Kevin Wallace1,*,
Alison Leslie2,
Tim Coulson1
Journal of Animal Ecology
9/10/12
1Division of Ecology and
Evolution, Imperial College London, Silwood Park, Berkshire, UK
2Department of Conservation
Ecology and Entomology, Faculty of Agrisciences, University of Stellenbosch,
Matieland, South Africa
*Correspondence author.
E-mail: k.wallace08@imperial.ac.uk
Summary
Crocodile populations are
size-structured, and for populations that are subject to harvesting, removal is
typically size selective. For this reason, size-structured matrix models are
typically used to analyse the dynamics of crocodile populations. The boundaries
between the size classes used to classify individuals in these models are
typically chosen arbitrarily. This is problematic because results can depend
upon the number and width of size classes.
The recent development of
continuous character population models termed integral projection models (IPM)
has removed the need to arbitrarily classify individuals. These models are yet
to be applied to harvested animal populations.
Using information obtained
from the literature, we develop an IPM for crocodiles. We use perturbation
analyses to investigate how altering size-specific demographic rates influences
the population growth rate and the strength of selection on snout to vent
length.
We find that perturbations can
lead to complex responses. Sensitivity analysis to population growth and fertility
selection reveals that the smallest animals and the sizes of early breeding
individuals and their eggs may have more influence on these population biology
parameters than previously thought.
Although our model is
relatively simple, our results show that IPM can be used to gain theoretical
insight into the possible consequences of altering size-specific demographic
rates on the population and evolutionary ecology of harvested populations.
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