Reproductive competition and fecal testosterone in wild male giant pandas (<Emphasis Type="Italic">Ailuropoda melanoleuca</Emphasis>) |
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Authors: | Yonggang?Nie Ronald?R?Swaisgood Zejun?Zhang Xiaobin?Liu Email author" target="_blank">Fuwen?WeiEmail author |
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Institution: | (1) Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, 1-5 Beichen West Road, 100101 Beijing, China;(2) Graduate University of the Chinese Academy of Sciences, Yuquan Road, 100039 Beijing, China;(3) San Diego Zoo Institute for Conservation Research, 15600 San Pasqual Valley Road Escondido, P.O. Box 120551, San Diego, CA 92112, USA;(4) Institute of Rare Animals and Plants, China West Normal University, 1 Shida Road, 637002 Nanchong, Sichuan, China;(5) Foping National Nature Reserve, Foping, 723400 Shaanxi, China; |
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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. |
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