Sickly birds "pretend to be well" in company

Sick zebra finches pretend to be well if their buddies are around, according to scientists from the University of California, Berkeley.

Patrícia Lopes, who is interested in the evolutionary benefits of living in social groups, wanted to know how the social context affects zebra finches - which are highly social birds - when they are sick.

The team gave the finches a small dose of a protein that the birds' immune systems recognised as foreign, triggering an immune response. In other words, the protein made the birds feel unwell.

When the sick birds were in isolation, Dr Lopes explained, they "demonstrated high intensity of sickness behaviours, while sick birds in the colony did not behave differently from birds that were [well]".

There was no difference in the birds' immune system responses, so physically, they should have been experiencing the same symptoms.

The team is now trying to find out whether birds that do not rest and recuperate when they are ill suffer any physical consequences.

Dr Lopes thinks that the findings are applicable to a wide variety of species. In fact, similar observations have previously been made in rodents.

She explained the wider evolutionary context to me as follows:

"It is widely accepted that one of the downsides of social living is increased parasite transmission. At the same time, it increases your chances of encountering mates. The animal world is all about optimising your time in order to have as many successful offspring as possible.

"If feeling sick will reduce your chances of passing on your genes at a given moment, than it might be advantageous in evolutionary terms to ignore it for the time being and reproduce - even if it kills you!"