Reproductive competition and fecal testosterone in wild male giant pandas (Ailuropoda melanoleuca)

Abstract

The giant panda (Ailuropoda melanoleuca) is notoriously difficult to study in the wild, but its interesting reproductive ecology makes the effort worthwhile. Perhaps more than most species, the panda is energy-limited, which alters the cost/benefit analysis of its reproductive ecology. Using global positioning system/very high frequency radiocollars to locate mating aggregations, we used behavioral observations and fecal testosterone assays to gain insight into male panda reproductive effort and strategies, and test theories relating to reproductive competition. Male pandas initially competed fiercely for access to females that were about to be fertile, but once male competitive status was determined, aggression rates declined. Contact aggression was only observed during the first 2 days of mating aggregations; thereafter, it was replaced with noncontact aggression and avoidance. Agonistic interactions were highly asymmetrical, with contest losers (subordinates) showing less aggression and more avoidance than contest winners (dominants), both before and after contest outcome was established. The competitively superior male displayed mate-guarding tactics and secured all observed copulations. Contrary to theoretical predictions, testosterone levels did not predict aggression levels or contest winners and also were not affected by winning or losing a contest. Body size appeared to be the primary determinant of contest outcome. We discuss our findings in light of theoretical predictions, such as those arising from the "challenge hypothesis," in the context of the giant panda's foraging and nutritional ecology.

Inbreeding and inbreeding avoidance in wild giant pandas

“…Although genetic (Hu, Zhan, Qi, & Wei, ; Zhan et al., ) and limited behavioural (Pan et al., ; Zhang et al., ) data indicate that natal dispersal in giant pandas is female‐biased, the question of inbreeding avoidance has never been addressed directly in this species. Despite substantive challenges to locating and observing this reclusive animal, detailed behavioural observations based on radiotelemetry have illuminated the basic reproductive ecology of this species (Nie, Swaisgood, Zhang, Liu, & Wei, ; Pan et al., ; Schaller, Hu, Pan, & Zhu, ). Giant pandas are seasonally polygynous.…”

Hearing sensitivity in context: Conservation implications for a highly vocal endangered species

“…5). While, the information content of these formants is not known, it is likely that being able to identifying the quality and identify of same-sex competitors would be adaptive; as males typically engage in aggressive competitive interactions for breeding access to sexually receptive females (Nie et al, 2012). In contrast to bleats and growls, our inspection of chirps did not demonstrate the presence of formants per se.…”

“…Courtship and breeding are coordinated through multimodal signaling, however acoustic signals are prominent, especially during the peri-ovulatory period (Owen et al, 2013). The vocal repertoire of adult giant pandas ranges from intensity-graded agonistic vocalizations (Nie et al, 2012) to information-rich affiliative vocalizations (Kleiman and Peters, 1990). For example, characteristics of female chirps vary according to female reproductive stage (Charlton et al, 2010a), and characteristics of bleats contain information about male androgen levels and size (Charlton et al, 2011(Charlton et al, , 2012(Charlton et al, , 2009b, female age (Charlton et al, 2009b) and the identity of male and female callers (Charlton et al, 2009a,c).…”

Exposure to Odors of Rivals Enhances Sexual Motivation in Male Giant Pandas

“…Giant pandas are highly promiscuous [20], and the females' fertile period lasts for only 1–3 days each year [32]. Therefore, it might be a better strategy for male giant pandas to locate and guard estrous females than to guard territories, as opportunities to fertilize females are rare [33].…”

“…As intra-male competition is critical to social structure in giant pandas in the wild [20], [33], our data suggest that exposing males to the odor of other males in addition to facilitating hetero-sex chemical communication [15] may be a useful technique to enhance captive breeding in this endangered species. Needless to say, whether increased sexual motivation actually facilitates mating and leads to improve reproductive success requires further study.…”