Introduction

A central question in life history research is the extent of variation and potential constraints of life history traits within a species and between closely related species. The life history of any species is determined by developmental and reproductive rates as well as reproductive effort spent over its lifetime (Stearns, 1992). These traits are usually assessed by gestation length, number and size of offspring at birth, body mass and age at weaning, patterns of postnatal growth, age at first reproduction, interbirth interval, and lifespan. Intraspecific variation in life history pattern has been found in non-human primate species in the wild, and is often attributed to different socioecological factors such as social status, group size, predation risk, diet, and abiotic environmental conditions (Kappeler and Perreira, 2003; Jones, 2011). Thus, for example, in baboons, it was described that some life history patterns such as age at first reproduction or longevity are affected by rank and the quality of social bonds, matriline, nutritive condition and parasite load (e.g. Altmann and Alberts, 2003; Altmann et al., 2010, 2012; Silk et al., 2010; Gesquière et al., 2011). In a controlled laboratory setting, experimentally induced caloric restriction has been found to affect life history patterns such as longevity in rhesus macaques (Colman et al., 2009; but see Mattison et al., 2012 for contrary results in another colony). In mouse lemurs caloric restriction does not generally seem to affect aging (Dal-Pan et al., 2011), but lifespan was extended under caloric restriction when food was supplemented with resveratrol (Marchal et al., 2013). Interspecific life history variation is common between species of different primate lineages and forms the basis for life history theory (e.g. Stearns, 1992; Kappeler and Perreira, 2003; Zimmermann and Radespiel, 2007, 2014). It is postulated that life history trait variation between closely related species should be minor, due to a long common history in the past and the same phylogenetic constraints shaping life history (Harvey and Clutton-Brock, 1985; Kamilar and Cooper, 2013). Thus, it is important to understand which determinants modify the variation of life history patterns in a species to get insight into environmental and phylogenetic plasticity.