Canoeing down the Silver Springs river is much like canoeing on any springs in Florida. The water is a gorgeous crystal clear and consistently cool, huge knotty cypress trees line the riverbanks, and gators and turtles can be seen basking in the sunlight or barely visible with their heads above the water vegetation.
It’s common to see all sorts of birdlife like great blue herons, cormorants, and ibis wading along the shorelines or perched in the trees.
There is one species that you can see in Silver Springs that you won’t see in any other spring or anywhere else in Florida. This is the Rhesus Macaque.
Naturally, I was longing to get a glimpse of these unusual spring residents on my first trip to Silver Springs. As we rounded a bend, we heard shouts from the other kayakers on the river. Sure enough, the trees were filled with monkeys.
We stationed our canoe a safe ten or twelve feet from the nearest alligator, who was resting stock-still among the water lilies near the shore, also watching the monkeys, and settled in to watch the show.
Watching the monkeys was truly pure joy. Youngsters played together among the trees while their elders searched for tender new leaves to eat.
The young monkeys seemed to be especially fond of a game in which they would hang from a branch, play fighting with one another, until one dropped into a palmetto below, causing the huge fronds to shake like a green trampoline.
Older monkeys calmly navigated the branches over our heads, looking down at us with utter indifference. The presence of a Labrador in somebody’s boat caused considerably more reaction from the monkeys, who took up a defensive stance and shouted at the dog.
As I clicked vigorously away, I found myself shocked by just how natural this invasive species appeared as they plucked the new growth from the cypress trees, draped around the branches as comfortably as the Spanish moss.
How did monkeys come to be in Silver Springs?
Rhesus Macaques, which are indigenous to Asia, have lived in the park for around 80 years. You’ll hear all kinds of stories about how they came to be here as you chat with fellow canoeists and kayakers on the river. A common rumor is that the monkeys were released when the 1939 movie “Tarzan Finds a Son” was filmed at the springs, but in fact these monkeys were present well before this movie was shot.
According to Dr. Brian W. Ogle, assistant professor of anthrozoology at Beacon College in Leesburg, Florida, the monkeys were introduced in the 1930s. Six monkeys were let go on an island by a local glass bottom tour boat operator knowns as “Colonel Tooey”, who had bought the monkeys from a primate dealer in New York City with the intention of creating a tourist attraction.
He believed that the monkeys were unable to swim and would remain on the small island. Clearly this was not the case. When the monkeys quickly swam across the river and escaped into the woods, six more were brought in.
Soon, a breeding population was established in the area. They had plenty of room to roam across the 5000 acre park with plenty of access to fresh water and food.
The history of monkeys in Silver Springs
By the 1980’s, there were nearly four hundred monkeys along the Silver River. During the period from 1984 to 2012, nearly 1,000 monkeys were trapped and removed, with the majority of them being sold for biomedical research in order to reduce population growth. Dozens of females were also sterilized.
Not surprisingly, there was extensive public controversy about this practice and it was stopped in 2012. Management strategies have since been suggested, including culling young adults before they reach maturity and sterilizing most adult females, but these tactics have also met with public outcry.
Since 2012, the monkey population has exploded again to around 200 or 300 individuals. They have no reason to limit themselves to the area around the springs and have been found raiding deer feeders and generally making a nuisance of themselves on neighboring properties.
Young males leaving their troops have wandered as many as a hundred miles from the park, turning up as far away as Sarasota and Tallahassee. Breeding populations have already spread into the Ocklawaha River and could easily continue establishing new colonies throughout the state.
The problem with invasive monkeys
Introduced species rarely integrate into their new environment without some problems and the Rhesus Macaque is no exception. Ever since their introduction, there have been problems, and at the population increases, these concerns become more pressing.
Rhesus Macaques are known for being quite bold and even aggressive towards people. It is not uncommon for a troop to chase people out of their territory. The park has been closed twice since 2016 during times when monkeys showed increased aggression towards humans, including one incident where monkeys chased a family along a boardwalk.
Herpes B Virus
Of particular concern to wildlife management and health professionals is the fact that many of these monkeys carry a form of the herpes virus known as herpes B. This form of herpes is quite rare and is often deadly when it spreads to humans.
It is rare for herpes to spread from monkeys to people. In fact, there has never been a confirmed report of a person contracting herpes be from a wild macaque, despite at least 18 reports of macaque bites and scratches in Florida.
However, 50 incidences of Herpes B virus infection from macaques in laboratories have occurred when individuals working in the laboratory were bitten or scratched. Nearly half of these cases were fatal, and other infected people suffered permanent neurological damage.
We aren’t sure why the herpes virus appears to spread so readily in captive monkeys while no infection has been noted in wild monkeys, and research is still ongoing. It may be simply a matter of luck that nobody has become infected so far.
About 25% of the monkeys in Silver Springs have Herpes B virus and about 4 to 14% of them may be shedding the virus by mouth at any given time, so it may simply be that bites so far have come from individuals not actively shedding the virus.
Other issues suggested by previous monkey introductions
Where Rhesus monkeys have been introduced into other areas of the United States, they have caused significant issues. Populations of these monkeys are maintained in South Carolina and have been introduced in the Florida Keys as well, all maintained by laboratories. A huge population has been established in Puerto Rico.
- Tidal creeks around a population of 3000 monkeys on Morgan Island in South Carolina have been found to have elevated levels of E Coli and fecal coliform bacteria.
- Rhesus monkeys destroyed endangered red mangroves that grew along the coastline of the Florida key islands where they were introduced, leading to shoreline erosion and eventually prompting to remove all the monkeys
- Macaques decimated populations of four separate species of shorebirds in the Florida Keys islands where they were introduced.
- A US Department of Agriculture study found that monkeys introduced to Southwest Puerto Rico causes nearly $300,000 in crop damages every year and over a million in management costs. In an attempt to control their population in Puerto Rico, they are routinely trapped and euthanized.
While it is unknown exactly what impact these monkeys are having on the wildlife around Silver Springs, they have been observed consuming as many as 50 species of plants. They were a significant predator of artificially placed quail eggs during an environmental impact study.
As in so many cases of introduced species, the solution to the problem of Rhesus monkeys in Silver Springs is a complicated one. Spring goers like myself love to watch the monkeys and feel an affiliation with these incredibly human-like animals with their complicated social structure and strong family bonds.
They remain a primary attraction to the springs and many locals are staunch proponents of their presence. On the other hand, like all introduced species, these monkeys may represent a threat to the ecology of their new environment.
Furthermore, a reputation for negative interactions with humans, their property, and their crops, including the potential spread of disease, makes the continued presence and further spread of these monkeys problematic.
It is yet to be determined what measures, if any, will be taken to control the population of Rhesus Macaques in Silver Springs. In the meantime, I will continue enjoying this unique creature whenever I go to the springs.