Dryad Item 10.5061/DRYAD.1B8M917

• Main Author: Griffen, Blaine D.
• Format: Dataset
• Language: unknown
• Published: DRYAD 2019
• Subjects: (:tba); Mirounga leonina; Intermittent breeding; Life history; marine mammal; individual heterogeneity; Lifetime reproductive output; body mass; Dynamic state variable model; reproductive skipping; Stochastic dynamic programming; survival; Life sciences; medicine and health care; envir; anthro-se; Elephant Seal; Elephant Seals; Southern Elephant Seal; Southern Elephant Seals
• Online Access: https://doi.org/10.5061/DRYAD.1B8M917

Intermittent breeding by which organisms skip some current reproductive opportunities in order to enhance future reproductive success is a common life history tradeoff among long-lived, iteroparous species. The southern elephant seal Mirounga leonina engages in intermediate breeding when body condition is low. While it is anticipated that this strategy may increase the lifetime reproductive output of this species, the conditions under which reproductive skipping are predicted to occur are not clear. Here I develop a dynamic state variable model based on published data that examines when southern elephant seals are predicted to optimally skip reproduction in order to maximize lifetime reproductive output as a function of current body mass, maternal age, and survivorship. I demonstrate that the optimal reproductive strategy for this species can include reproductive skipping, and that the conditions where this is optimal depend on patterns of mass-dependent adult female survival. I further show that intermittent breeding can increase lifetime reproductive output, and that the magnitude of this benefit increases with the ability of individual animals to replenish depleted body mass through foraging. Finally, I show that when the environment is variable and foraging is reduced in bad years, the benefit of adopting an optimal strategy that includes reproductive skipping increases asymptotically with the frequency of bad years. These results highlight the importance of characterizing the pattern of adult survival in this species, as well as the need to identify other factors that may influence the prevalence and benefits of reproductive skipping. Model.v2This is the R code for implementing the model described in the paper using backward iteration. The parameters listed in the top section of the code can be modified to replicate the various results reported in the paper.Model.v3.R