Reproductive sharing and proximate factors mediating cooperative breeding in the African wild dog (Lycaon pictus)
Although dominant African wild dogs (Lycaon pictus) are generally believed to be the sole breeders within a pack, earlier behavioral and endocrine data suggest that reproduction could be shared with subordinates. We performed an extensive behavioral, demographic, and genetic evaluation of a wild dog population in South Africa to examine the level of such sharing and the proximate mechanisms influencing reproductive contributions of each sex. While a majority of pups were born to dominants because of a lack of subordinate potential breeders, we discovered a substantial portion of reproductive sharing between dominants and subordinates. Compared with alpha females that mated annually, subordinate beta females bred in 54.5% of years whereas thetas never bred. The three top-ranking males all sired pups (56.0%, 32.0%, and 12.0%, respectively) when three or more adult males were present. With only two pack males, alpha and beta individuals shared reproduction nearly equally (55.2% and 44.8%, respectively), and litters of mixed paternity were discovered on eight of 15 (53.3%) occasions. A skewed adult sex-ratio and frequent alpha mortalities for females and behavioral aggression in males allowed most individuals to attain dominant status in their lifetime, creating a constantly shifting social hierarchy. Genetic parentage results corresponded to reported hormone profiles, suggesting physiological suppression in some lower-ranked individuals of both sexes. Thus, a combination of demographic, behavioral, and hormonal proximate factors mediates reproductive partitioning in wild dogs. We conclude that reproductive sharing can be significant in this species, especially for males that have less robust suppressive mechanisms than females.
KeywordsDominance Lycaon pictus Multiple parentage Proximate mechanisms Reproductive sharing Subordinate breeding
We thank Ezemvelo KwaZulu-Natal Wildlife, especially the management teams at Hluhluwe-Imfolozi Park and the uMkhuze section of iSimangaliso Wetland Park. We also appreciate the assistance of Thanda Private Game Reserve and their wildlife management team. We are grateful to Rob Fleischer, Emily Latch, Sarah Haas, Kalon Armstrong, and Nancy Rotzel of the Smithsonian's Center for Conservation and Evolutionary Genetics for laboratory support and assistance with protocols and procedures. Sarah Arnoff, Jan Graf, Gabriella Flacke, Mariana Venter, Carla Naude-Graaff, Sboniso (Zama) Zwane, and Chris Kelly provided invaluable assistance in monitoring and sample collection in the field. This research was supported by funding from the Smithsonian Institution Undersecretary for Science Endowment, University of Pretoria, Rotterdam Zoo Thandiza Fund, Humboldt State University, Conservation Endowment Fund of the Association of Zoos and Aquariums, Disney Wildlife Conservation Fund, Knowsley Safari Park, DST-NRF Centre of Excellence for Invasion Biology, Khaki Fever Work Wear, Pittsburgh Zoo Conservation Fund, and the Morris Animal Foundation. International travel was generously provided by British Airways.
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