I’m interested in understanding why animals of the same species seem to vary so much. Why are some bigger than others? Why do some live longer? Why are some so susceptible to infections? Is this variation due to genetic differences or variation in the environment? Animals have limited energy which they must divide between growing, reproducing, rearing offspring and immunity to parasites. These characteristics all affect the number of offspring they produce, and through natural selection, genetic variation in such characteristics leads to evolution. In wild populations, animals vary hugely in how many parasites they harbour. My favourite question right now is: what determines how big a parasite infection an animal gets, and how badly that infection affects them? I’m an evolutionary ecologist by training, and have spent time doing fieldwork on sheep on a remote Scottish island, and on elephants in the Burmese jungle. I find the struggle between parasites and their hosts absolutely fascinating, and the diversity of life-cycles that parasites have evolved truly staggering. I’m looking forward to talking about how hosts and parasites are continually evolving to get on top and how studies in the wild can help us to understand these interactions better.