[MARMAM] New publication on the viability of two bottlenose dolphin populations--importance of reproduction v.s. survival

Oliver Manlik o.manlik at unsw.edu.au
Fri Apr 22 06:06:37 PDT 2016

Dear Colleagues,

my co-authors and I are pleased to announce the recent publication of our
paper titled "The relative importance of reproduction and survival for the conservation of two dolphin populations". The study provides population viability forecasts for two bottlenose dolphin populations in Australia (Shark Bay & Bunbury), and assess the importance of reproduction and survival for the conservation of these populations.

The paper was published in the open-access journal Ecology and Evolution and is freely available for 'early view' at:


or for download and comments via Researchgate at:


You may also contact me directly with any queries. The abstract is below.

Oliver Manlik


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 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 modelling for conservation should also take into account the magnitude of vital rate changes that could be attained under alternative management scenarios.

Oliver Manlik
Biological, Earth and Environmental Sciences (BEES)
University of New South Wales
Sydney, NSW 2052
Ph: 02-9385-2198
E-mail: o.manlik at unsw.edu.au<mailto:o.manlik at unsw.edu.au>



Sydney Society for Conservation Biology

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