DOI: 10.5061/dryad.4b8gthtp1
title: A comparison of sex-specific senescence patterns in a long-lived marine mammal

description: 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. 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. 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. 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.
description: Every Weddell seal pup born in the Erebus Bay study area has been
 marked in the interdigital webbing of the rear flippers with unique
 livestock tags. Each year surveys are conducted throughout the study area
 to record every seal present. This information has been processed to
 create encounter histories of individuals that were used in modeling
 age-specific probabilities of survival and detection.  
description: # A comparison of sex-specific senescence patterns in a long-lived marine
 mammal
 [https://doi.org/10.5061/dryad.4b8gthtp1](https://doi.org/10.5061/dryad.4b8gthtp1) ## Description of the data and file structure These data include encounter histories of Weddell seals that were born between 1982 and 2016 in the Erebus Bay study area. Encounter histories start at age 3 for each individual and include observations from 1985-2019. ### Files and variables #### File: EH\_female.rds **Description:** This file includes encounter histories of female Weddell seals from 1985-2019. The encounter history begins at age 3 for each individual. Each row is associated with an encounter history for a single individual. Each column represents each year of the encounter history.  The following values represent different states: 0: Zero represents an individual that was not recaptured in that year and has yet to be seen for the first time after age 2 or was not subsequently seen again after final recapture. 1: One represents an individual that was recaptured in that year.  2: Two represents an individual that was not recaptured in that year but was subsequently seen in a later year. #### File: EH\_male.rds **Description:** This file includes encounter histories of male Weddell seals from 1985-2019. The encounter history begins at age 3 for each individual. Each row is associated with an encounter history for a single individual. Each column represents each year of the encounter history.  The following values represent different states: 0: Zero represents an individual that was not recaptured in that year and has yet to be seen for the first time after age 2 or was not subsequently seen again after final recapture. 1: One represents an individual that was recaptured in that year.  2: Two represents an individual that was not recaptured in that year but was subsequently seen in a later year. ## Code/software The statistical computing program R will be required to load and view these data.