Recovery potential of a western lowland gorilla population following a major Ebola outbreak: results from a ten year study

Investigating the recovery capacity of wildlife populations following demographic crashes is of great interest to ecologists and conservationists. Opportunities to study these aspects are rare due to the difficulty of monitoring populations both before and after a demographic crash. Ebola outbreaks in central Africa have killed up to 95% of the individuals in affected western lowland gorilla (Gorilla gorilla gorilla) populations. Assessing whether and how fast affected populations recover is essential for the conservation of this critically endangered taxon. The gorilla population visiting Lokoué forest clearing, Odzala-Kokoua National Park, Republic of the Congo, has been monitored before, two years after and six years after Ebola affected it in 2004. This allowed us to describe Ebola's short-term and long-term impacts on the structure of the population. The size of the population, which included around 380 gorillas before the Ebola outbreak, dropped to less than 40 individuals after the outbreak. It then remained stable for six years after the outbreak. However, the demographic structure of this small population has significantly changed. Although several solitary males have disappeared, the immigration of adult females, the formation of new breeding groups, and several birth events suggest that the population is showing potential to recover. During the outbreak, surviving adult and subadult females joined old solitary silverbacks. Those females were subsequently observed joining young silverbacks, forming new breeding groups where they later gave birth. Interestingly, some females were observed joining silverbacks that were unlikely to have sired their infant, but no infanticide was observed. The consequences of the Ebola outbreak on the population structure were different two years and six years after the outbreak. Therefore, our results could be used as demographic indicators to detect and date outbreaks that have happened in other, non-monitored gorilla populations.     

Does breeding population trajectory and age of nesting females influence disparate nestling sex ratios in two populations of Cooper's hawks?

Offspring sex ratios at the termination of parental care should theoretically be skewed toward the less expensive sex, which in most avian species would be females, the smaller gender. Among birds, however, raptors offer an unusual dynamic because they exhibit reversed size dimorphism with females being larger than males. And thus theory would predict a preponderance of male offspring. Results for raptors and birds in general have been varied although population‐level estimates of sex ratios in avian offspring are generally at unity. Adaptive adjustment of sex ratios in avian offspring is difficult to predict perhaps in part due to a lack of life‐history details and short‐term investigations that cannot account for precision or repeatability of sex ratios across time. We conducted a novel comparative study of sex ratios in nestling Cooper's hawks (Accipiter cooperii) in two study populations across breeding generations during 11 years in Wisconsin, 2001–2011. One breeding population recently colonized metropolitan Milwaukee and exhibited rapidly increasing population growth, while the ex‐Milwaukee breeding population was stable. Following life‐history trade‐off theory and our prediction regarding this socially monogamous species in which reversed sexual size dimorphism is extreme, first‐time breeding one‐year‐old, second‐year females in both study populations produced a preponderance of the smaller and cheaper sex, males, whereas ASY (after‐second‐year), ≥2‐year‐old females in Milwaukee produced a nestling sex ratio near unity and predictably therefore a greater proportion of females compared to ASY females in ex‐Milwaukee who produced a preponderance of males. Adjustment of sex ratios in both study populations occurred at conception. Life histories and selective pressures related to breeding population trajectory in two age cohorts of nesting female Cooper's hawk likely vary, and it is possible that these differences influenced the sex ratios we documented for two age cohorts of female Cooper's hawks in Wisconsin.     

Morphological variation of introduced species: The case of American mink (Neovison vison) in Spain

We studied the morphology of American mink Neovison vison in five out of the six introduced populations in Spain. The spatial and temporal variation of body weight (BW), body length (BL), tail length, hind-foot length and ear length were analysed. Temporal trends in BW and BL in relation to years since mink introduction were also analyzed. In addition, we tested the effect of sex, age (juvenile, subadult and adult) and age–sex interaction, on each parameter. Morphological parameters differed between populations, illustrating the high variability of body size of American mink in different environments, and the phenotypic plasticity of the species. Annual variations were synchronized between populations, suggesting a large-scale effect on all of them. BW and BL showed a decreasing trend in both males and females in relation to years since introduction. This decrease may be related to mink's diet. Differences in sex and age were found, pointing to sexual dimorphism in adults, subadults and juveniles. The dimorphism in non-adult individuals suggests that subadult males may have a competitive advantage from subadult females in feeding and/or hunting on bigger prey from an early age (resource partitioning hypothesis).     

Genetic structure,spatial organization,and dispersal in two populations of bat‐eared foxes

We incorporated radio‐telemetry data with genetic analysis of bat‐eared foxes (Otocyon megalotis) from individuals in 32 different groups to examine relatedness and spatial organization in two populations in South Africa that differed in density, home‐range sizes, and group sizes. Kin clustering occurred only for female dyads in the high‐density population. Relatedness was negatively correlated with distance only for female dyads in the high‐density population, and for male and mixed‐sex dyads in the low‐density population. Home‐range overlap of neighboring female dyads was significantly greater in the high compared to low‐density population, whereas overlap within other dyads was similar between populations. Amount of home‐range overlap between neighbors was positively correlated with genetic relatedness for all dyad‐site combinations, except for female and male dyads in the low‐density population. Foxes from all age and sex classes dispersed, although females (mostly adults) dispersed farther than males. Yearlings dispersed later in the high‐density population, and overall exhibited a male‐biased dispersal pattern. Our results indicated that genetic structure within populations of bat‐eared foxes was sex‐biased, and was interrelated to density and group sizes, as well as sex‐biases in philopatry and dispersal distances. We conclude that a combination of male‐biased dispersal rates, adult dispersals, and sex‐biased dispersal distances likely helped to facilitate inbreeding avoidance in this evolutionarily unique species of Canidae.     

New evidence from observations of progressions of mandrills (Mandrillus sphinx): a multilevel or non-nested society?

African papionins are well known for the diversity of their social systems, ranging from multilevel societies based on one-male-multifemale units (OMUs) to non-nested societies. However, the characteristics of Mandrillus societies are still unclear due to difficult observational conditions in the dense forests of central Africa. To elucidate the characteristics of mandrill societies and their social systems, I analysed the age–sex compositions, behaviours, and progression patterns of their horde/subgroups using videos of them crossing open places. The progressions were very cohesive, and the very large aggregations (169–442 individuals) had only 3–6 adult males (1.4–1.8 % of all individuals) and 11–32 subadult males (6.5–7.2 %). No herding behaviours were observed in the males, and most of the small clusters within the progressions were not analogous to the OMUs of a multilevel society but instead consisted of only adult females and immatures. The progressions of alert mandrills showed patterns similar to those observed in a non-nested social system: females with dependent infants were concentrated toward the rear and adult and subadult males toward the front. These results suggest that cohesive aggregations and a female-biased sex ratio are common characteristics of mandrill species. Mandrills may form female-bonded and non-nested societies, although their fission–fusion dynamics may be different from those typical of savannah baboons.     

Proximate causes of sexual size dimorphism in Colorado pikeminnow, a long‐lived cyprinid

Evidence for sexual size dimorphism (SSD) and its possible causes were examined in the endangered Colorado pikeminnow Ptychocheilus lucius, a large, piscivorous, cyprinid endemic to the Colorado River system of North America. Individuals representing 18–24% of the upper Colorado River population were captured, measured, sexed and released in 1999 and 2000. Differing male and female total length‐(L_T) frequency distributions revealed SSD with females having greater mean and maximum sizes than males. Although both sexes exhibit indeterminate post‐maturity growth, growth trajectories differed. The point of trajectory divergence was not established, but slowed male growth might coincide with the onset of maturation. Differing growth rate was the dominant proximate cause of SSD, accounting for an estimated 61% of the observed difference in mean adult L_T. The degree of SSD in adults, however, was also related to two other factors. Evidence suggests males become sexually active at a smaller size and earlier age than females; a 2 year difference, suggested here, accounted for an estimated 12% of the between‐sex difference in mean adult L_T. Temporal shifts in gender‐specific survival accounted for an additional 27% of the observed between‐sex difference in mean adult L_T. Estimated age distributions indicated a higher number of older females than older males and more younger males than younger females in the population during the period of sampling. Dissimilarity of age distributions was an unexpected result because the male : female population sex ratio was 1 : 1 and estimates of long‐term annual survival for adult males and females were equal (88%). Future assessments of SSD in this population are apt to vary depending on the prior history of short‐term gender‐specific survival. Without recognizing SSD, non‐gender‐specific growth curves overestimate mean age of adult females and underestimate mean age of adult males of given L_T. Assuming age 8 years for first reproduction in males and age 10 years for females, the adult male : female ratio was estimated as 1·1 : 1 and mean adult age, or generation time, was estimated as 16·4 years for males and 18·4 years for females.     

Demography and life history of Thomas langurs (Presbytis thomasi)

Life history data from wild primate populations are necessary to explain variation in primate social systems and explain differences between primates and other mammals. Here we report life history data from a 12.5-year study on wild Thomas langurs. Mean age at first reproduction was 5.4 years and the sex ratio at birth was even. The mean interbirth interval (IBI) after a surviving infant was 26.8 mo, after nonsurviving infants 17.7 mo, and combined 22.0 mo. Mean annual birth rate of adult females was 0.44, while reaching a peak at 6 years of age and showing no decrease with age. Mortality was highest during the first year of life (48.0% for males and 43.0% for females) and consistently higher for males than females. The oldest female observed during the study was estimated to be 20 years of age, whereas the oldest male disappeared at age 13 years, indicating that males die at a much earlier age than females. A Leslie matrix based on these estimates yielded a growth rate of 1.01, which is comparable to the nonsignificant increase in density indicated by our long-term field data. A comparison with life history data for sympatric frugivorous primates suggests that folivory might be associated with faster life history.     

Using multivariate adaptive regression splines to estimate subadult age from diaphyseal dimensions

Subadult age estimation is considered the most accurate parameter estimated in a subadult biological profile, even though the methods are deficient and the samples from which they are based are inappropriate. The current study addresses the problems that plague subadult age estimation and creates age estimation models from diaphyseal dimensions of modern children. The sample included 1,310 males and females between the ages of birth and 12 years. Eighteen diaphyseal length and breadth measurements were obtained from Lodox Statscan radiographic images generated at two institutions in Cape Town, South Africa, between 2007 and 2012. Univariate and multivariate age estimation models were created using multivariate adaptive regression splines. k‐fold cross‐validated 95% prediction intervals (PIs) were created for each model, and the precision of each model was assessed. The diaphyseal length models generated the narrowest PIs (2 months to 6 years) for all univariate models. The majority of multivariate models had PIs that ranged from 3 months to 5 and 6 years. Mean bias approximated 0 for each model, but most models lost precision after 10 years of age. Univariate diaphyseal length models are recommended for younger children, whereas multivariate models are recommended for older children where the inclusion of more variables minimized the size of the PIs. If diaphyseal lengths are not available, multivariate breadth models are recommended. The present study provides applicable age estimation formulae and explores the advantages and disadvantages of different subadult age estimation models using diaphyseal dimensions. Am J Phys Anthropol 154:376–386, 2014. © 2014 Wiley Periodicals, Inc.     

Lifetime patterns of pairing success in male Ortolan Buntings Emberiza hortulana

Analyses of lifetime fitness in birds are typically based on estimates of breeding success, in particular the number of offspring fledged. Small and isolated bird populations often have a male‐skewed adult sex ratio, so that male lifetime productivity depends to a large degree on pairing success, but few studies have focused on patterns of lifetime pairing success. The Norwegian population of Ortolan Buntings Emberiza hortulana is strongly male‐skewed, such that in any year about half of all males are unpaired. Pairing success of first‐year males (16–44%) was significantly lower than for older males (52–89%). Lifetime pairing success was correlated with lifespan and was strongly skewed, with a majority of males being paired only once or never, and only 11% paired three or more times despite a stable lifetime annual survival rate of 63%. Males that were paired in one year were more likely to be paired the next year than males that were unpaired in the previous year. The shortage of females caused even the older males to have a substantial probability of becoming unpaired, and 49% of long‐lived males (known as adults for at least 4 years) were unpaired after years in which they were paired. Pairing success in the Ortolan Bunting therefore follows similar age‐related and lifetime patterns in breeding success documented in other species. However, even the older males ran a high risk of not being paired, contrasting with earlier distinctions between pre‐breeding and breeding lifespans. I discuss the importance of knowledge of pairing success for the management of endangered and declining populations.     

Can a spider web be too sticky? Tensile mechanics constrains the evolution of capture spiral stickiness in orb-weaving spiders

Owing to habitat loss and fragmentation, large mammal populations all over the world are becoming increasingly small and isolated. It is therefore a conservation priority to understand mechanisms influencing the demography of such populations, which can easily be driven to extinction. The Przewalski's horse Equus ferus przewalskii remains one of the world's most endangered species and reintroduced animals are still vulnerable. Over 9 years, we analysed factors affecting mortality and female fecundity at the individual level in a predator-free, closed population of Przewalski's horses, which grew from 11 to 55 individuals. Similar to other wild equids, the annual growth rate of the population was r =0.169. Typically, adult mortality was much lower than juvenile mortality, the latter being correlated with neither inbreeding coefficient of foals nor population density. We found no link between female fecundity and operational sex ratio of the herd, or inbreeding coefficient, lactation status and body condition of the mares. Although food therefore seemed not to be limiting in this population, density (number of horses ha⁻¹) clearly reduced fecundity, especially in subadult mares. Thus, our results show that space can slow the growth rate of a population before resources become limited, a potential source of concern for increasingly shrinking habitats of endangered large mammals. Possible mechanisms causing this may be found in incest avoidance or other social parameters. Finally, in large herbivores, population density is said to exert influence in a sequential order: juvenile survival first, followed by fecundity of young females, then adult females, and adult survival last. Although we observed no link between density and juvenile survival in the studied population, our results otherwise support this hypothesis.     

Survival,density and population composition of bellbirds (Anthornis melanura) on the Poor Knights Islands,New Zealand

Abstract

Annual survival by age, sex and population size and structure were estimated for bellbirds (Anthornis melanura) from a banding study undertaken on 66 ha Aorangi Island, the Poor Knights Islands, during the period 1978–86. The most parsimonious model showed that survival varied little with age and between years, and survival of males was significantly greater than that of females. Recapture probabilities of males and females were similar, but did vary with age and among years. There was a greater proportion of adult males than adult females and sub‐adult males and females in the population, and among adults the male bias in the population was greater during the breeding season than at other times of the year. The high density of bellbirds on the Poor Knights and larger size of males may explain the reduced survival of females relative to that of males.     

Effects of Isolation on Stress Responses to Novel Stimuli in Subadult Chickens (Gallus gallus)

Extensive research has examined the effects of social isolation in neonatal and adult animal populations, but few studies have examined the effect of social isolation in early adulthood. Animals reaching reproductive age often experience extensive social changes as they leave their natal site, and a social stressor like isolation may uniquely affect this age group. Furthermore, adolescence is a time when sex differences in behavior become more pronounced. As such, the effects of social stressors are likely to vary by sex. In this study, we used noninvasive methods to evaluate stress responses to social change in male and female subadult chickens (Gallus gallus). Half of the birds experienced regular sessions of social isolation over the course of 2 wk, while the other half were never isolated. Subsequently, all of the animals were exposed to a suite of three novel probes, including an open‐field test. We monitored the birds’ behavioral (head movements) and physiological (fecal glucocorticoid metabolites, FGM) response to the tests. Our results indicate that, for subadult chickens, the effect of social isolation is sex dependent: Male FGM and behavioral responses did not change with subsequent experiences, in contrast to females. Females also exhibited more social reinstatement behavior compared to males. Our results are consistent with the expectations of differences between the sexes based on changes in the social environment due to sex‐biased dispersal patterns. For both sexes, the FGM and behavioral responses varied independently, which highlights the necessity for multiple measures of stress in animal populations.     

Population ecology of the velvet gecko,Oedura lesueurii in south eastern Australia: Implications for the persistence of an endangered snake

Abstract Ecological specialization, such as major dependence upon a single‐prey species, can render a predator taxon vulnerable to extinction. In such cases, understanding the population dynamics of that prey type is important for conserving the predator that relies upon it. In eastern Australia, the endangered broad‐headed snake Hoplocephalus bungaroides feeds largely on velvet geckos (Oedura lesueurii). We studied growth, longevity and reproduction in a population of velvet geckos in Morton National Park in south‐eastern Australia. We marked 458 individual geckos over a 3‐year period (1992–1995) and made yearly visits to field sites from 1995–2006 to recapture marked individuals. Female geckos grew larger than males, and produced their first clutch at age 4 years. Males can mature at 2 years, but male–male combat for females probably forces males to delay reproduction until age 3 years. Females lay a single clutch of two eggs in communal nests in November, and up to 22 females deposited eggs in a single nest. Egg hatching success was high (100%), and juveniles had high survival (76%) during their first 6 months of life. Velvet geckos are long‐lived, and the mean age of marked animals recaptured after 1995 was 6.1 years (males) and 8.4 years (females). Older females (7.5–9.5 years) were all gravid when last recaptured. Like other temperate‐climate gekkonids, O. lesueurii has a ‘slow’ life history, and population viability could be threatened by any factors that increase egg or adult mortality. Two such factors – the removal of ‘bush rocks’ for urban gardens, and the overgrowth of rock outcrops by vegetation – could render small gecko populations vulnerable to extinction. In turn, the reliance of predatory broad‐headed snakes on this slow‐growing lizard species may increase its vulnerability to extinction.     

Sex‐specific density‐dependent secretion of glucocorticoids in lizards: insights from laboratory and field experiments

Negative density feedbacks have been extensively described in animal species and involve both consumptive (i.e. trophic interactions) and non‐consumptive (i.e. social interactions) mechanisms. Glucocorticoids are a major component of the physiological stress response and homeostasis, and therefore make a good candidate for proximate determinants of negative density feedbacks. Here, we combined laboratory and field experiments with enclosed populations to investigate the relationship between density, social stress and plasma corticosterone levels in the common lizard Zootoca vivipara. This species exhibits strong negative density feedbacks that affect females more than males, and its life history is sensitive to experimentally‐induced chronic elevation of corticosterone plasma levels. We found that prolonged crowding in the laboratory can trigger a chronic secretion of corticosterone independent from food restriction. In the field experiments, corticosterone levels of females were not affected by population density. Corticosterone levels of males increased with population density but only during the late activity season in a first field experiment where we manipulated density. They also increased with density during the mating season but only in populations with a female‐biased sex ratio in a second field experiment where we crossed manipulated density and adult sex ratio. Altogether, our results provide limited evidence for a role of basal corticosterone secretion in density feedbacks in this species. Context and density‐dependent effects in males may arise from changes in behavior caused by competition for resources, male–male competition, and mating.     

Group Choice by Subadult Bighorn Rams: Trade-offs between Foraging Efficiency and Predator Avoidance

In addition to sexual segregation, many social ungulates show varying degrees of age segregation, especially among males. We investigated factors affecting group choice by subadult male bighorn sheep, using census data collected between 1982 and 1998 in a marked population. We examined whether group composition varied with population size and structure. Changes in total population size were correlated with the number of yearling males and yearling females, but not with the size of other sex-age classes. In years of high population size, female groups were larger than in years of low population size, while mixed sex-age and subadult groups showed a nonsignificant trend in the same direction. Typical group sizes of bachelor groups and the occurrence of mixed or bachelor groups were not affected by population size. When there were few subadult males in the population, groups of subadult males were less frequent than in years with many subadult males in the population, but the typical group size did not change. Subadult males were rarely seen in peer groups, and switched from female groups in spring to bachelor groups in autumn. An individual's choice of group type is affected by its body mass, but also by the availability of enough potential group mates to provide sufficient predator-detection efficiency.     

Sex allocation and sex‐specific parental investment in an endangered seabird

Biased offspring sex ratio is relatively rare in birds and sex allocation can vary with environmental conditions, with the larger and more costly sex, which can be either the male or female depending on species, favoured during high food availability. Sex‐specific parental investment may lead to biased mortality and, coupled with unequal production of one sex, may result in biased adult sex ratio, with potential grave consequences on population stability. The African Penguin Spheniscus demersus, endemic to southern Africa, is an endangered monogamous seabird with bi‐parental care. Female adult African Penguins are smaller, have a higher foraging effort when breeding and higher mortality compared with adult males. In 2015, a year in which environmental conditions were favourable for breeding, African Penguin chick production on Bird Island, Algoa Bay, South Africa, was skewed towards males (1.5 males to 1 female). Males also had higher growth rates and fledging mass than females, with potentially higher post‐fledging survival. Female, but not male, parents had higher foraging effort and lower body condition with increasing number of male chicks in their brood, thereby revealing flexibility in their parental strategy, but also the costs of their investment in their current brood. The combination of male‐biased chick production and higher female mortality, possibly at the juvenile stage as a result of lower parental investment in female chicks, and/or at the adult stage as a result of higher parental investment, may contribute to a biased adult sex ratio (ASR) in this species. While further research during years of contrasting food availability is needed to confirm this trend, populations with male‐skewed ASRs have higher extinction risks and conservation strategies aiming to benefit female African Penguin might need to be developed.     

What lies beneath? Population dynamics conceal pace‐of‐life and sex ratio variation,with implications for resilience to environmental change

Life‐history and pace‐of‐life syndrome theory predict that populations are comprised of individuals exhibiting different reproductive schedules and associated behavioural and physiological traits, optimized to prevailing social and environmental factors. Changing weather and social conditions provide in situ cues altering this life‐history optimality; nevertheless, few studies have considered how tactical, sex‐specific plasticity over an individual's lifespan varies in wild populations and influences population resilience. We examined the drivers of individual life‐history schedules using 31 years of trapping data and 28 years of pedigree for the European badger (Meles meles L.), a long‐lived, iteroparous, polygynandrous mammal that exhibits heterochrony in the timing of endocrinological puberty in male cubs. Our top model for the effects of environmental (social and weather) conditions during a badger's first year on pace‐of‐life explained <10% of variance in the ratio of fertility to age at first reproduction (F/α) and lifetime reproductive success. Conversely, sex ratio (SR) and sex‐specific density explained 52.8% (males) and 91.0% (females) of variance in adult F/α ratios relative to the long‐term population median F/α. Weather primarily affected the sexes at different life‐history stages, with energy constraints limiting the onset of male reproduction but playing a large role in female strategic energy allocation, particularly in relation to ongoing mean temperature increases. Furthermore, the effects of social factors on age of first reproduction and year‐to‐year reproductive success covaried differently with sex, likely due to sex‐specific responses to potential mate availability. For females, low same‐sex densities favoured early primiparity; for males, instead, up to 10% of yearlings successfully mated at high same‐sex densities. We observed substantial SR dynamism relating to differential mortality of life‐history strategists within the population, and propose that shifting ratios of ‘fast’ and ‘slow’ life‐history strategists contribute substantially to population dynamics and resilience to changing conditions.     

The African savannah elephant population in Kidepo Valley National Park, Uganda: changes in size and structure from 1967 to 2000

The age and sex structure of the elephant population in Kidepo Valley National Park were studied using recognition files. Moreover, population trends were reviewed using past studies. From 1967 to 2000, the elephant population varied between 200 and 500 individuals. Of the minimum number of 374 elephants found to use the Park, 352 were individually identified. Seventy‐nine per cent of these were recorded in 29 families ranging from three to 22 animals with a mean group size of ten. Young animals dominated the population (45% aged 0–9.9 years), while 11% were 10–14.9 years of age and only 18% over 25 years of age. Overall, males constituted 45% of the population, but only 32% of the individuals in the 10–14.9‐year age class were males. Individuals ≥15 years of age displayed a skewed sex ratio of 1 : 1.4 in favour of females. The extent of skew was greatest among mature animals (≥25 years of age), which had four times as many females as males. The skewed age structure in the year 2000 caused by poaching and drought, led to a significant difference between the age distribution in 1970 and 2000. Recent counts suggest that the Kidepo elephant population may be increasing.     

Rank relations of juvenile and subadult natal males of Barbary macaques (Macaca sylvanus) at Affenberg Salem

Rank relations of more than 100 juvenile and subadult natal Barbary macaque males were analyzed. Hierarchical relations among individuals of the same age were established early during the first year of life. With few exceptions concerning infants from very high-ranking genealogies, males dominated female peers regardless of maternal rank. Males started to outrank females from older cohorts during the second year of life and completed the process of rank reversal with adult females at 5-6 years of age. An age-graded dominance pattern existed among males from different birth cohorts. Only 3 rank reversals between males from different cohorts were observed. Rank reversals among males of the same birth cohort occurred more frequently. Rank position of a male among his male peers was influenced by birth order, by maternal rank, and by the presence of juvenile brothers. Most males without juvenile brothers had low positions, regardless of maternal rank. Males born late in the birth season were also low-ranking, even when juvenile brothers were present. There was no cohort where ranking among males was determined by maternal rank alone, as is the case in rhesus monkeys and Japanese macaques. Adult/subadult male carriers had no noticeable effect on rank positions of 'their' infants. It is suggested that a weaker influence of Barbary macaque mothers on rank of their sons is related to very early integration of male infants in male social/play groups.     

Life history parameters and diet of Risso's dolphins,Grampus griseus,from southeastern South Africa

The life history of Risso's dolphins (Grampus griseus) remains poorly known and data from strandings can help provide important information. Data from 126 Risso's dolphins stranded or bycaught along the southeastern coastline of South Africa between 1958 and 2017 were analyzed in relation to their sex, age structure, and diet. Mean estimated length at birth was 146.9 cm, while maximum length was 325 cm for males and 313 cm for females; small sample sizes precluded detailed examination of sexual dimorphism. Age estimates for 33 individuals (14 males, 17 females, 2 unknown sex) indicated a maximum age of 13 years (males) and 17 years (females), respectively; the oldest animal was 19 years (unknown sex). Mean length and age at attainment of sexual maturity were estimated at 280 cm and 7.1 years in males and at 282 cm and 7.7 years in females. Stomach contents from 27 individuals showed that diets of immature and mature males and females overlapped and consisted predominantly of cephalopods. Reported strandings decreased between 2000 and 2017, possibly due to a lack of reporting associated with a ban on driving on beaches or related to the collapse of the local “chokka” squid (Loligo reynaudii) fishery in 2014–2015.