Green monkeys – From Pets to Island Nuisance 

Sint Maarten

On St. Maarten, the introduced green monkey populations have more than quadrupled in the wild since 2020. With easy access to resources and no natural predators, these monkeys have been able to rapidly reproduce and are a threat to human health and cause social harm. Small islands typically have very delicately balanced ecosystems, so a population boom within a single species, especially non-native, can devastate the unique local biodiversity.  

Green Monkey. Photo credit: Charmain Jansen van Rensburg

Green Monkeys 

The green monkey (Chlorocebus sabaeus) is native to Africa and was introduced – whether intentionally or unintentionally – to several Caribbean islands including St Kitts, Nevis, Barbados, St Martin/St Maarten, and Tortola. St. Maarten has officially recorded these monkeys since the 1970s, however older residents tell stories of green monkeys being common household pets in the 1950s.  

Green monkeys can thrive in a wide variety of habitats, as their native region in West Africa stretches from Senegal to The Gambia. In their native habitat, green monkeys are seasonal breeders, meaning they only breed when fruit is most abundant, typically tied to the rainy season.  This creates an interesting change when these monkeys inhabit more fertile lands, such as St. Maarten, where food can be found in abundance year-round. Now instead of their breeding season being limited to a few months, green monkeys can reproduce year-round, which helps explain the recent population boom.   

Population Explosion 

Green Monkey. Photo credit: Francesco Ungaro

In 2020, a six-month survey by the Nature Foundation St. Maarten was conducted to better understand the local green monkey population on St. Maarten, as well as to define the overall impact, community perception and financial requirements to manage these issues.  Through this study, it was estimated that there were at least 450 monkeys on the Dutch side of the island alone. This study was duplicated in 2022, and nearly 2,000 monkeys were documented within the same area.  

During both the 2020 and 2022 surveys, 93% of the interviewed local residents on St. Maarten stated that something needed to be done to manage these monkey populations.  If left unchecked, St. Maarten could be in the same position as its neighbor St. Kitts, which counted nearly 38,000 monkeys in 2020.  Although popular among tourist, the monkeys of St. Kitts are devasting local agricultural, with 50-75% of local farms negatively affected by these monkeys. Also, negative impacts on native flora and fauna have been documented. 

These monkeys can be a significant threat to people, and already a number of communities on St Maarten are reporting that their monkey populations have become territorial and are increasingly aggressive towards residents and their pets. Furthermore, these monkeys can carry many diseases without symptoms which can be passed on to humans.   

Preserving Biodiversity 

The importance of managing invasive alien species has been recognized globally through the Sustainable Development Goals (SDGs) and the historic Kunming-Montreal Global Biodiversity Framework. The management of established invasive alien species be challenging amongst others due to conflicting values, ideas, (limited) scientific studies and social acceptance among governments, researchers, fishermen, farmers and other citizens and practical and affordable considerations. 

Funding from the Ministries of Public Housing, Environment, Spatial Planning, and Infrastructure (VROMI) and Tourism, Economic Affairs, Transport and Telecommunication (TEATT) has been set aside to address the invasive green monkey on St. Maarten. The Invasive Species Project, to be led by the Nature Foundation, will develop a plan to effectively manage the monkey issues moving forward. Spanning three years, the project will include multiple management techniques to control further population growth.  The overall goal is to minimize the negative effects the remaining population will have on the island’s biodiversity and native species.   

More information 



The Dutch Caribbean Nature Alliance (DCNA) supports science communication and outreach in the Dutch Caribbean region by making nature related scientific information more widely available through amongst others the Dutch Caribbean Biodiversity Database, DCNA’s news platform BioNews and through the press. This article is part of a series of articles on ‘Invasive Alien Species in the Dutch Caribbean”. This article contains the results from several scientific studies but the studies themselves are not DCNA studies. No rights can be derived from the content. DCNA is not liable for the content and the in(direct) impacts resulting from publishing this article.   

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