The relative importance of reproduction and survival for the viability of slow-growing animal populations: lessons learned from two dolphin populations
Manlik, O., McDonald, J.A., Mann, J., Smith, H., Bejder, L., Krützen, M., Connolly, R., Heithaus, M.R. and Sherwin, W.B. (2013) The relative importance of reproduction and survival for the viability of slow-growing animal populations: lessons learned from two dolphin populations. In: 20th Biennial Conference on the Biology of Marine Mammals, 9 - 13 December, Dunedin, New Zealand.
Given limited resources and time for conservation actions, it is crucial to focus wildlife management recommendations on vital rates that have the greatest impact on population viability. It has been proposed that in slow-growing animal populations, including most marine mammals, adult survival has a greater influence on population growth than reproduction. The implication of this principle is that adult survival is more important for population viability than reproduction. Here we evaluate the relative importance of reproduction and survival for the viability of two bottlenose dolphin (Tursiopscf. aduncus) populations in Western Australia: a large, apparently stable population (Shark Bay) and a smaller one (Bunbury) that was forecast to decline. Consistent with previous studies, adult survival had the greatest effect on population trajectories when altering vital rates by equal proportions (+/− 4%). However, our alternative analytical approaches suggest that reproduction may be considerably more important. We show that (1) reproductive output is higher, and adult survival is lower in the stable population; (2) the difference in viability between the two population is best explained by the difference in reproductive rates; (3) reproductive rates are variable, whereas survival rates are relatively constant over time (12-year time period for Shark Bay);(4) perturbations based on this observed natural variation (+/− 1 SD) indicate that population dynamics are much more influenced by reproduction than by adult survival. Our findings highlight the importance of reproduction—even in slow-growing populations—and the need to assess the effect of natural variation in vital rates on population viability.
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|Murdoch Affiliation:||School of Veterinary and Life Sciences|
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