Data from: Evaluating the importance of individual heterogeneity in reproduction to Weddell seal population dynamics using integral projection models

Identifying and accounting for unobserved individual heterogeneity in
vital rates in demographic models is important for estimating
population-level vital rates and identifying diverse life-history
strategies, but much less is known about how this individual heterogeneity
influences population dynamics. We aimed to understand how the
distribution of individual heterogeneity in reproductive and survival
rates influenced population dynamics using vital rates from a Weddell seal
population by altering the distribution of individual heterogeneity in
reproduction, which also altered the distribution of individual survival
rates through the incorporation of our estimate of the correlation between
the two rates and assessing resulting changes in population growth. We
constructed an integral projection model (IPM) structured by age and
reproductive state using estimates of vital rates for a long-lived mammal
that has recently been shown to exhibit large individual heterogeneity in
reproduction. Using output from the IPM, we evaluated how population
dynamics changed with different underlying distributions of unobserved
individual heterogeneity in reproduction. Results indicate that the
changes to the underlying distribution of individual heterogeneity in
reproduction cause very small changes in the population growth rate and
other population metrics. The largest difference in the estimated
population growth rate resulting from changes to the underlying
distribution of individual heterogeneity was less than 1%. Our work
highlights the differing importance of individual heterogeneity at the
population level compared to the individual level. Although individual
heterogeneity in reproduction may result in large differences in the
lifetime fitness of individuals, changing the proportion of above- or
below-average breeders in the population results in much smaller
differences in annual population growth rate. For a long-lived mammal with
stable and high adult-survival that gives birth to a single offspring,
individual heterogeneity in reproduction has a limited effect on
population dynamics. We posit that the limited effect of individual
heterogeneity on population dynamics may be due to canalization of
life-history traits.