The effects of body size and climate on post‐weaning survival of elephant seals at <scp>H</scp>eard <scp>I</scp>sland

McMahon, Clive R.; New, Leslie; Fairley, E.J.; Hindell, Mark A.; Burton, Harry R.

doi:10.1111/jzo.12279

Cited by 12 publications

(23 citation statements)

References 49 publications

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“…There is a cost to mothers when conditions are poor because they produce and wean smaller pups with lower survival prospects (McMahon, Harcourt, Burton, Daniel, & Hindell, 2017;McMahon, New, Fairley, Hindell, & Burton, 2015), negatively influencing population growth New, Clark, & Costa, 2014;Schwarz, Hindell, McMahon, & Costa, 2012). Firstly, there was limited spatial context available, and so clear regional attribution for the observed differences could not be made.…”

Section: Our Knowledge Of the Basic Biology And Distribution Of Southernmentioning

confidence: 99%

Decadal changes in habitat characteristics influence population trajectories of southern elephant seals

Hindell

Sumner

Bestley

et al. 2017

Global Change Biology

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Understanding divergent biological responses to climate change is important for predicting ecosystem level consequences. We use species habitat models to predict the winter foraging habitats of female southern elephant seals and investigate how changes in environmental variables within these habitats may be related to observed decreases in the Macquarie Island population. There were three main groups of seals that specialized in different ocean realms (the sub-Antarctic, the Ross Sea and the Victoria Land Coast). The physical and climate attributes (e.g. wind strength, sea surface height, ocean current strength) varied amongst the realms and also displayed different temporal trends over the last two to four decades. Most notably, sea ice extent increased on average in the Victoria Land realm while it decreased overall in the Ross Sea realm. Using a species distribution model relating mean residence times (time spent in each 50 × 50 km grid cell) to 9 climate and physical co-variates, we developed spatial predictions of residence time to identify the core regions used by the seals across the Southern Ocean from 120°E to 120°W. Population size at Macquarie Island was negatively correlated with ice concentration within the core habitat of seals using the Victoria Land Coast and the Ross Sea. Sea ice extent and concentration is predicted to continue to change in the Southern Ocean, having unknown consequences for the biota of the region. The proportion of Macquarie Island females (40%) utilizing the relatively stable sub-Antarctic region, may buffer this population against longer-term regional changes in habitat quality, but the Macquarie Island population has persistently decreased (-1.45% per annum) over seven decades indicating that environmental changes in the Antarctic are acting on the remaining 60% of the population to impose a long-term population decline in a top Southern Ocean predator.

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Section: Our Knowledge Of the Basic Biology And Distribution Of Southernmentioning

confidence: 99%

Decadal changes in habitat characteristics influence population trajectories of southern elephant seals

Hindell

Sumner

Bestley

et al. 2017

Global Change Biology

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“…For elephant seals, the risk of mortality is highest in the first year of life, and under-yearling mortality can exceed 40% (Pistorius et al 1999, McMahon et al 2015. Generous allocation of maternal energy during lactation is valuable for offspring as the transition from nutritional dependence to independence is abrupt, requiring offspring to adjust to a sudden, complete change in nutrient availability.…”

Section: Selection On Weaning Massmentioning

confidence: 99%

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

Oosthuizen

Altwegg

Nevoux

et al. 2018

Oikos

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Early developmental conditions contribute to individual heterogeneity of both phenotypic traits and fitness components, ultimately affecting population dynamics. Although the demographic consequences of ontogenic growth are best quantified using an integrated measure of fitness, most analyses to date have instead studied individual fitness components in isolation. Here, we estimated phenotypic selection on weaning mass in female southern elephant seals Mirounga leonina by analyzing individual‐based data collected between 1986 and 2016 with capture–recapture and matrix projection models. In support of a hypothesis predicting a gradual decrease of weaning mass effects with time since weaning (the replacement hypothesis), we found that the estimated effects of weaning mass on future survival and recruitment probability was of intermediate duration (rather than transient or permanent). Heavier female offspring had improved odds of survival in early life and a higher probability to recruit at an early age. The positive link between weaning mass and recruitment age is noteworthy, considering that pre‐recruitment mortality already imposed a strong selective filter on the population, leaving only the most ‘robust’ individuals to reproduce. The selection gradient on asymptotic population growth rate, a measure of mean absolute fitness, was weaker than selection on first‐year survival and recruitment probabilities. Weaker selection on mean fitness occurs because weaning mass has little impact on adult survival, the fitness component to which the population growth of long‐lived species is most sensitive. These results highlight the need to interpret individual variation in phenotypic traits in a context that considers the demographic pathways between the trait and an inclusive proxy of individual fitness. Although variation in weaning mass do not translate to permanent survival differences among individuals in adulthood, it explains heterogeneity and positive covariation between survival and breeding in early life, which contribute to between‐individual variation in fitness.

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“…Much of what is known about the factors impacting first‐year survival stems from studies linking resightings data to an individual's condition at departure from its natal site. For example, in pinnipeds, increased girth, length, weight, and level/quality of parental provision are known to impact first‐year survival (Baker, ; Hall, McConnell, & Barker, ; McMahon et al, ), which likely relates to initial dive capabilities, development, and subsequent restrictions on foraging ability (Hindell et al, ; Irvine, Hindell, Hoff, & Burton, ). Juvenile survival rates have also been linked to climatic indices (e.g., El Nino Southern Oscillation), possibly due to changes in the abundance and distribution of resources, which can impact parental provisioning during lactation (and thus initial condition), alongside prey availability post‐weaning (Beauplet, Barbraud, Chambellant, & Guinet, ; McMahon & Burton, ).…”

Section: Introductionmentioning

confidence: 99%

High mortality rates in a juvenile free‐ranging marine predator and links to dive and forage ability

Cox

Authier

Orgeret

et al. 2019

Ecology and Evolution

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1. High juvenile mortality rates are typical of many long-lived marine vertebrate predators. Insufficient development in dive and forage ability is considered a key driver of this. However, direct links to survival outcome are sparse, particularly in free-ranging marine animals that may not return to land.2. In this study, we conduct exploratory investigations toward early mortality in juvenile southern elephant seals Mirounga leonina. Twenty postweaning pups were equipped with (a) a new-generation satellite relay data tag, capable of remotely transmitting fine-scale behavioral movements from accelerometers, and (b) a location transmitting only tag (so that mortality events could be distinguished from device failures). Individuals were followed during their first trip at sea (until mortality or return to land). Two analyses were conducted. First, the behavioral movements and encountered environmental conditions of nonsurviving pups were individually compared to temporally concurrent observations from grouped survivors. Second, common causes of mortality were investigated using Cox's proportional hazard regression and penalized shrinkage techniques.3. Nine individuals died (two females and seven males) and 11 survived (eight females and three males). All but one individual died before the return phase of their first trip at sea, and all but one were negatively buoyant. Causes of death were variable, although common factors included increased horizontal travel speeds and distances, decreased development in dive and forage ability, and habitat type visited (lower sea surface temperatures and decreased total [eddy] kinetic energy).4. For long-lived marine vertebrate predators, such as the southern elephant seal, the first few months of life following independence represent a critical period, when small deviations in behavior from the norm appear sufficient to increase mortality risk. Survival rates may subsequently be particularly vulnerable to changes in climate and environment, which will have concomitant consequences on the demography and dynamics of populations. | 411COX et al.

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The effects of body size and climate on post‐weaning survival of elephant seals at Heard Island

Cited by 12 publications

References 49 publications

Decadal changes in habitat characteristics influence population trajectories of southern elephant seals

Decadal changes in habitat characteristics influence population trajectories of southern elephant seals

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

High mortality rates in a juvenile free‐ranging marine predator and links to dive and forage ability

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