Photo by David Ellifrit, Centre for Whale Research.

David Ellifrit, Centre for Whale Research.

Post reproductive mother and son.

Current research projects

Dr Darren Croft: The Evolution of Prolonged Post-Reproductive Lifespan in a Non-Human Mammal. 

Funded by NERC

Understanding why females stop reproduction prior to the end of their lives is a key objective in the biological, medical and social sciences. In traditional human societies for example, women typically have their last child at 38 but may live for a further 20 years or so. This phenomenon is by no means restricted to humans and across many species of mammals, birds and fish, females may have a lifespan that extends far beyond their last birth. Currently however, almost nothing is known about the forces that have shaped the post-reproductive lifespan in non-human animals that live in close-knit family groups. In this Dr Croft and colleagues are studying two populations of killer whales Orcinus orca that live off the coast of North America. Killer whales have the longest post-reproductive lifespan of all non-human animals; females stop reproducing in their 30s-40s but can survive into their 90s. Using data collected over the last three decades during which time more than 600 whales have been recorded this project is examining how social factors shape fertility and survival in the two populations. This programme of research promises to advance our understanding of how natural selection has shaped life history evolution in species that live in close-knit family groups. This project will provide the first test of the current evolutionary theory for the evolution of menopause in non-human animals and the outputs of this work will provide an informative comparison for the evolution of human life history.