Lifetime reproductive success of female mountain gorillas

Abstract

Studies of lifetime reproductive success (LRS) are important for understanding population dynamics and life history strategies, yet relatively little information is available for long-lived species. This study provides a preliminary assessment of LRS among female mountain gorillas in the Virunga volcanoes region. Adult females produced an average of 3.6 ± 2.1 surviving offspring during their lifetime, which indicates a growing population that contrasts with most other great apes. The standardized variance in LRS (variance/mean(2) = 0.34) was lower than many other mammals and birds. When we excluded the most apparent source of environmental variability (poaching), the average LRS increased to 4.3 ± 1.8 and the standardized variance dropped in half. Adult lifespan was a greater source of variance in LRS than fertility or offspring survival. Females with higher LRS had significantly longer adult lifespans and higher dominance ranks. Results for LRS were similar to another standard fitness measurement, the individually estimated finite rate of increase (λ(ind) ), but λ(ind) showed diminishing benefits for greater longevity.

Quadratic relationships between group size and foraging efficiency in a herbivorous primate

“…Time spent feeding was significantly longer in larger groups, but the increase was only three percentage points across a three-fold variation in group size 39 . Dominance rank did also not have a significant effect on the energy intake rates or the proportion of time spent traveling, and rank-related differences in female reproductive success might be due to female quality rather than contest competition 41,50,51 . Thus, both types of intragroup feeding competition (WGS and WGC) appear to be weak in this species 44 .…”

Humans are not cooperative breeders but practice biocultural reproduction

“…It is important to distinguish LRE from a related measure called lifetime reproductive success (LRS). The LRS of a female equals the total number of surviving offspring that she produces in her lifetime (Robbins et al, 2011). It is well known that humans have the highest RS of all primates and a RS higher than many mammals (Bogin 2001;Walker et al, 2008).…”

What cortisol can tell us about the costs of sociality and reproduction among free‐ranging rhesus macaque females on Cayo Santiago

“…All three traits are characteristic of high-ranking in females in a number of primates, and thus high dominance status is generally a good predictor of high LRS [Pusey, 2012]. Another major predictor of variation in LRS in female primates is longevity: females that live longer produce more offspring [Rhine et al, 2000; Robbins et al, 2011]. In the rhesus population on Cayo Santiago, females begin reproducing at 3–4 years of age and attain full adult body size at approximately 5–6 years of age.…”

“…In species where rank increases with age, females who lived longer may have higher rank simply because they have had more time in which to achieve it [Robbins et al, 2011]. Some studies conducted with wild primate populations have provided data that support the prediction that high dominance status has survival benefits for adult females [Pusey, 2012].…”