Published: 16 March 2022 at 23:00
Play amongst adult howler monkeys increases during competitive foraging
New research has discovered that adult howler monkeys use play to avoid conflict and reduce group tension, with levels of play increasing when they are faced with scarce resources.
The study, carried out by a team of researchers from Spain, Brazil and the UK, and published in the journal Animal Behaviour, focuses on the activity of two subspecies of howler monkey: the Mexican howler (Alouatta palliata mexicana) and the golden-mantled howler (Alouatta palliata palliata).
The researchers examined how play varies with age, and they measured the amount of time adults play with other adults and with juvenile monkeys within their groups.
Howler monkey play involves individuals hanging from their tails and making facial expressions and signals, such as shaking their heads. However, play is an energy-costly activity for howler monkeys, who generally have an inactive lifestyle due to their mainly leaf-based diet.
By studying seven different groups of howler monkeys in the rainforests of Mexico and Costa Rica, the researchers found that the amount of adult play is linked to the number of potential playmates, increasing in line with the size of the group. Adults spend more time playing with other adults, rather than juveniles, and adult females spend more time engaged in play than adult males.
Crucially, the researchers found that play amongst adults increases in line with time spent foraging on fruit. Howler monkeys typically eat leaves, and fruit is a highly prized resource that generates competition amongst the monkeys.
Howler monkeys do not have a fixed social hierarchy within their groups to navigate competition and conflict, and they do not engage in collective grooming, which is used by some primates for group cohesiveness and tension reduction. Instead, the study authors believe play has a key role in helping howler monkeys regulate relationships within their social group and avoid conflict.
Co-author Dr Jacob Dunn, Associate Professor in Evolutionary Biology at Anglia Ruskin University (ARU), said:
Lead author Dr Norberto Asensio, of University of the Basque Country, said: