The Presence of Non-Native Monkeys in Puerto Rico
Puerto Rico is home to monkey populations, though these primates are not native to the island. Their presence stems from introductions related to scientific research. These monkeys have established wild colonies, representing an invasive species. Their existence impacts local ecosystems and human activities.
The Arrival of Non-Native Primates
The introduction of non-native monkeys to Puerto Rico began in the late 1930s for biomedical research. In 1938, primatologist Clarence Carpenter brought approximately 450 rhesus macaques from India to Cayo Santiago, an island off Puerto Rico’s eastern shore. This island, known as “Monkey Island,” became the Caribbean Primate Research Center, a dedicated facility. Its initial goal was to study primate social and sexual behaviors in a semi-wild environment.
Another source of free-ranging monkey populations was the La Parguera Primate Facility, operated by the University of Puerto Rico’s Medical Sciences Campus from 1961 to 1982. This facility introduced rhesus and patas monkeys to peninsulas in southwest Puerto Rico, including Isla Cueva and Isla Guayacan, to supply animals for programs like the Sabin Poliomyelitis Virus Vaccine Program. By the 1970s, the rhesus colony at La Parguera expanded to over 1,000 individuals. Monkeys from both La Parguera and Cayo Santiago escaped their enclosures, establishing wild populations on the main island.
Species and Their Habitats
Wild populations of non-native monkeys in Puerto Rico primarily include rhesus macaques (Macaca mulatta), patas monkeys (Erythrocebus patas), and, to a lesser extent, squirrel monkeys (Saimiri sciureus). Rhesus macaques are Old World monkeys, typically light brown or gray with pink faces and long tails. They are highly adaptable and can be found in various habitats, including subtropical areas, semiarid plains, farmlands, and urban environments.
The largest rhesus macaque population, approximately 1,800 individuals, lives on Cayo Santiago, an islet off Humacao. On the main island, free-ranging rhesus macaques are concentrated in the southwest region, particularly in Lajas, Cabo Rojo, and San Germán. Patas monkeys, also Old World primates, are known for their speed and terrestrial habits. Their populations are predominantly found in the southwest’s Sierra Bermeja region, covering an estimated range of about 600 square kilometers alongside rhesus macaques. Squirrel monkeys, originating from Central and South America, have also been observed, though their distribution and population size are less widely reported than the other two species.
Ecological and Public Health Implications
Non-native monkey populations in Puerto Rico have ecological and public health implications. Ecologically, these monkeys compete with native wildlife for resources and alter natural habitats. On Desecheo Island, introduced rhesus macaques contributed to the decline of seabird species and native reptiles, also modifying vegetation structure. On the main island, their foraging habits cause substantial damage to agricultural crops, leading to economic losses for farmers. Commercial farmers reported losses increasing from $1.13 million to over $1.46 million annually between 2002 and 2006, often forcing them to switch to less profitable crops.
From a public health perspective, these monkeys can transmit diseases to humans and livestock. Rhesus macaques, for example, can carry the B-virus (Cercopithecine herpesvirus 1), which is highly fatal to humans if not treated promptly. While the risk of transmission is generally considered low, contact with bodily fluids from infected monkeys can be dangerous. Free-ranging monkeys have also shown exposure to human pathogens like dengue viruses and Leptospira species, suggesting a role in disease ecology. As monkey populations expand into urban areas, the likelihood of human-monkey interactions and disease exposure increases.
Management and Conservation Efforts
Managing non-native monkey populations in Puerto Rico involves strategies to mitigate their impacts and control their numbers. Government agencies, including the Puerto Rico Department of Natural and Environmental Resources (DNER) and the U.S. Department of Agriculture’s Wildlife Services (USDA-APHIS-WS), are involved in these efforts. These efforts include monitoring programs to track population sizes and distributions.
Population control measures are used, though they are often complex and face challenges. For example, rhesus macaques were removed from Desecheo Island using methods like precision shooting and trapping to restore ecological integrity. Public education campaigns inform residents about the risks of interacting with these animals, particularly regarding disease transmission. The DNER’s long-term objective is the suppression or complete removal of these invasive monkeys from Puerto Rico, recognizing their adverse effects on the native environment and agricultural interests. Challenges such as funding limitations and the monkeys’ adaptability to removal techniques continue to complicate management efforts.