In this instalment of Naturally Speaking Shorts we present a double-interview as Shaun Killen chats with Prof Mark Haussmann (Bucknell University) and Dr Simon Babayan (University of Glasgow). Mark studies the physiological and ecological factors underlying ageing in animals, while Simon studies how ecology interacts with the mechanics of the immune system in wild and laboratory animals. Why do some animal species age faster than others? How do parasites control their hosts? In this short episode, listen as Mark and Simon touch on these issues and offer some advice to aspiring young scientists.