SAN DIEGO, Feb. 19 (UPI) -- There may be fewer rhesus macaque monkeys in central Florida than previously thought, and far less of their diets is made up of food given to them by humans, according to a study in Silver Springs State Park.
The monkeys, which have been spotted as far north as Jacksonville and as far south as Orlando, have alternately been considered a threat to humans and a popular attraction for both locals and tourists since the late 1930s.
The population has gone up and down since three pairs of the monkeys were released in the park in 1938 by a tour guide in the hope they would bring more people to Silver Springs and the Silver River, according to the New York Post.
The Orlando Sentinel reports there were 78 in Florida as of 1963, and estimates put the total state population in the high hundreds to low thousands, though researchers say there is no definitive estimate. A trapper claimed to have captured 772 of the monkeys between 1998 and 2012, selling them to a biomedical research facility, suggesting estimates in the thousands are closer to reality.
While there are no signs in Silver Springs about the monkeys, people are advised not to feed or interact with them, though it inevitably happens. The assumption has been that provisioning -- humans giving them food -- kept the colony living in the park for food, but adapting to the available plant life worked out much better than waiting for people, the researchers found.
"From the park's perspective, they know that provisioning occurs, and their sense is that it's because of this provisioning that this population persists," Erin Riley, an anthropologist at San Diego State University, said in a press release. "What our data show is that provisioning actually doesn't occur that often anymore, and as a result the monkeys have learned to rely primarily on local food."
For a study published in the journal Primates, two San Diego State University researchers studied the monkey population in Silver Springs State Park, their environment, and interviewed park rangers and visitors who interact with or are aware of the monkeys from January to May 2013.
In the park, the researchers counted 118 monkeys -- a little more than half what a previous study estimated -- which was a lower number than researchers expected. The population lives in four groups in separate parts of the park, according to Riley and to previous studies.
The researchers found 87.5 percent of the monkeys' diets were leaves and other plant parts, 66.5 percent of which was ash tree. Monkeys and humans saw each other -- 80 percent of boats seen by the researchers encountered the monkeys -- but someone on a boat offered food to the monkeys just 11.5 percent of the time.
The monkey population is thought to have grown significantly in the state in recent years as more of them have been seen further from the park, and in greater numbers.
While Riley notes it is easy to think you see more animals than are there if not properly trained, biologists in the state it's easy for the monkeys to spread and go in and out of the park. The monkeys have been seen as far south as Orlando, about 80 miles from the park, and as far north as Jacksonville, which is more than 100 miles away.
"I suspect that there are some monkeys that have spread out of the national forest, and it's not unreasonable to think they've gone down to Lake Griffin," Bob Gottschalk, a biologist who studied the monkeys for eight years, told the Sentinel. "Once you get that far south you get into Lake County."
The park does not acknowledge the monkeys as officially being at the park because they do not want to encourage people to visit them. Researchers said that although the animals carry disease, the river acts as a natural barrier and close enough contact with a human, direct feeding, happened only twice. The researchers suggest at least putting up signs, making people aware that the monkeys are there and should not be fed.
"A lot of people enjoy having them as part of the park experience -- they really kind of show them off to out-of-towners," Riley said of the animals, which many people mistakenly think are natural to the wild areas of Florida they are found in. "The local authorities, like the Fish and Wildlife Service, have been less thrilled with the monkeys. Their purview is to maintain a natural environment, and these animals are not natural to this area. They have concerns about the local ecological impact of these animals, and then there are also health issues if people interface and get close to them."