/ 10 July 2015

Understanding the species

Professor Nigel Bennett is still perplexed with certain aspects of how mole-rats breed.
Professor Nigel Bennett is still perplexed with certain aspects of how mole-rats breed.

Nigel Bennett is a professor of zoology at the University of Pretoria (UP), occupies the department of science and technology/National Research Foundation (NRF) Research Chair in Mammalian Behavioural Ecology and Physiology and holds the UP Austin Roberts Chair of African Mammalogy. His research focus is ecology, animal physiology and behaviour and he uses the African mole-rat as his model animal. He has undertaken a remarkable journey into African mole-rats; his work has provided some impressive insight into the species.

“Some African mole-rats are solitary and others are social, occurring in colonies where reproduction is restricted to a single reproductive female and two male consorts,” says Bennett. “I have been trying to unravel why some species are solitary and others social. In addition, I have also been trying to establish how reproduction is suppressed in the non-breeding females by the breeding female.”

Bennett and his co-workers have also investigated the evolution of sociality. Through this work, Bennett has come to realise that it could be the food source, resource distribution and patterns of rainfall that dictate whether the mole-rat is solitary or social.  “Furthermore, it would appear that in the social species, the breeding female somehow brings about reproductive suppression by a physiological mechanism,” he adds. 

Unlike other researchers investigating co-operative breeding in mammals, Bennett has undertaken a multi-faceted approach that has led to an integrated understanding of reproductive suppression in mole-rats. His work has set the benchmark in understanding the phylogenetic and ecological constraints regulating reproductive success and social evolution in mammalian species. His research record ranks him among the top researchers studying social regulation of reproduction in any group of mammals in the world.

It’s a fascinating line of work and Bennett’s steps along this road started when he undertook his honours degree in zoology at the University of Bristol in the United Kingdom. There he investigated the effect of photoperiod on seasonal breeding in the Japanese quail. He then went on to complete his PhD at the University of Cape Town (UCT), where he started his investigations into the factors that promote social living in African mole-rats. “I have always been interested in why some organisms adopt a social lifestyle and others do not. As a young boy I was fascinated by how wood ants worked for the common good of a queen. My interest in mole-rats came when I was an undergraduate and read a seminal paper by Jennifer Jarvis on co-operative breeding in the naked mole-rat,” says Bennett. 

“On obtaining a position as a doctoral student at UCT I wanted to see if this was a feature common to other African mole-rats and this is where the passion was ignited. I went on to study the Damaraland mole-rat and also found it to have an incredible social organisation, similar to that of social insects and termites. These qualities include the reproductive division of labour and a work-related division of labour, where some groups work hard and some do very little work.”

One of Bennett’s greatest achievements to date was when he demonstrated that the Damaraland mole rat is a eusocial species (a species in which a single female produces the offspring and the non-reproductive individuals co-operate in caring for the young). “The Damaraland mole-rat shares many characteristics with social termites and ants,” says Bennett. Currently holding an A-rating with the National Research Foundation, Bennett has also been a visiting professor at the School of Chemical and Biological Sciences, Queen Mary College, University of London, since 2005 and more recently was a visiting professor at the department of zoology, King Saud University, Saudi Arabia. 

“I have been fortunate to have been awarded the University of Pretoria’s Chancellor’s Medal for research twice and the Exceptional Academic Achiever Award for the past 12 years,” says Bennett. “I also received the University of Pretoria Commemorative Research Medal for being one of the top 100 scientists in 100 years, which was a huge honour.”

It is an illustrious career with an impressive track record and fascinating research results; Bennett has published 275 papers in international, peer-reviewed scientific journals and co-authored a specialist book published by Cambridge University Press. 

Bennett is a driving force in his chosen field and isn’t showing signs of stopping his commitment to finding the answers.

“After nearly three decades of research on the reproduction of social African mole-rats, I still have not been able to determine how the breeding female actually inhibits reproduction in the physiologically suppressed non-reproductive females in the colony,” he says.