Behavioral responses to physical impairment and disability in free-ranging Japanese macaques at the Awajishima Monkey Center: (a) Adult male (Gatsu) without hands and with foot deformities, walking in his usual bipedal manner on the roof of ‘a structure at the Monkey Center; (b) Bipedal adult male (Gatsu) jumping from a wall; (c) An adult with a manual disability grabs and eats a piece of sweet potato; (d) A group of disabled and non-disabled monkeys engaged in social grooming; (e) Young woman (Monmo) with extensive malformations on all four limbs, walking in quadruped using elbows; (f) A disabled adult female grooms a non-disabled person, using grooming gestures specific to the disability; (g, h). A non-disabled adult man (Propeller) holds and cares for a disabled baby (Nina) while Nina’s mother (Kuemodoki) sits nearby (photos by BMS); (i) An adult female with very malformed hands (Pikaru) pinches grain in an eating gesture specific to disability; (photos by SET unless otherwise noted). Credit: American Journal of Primatology (2023). DOI: 10.1002/ajp.23579
Primates demonstrate a remarkable ability to modify their behaviors to adapt to their disabilities and physical deficiencies, according to a new review of the literature by Concordia researchers.
Whether disabilities are the result of birth defects or injuries, many primate species have demonstrated behavioral flexibility and innovation to compensate for their disabilities. They also benefited from the flexible and innovative behavior of their mothers early in life and that of their peers within their population group as they aged.
Researchers from the Primatology and Interdisciplinary Environmental Studies (PIES) Laboratory reviewed 114 studies and published their results in the American Journal of Primatology.
The survey also revealed something the researchers hadn’t expected.
“Brogan Stewart, a doctoral candidate and lead author of the paper, noticed that a high proportion of papers mentioned a link to human activity as a potential or actual cause of impairment,” says co-corresponding author Sarah Turner, associate professor in the Department of Geography, Planning and Environment in the Faculty of Arts and Sciences.
“Disabilities may be the result of primates being caught in traps intended for other animals or by farmers trying to deter crops from feeding. Perhaps they are the result of a collision with a vehicle , or there are sometimes links between the genetics of a small population and deficiencies or diseases transmitted from people or contaminants in the environment.
The studies consulted dated between 1931 and 2023 and identified 125 species. Chimpanzees were the most studied, accounting for 25 percent of articles. Other commonly identified species include Japanese macaques, rhesus macaques, crab-eating macaques, and olive baboons.
More than 90 percent of disabilities were identified as deformities, injuries or illnesses or conditions. Macaques have been the subject of the greatest number of studies on malformations, while chimpanzees have been the subject of the greatest number of studies on injuries, diseases or conditions.
The researchers identified three themes in the literature studied:
- The central role of behavioral flexibility: Although physically weakened or disabled, primates were able to adjust their species-typical behaviors to survive, reproduce and thrive. For example, some chimpanzees have been observed using two or three limbs to move around instead of their usual four limbs.
- The importance of maternal and congenital care and social environment: While all primates need their mothers from the beginning of their lives, mothers of babies with disabilities will provide additional care and modify their own behavior as needed of their offspring. Likewise, other members of their group will sometimes modify their own species-typical care to help a disabled co-member. For example, an adult male Japanese macaque adopted a young orphaned disabled monkey and carried him while he moved on three limbs during the group’s trip.
- The potential for innovation: Disabled primates have been seen developing new ways to participate in grooming, carrying their offspring, and feeding. These usually involved new ways of using their limbs, such as pinching branches with their forearms against their torso to eat.
For Turner and his team, the findings open new avenues of research and provide valuable insights into primates’ adaptive capabilities, their resilience, and the many unexpected impacts that human activity can have on non-human animals.
“Some people at the Awajishima Monkey Center, where we do our field work, have significant physical disabilities, but they go about their lives and do the things that other monkeys do,” Turner says. “They find ways to modify their behaviors, such as unique movement styles, ways of carrying their babies, foraging and feeding techniques, and individual styles of social grooming, to compensate for physical deficiencies.”
Stewart adds: “We wonder if having physical disabilities comes at a cost to them. And when they compensate them, is there a cost to that? I am doing my doctoral research on the complexity of behavioral patterns associated with Japanese macaques with physical disabilities. Hopefully this research will give us more information about the consequences of disability for free-ranging and wild primates.
More information:
Brogan M. Stewart et al, Primates and disability: behavioral flexibility and implications for resilience to environmental change, American Journal of Primatology (2023). DOI: 10.1002/ajp.23579
Provided by Concordia University
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