Age-Specific Survival in Five Populations of Ungulates: Evidence of Senescence

Abstract

Methodological problems in describing patterns of senescence in wild populations have until recently impeded progress in understanding the evolution of a process that decreases individual fitness. We investigated age-and sex-specific survival in five populations of three species of ungulates (roe deer, Capreolus capreolus; bighorn sheep, Ovis canadensis; and isard, Rupicapra pyrenaica), using recent statistical developments of capture-mark-recapture models and long-term (12 to 22 yr) data on marked individuals. The yearly survival of females aged 2-7 yr was remarkably similar and very high (92-95%) in all five populations. Survival of adult males varied among species and populations. Survival decreased from 8 yr onward for both sexes in all populations, suggesting that senescence was a common phenomenon. Male survival was lower than female survival, and the gender difference increased with age. The extent of sex differences in survival was related neither to sexual dimorphism in mass nor to the level of polygyny, suggesting that species differences in social behavior, particularly mating system and the level of malemale aggression, may be more important than simply the level of polygyny in explaining sexual differences in survival. Our results underline the advantages of long-term monitoring of marked individuals for the study of evolutionary ecology.

Factors Influencing Survival of Female Elk in a Harvested Population

“…We found that age was the only covariate included in top models with a significant relationship to survival. We found a weak negative relationship between age and survival, which was consistent with age-specific variation in survival found in other ungulate populations (Loison et al 1999;Gaillard et al 2000;Festa-Bianchet et al 2003). A negative relationship between survival and age in the Fort Riley population could be due to hunters avoiding harvesting a calf or yearling, and thereby increasing the mortality risk for adult female elk in older age-classes (Wright et al 2006).…”

A model for first‐estimates of species‐specific, age‐specific mortality from centralized band‐recovery databases

“…Compared to the metaanalysis technique of Promislow (1991) and the large-scale targeted data collection of studies such as Loison et al (1999), a mortality structure may be estimated for more species, using data that are already collected. Compared with the use of MRLs to estimate population mortality parameters, our technique gives a direct estimate of the complete mortality curve, rather than estimating a single parameter of it.…”

“…Some authors have built databases of mortality structures for multiple species (e.g., Promislow 1991, Loison et al 1999. However, these analyses have generally considered only a limited number of species for which the authors have been able to access high-cost population actuarial datasets, many of which have used transversal life-table approaches, and so relied on assumptions such as zero population growth in order to estimate mortality structure.…”

Reversal of response to artificial selection on body size in a wild passerine

“…In age-structured populations, the contribution of an individual to future generations (reproductive value) depends on age-specific transitions among different phenotypic categories affecting their fecundity and survival (Caughley, 1966;. For instance, natural mortality rates in large ungulates are typically low for prime aged adults, and higher for young and old individuals (Gaillard et al, 1998;Loison et al, 1999). Exploited populations will have harvest mortality interfering with natural mortality, changing the distribution of reproductive values by affecting age classes differently (Langvatn and Loison, 1999;Solberg et al, 2000;Engen et al, 2014b).…”