Though they might worry about their own waistlines, visitors to Ohama park here don't seem to be bothered by its roly-poly "metabolic monkeys"--in fact, they happily overfeed them.
The rise in primate rotundity is alarming the municipal park's overseers.
Visitors love to offer the macaques snacks, bread or even leftovers from their meals, officials say. And the monkeys love to chow it all down.
The park has no full-time zookeeper. Some 50 Macaca mulatta monkeys roam in their enclosure.
Some have grown so big they are two or three times heavier than average weight.
Many monkeys find it too hard to move in the 420-square-meter enclosure.
Visitors react with insults or pitying comments, the officials said.
One official says he has had to explain that a particular monkey with a swollen abdomen isn't pregnant--it simply has a pot belly.
About 30 percent of the monkeys appear to be overweight, with the group's top five leaders weighing in at 15 kilograms or more.
The heaviest male tips the scales at an astonishing 29.2 kg.
In comparison, the average male Macaca mulatta monkey weighs between 5 and 11 kg, according to the Environment Ministry.
Alarmed park officials last year put them on a diet, switching their food to a less fattening type, but such efforts have been in vain because visitors continue to feed the creatures.
Anywhere from 10 to 20 people feed the monkeys each day, ignoring the four warning signs.
A nearby resident said she regularly comes to give the troupe bits left over from her breakfast, or bananas and peanuts. "I feel sorry for the small monkeys, who are often robbed of their share by the larger ones," she said.
Shoji Hasegawa, head of the park's administrative office, said the park assumed the amount of food it provided was adequate because the monkeys always ate it all up.
To keep people from tossing food into the monkey space, the city government is debating whether to erect a fence around it this fiscal year, Hasegawa said.
Akira Kato, chief of the Japan Monkey Center, a zoo and research center in Inuyama, Aichi Prefecture, said measures to prevent visitors from throwing food should be put in place immediately. Giving the animals an unrestricted supply of food is tantamount to abuse, he said.
"It is shocking to hear there is a park that still treats animals like that," he said.