Sociable crows are healthier, finds Anglia Ruskin University study
Being sociable is good for you, it seems, at least if you’re a crow.
Research led by Dr Claudia Wascher of Anglia Ruskin University has shown that carrion crows living in large social groups are healthier than those that have fewer social interactions.
Dr Washer and colleagues studied a population of captive carrion crows over six years, monitoring their behaviour in different-sized groups.
They measured friendship by ranking the birds using a sociality index, and also studied the crows’ droppings to check for a gastrointestinal parasite called coccidian oocyst, which is a significant threat to the health of birds.
While it might be expected that group living would lead to increased exposure to parasites and disease transmission, the study found the opposite.
The researchers found crows with strong social bonds, living with more relatives and in larger groups excreted a significantly smaller proportion of droppings containing the parasites than the less sociable birds.
Dr Wascher, senior lecturer in biology at ARU, said: “Crows are a highly social bird and we found that crows with the strongest social bonds excreted fewer samples containing coccidian oocyst, which is a common parasite in birds.
“It is a commonly-held belief that animals in larger groups are less healthy, as illness spreads from individual to individual more easily. We also know from previous studies that aggressive social interactions can be stressful for birds and that over time chronic activation of the physiological stress response can dampen the immune system, which can make individuals more susceptible to parasites.
“Therefore the results from our six-year study, showing a correlation between sociability and health, are significant. It could be that having close social bonds reduces stress levels in crows, which in turn makes them less susceptible to parasites.
“It could also be that healthier crows are more sociable. However, as many of the birds we studied were socialising within captive family groups, dictated by the number of crows within that family, we believe that social bonds in general affect the health of crows, and not vice versa.”
The study, published in the journal Animal Behaviour, did not find a connection between health and dominance of crows dominance within the group. But it found that 33 per cent of male crows carried the parasite, slightly more than the 28 per cent of females.
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