male, multiple-female cages with male-biased sex ratios. This study uses data from sugar glider groups in natural populations to assess the probability of male dominance hierarchies and the opportunity for codominant father±son coalitions. Nesting groups of sugar gliders were found to have female-biased sex ratios ranging from 1:1.5 to 1:2.7 males:females. The dispersing sex was male ± there were four records of recruitment into the natal group, all of which were female. Only one example was found of a long-term adult male association between a father and putative son, which did not occur in the natal group of the son. The evidence suggests that though father±son associations may occur, the opportunities for male dominance hierarchies or male coalitions are rare in sugar glider nesting groups in the natural environment.

The sugar glider Petaurus breviceps is generally considered to be a polygynous, group-nesting species. However, recent captive studies have indicated that dominance hierarchies and shared codominance amongst males formed when males were housed in multiple-male, multiple-female cages with male-biased sex ratios. This study uses data from sugar glider groups in natural populations to assess the probability of male dominance hierarchies and the opportunity for codominant father±son coalitions. Nesting groups of sugar gliders were found to have female-biased sex ratios ranging from 1:1.5 to 1:2.7 males:females. The dispersing sex was male ± there were four records of recruitment into the natal group, all of which were female. Only one example was found of a long-term adult male association between a father and putative son, which did not occur in the natal group of the son. The evidence suggests that though father±son associations may occur, the opportunities for male dominance hierarchies or male coalitions are rare in sugar glider nesting groups in the natural environment.

No abstract

The sex with the higher potential reproductive rate is expected to mate polygamously unless there are temporal or spatial constraints on mate availability. We investigated whether such constraints were evident in a population of the monogamous seahorse Hippocampus whitei (family Syngnathidae). Across the whole study site, breeding was more asynchronous than expected by chance. Our findings are thus compatible with the hypothesis that asynchronous breeding may promote and/or maintain monogamy. Asynchrony per se was unlikely to explain monogamy entirely, however, as temporal opportunities for polygamy remained and the males that were nearest one another had the lowest level of asynchrony. Moreover, each animal's home range overlapped with home ranges of potential mates other than their partner, implying a lack of spatial constraints on polygamy. We suggest that H. whitei mated monogamously because the benefits of polygamy were reduced by (1) only small differences in the potential reproductive rates of males and females and/or (2) a mate familiarity effect that increased reproductive success in successive matings. Further research could investigate relationships between mating pattern and varying intersexual differences in potential reproductive rates across syngnathid species.