Age, state, environment, and season dependence of senescence in body mass

Svenja B. Kroeger, Daniel T. Blumstein, Kenneth B. Armitage, Jane M. Reid, Julien G. A. Martin

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)
15 Downloads (Pure)


Senescence is a highly variable process that comprises both age-dependent and state-dependent components and can be greatly affected by environmental conditions. However, few studies have quantified the magnitude of age-dependent and state-dependent senescence in key life-history traits across individuals inhabiting different spatially structured and seasonal environments. We used longitudinal data from wild female yellow-bellied marmots (Marmota flaviventer), living in two adjacent environments that differ in elevation and associated phenology, to quantify how age and individual state, measured as “time to death,” affect body mass senescence in different environments. Further, we quantified how patterns of senescence differed between two biologically distinct seasons, spring, and late summer. Body mass senescence had an age-dependent component, expressed as a decrease in mass in old age. Overall, estimated age-dependent senescence was greater in females living in the more favorable lower elevation environment, than in the harsher higher elevation environment, and greater in late summer than in spring. Body mass senescence also had a state-dependent component, captured by effects of time to death, but only in the more favorable lower elevation environment. In spring, body mass gradually decreased from 2 years before death, whereas in late summer, state-dependent effects were expressed as a terminal decrease in body mass in the last year of life. Contrary to expectations, we found that senescence was more likely to be observed under more favorable environmental conditions, rather than under harsher conditions. By further demonstrating that senescence patterns differ among seasons, our results imply that within-year temporal environmental variation must be considered alongside spatial environmental variation in order to characterize and understand the pattern and magnitude of senescence in wild populations.
Original languageEnglish
Pages (from-to)2050-2061
Number of pages12
JournalEcology and Evolution
Issue number4
Early online date18 Jan 2018
Publication statusPublished - Feb 2018

Bibliographical note

Funded by
Natural Environment Research Council
National Geographic Society
UCLA (Faculty Senate and the Division of Life Sciences)
Rocky Mountain Biological Laboratory research. Grant Numbers: DBI 0242960, 0731346
NSF. Grant Numbers: IDBR-0754247, DEB-1119660, DEB-1557130


  • aging
  • altitude
  • late life
  • lifespan
  • natural population
  • reverse age


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