UC Riverside

Cooperative breeding is an evolutionarily curious behavior, because helpers appeared to altruistically forgo opportunity for their own reproduction. In a population of Kalij Pheasants Lophura leucomelanos introduced to Hawai'i, we recorded cooperative breeding behaviors including caring for chicks, defending against conspecific intruders, and vigilance against predators. While cooperative breeding mostly occurs in altricial species, in which offspring need substantial parental care to survive, such behavior in the precocial Kalij Pheasants with relatively independent offspring provides an excellent opportunity to examine cooperative breeding and its influencing factors without the constraint of intense offspring needs. In our study population, Kalij pheasants formed stable social groups that usually contained one female and one to six males, and larger groups maintained larger year-round home ranges in general. One male was dominant among others within a social group, and age was the only factor found to determine dominance, indicating helpers can possibly stay in social groups and queue for dominance. Because high density was observed, we hypothesized that breeding habitat may be saturated, and that subordinate males cannot establish independent breeding habitat and subsequently remain in social groups. The removal of about one third of social groups resulted in a significant decrease in number and proportion of multiple male groups, and suggested that habitat saturation contributed to cooperative breeding in this population. To examine if helpers gained genetic benefits, we used 12 autosomal microsatellites and applied relatedness and parentage analyses to 88 adult and 82 offspring samples. On one hand, we found 34.4% subordinate males were related to the dominant male of the social group, indicating some helpers can gain inclusive fitness by helping kin. On the other hand, subordinate males fathered 16.5% of offspring sampled, suggesting that helpers can gain direct fitness be participate in reproduction. These results helped to understand the maintenance of cooperative breeding in this population; however, the causes for cooperative breeding can be complex in reality. In addition to examined factors, group-living benefits and life history traits may also have played a role in cooperative breeding in Kalij Pheasants.