We compare the nursing behavior of two species, African lions(Panfhera Leo) and spotted hyenas(Crocuta Craig Packer crocuta), and show that non-offspring nursing is much less common in hyenas than lions. Hyenas spend less time with their cubs, are more alert during the suckling attempts of cubs, and more frequently resist the attempts of non-offspring. Vigilance against milk theft may therefore influence the distribution of non-offspring nursing across species. Our detailed study of non-offspring nursing in lions shows that females preferentially nurse their own offspring and that cubs are more surreptitious when attempting to suckle from other females. Non-offspring nursing in lions is most common when the costs are lowest. First, non-offspring nursing is more common among close kin. Second, females with small litters, and presumably more milk to spare, give a higher proportion of their nursing to non-offspring. Third, females give a higher proportion of their nursing to non-offspring as their own cubs grow older and need less milk. Cubs reared in créches do not appear to gain more milk that cubs raised alone, and females do not show any evidence of reciprocity in nursing one another's offspring. We suggest that non-offspring nursing in lions occurs as a by-product of the females' communal defense of their cubs against infanticide.
Bibliographical noteFunding Information:
We thank the Director of Tanzania National Parks, the Coordinator of the Serengeti Wildlife Research Institute, and the Tanzanian National Scientific Research Council for permission and facilities. Barbie Allen provided invaluable logistical support. Our research has been supported by the H. F. Guggenheim Foundation, the National Geographic Society, the Royal Society of Great Britain, the Eppley Foundation for Research, the American Philosophical Society, Sigma Xi, Hewlett-Packard, the National Institute of Mental Health (grant MH15181), the Graduate School of the University of Minnesota, the National Science Foundation (grants BSR 8406935 and 8507087). We performed most of the analysis for this article during a sabbatical year with fellowships from the J. S. Guggenheim Foundation. We thank the Zoology Department, Oxford University, for hospitality and computer facilities, Alan Grafen, Mark Pagel, and Christopher Bingham for statistical advice, and Tim Caro and Donald Kramer for comments on the manuscript.
- Kin selection
- Non-offspring nursing
- Parental care
- Spotted hyenas