Increased juvenile survival may not be universally linked to longevity: ecological, social and life-history drivers of age-specific mortality in birds

Abstract

A classical prediction of the traditional evolutionary theories of ageing (tETA) is that longevity should be positively correlated with survival early on in life. However, large and unexplained variation exists in juvenile survival-longevity combinations. Here, we provide the first comparative study investigating the life-history, ecological and social correlates of juvenile survival, longevity and their combinations in 204 bird species. Overall, both measurements were positively correlated, but multiple survivals combinations evolved, some in accordance with tETA ("positive JS-L combinations") while others contrasting it ("JS-L mismatches"). Positive JS-L combinations covaried with the pace of life proxies, whereas mismatching combinations covaried with the growing season length, where long growing seasons promoted juvenile survival, while short growing seasons promoted longevity. Interestingly, sociality explained only positive combinations, while life-history and ecological traits explained both positive and mismatching combinations. Overall, these findings challenge a main prediction of the tETA, and identify key evolutionary forces driving the coevolution between juvenile survival and longevity.