Survival improvements of marine mammals in zoological institutions mirror historical advances in human longevity.

An intense public debate has fuelled governmental bans on marine mammals held in zoological institutions. The debate rests on the assumption that survival in zoological institutions has been and remains lower than in the wild, albeit the scientific evidence in support of this notion is equivocal. Here, we used statistical methods previously applied to assess historical improvements in human lifespan and data on 8864 individuals of four marine mammal species (harbour seal, ; California sea lion, ; polar bear, ; common bottlenose dolphin, ) held in zoos from 1829 to 2020.

Species delineation and genetic structure of two species ( and ) on Madagascar and the Comoro archipelago.

Cryptic species diversity is known to be common in bats but remains challenging to study in these mammals, whose natural history traits render their sampling and monitoring challenging. For these animals, indirect genetic approaches provide a powerful tool to gain insight into the evolutionary history and ecology of cryptic bat species. The speciation history of the polyphyletic species group (Molossidae) is poorly understood, including those found on western Indian Ocean islands.

Lifespan decreases with proportion of sons in males but not females of zoo-housed tigers and lemurs.

Several studies have shown higher costs of rearing sons than daughters in mammals where males are larger than females. These studies typically focus on females by examining how the offspring sex ratio during a single reproductive event affected mothers' subsequent reproduction or survival probability. Here, we examine relationships between offspring sex ratio during single or multiple reproductive events and several survival metrics in mothers and fathers, using data from zoo-housed tigers (Panthera tigris) and ruffed lemurs (Varecia sp.

Sex-specific actuarial and reproductive senescence in zoo-housed tiger (Panthera tigris): The importance of sub-species for conservation.

A fifth of all known species are currently classified as threatened in the wild: the rate of biodiversity loss is rapid, continuous, and mostly due to anthropogenic activities. To slow down this decline, the accurate estimation of demographic parameters for threatened species is critical. With this aim, zoo institutions play an important role, giving access to data on zoo-housed animals, which aids researchers working on species life-history traits and intrinsic factors influencing the fitness of both sexes, such as age.

Pathogens Shape Sex Differences in Mammalian Aging.

Understanding the origin of sex differences in lifespan and aging patterns remains a salient challenge in both biogerontology and evolutionary biology. Different factors have been studied but the potential influence of pathogens has never been investigated. Sex differences, especially in hormones and resource allocation, generate a differential response to pathogens and thereby shape sex differences in lifespan or aging.

Variation in the ontogenetic allometry of horn length in bovids along a body mass continuum.

Allometric relationships describe the proportional covariation between morphological, physiological, or life-history traits and the size of the organisms. Evolutionary allometries estimated among species are expected to result from species differences in ontogenetic allometry, but it remains uncertain whether ontogenetic allometric parameters and particularly the ontogenetic slope can evolve. In bovids, the nonlinear evolutionary allometry between horn length and body mass in males suggests systematic changes in ontogenetic allometry with increasing species body mass.

Sex differences in adult lifespan and aging rates of mortality across wild mammals.

In human populations, women consistently outlive men, which suggests profound biological foundations for sex differences in survival. Quantifying whether such sex differences are also pervasive in wild mammals is a crucial challenge in both evolutionary biology and biogerontology. Here, we compile demographic data from 134 mammal populations, encompassing 101 species, to show that the female's median lifespan is on average 18.

Variation in actuarial senescence does not reflect life span variation across mammals.

The concept of actuarial senescence (defined here as the increase in mortality hazards with age) is often confounded with life span duration, which obscures the relative role of age-dependent and age-independent processes in shaping the variation in life span. We use the opportunity afforded by the Species360 database, a collection of individual life span records in captivity, to analyze age-specific mortality patterns in relation to variation in life span. We report evidence of actuarial senescence across 96 mammal species.

Maternal reproductive senescence shapes the fitness consequences of the parental age difference in ruffed lemurs.

In humans, pronounced age differences between parents have deleterious fitness consequences. In particular, the number of children is lower when mothers are much older than fathers. However, previous analyses failed to disentangle the influence of differential parental age from a direct age effect of each parent.

High reproductive effort is associated with decreasing mortality late in life in captive ruffed lemurs.

Evolutionary theories of senescence predict that a high allocation to reproduction during early life should have long-term deleterious consequences on future reproduction or survival because individuals have to face an energy allocation trade-off between reproductive effort and the maintenance of body condition. Using a high-quality dataset from 1,721 red ruffed lemurs (RRL, Varecia rubra) and 3,637 black and white ruffed lemurs (BWRM, V. variegata) living in captivity, we tested the existence of a trade-off between reproductive effort and late-life survival after accounting for possible confounding effects of natal environmental conditions.

Comparative analyses of longevity and senescence reveal variable survival benefits of living in zoos across mammals.

While it is commonly believed that animals live longer in zoos than in the wild, this assumption has rarely been tested. We compared four survival metrics (longevity, baseline mortality, onset of senescence and rate of senescence) between both sexes of free-ranging and zoo populations of more than 50 mammal species. We found that mammals from zoo populations generally lived longer than their wild counterparts (84% of species).

Does sexual selection shape sex differences in longevity and senescence patterns across vertebrates? A review and new insights from captive ruminants.

In most mammals, both sexes display different survival patterns, often involving faster senescence in males. Being under intense sexual competition to secure mating opportunities, males of polygynous species allocate resources to costly behaviors and conspicuous sexual traits, which might explain these observed differences in longevity and senescence patterns. However, comparative studies performed to date have led to conflicting results.

Does tooth wear influence ageing? A comparative study across large herbivores.

We test whether the intensity of tooth wear influences the strength of actuarial senescence across species of large herbivores. We collected from the literature data on tooth wear in the wild (measured as the slope of the regression of log-transformed M1 crown height on age), longevity (measured as the age at which 90% of individuals are dead) and two metrics of actuarial senescence in captive populations (rate of senescence between 6 and 12 years of age and Gompertz rate of senescence). Between-species differences and variation in tooth height accounted for most of the observed variation in tooth wear among large herbivores: tooth height and tooth wear were positively correlated.

Males do not senesce faster in large herbivores with highly seasonal rut.

Patterns of actuarial senescence vary among long-lived species. A proposed explanation of the evolution of species-specific senescence patterns is that increased levels of energy allocation to intra-male competition decrease the amount of energy available for somatic maintenance, leading to earlier or faster actuarial senescence. Previous studies did not provide support for such relationships, but did not focus on the intensity of allocation likely to shape inter-specific variation in actuarial senescence in males.