Offspring Hormones Reflect the Maternal Prenatal Social Environment: Potential for Foetal Programming?

Females of many species adaptively program their offspring to predictable environmental conditions, a process that is often mediated by hormones. Laboratory studies have shown, for instance, that social density affects levels of maternal cortisol and testosterone, leading to fitness-relevant changes in offspring physiology and behaviour. However, the effects of social density remain poorly understood in natural populations due to the difficulty of disentangling confounding influences such as climatic variation and food availability. Colonially breeding marine mammals offer a unique opportunity to study maternal effects in response to variable colony densities under similar ecological conditions. We therefore quantified maternal and offspring hormone levels in 84 Antarctic fur seals (Arctocephalus gazella) from two closely neighbouring colonies of contrasting density. Hair samples were used as they integrate hormone levels over several weeks or months and therefore represent in utero conditions during foetal development. We found significantly higher levels of cortisol and testosterone (both P < 0.001) in mothers from the high density colony, reflecting a more stressful and competitive environment. In addition, offspring testosterone showed a significant positive correlation with maternal cortisol (P < 0.05). Although further work is needed to elucidate the potential consequences for offspring fitness, these findings raise the intriguing possibility that adaptive foetal programming might occur in fur seals in response to the maternal social environment. They also lend support to the idea that hormonally mediated maternal effects may depend more strongly on the maternal regulation of androgen rather than cortisol levels

Female reproductive competition explains variation in prenatal investment in wild banded mongooses

PublishedArticleFemale intrasexual competition is intense in cooperatively breeding species where offspring compete locally for resources and helpers. In mammals, females have been proposed to adjust prenatal investment according to the intensity of competition in the postnatal environment (a form of ‘predictive adaptive response’; PAR). We carried out a test of this hypothesis using ultrasound scanning of wild female banded mongooses in Uganda. In this species multiple females give birth together to a communal litter, and all females breed regularly from one year old. Total prenatal investment (size times the number of fetuses) increased with the number of potential female breeders in the group. This relationship was driven by fetus size rather than number. The response to competition was particularly strong in low weight females and when ecological conditions were poor. Increased prenatal investment did not trade off against maternal survival. In fact we found the opposite relationship: females with greater levels of prenatal investment had elevated postnatal maternal survival. Our results support the hypothesis that mammalian prenatal development is responsive to the intensity of postnatal competition. Understanding whether these responses are adaptive requires information on the long-term consequences of prenatal investment for offspring fitness.ER

Review of the global research on Hyaenidae and implications for conservation and management

1. Despite the ecological importance of the four extant species of Hyaenidae, and the threats they face globally, there has been no review of the nearly 100 years of published research on hyaenas, nor has there been a synthesis of management-related literature regarding these species. 2. We reviewed 907 studies on Hyaenidae, summarized broad temporal, geographic and topical trends, and evaluated findings from management-related research to determine ways forward for hyaena conservation management. Since the first known study in 1939, most have focused on spotted hyaena (Crocuta crocuta; 75% of all studies), yet overall publications for Hyaenidae have increased by 372% in recent decades. 3. Only 44 of the 67 hyaena range states were represented across publications, with nearly half of all studies conducted in Kenya (18%), South Africa (16%) and Tanzania (13%). Twenty-eight countries had fewer than five studies. Ecology and diet were the most-studied topic areas. The least-studied topics were disease and physiology. 4. Studies on human–hyaena interactions were highly variable in topic, with infrastructure impacts and Hyaenidae benefits to people covered the least. All species were reported to have consumed anthropogenic diet items. Mortality data were included within 11% of publications, with 79% of recorded hyaena mortality constituting anthropogenic causes, although there were few targeted studies on the subject. Lastly, 12% of publications involved community engagement in their methods. 5. There is a significant bias among species, topics and range states across Hyaenidae studies, and little data explicitly related to human–hyaena coexistence. Our management-focused synthesis suggests that research on Hyaenidae could better reflect large carnivore conservation and management inquiry by increasing studies focused on human interactions with Hyaenidae. To address research gaps and inform Hyaenidae management, we recommend increasing applied research outside of protected areas and using interdisciplinary, community-involved methods to increase foundational knowledge on understudied hyaena species, habitats and locations

Reproductive endocrinology of zoo-housed aardwolves

Knowledge regarding the relationship between endocrine parameters and reproductive activity can offer important insights into how social and environmental factors influence the reproductive success of mammals. Although components of both the physical and social environment affect endocrine regulation of reproduction, less is understood about the potential role of interactions between different endocrine axes on reproductive activity. We evaluated temporal patterns of reproductive and adrenocortical steroids in two male and three female aardwolves (Proteles cristata) housed in captivity at Brookfield Zoo, Chicago, USA. We found seasonal variation in faecal androgens, estrogens, and progestagens, which provide support for previous observations of the aardwolf as a seasonal breeder. However, the timing of peak endocrine activity did not correspond to observations from wild populations. Our interpretation is that this discrepancy is caused by photoperiodic regulation of reproductive activity. We found a positive relationship between faecal androgens and faecal glucocorticoid metabolites in males and a positive relationship between faecal estrogens and faecal glucocorticoid metabolites in females when housed with conspecifics but not when housed alone. We also found a positive but asymptotic relationship between faecal progestagens and faecal glucocorticoid metabolites. We argue that these observations indicate a potential effect of reproductive endocrine activity on the hypothalamic-pituitary adrenal axis, which could result in interesting physiological trade-offs in male reproductive tactics and female prepartum maternal investment because of the negative effects of long-term glucocorticoid elevation on reproductive performance. Finally, our results suggest that social and environmental factors interact in regulating many aspects of endocrine fluctuations in this mostly solitary species.D. Marneweck, F. Dalerum and A. Ganswindt were supported by the National Research Foundation of South Africa, and F. Dalerum and A. Ganswindt were further supported by research fellowships from University of Pretoria.http://acta.zbs.bialowieza.pl/hb2013ab201

Intrasexual competition and sexual selection in cooperative mammals

In most animals, the sex that invests least in its offspring competes more intensely for access to the opposite sex and shows greater development of secondary sexual characters than the sex that invests most1,2. However, in some mammals where females are the primary care-givers, females compete more frequently or intensely with each other than males3–5. A possible explanation is that, in these species, the resources necessary for successful female reproduction are heavily concentrated and intrasexual competition for breeding opportunities is more intense among females than among males. Intrasexual competition between females is likely to be particularly intense in cooperative breeders where a single female monopolizes reproduction in each group6. Here, we use data from a twelve-year study of wild meerkats (Suricata suricatta), where females show high levels of reproductive skew, to show that females gain greater benefits from acquiring dominant status than males and traits that increase competitive ability exert a stronger influence on their breeding success. Females that acquire dominant status also develop a suite of morphological, physiological and behavioural characteristics that help them to control other group members. Our results show that sex differences in parental investment are not the only mechanism capable of generating sex differences in reproductive competition and emphasize the extent to which competition for breeding opportunities between females can affect the evolution of sex differences and the operation of sexual selection