In recent times, there has been a lot of interest among primatologists in studying object handling and tool-use in non-human primates such as apes and chimpanzees. A study from IISER Mohali has looked into how long-tailed macaques (Macaca fascicularis umbrosus) in Greater Nicobar Island handle objects and use tools to simplify their efforts.
The researchers observed interesting behaviour related to object manipulation and tool use in six behavioural contexts involving eight different types of objects. They also saw that males were more frequently involved in tool use than females. The results of the study are published in the International Journal of Primatology.
There is a crucial difference between tool use and object use. A tool helps the user get better outcomes. Jayashree Mazumder, first author of the paper explains in an email to The Hindu: “When we change either the function or structure... of an object, we make it a tool. But when we use an item in the manner it is supposed to be used, we are not making it a tool… it is an object use.”
Identifying individuals
Observing the long-tailed macaques from a distance of about 10 metres for close to four months, Ms Mazumder, who is working for her PhD at IISER Mohali, has developed a catalogue of the individuals studied. Each individual was identified based on marks on the face or body. “Identifying adults is easy. They are like humans with distinct features, for example, presence of black or white spots in different locations of the face, scar marks, body size, sex and behaviour. The juveniles and sub-adults were slightly difficult but they too can be identified in a similar fashion,” says Ms Mazumder.
Stefano S.K. Kaburu, professor at the University of Wolverhampton, U.K., a co-author of the paper introduced her to the behavioural data collecting software and guided her in designing the study methods.
Prevalent in males
As per their observations, 14 individuals used tools, and tool-use was more common among males. “The biased nature of tool-use could be due to many reasons. It has been hypothesised that the weight of the individual has something to do with the tool-culture. Again, the tool activity itself also defines who uses them more often, says Ms Mazumder.
She gives the example of how among chimpanzees, females excel in fishing, which they learn from their mothers. Males, on the other hand, become adept in hunting, which they pick up from their peers. “Thus there could be social, ecological as well as demographic factors that could decide how tool-culture is divided among the animals. But we need more studies to come to any conclusion,” she says.
According to her, the most exciting part was how the macaques decide what tool and technology to use. “Some of the macaques had few trials and errors, but it did not take them long to understand that the technique or tool was not providing the best outcome, and therefore, they were very quick in switching,” she says.
Though the long-tailed macaques are further from humans in relatedness than chimpanzees or apes, this study could offer a perspective on evolutionary origins of tool use behaviour.
