Principal Investigator: Professor Tim Clutton-Brock, FRS
Supported by an ERC Advanced grant, we currently run research into the development and behaviour of Damaraland mole-rats (Fukomys damarensis). We maintain around sixty breeding colonies of mole-rats in tube systems (4-16m tubing/ group) at our study site in the South African Kalahari; all animals (c.300 at any time) are individually marked; and our work involves the regular measurement, weighing and hormonal monitoring of all individuals in our colonies. In addition, we monitor and experiment with wild colonies both at the KRC and elsewhere in the Southern Kalahari.
Damaraland mole-rats are a cooperative or eusocial species living in southern Africa. They live in groups of up to 40 individuals with one female monopolising reproduction and supressing all other females of the group. The colonies forage by cooperatively building extensive burrows that provide access to tubers and roots which are the sole source of food and water. All colony members contribute to establishing one or several communal food stores and provide care (huddling, retrieving) to offspring born to the single reproductive female. Damaraland mole-rat life-histories appear to be broadly similar to those of naked mole-rats though Damaralands more commonly outbreed and males are larger than females.
The aim of the project is to provide an integrated understanding of social evolution and organisation in mammalian societies. In particular, we aim to understand the causes and consequences of individual differences in cooperative behaviour and growth and to determine whether they represent alternative strategies which maximise direct and indirect components of fitness or whether they are a non-adaptive consequence of environmental or social constraints. To do this we are investigating the effects of condition and maternal hormones on behaviour, growth and reproductive success in captive and wild Damaraland mole-rats. We are also investigating the effects of variation in the size, timing and sex ratio of litters on development and cooperative behaviour. Finally, we are exploring the social and ecological factors affecting rates of aging in breeders and helpers.
Our facilities in the Kalahari allow for experiments at the colony level and provide one of the few opportunities to gain causal understanding of the effects of physical and social environment on behavioural organisation of mole-rat societies. We use manipulations of group composition (size, kinship), food availability, growth rates and endocrine parameters to investigate the consequences for reproductive suppression, division of labour, adaptive plasticity, telomere dynamics, oxidative stress and the expression of maternal effects.
Current research is investigating:
- the dynamic of colonies
- the extent and causes of reproductive suppression
- the division of labour within colonies
- maternal effect on development
- social factors affecting ageing
More information about current projects can be found by clicking on the group members’ names below.
Damaraland Mole-rat Project
Variation in cooperative behaviour, life-histories and individual fitness in Damaraland mole-rat
My main research interest is the evolution and the maintenance of helping and seemingly altruistic behaviour in animals. My interest originates from a deep fascination for animals and in particular for animal behaviour and the attempt to understand why animals and humans behave as they do and which forces and factors shaped the evolution of behaviour.
My approach is explicitly empirical and I use behavioural experiments conducted in natural populations and under controlled laboratory conditions combined with observational studies in the wild. Previously my research included mainly cooperatively breeding species such as meerkats and cichlid fish but I also contributed to research projects on house mice and flycatchers during my studies in Vienna and Sweden.
In my current project I investigate the proximate mechanisms underlying individual variation in cooperative behaviour and their consequences for life-histories and individual fitness in the cooperatively breeding Damaraland mole-rat (Fukomys damarensis). We will study colonies in artificial tunnel systems, which allow detailed behavioural observations and experimental manipulation and study a permanently marked, wild population of mole-rats at the Kuruman River Reserve (Northern Cape, South Africa).
Life history trade-offs in co-operative breeders
The social mole-rats, of which Damaraland mole-rats present an extreme case, are physiological enigmas, as exemplified by their ability to withstand hypoxia, their resistance to cancer-like phenotypes, and their extraordinary longevity. Such characteristics have catapulted social mole-rats (largely naked mole-rats) into the limelight as model organisms in medicine. Nonetheless, little effort has examined the proximate basis of mole-rat life histories from an ecological perspective. With my PhD research, I will investigate life history covariation in Damaraland Mole-rats using a combination of field and laboratory-based studies. Specifically I hope to quantify the relative costs and benefits of reproduction or non-reproduction in terms of growth and ageing, and more widely probe the link between sociality and longevity in mammals. I am also interested in the capacity of hormones to integrate suites of traits – behaviour, physiology, life history- and thereby potentially constrain or facilitate life history evolution, for which I will use the Damaraland Mole-Rat as a case study.
Socio-endocrine mechanisms of individual variation in cooperative behaviours
Large differences in cooperative effort are a universal characteristic of cooperative societies. There is growing evidence suggesting that individuals can adjust their cooperative investment as a function of its costs and benefits, yet the physiological causes and evolutionary consequences of this variation remain largely unknown. Unravelling the mechanisms of cooperative investments’ plasticity, both within and between individuals, is essential to develop a more comprehensive understanding of how cooperation works in nature. Steroid hormones such as the glucocorticoid stress hormones and androgens (testosterone) may be pivotal for individuals to adjust their level of cooperation as a consequence of their secretions’ combined ability to integrate internal and social cues and exert profound phenotypical effects, including developmental ones. These can occur as early as conception and have been highlighted to mediate early-life environment’s long-term and irreversible consequences on offspring phenotypes. However, the exciting possibility that cooperative phenotypes may be programmed prenatally has remained untested. My research on the Damaraland mole-rat combines correlative and experimental approaches, in which pregnant females and helpers’ endocrine system or social environment are manipulated, to investigate the short and long-term effects of steroid hormones in shaping individual phenotypes as a function of perceived social environment. Furthermore, the pleiotropic effects of steroids make them ideal candidates to question the existence and mechanisms of potential life history trade-offs in which cooperative investments would be constrained by investment in competing phenotypical traits. I hope that my research will promote a more integrative view of cooperation which I believe has the potential to reveal major insights into the adaptive character of individual variation in cooperative behaviour.
University of Pretoria, South Africa & University of Neuchâtel, Switzerland
Oxidative stress in Damaraland mole-rats
Helping frequently takes the form of energetically demanding activities, which involve high cellular oxygen consumption and the creation of by-product reactive oxygen species (ROS). ROS production can lead to oxidative stress (OS) and consequent cellular damages if its production is not counter-balanced by defence mechanisms such as antioxidants raising the question of whether OS represents a physiological cost of helping. Because antioxidants are limiting resources their allocation can face trade-offs, such as that between self-maintenance and reproduction. In cooperative breeding societies, where reproduction is monopolised by a minority of individuals, one may question whether breeders and non-breeders differ in the way they deal with such trade-off. Damaraland mole-rats offer an ideal study system to investigate these questions since reproduction is monopolized by a minority of breeders who are assisted by a majority of reproductively suppressed helpers displaying large individual variation in helping effort. My PhD aims to investigate: i) whether individual variation in helping behaviour is accompanied by variation in oxidative profile and if this can impact future reproductive success; ii) whether the need for increased helping effort differently affects breeders and helpers oxidative profile and iii) how breeding possibilities may affect OS and the optimal allocation of defences towards self-maintenance and reproductive functions.