Phenotypic selection and covariation in the life‐history traits of elephant seals: heavier offspring gain a double selective advantage

Oosthuizen, W. Chris; Altwegg, Res; Nevoux, Marie; Bester, M.N.; Bruyn, P. J. Nico de

doi:10.1111/oik.04998

Cited by 23 publications

(33 citation statements)

References 114 publications

(175 reference statements)

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“…I assumed pup mortality to be mortality before the end of the first year of life. Oosthuizen, Altwegg, Nevoux, Bester, and de Bruyn () followed 746 pups from birth onward between 1986 and 2016. They examined survival as a function of mass at weaning and found that survival increased with pup size; however, they were unable to determine whether this relationship was linear, saturating, or even unimodal.…”

Section: Methodsmentioning

confidence: 99%

“…Pup mass at weaning ( m p ) is a function of initial maternal mass at parturition, as mass is transferred via nursing directly from the mother to the pup (McCann et al., ):

m_{normalp} = 0.171 false(\pm 0.05 false) \times m_{i} + 31.457 false(\pm 24.3 false),

where m i in this instance is initial maternal mass at parturition. Based on observed sizes of weaned pups, I capped m p at 160 kg (McCann et al., ; Oosthuizen et al., ; Postma et al., ).…”

Section: Methodsmentioning

confidence: 99%

“…I used WebPlotDigitizer to digitize the data infigure 6fromPostma et al (2013a), from which I derived the following equation (insufficient information was given to enable determining standard deviations of parameter estimates, I therefore assume 5% variation):Pup mass at weaning (m p ) is a function of initial maternal mass at parturition, as mass is transferred via nursing directly from the mother to the pup(McCann et al, 1989):where m i in this instance is initial maternal mass at parturition. Based on observed sizes of weaned pups, I capped m p at 160 kg(McCann et al, 1989;Oosthuizen et al, 2017;Postma et al, 2013a).…”

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confidence: 99%

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Reproductive skipping as an optimal life history strategy in the southern elephant seal,Mirounga leonina

Griffen

2018

Ecology and Evolution

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Intermittent breeding by which organisms skip some current reproductive opportunities in order to enhance future reproductive success is a common life history trade‐off 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.

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Section: Methodsmentioning

confidence: 99%

“…Pup mass at weaning ( m p ) is a function of initial maternal mass at parturition, as mass is transferred via nursing directly from the mother to the pup (McCann et al., ):

m_{normalp} = 0.171 false(\pm 0.05 false) \times m_{i} + 31.457 false(\pm 24.3 false),

where m i in this instance is initial maternal mass at parturition. Based on observed sizes of weaned pups, I capped m p at 160 kg (McCann et al., ; Oosthuizen et al., ; Postma et al., ).…”

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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Reproductive skipping as an optimal life history strategy in the southern elephant seal,Mirounga leonina

Griffen

2018

Ecology and Evolution

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“…For clarity of presentation we did not incorporate marker (tag) loss in the state process (Oosthuizen, Altwegg, Nevoux, Bester, & de Bruyn, 2018), although tag loss is known to occur at a low rate. As a consequence, the apparent survival estimates we obtain will be biased low.…”

Section: Multievent-robust Design: the State Processmentioning

confidence: 99%

Making use of multiple surveys: Estimating breeding probability using a multievent‐robust design capture–recapture model

Oosthuizen

Pradel

Bester

et al. 2019

Ecology and Evolution

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Increased environmental stochasticity due to climate change will intensify temporal variance in the life‐history traits, and especially breeding probabilities, of long‐lived iteroparous species. These changes may decrease individual fitness and population viability and is therefore important to monitor. In wild animal populations with imperfect individual detection, breeding probabilities are best estimated using capture–recapture methods. However, in many vertebrate species (e.g., amphibians, turtles, seabirds), nonbreeders are unobservable because they are not tied to a territory or breeding location. Although unobservable states can be used to model temporary emigration of nonbreeders, there are disadvantages to having unobservable states in capture–recapture models. The best solution to deal with unobservable life‐history states is therefore to eliminate them altogether. Here, we achieve this objective by fitting novel multievent‐robust design models which utilize information obtained from multiple surveys conducted throughout the year. We use this approach to estimate annual breeding probabilities of capital breeding female elephant seals (Mirounga leonina). Conceptually, our approach parallels a multistate version of the Barker/robust design in that it combines robust design capture data collected during discrete breeding seasons with observations made at other times of the year. A substantial advantage of our approach is that the nonbreeder state became “observable” when multiple data sources were analyzed together. This allowed us to test for the existence of state‐dependent survival (with some support found for lower survival in breeders compared to nonbreeders), and to estimate annual breeding transitions to and from the nonbreeder state with greater precision (where current breeders tended to have higher future breeding probabilities than nonbreeders). We used program E‐SURGE (2.1.2) to fit the multievent‐robust design models, with uncertainty in breeding state assignment (breeder, nonbreeder) being incorporated via a hidden Markov process. This flexible modeling approach can easily be adapted to suit sampling designs from numerous species which may be encountered during and outside of discrete breeding seasons.

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“…Specifically, we determined whether the somatic costs of breeding at the earliest possible age compromise females' body mass and their ability to allocate resources to future offspring, if they survived and bred again in the following year. The short-term somatic costs of early reproduction are potentially important for allocation to offspring, as maternal body mass is the key determinant of weaning mass (Arnbom, Fedak, & Boyd, 1997;Fedak, Arnbom, & Boyd, 1996) and thus offspring fitness components (Oosthuizen, Altwegg, Nevoux, Bester, & De Bruyn, 2018) in elephant seals.…”

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confidence: 99%

Individual heterogeneity in life‐history trade‐offs with age at first reproduction in capital breeding elephant seals

et al. 2019

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Recruitment age plays a key role in life‐history evolution. Because individuals allocate limited resources among competing life‐history functions, theory predicts trade‐offs between current reproduction and future growth, survival and/or reproduction. Reproductive costs tend to vary with recruitment age, but may also be overridden by fixed individual differences leading to persistent demographic heterogeneity and positive covariation among demographic traits at the population level. We tested for evidence of intra‐ and inter‐generational trade‐offs and individual heterogeneity relating to age at first reproduction using three decades of detailed individual life‐history data of 6,439 capital breeding female southern elephant seals. Contrary to the predictions from trade‐off hypotheses, we found that recruitment at an early age was associated with higher population level survival and subsequent breeding probabilities. Nonetheless, a survival cost of first reproduction was evident at the population level, as first‐time breeders always had lower survival probabilities than prebreeders and experienced breeders of the same age. However, models accounting for hidden persistent demographic heterogeneity revealed that the trade‐off between first reproduction and survival was only expressed in “low quality” individuals, comprising 35% of the population. The short‐term somatic costs associated with breeding at an early age had no effect on the ability of females to allocate resources to offspring in the next breeding season. Our results provide strong evidence for individual heterogeneity in the life‐history trajectories of female elephant seals. By explicitly modeling hidden persistent demographic heterogeneity we show that individual heterogeneity governs the expression of trade‐offs with first reproduction in elephant seals.

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Phenotypic selection and covariation in the life‐history traits of elephant seals: heavier offspring gain a double selective advantage

Cited by 23 publications

References 114 publications

Reproductive skipping as an optimal life history strategy in the southern elephant seal,Mirounga leonina

Reproductive skipping as an optimal life history strategy in the southern elephant seal,Mirounga leonina

Making use of multiple surveys: Estimating breeding probability using a multievent‐robust design capture–recapture model

Individual heterogeneity in life‐history trade‐offs with age at first reproduction in capital breeding elephant seals

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