Animal welfare activists have scored several victories in recent years in their efforts to mandate better treatment of chimpanzees. Now they are asking a federal agency to make similar changes to the housing and treatment of monkeys.

Chimpanzees are the closest relatives of human beings, and a dwindling need for them in research, along with increasing recognition of their social and physical needs, led to a decision by the National Institutes of Health in 2013 to retire most chimps it owns from use in research. The N.I.H. also required that they be housed in ways that suit their natural social groups and behavior.

Those decisions affect the lives of hundreds of chimps owned by the N.I.H., but there are an estimated 110,000 monkeys in the country in research laboratories alone. Monkeys are more distant from humans than chimps, but they are still highly social primates, and animal welfare groups are lobbying for them to be housed in social groups and that infants not be removed from their mothers until they normally would be weaned.

Theodora Capaldo, the head of the New England Anti-Vivisection Society, said, “If we can do it for chimpanzees, we can do it for all primates.”