skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Variation of annual apparent survival and detection rates with age, year and individual identity in male Weddell seals ( Leptonychotes weddellii ) from long‐term mark‐recapture data
Title: Variation of annual apparent survival and detection rates with age, year and individual identity in male Weddell seals ( Leptonychotes weddellii ) from long‐term mark‐recapture data
Abstract Exploring age‐ and sex‐specific survival rates provides insight regarding population behavior and life‐history trait evolution. However, our understanding of how age‐specific patterns of survival, including actuarial senescence, compare between the sexes remains inadequate. Using 36 years of mark‐recapture data for 7,516 male Weddell seals (Leptonychotes weddellii) born in Erebus Bay, Antarctica, we estimated age‐specific annual survival rates using a hierarchical model for mark‐recapture data in a Bayesian framework. Our male survival estimates were moderate for pups and yearlings, highest for 2‐year‐olds, and gradually declined with age thereafter such that the oldest animals observed had the lowest rates of any age. Reports of senescence in other wildlife populations of species with similar longevity occurred at older ages than those presented here. When compared to recently published estimates for reproductive Weddell seal females, we found that peak survival rates were similar (males: 0.94, 95% CI = 0.92–0.96; females: 0.92, 95% CI = 0.93–0.95), but survival rates at older ages were lower in males. Age‐specific male Weddell seal survival rates varied across years and individuals, with greater variation occurring across years. Similar studies on a broad range of species are needed to contextualize these results for a better understanding of the variation in senescence patterns between the sexes of the same species, but our study adds information for a marine mammal species to a research topic dominated by avian and ungulate species.  more » « less
Award ID(s):
1640481
PAR ID:
10459847
Author(s) / Creator(s):
 ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Population Ecology
Volume:
62
Issue:
1
ISSN:
1438-3896
Format(s):
Medium: X Size: p. 134-150
Size(s):
p. 134-150
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, Frontiers in Ecology and Evolution)
    Gray, David A (Ed.)
    The lifetime fitness of an individual is determined by the integrated results of survival and reproduction. Improving our understanding of variation in survival senescence within and between species will therefore provide greater insight into the evolution of different life history strategies. Survival is influenced by multiple factors, consequently, variation in patterns of senescence is expected between individuals and sexes and across mating systems and the continuum of life history strategies. To date there is little consensus regarding the mechanisms driving the evolution of sex differences in actuarial senescence, necessitating the need for studies of sex-specific senescence for species across a wide range of life histories. The Weddell seal is a species of long-lived mammal that displays moderate polygyny and little sexual size dimorphism, which makes it an unusual species compared to other long-lived mammals that share the polygynous mating system. Here we used 37 years of data for 1,879 female and 1,474 male Weddell seals from Erebus Bay, Antarctica, to estimate and compare sex-specific patterns of survival rates using basis splines which allow flexible modeling of age-specific patterns. We found that males had lower rates of survival throughout life and higher rates of actuarial senescence after early adulthood compared to females. These results add to our understanding of sex-specific survival rates in the species and contribute information for a long-lived, polygynous species that should aid in achieving a broader understanding of aging between sexes and across the tree of life. 
    more » « less
  2. ; ; ; ; ; ; ; ; (, Ecology and Evolution)
    Abstract Sex‐related differences in vital rates that drive population change reflect the basic life history of a species. However, for visually monomorphic bird species, determining the effect of sex on demographics can be a challenge. In this study, we investigated the effect of sex on apparent survival, recruitment, and breeding propensity in the Adélie penguin (Pygoscelis adeliae), a monochromatic, slightly size dimorphic species with known age, known sex, and known breeding history data collected during 1996–2019 (n = 2127 birds) from three breeding colonies on Ross Island, Antarctica. Using a multistate capture–mark–recapture maximum‐likelihood model, we estimated apparent survival (), recapture (resighting) probability (), and the probability of transitioning among breeding states and moving between colonies (; colony‐specific non‐juvenile pre‐breeders, breeders, and non‐breeders). Survival rate varied by breeding status and colony, but not sex, and pre‐breeders had higher survival rates than breeders and non‐breeders. Females had a higher probability of recruiting into the breeding population each year and may enter the breeding pool at younger ages. In contrast, both sexes had the same probability of breeding from year to year once they had recruited. Although we detected no direct sex effects on survival, the variation in recruitment probability and age‐at‐first reproduction, along with lower survival rates of breeders compared to pre‐breeders, likely leads to shorter lifespans for females. This is supported by our findings of a male‐biased mean adult sex ratio (ASR) of 1.4 males for every female ( proportion of males = 0.57, SD = 0.07) across all colonies and years in this metapopulation. Our study illustrates how important it can be to disentangle sex‐related variation in population vital rates, particularly for species with complex life histories and demographic dynamics. 
    more » « less
  3. ; ; ; (, Molecular Ecology)
    ABSTRACT Males of polygynous mammals often do not live as long as females and, in some cases, exhibit evidence of earlier senescence. Patterns of DNA methylation (DNAm) have recently been used to predict chronological age in mammals. Whether DNAm also changes as a consequence of survival and senescence is largely untested in wild animals. In this study, we estimate mortality rates using recaptures of 2700 greater spear‐nosed bats,Phyllostomus hastatus, over 34 years and DNAm profiled for over 300 adult bats. In this species, one male typically controls mating access to a group of unrelated females. Bayesian analysis reveals that mortality risk in males is 1.8 times that of females, and comparison of age‐associated differences in DNAm indicates that DNAm changes 1.4 times faster in males than females. Therefore, even though the age of either sex is predicted by a common set of sites, the methylome of males is more dynamic than that of females. Sites associated with sex differences in the rate of DNAm change are sensitive to androgens and enriched on the X chromosome. Sites that exhibit hypermethylation are enriched in promoters of genes involved in the regulation of metabolic processes. Unexpectedly, subordinate males have higher mortality rates than reproductively dominant males and exhibit faster DNAm change than dominants at dozens of sites. Our results reveal that differences in mortality associated with sex and social status are reflected by changes in DNA methylation, providing novel insights into mechanisms of aging and mortality in this and likely other wild animal populations. 
    more » « less
  4. ; ; (, Marine Mammal Science)
    null (Ed.)
    Male–male contest behavior can contribute to spatial distributions of male pinnipeds during breeding seasons. To maximize breeding opportunities, the most competitive males would be expected to be surrounded by the highest numbers of reproductive‐age females. As information regarding fine‐scale spatial ecology of Weddell seals is lacking, we performed an exploratory study using kernel density analyses to evaluate age‐specific habitat use of male Weddell seals in Erebus Bay, Antarctica. Additionally, we investigated the relationship between age and number of surrounding reproductive‐age females using a competing set of regression models in a Bayesian framework that considered different functional forms of age while incorporating individual heterogeneity. As male adult Weddell seals aged, to at least 20 years, they were more likely to be found in areas associated with the greatest densities of reproductive‐age females, but individual heterogeneity also influenced the number of reproductive‐age female neighbors. The youngest males tended to haul out in offshore areas associated with better hunting, and older males tended to settle in more nearshore areas associated with more pup production. Our findings from this preliminary investigation indicate that male Weddell seal spatial behavior during the breeding season varies with age and individual and might be related to reproductive activity. 
    more » « less
  5. ; ; ; ; (, Journal of Animal Ecology)
    Abstract Actuarial senescence (called ‘senescence’ hereafter) often shows broad variation at the intraspecific level. Phenotypic plasticity likely plays a central role in among‐individual heterogeneity in senescence rate (i.e. the rate of increase in mortality with age), although our knowledge on this subject is still very fragmentary. Polyphenism—the unique sub‐type of phenotypic plasticity where several discrete phenotypes are produced by the same genotype—may provide excellent study systems to investigate if and how plasticity affects the rate of senescence in nature.In this study, we investigated whether facultative paedomorphosis influences the rate of senescence in a salamander,Ambystoma mavortium nebulosum. Facultative paedomorphosis, a unique form of polyphenism found in dozens of urodele species worldwide, leads to the production of two discrete, environmentally induced phenotypes: metamorphic and paedomorphic individuals. We leveraged an extensive set of capture–recapture data (8948 individuals, 24 years of monitoring) that were analysed using multistate capture–recapture models and Bayesian age‐dependent survival models.Multistate models revealed that paedomorphosis was the most common developmental pathway used by salamanders in our study system. Bayesian age‐dependent survival models then showed that paedomorphs have accelerated senescence in both sexes and shorter adult lifespan (in females only) compared to metamorphs. In paedomorphs, senescence rate and adult lifespan also varied among ponds and individuals. Females with good body condition and high lifetime reproductive success had slower senescence and longer lifespan. Late‐breeding females also lived longer but showed a senescence rate similar to that of early‐breeding females. Moreover, males with good condition had longer lifespan than males with poor body condition, although they had similar senescence rates. In addition, late‐breeding males lived longer but, unexpectedly, had higher senescence than early‐breeding males.Overall, our work provides one of the few empirical cases suggesting that environmentally cued polyphenism could affect the senescence of a vertebrate in nature, thus providing insights on the ecological and evolutionary consequences of developmental plasticity on ageing. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email