Animals have the ability to conceal sickness in certain social situations.
When they are sick, animals from a number of different species will eat and drink less, reduce activity and sleep more to conserve energy for recovery.
Scientists found this can change when animals are presented with the opportunity to mate or are in the presence of their young.
Patricia Lopes from the University of Zurich said: “The idea is that behaving sick helps animals recover from the disease and so this should be the default way to behave when sick.
“However, if being sick coincides with, for example, a unique opportunity to mate, animals may adjust their priorities and behave as though they are not sick.”
Prof Lopes reviewed a range of different social situations that affected the behaviour of sick animals, including presence of offspring, intruders and potential mates.
Findings showed animals, ranging from birds to monkeys, all demonstrated to conceal their sickness when other animals were present.
Prof Lopes added: “Recognising when animals are concealing their sickness is critical to how we both detect and control the spread of infectious diseases.”
The review was published in the journal Proceedings of the Royal Society B and also considers the implications of infectious diseases.