Rhesus Macaques: Living Wild and Free in Silver Springs, Florida
Due to an amusing oversight on the part of an enterprising tour guide, a growing population of Rhesus macaques now resides in Silver Springs, Florida. It’s rumored that the original group of Floridian monkeys escaped from the set of a Tarzan movie being filmed in Florida, but in reality they were imported in 1938 by Colonel Tooey, a tour guide who thought a small colony of monkeys would attract more business to his jungle boat tours. He “marooned” them on a man-made island in the middle of the Silver River – somehow under the impression that monkeys can’t swim. They can, and they left the island and swam across the river almost instantaneously. When the older monkeys from the original group started to die off, Tooey brought in another troop. The first troop chased away the younger troop, but when the new troop matured, they returned to raid females from the original group. The multiple troops that formed spread out, establishing the population. There has not been a negative impact of introducing this foreign species to Florida thus far, but as the population grows any problems the monkeys cause will become a larger issue – and more difficult to control.
Rhesus monkeys are predominantly vegetarian, eating a wide range of leaves, stems, bark, fruit, seeds, and roots, as well as a small amount of soil and occasionally insects. In Florida, researchers have observed the monkeys eating 48 different species of plant. The monkeys also steal human food, raid sheds, and forage scraps from trash cans and dumps around Silver Springs. Perhaps, due to this flexibility in diet, the monkeys won’t cause as much competition for food with the native species as a non-native species sometimes does.
As with any case in which a non-native species travels to a new environment, there are some expected risks to the local ecology. These potential risks include competition with local wildlife for plant food, and possibly creating a scarcity, as well as direct predation on the native species. The population of monkeys in Silver Springs has not yet reached a size where researchers can gauge the impact accurately, and it’s difficult to predict what will happen as the population grows. Biologist Bob Gottschalk, who studied the monkeys for three years, doesn’t believe there will be an ecological impact. Not a negative one, anyway. Gottschalk has seen no sign of competition for food between the monkeys and native animals, and unlike the native species, Gottschalk has observed the monkeys eating invasive plants like air potato and wild taro. Helping control these invasive species is actually a benefit to the Florida environment.
A more obvious issue than the environmental impact is the range of problems that will arise from the monkeys’ interaction with humans. The monkeys wander into public places and people’s private property, and as with any wild animal they can be aggressive when approached. This is a more serious problem than it seems. According to Clay Montegue’s technical report “Issues and Options Related to Management of Silver Springs Rhesus Macaques,” when researchers captured some of the monkeys and tested them for disease in 1992, 4 out of 7 tested positive for the herpes-B virus. The virus normally lies dormant in monkeys, but in some cases it may present symptoms similar to the herpes simplex virus in humans. When transmitted to a human through a bite or scratch, the herpes-B virus is almost always fatal. In the 32 documented cases of human infection, the mortality rate exceeds 80%. Survivors must take Acyclovir for the rest of their lives to avoid significant neurological deterioration caused by the virus. Chances of transmission are low, however; an infected monkey would need to bite a human while the virus was active to infect him, and the virus is usually dormant.
Problems will become more likely to occur as the monkey population grows, especially if people don’t discourage the monkeys from frequenting the human-populated areas. The fact that the monkeys are not native to Silver Springs makes them an attraction, and people actively seek them out. By feeding the monkeys, as with any wild animal, it’s likely that the monkeys will become used to the free food and therefore move closer into the town of Silver Springs and become more aggressive and bold with their interactions with humans. Citizens of Silver Springs have also reported the monkeys as a nuisance in picnic areas trying to steal food, and for destruction of property such as raiding and damaging an orange grove belonging to a Mr. Peoples in 1983. More monkeys will likely mean more problems. In an article called “The Bad Monkey Buffet,” Austin Sutton writes that in Thailand, where monkeys are a native species, a town called Lopburi has monkey issues to the extreme. In an attempt to appease a huge population of monkeys that harass the locals for food, Lopburi holds an annual festival in which locals pile over 2000 kg of fruit and vegetables into a pyramid as an offering to the monkeys. Whether it does appease the monkeys at all or not, the monkeys are still a huge problem, apparently harboring a sense of entitlement to the belongings (and food) of the town’s human residents. Even if the Rhesus Macaque population in Florida could grow with no restrictions or human interference, it would certainly be a long time before it grew large enough to cause a problem as big as Lopburi’s – but it isn’t impossible.
Many attempts have been made to control the monkey population in Silver Springs, and these efforts have slowed this population growth but never stopped it. In an article for Ocala Style, Steve Floethe says that in the ’80s and ’90s, the park where most of the monkeys lived tried to control the population by capturing the females and giving them to the College of Veterinary Medicine and the University of Florida to sterilize. This method did not prove very effective. Trappers with permits used to trap the monkeys to sell to research facilities as well, but when this practice became common knowledge the public outcry against it put an end to that method, although it did prove to be an effective way of controlling the population. Using baited traps, it’s possible to capture between 30 and 60 monkeys in a week. The fact that the monkeys have no natural predators in Florida means that without any sort of control, the population will explode. In this case, any environmental impact caused by the monkeys will quickly become evident.
The monkeys aren’t all bad, though. Colonel Tooey’s plan worked after all, and the monkeys attract tourists to Silver Springs from all over Florida. The locals all benefit from the boost to the Silver Springs economy that the tourism brings, and despite some irritation most of the locals like having the monkeys there. Petitions have successfully halted trapping, and kept state officials from enacting measures to eliminate the monkeys. Perhaps the monkeys don’t need to be removed from Florida. Or at least not entirely. The benefit they provide to the local economy seems a good argument for them to be allowed to stay, and the current small size of the population is no danger to the environment. But as the population grows, problems will arise. The monkeys travel in troops of 20-200, and as the overall population grows more troops will split off and spread out, turning a local problem into a state-wide one.
Although the monkeys haven’t created a problem yet, eventually they will. There are three solutions: to kill all of the monkeys, trap them and sell them to research facilities, or do nothing. Killing a huge number of monkeys to eliminate them as an invasive species would prove impractical for several reasons. It would obviously be difficult to hunt down so many individual monkeys, and the locals would almost certainly not allow it. And since the current population isn’t problematic, it’s not an issue serious enough to justify so much killing. Trapping the monkeys has already proved an effective way of removing them from the environment, but then there’s nothing to do with them other than sell them to research facilities that use monkeys to test cures for AIDS and other diseases. Nobody is going to pay to ship thousands of Rhesus Macaques across an ocean and back to their native habitat. Animal testing is not a humane practice, and trapping and selling the monkeys has already been tried and used for about ten years, until the locals petitioned to end it. With killing and trapping eliminated as options, the only method of control left – capture and sterilization – is ineffective and will only become more so as the population grows.
The only remaining option is to do nothing. If Silver Springs takes that route, as it likely will, the monkey population will explode due to their lack of natural predators in Florida and an abundance of food and space to spread out. Experts still can’t predict the exact environmental impact, but with a growing population it will soon become evident to some extent. As the monkeys spread out, they will become more likely to cause problems to both the environment and to people. In February of 2014, a lone Rhesus Macaque was seen roaming Tampa Bay, Florida. . . . 142 miles away from Silver Springs. Even if the monkeys never cause damage to the ecology of Silver River, eventually they’ll spread out into environments that are not as well suited to hosting hordes of monkeys. Perhaps when the monkeys become a serious nuisance to locals, they’ll allow officials to put measures to control the monkeys in place – probably too late. But for now, it seems the monkeys aren’t going anywhere.