Survivorship patterns in captive mammalian populations: implications for estimating population growth rates

Abstract

For species of conservation concern, ecologists often need to estimate potential population growth rates with minimal life history data. We use a survivorship database for captive mammals to show that, although survivorship scale (i.e., longevity) varies widely across mammals, survivorship shape (i.e., the age-specific pattern of mortality once survivorship has been scaled to maximum longevity) varies little. Consequently, reasonable estimates of population growth rate can be achieved for diverse taxa using a model of survivorship shape along with an estimate of longevity. In addition, we find that the parameters of survivorship shape are related to taxonomic group, a fact that may be used to further improve estimates of survivorship when full life history data are unavailable. Finally, we compare survivorship shape in captive and wild populations of the same species and find higher adult survivorship in captive populations but no corresponding increase in juvenile survivorship. These differences likely reflect a convolution of true differences in captive vs. wild survivorship and the difficulty of observing juvenile mortality in field studies.

Age‐related variation and temporal patterns in the survival of a long‐lived scavenger

“…Although evolutionary models predict that the negative effects of senescence should start at the age of first reproduction (Hamilton 1966), some authors consider that the joint opposite effects of an early life increase in performance and senescence should result in high and relatively stable performance in young adults (see Ricklefs 1998 for a discussion on mortality). This expectation is in agreement with numerous recent empirical results (see several examples for birds and mammals in Jones et al 2008 and an analysis of mammal survivorship patterns in Lynch et al 2010), in which organisms exhibit an increase in performance at young ages, a plateau of maximal performance during adulthood, and a decrease at old ages. Consequently, an individual lifetime can be divided into three different periods (Stearns 1992): youth, adulthood and senescent age.…”

In pursuit of peak animal welfare; the need to prioritize the meaningful over the measurable

“…Notwithstanding the slaughter or culling of captive animals, intensive captive environments for many species can be highly effective in safeguarding the physical health of animals in comparison to life in the wild where longevity is frequently curtailed by factors that can be readily eliminated in captivity (see Collins & Kays, ; Fraser ; Hill et al, ; Kaiser, Brasch, Castell, Schulz, & Clauss, ; Korte et al, ; Larson, Colchero, Jones, Williams, & Fernandez‐Duque, ; Lynch, Zeigler, Wells, Ballou, & Fagan, ; Mason, ). There are of course notable exceptions where the potential benefits afforded by captivity have not been realised (see Mason et al, ), often due to the inadequacy of prevailing husbandry practices as has been the case historically with elephants ( Elaphus maximus, Loxodonta africana) (see Clubb et al, ) and orang‐utan ( Pongo spp.)…”

Diet has independent effects on the pace and shape of aging in Drosophila melanogaster

“…Several researchers have suggested that we should compare survivorship on a time-standardized scale (e.g. Pearl 1928 ; Pearl and Miner 1935 ; Izmaylov et al 1993 ; Kowald et al 1993 ; Lee and Goldstein 2003 ; Carnes et al 2006 ; Lynch et al 2010 ; Baudisch 2011 ) and this approach has been adopted by many recent aging studies (Lynch et al 2010 ; Baudisch 2011 ; Baudisch et al 2013 ; Jones et al 2014 ; Bansal et al 2015 ).…”