Interspecific social learning
Many animals forage in mixed species groups that move together through the landscape in search of food. Often these groups form because the different species all eat the same food, and with more animals helping to look for food it increases the odds of finding something to eat. There are some exceptions to this - sometimes each species specializes on a particular food source and the animals hang out together because being in a larger group means that they’re less susceptible to predators. There’s been lots of great work applying game theoretical approaches to predict things like optimal group size and species composition (also see this for a great overview of mixed species bird flocks).
It’s well known that social learning occurs between animals of the same species, but during my PhD I wanted to see whether I could demonstrate it happening across species. I came up with an experiment to test for this in two bird species that commonly form mixed species flocks in Wytham Woods, Oxford UK. To start, I would teach one species to associate an unfamiliar sound with danger (i.e. play a sound while showing them a fake hawk). After a few days, when I thought they’d learned to recognize the sound, I added a bird of a different species to the aviary and for a few days played the same sound occasionally, but without the hawk model. The idea was that if the original birds indeed associated the sound with danger, they’d have some kind of predator response such as hiding in the foliage, and the new bird would learn to also associate the sound with danger. After a few days, I tested the new bird alone to see if they had a response to the sound. Amazingly, the birds would fly away when they heard the test sound, meaning they had learned to associate it with danger even though they’d never actually been exposed to the hawk. Even more interesting, this was evidence that a learned behavior could be transmitted across species boundaries. Evolutionarily, it makes sense that animals would learn not just from conspecifics but from any species that might provide social information that increases the odds of survival.
Graphical overview of the study made by the talented Megan Bishop. Lots of thought went into the experimental design, particularly in choosing the treatment and control stimuli, schedule of exposure the stimuli, and ensuring there were enough replicates collected while birds were still in their winter flocks. Figure from Keen et al. 2020
The species used in the study, both part of the Paridae family, Parus major and Cyanistes caeruleus.
Image credit: Nataba, Adobe Stock images