Food availability affects adult survival trajectories depending on early developmental conditions

Abstract

Food availability modulates survival in interaction with (for example) competition, disease and predators, but to what extent food availability in natural populations affects survival independent of these factors is not well known. We tested the effect of food availability on lifespan and actuarial senescence in a large population of captive zebra finches by increasing the effort required to obtain food, reflecting natural contrasts in food availability. Food availability may not affect all individuals equally and we therefore created heterogeneity in phenotypic quality by raising birds with different numbers of siblings. Low food availability had no effect on lifespan for individuals from benign developmental conditions (raised in small broods), but shortened lifespan for individuals from harsh developmental conditions. The lifespan difference arose through higher baseline mortality rate of individuals from harsh developmental conditions, despite a decrease in the rate of actuarial senescence. We found no evidence for sex-specific environmental sensitivity, but females lived shorter than males due to increased actuarial senescence. Thus, low food availability by itself shortens lifespan, but only in individuals from harsh developmental conditions. Our food availability manipulation resembles dietary restriction as applied to invertebrates, where it extends lifespan in model organisms and we discuss possible reasons for the contrasting results.

Male but not female zebra finches with high plasma corticosterone have lower survival

“…By 1 March 2017, 61 of the 91 birds (67%) sampled in 2014 and 59 of the 120 birds (49%) sampled in 2015 had died a natural death, well in agreement with the age‐dependent survival rates we observed in this population (Briga et al., ). Some birds ( N = 49) were sampled twice, and of the 162 birds sampled in total, 107 (66%) had died (Table S1).…”

“…Males with higher SI‐CORT concentrations had higher mortality (Figure ; z = 3.37, p = .0007), while there was no discernible association between SI‐CORT and survival in females (Figure ; z = 0.33, p = .74). Additionally, as previously observed in this population (Briga et al., ), there was an effect of sex on survival, independently of CORT variables, with females having lower survival than males (Figure ; Table ). These results remained unchanged when controlling for early and late environmental conditions: rearing brood size, foraging treatment and their interaction (Table S2).…”

Early‐life telomere length predicts lifespan and lifetime reproductive success in a wild bird

“…The probability of survival from fledging onwards was not predicted by early‐life TL or sex, but did depend on hatch year (Survival analysis; Table a), with individuals that hatched in 2010 having a longer lifespan than the birds hatched in other years (Supporting Information Figure ). Effects of developmental conditions may be age‐dependent (Briga, Koetsier, Boonekamp, Jimeno, & Verhulst, ), and we therefore analysed the association between TL and survival in more detail. The probability of surviving the first 12 months (early‐life survival) was not predicted by TL (Table b and Figure ), whilst controlling for sex and hatch year (see Supporting Information Figure a showing no association between TL and lifespan for individuals that died within 12 months).…”

What have humans done for evolutionary biology? Contributions from genes to populations

“…In demography it has improved estimates of population-level parameters such as life-expectancy and demographic rates [35] and, in ecology and evolution, it has been used to quantify ageing rates [37,38], developmental plasticity, and behavioural syndromes [39]. Other examples of knowledge transfer from human to non-human systems include the occurrence of latelife mortality plateaus [40] and the convergence of mortality rates of high-and low-quality cohorts [41], both described in humans long before in any other species [42][43][44]. Many concepts originating from human demographic research have, therefore, provided key insights that are applicable far beyond humans.…”