The relative importance of reproduction and survival for the conservation of two dolphin populations

Manlik, Oliver, Mcdonald, Jane A., Mann, Janet, Raudino, Holly C., Bejder, Lars, Krutzen, Michael, Connor, Richard C., Heithaus, Michael R., Lacy, Robert C. and Sherwin, William B. (2016) The relative importance of reproduction and survival for the conservation of two dolphin populations. Ecology and Evolution, 6 11: 3496-3512. doi:10.1002/ece3.2130

Author Manlik, Oliver
Mcdonald, Jane A.
Mann, Janet
Raudino, Holly C.
Bejder, Lars
Krutzen, Michael
Connor, Richard C.
Heithaus, Michael R.
Lacy, Robert C.
Sherwin, William B.
Title The relative importance of reproduction and survival for the conservation of two dolphin populations
Journal name Ecology and Evolution   Check publisher's open access policy
ISSN 2045-7758
Publication date 2016-06-01
Sub-type Article (original research)
DOI 10.1002/ece3.2130
Open Access Status DOI
Volume 6
Issue 11
Start page 3496
End page 3512
Total pages 17
Place of publication Hoboken, NJ, United States
Publisher John Wiley & Sons
Language eng
Formatted abstract
It has been proposed that in slow-growing vertebrate populations survival generally has a greater influence on population growth than reproduction. Despite many studies cautioning against such generalizations for conservation, wildlife management for slow-growing populations still often focuses on perturbing survival without careful evaluation as to whether those changes are likely or feasible. Here, we evaluate the relative importance of reproduction and survival for the conservation of two bottlenose dolphin (Tursiops cf aduncus) populations: a large, apparently stable population and a smaller one that is forecast to decline. We also assessed the feasibility and effectiveness of wildlife management objectives aimed at boosting either reproduction or survival. Consistent with other analytically based elasticity studies, survival had the greatest effect on population trajectories when altering vital rates by equal proportions. However, the findings of our alternative analytical approaches are in stark contrast to commonly used proportional sensitivity analyses and suggest that reproduction is considerably more important. We show that

1. in the stable population reproductive output is higher, and adult survival is lower;
2. the difference in viability between the two populations is due to the difference in reproduction;
3. reproductive rates are variable, whereas survival rates are relatively constant over time;
4. perturbations on the basis of observed, temporal variation indicate that population dynamics are much more influenced by reproduction than by adult survival;
5. for the apparently declining population, raising reproductive rates would be an effective and feasible tool to reverse the forecast population decline; increasing survival would be ineffective.

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. We echo others in cautioning against generalizations based on life-history traits and recommend that population modeling for conservation should also take into account the magnitude of vital rate changes that could be attained under alternative management scenarios.
Keyword Bottlenose dolphin
Population dynamics
Population viability
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
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