Is group size related to longevity in mammals?

Abstract

Life-history theory predicts that reduced extrinsic risk of mortality should increase species longevity over evolutionary time. Increasing group size should reduce an individual's risk of predation, and consequently reduce its extrinsic risk of mortality. Therefore, we should expect a relationship between group size and maximum longevity across species, while controlling for well-known correlates of longevity. We tested this hypothesis using a dataset of 253 mammal species and phylogenetic comparative methods. We found that group size was a poor predictor of maximum longevity across all mammals, as well as within primates and rodents. We found a weak but significant group-size effect on artiodactyl longevity, but in a negative direction. Body mass was consistently the best predictor of maximum longevity, which may be owing to lower predation risk and/or lower basal metabolic rates for large species. Artiodactyls living in large groups may exhibit higher rates of extrinsic mortality because of being more conspicuous to predators in open habitats, resulting in shorter lifespans.

Life histories and the evolution of cooperative breeding in mammals

“…marmots [50] and Siberian jays [51]). There is also no association between cooperative breeding and species differences in age of first reproduction or longevity, and a previous study between longevity and group size also suggested that differences in the pace of life are not linked to the evolution of sociality in mammals [52].…”

Untested assumptions about within-species sample size and missing data in interspecific studies

“…Moreover, body size differences can indicate differences in life history (see Vitone et al 2004;Webster et al 2004;Møller 2006b;Kamilar et al 2010), which may also involve factors that influence the probability of sampling. Accordingly, body mass was recorded as the mean mass of males and females from the breeding season, as reported by Cramp andPerrins (1977-1994).…”

What drives flexibility in primate social organization?

“…Intraspecific variation in primates has since been examined at several different levels of analysis, including among age/sex classes, across seasons or generations (temporal) within a single site, among groups within a single site, and among sites or populations (geographic) ( Table 1). However, despite its importance to understanding broad-scale patterns of diversity, studies examining intraspecific variation in primate behavior and ecology are comparatively sparse (Foster and Endler 1999;Kappeler et al 2013), and the large majority of comparative studies have continued to focus on species' norms (e.g., mean values) at the interspecific level (Clutton-Brock and Harvey 1977;Terborgh 1983;Sterck et al 1997;Lee 1999;Nunn 1999;Kamilar et al 2010).…”

“…The WorldClim database has been frequently used in comparative ecology studies to quantify abiotic conditions and, therefore, as a proxy for habitat characteristics (e.g., Graham et al 2012;Kamilar et al 2012;Kamilar and Beaudrot 2013). Furthermore, these data have been well correlated with habitat types on the ground (e.g., Kamilar et al 2010). The climate data were extracted for the geographic location of each site using ArcGIS 9.0.…”

“…The model with the lowest AICc value is considered the best and all models within two AICc units of this best model are also treated as equally good (Burnham and Anderson 2002). Using AICc (and related metrics) for model selection is becoming increasingly common in comparative biology research (Kamilar et al 2010Garamszegi 2011;Tecot et al 2012).…”