Golden lion tamarins hear the call of the wild

Golden lion tamarins use unique vocal calls to help their offspring learn valuable life skills, according to new research led by the University of St Andrews.

Teaching, where an individual’s modified behaviour enhances the learning of another individual, at a cost, or no direct benefit to themselves, is a central aspect of human culture. However, there are few examples of teaching in other species.

The new study, led by scientists from the School of Biology at the University and published in the International Journal of Primatology, reveals that juvenile golden lion tamarins can learn through food-offering calls about the availability of food at a substrate, which is consistent with (but does not prove) teaching in this species.

Food-offering calls in golden lion tamarins are usually emitted by adults prior to transferring food to young. Previous research showed that adults change the context in which those calls are used, potentially to teach the young where they should forage for prey. However, it was not known whether juveniles learn from those calls, an essential criterion for teaching.

The team of scientists focused on whether juveniles would learn to associate food-offering calls with a novel foraging substrate, as a step towards assessing whether those calls qualify as teaching behaviour in golden lion tamarins.

Wild groups of tamarins with young were given access for a few weeks to a novel substrate containing food. Some groups had access to the substrate on its own while other groups had food-offering calls being played back while they had access to that substrate. By looking at the differences between the juveniles in the different conditions, this allowed the researchers to assess any immediate effects of the calls. The groups were then given access to the substrate (without any playback) six month later, when the juveniles were now independent from the adults, in order to investigate the long-term effects of the calls.

Lead academic Dr Camille Troisi from the Centre for Social Learning & Cognitive Evolution at the University said: “Using a vocal playback paradigm, we found that food-offering calls had both short and long-term effects on the juveniles’ behaviour. Food-offering calls had an immediate effect on juveniles’ interactions with the novel substrate, whether they inserted their hands into the substrate and their eating behaviour, as well as long-term effects on eating behaviour at the substrate.”

The findings support hypotheses suggesting that teaching may be more likely to evolve in cooperatively breeding species, where the cost of the behaviour is shared between different individuals, particularly in species with complex ecological niches, where juveniles have a lot to learn in a short amount of time.