An invasive alien species, a major export for research

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A rhesus macacque in Mauritius. Representative image. Photo: Miwok/Flickr CC BY NC ND 2.0

Macaque monkeys live as both captive and wild animals in Mauritius. The number of the wild population is estimated at 25,000 to 35,000 animals, it is not known how many exist in captivity, but the figure is in the tens of thousands. The reason for a high number of captives is that Mauritius is one of the world’s largest exporters of apes for the global research industry – primarily to the United States and Europe. Up to 10,000 primates are exported from Mauritius each year. Ecologist Vincent Florens explains how the animals arrived in Mauritius and how their presence has affected the island’s natural environment.

How long has Maurice been involved?

Macaques are native to Southeast Asia and were almost certainly introduced as pets to Mauritius by the Dutch around 1602.

In 1985, a private company, Bioculture, began breeding macaques for research. The government did not oppose it. Macaques are closely related to humans and can help provide data on medical issues. For example, experimental trials on macaques have led researchers to understand the effectiveness of new drugs and vaccines against several infectious diseases, such as AIDS, influenza, smallpox and hepatitis.

Macaques were first exported from Mauritius for research purposes in 1985. Initially, wild animals were to be captured to supply research. These were usually caught in forested areas of islands, in national parks, nature reserves, on mountains and in woods along rivers.

Today, they are both wild caught and bred in captivity for research. In 2020, 10,827 macaques were exported from the country.

Wild macaques are needed to support captive breeding, a supply of at least a few thousand females each year. This is to avoid genetic inbreeding issues that can arise in captive populations. And because the breeding ability of captive-bred animals tends to decline, and other issues like aging of breeding animals.

How does trade affect their numbers?

The intensity of wildlife trapping may vary over time depending on the needs of breeding programs. In times of low or no trapping, the population of wild macaques usually increases gradually, which I have observed while researching vegetation dynamics in Mauritius for about 20 years. Calls and animal sightings are more common when visiting forest areas, as well as by the size of the groups seen.

Conversely, there have been periods of heavy trapping, such as when several companies obtained operating permits several years ago. This has resulted in a very marked drop in encounters where macaques were previously abundant.

What impact do macaques have on the natural environment?

To appreciate the impact of macaques on the natural environment of Mauritius, one must first remember that they were introduced by humans to the island. Macaques are not part of the natural environment of Mauritius, they are like rats in this regard.

The macaque is what is called an “exotic species” in Mauritius. This means that the many native, and often unique, animals and plants of Mauritius – found in one of the world’s biodiversity hotspots – have never been exposed to animals like macaques. This means that the plants and animals that lived there, the endemic species, did not develop any evolutionary characteristics that would protect them from the alien apes.

Mauritius already has one of the highest endemic species extinction rates in the world. They are among the most endangered in the world. For example, last year Botanical Gardens Conservation International ranked Mauritius as the second worst country in the world in terms of the proportion of tree species threatened with extinction. Massive deforestation is the most direct and immediate driver of biodiversity loss, removing 95.6% of the original ecosystem.

Macaques have played and continue to play a central role in this situation. They are formidable predators capable of plundering bird nests to eat eggs and chicks. Macaques also chew the soft hearts of many plants like orchids, especially the larger species, killing them. Today, orchids are the plant family that has suffered the highest rate of extinction – 20 of the 91 known species appear to have disappeared since 1769 in Mauritius. Many macaque-vulnerable orchids now cling to survival in small numbers in places like steep cliffs, which are least accessible to macaques.

Macaques destroy the fruits of many native trees before they mature. This kills the seeds inside, such as those of the ‘Dodo-tree’ and many species of ebony. This has made forests less hospitable to native frugivores such as the endangered flying fox.

Macaques also destroy flowers of many species, breaking branches and chewing seedlings. Their activities deprive native wildlife of their natural foods, which in turn contributes to their further decline. For example, macaques destroyed about 95% of the fruits of some endemic trees before the endemic Mascarene fruit bat had a chance to feed on those fruits. This in turn causes the flying fox to seek food elsewhere, including on commercial trees in gardens and orchards. Unfortunately, this led to the Mauritian government taking action against the flying foxes, killing them by the thousands. This has upgraded the flying fox’s conservation status to Endangered on the International Union for Conservation of Nature’s Red List.

How to better manage them?

Wild macaques in Mauritius are an extremely harmful invasive alien species, destructive to many animal and plant species which are heading towards extinction partly because of the macaques.

The ideal management in such a situation is eradication, just as goats and rabbits were eradicated from Round Island in the 1970s and 1980s. This saved its highly endangered flora and fauna from extinction.

However, the eradication of macaques can be difficult in the remaining forests of Mauritius, which are large and cover 80 km2. It may be more feasible in the short term to eradicate them from isolated pockets of habitat or to control their numbers well below what they are now.

This can be done by intensive trapping or construction of macaque-proof fences, especially in and around the most important biodiversity areas respectively.

Each of the monkeys exported each year for research purposes is subject to a tax of US$125 which helps raise funds for biodiversity conservation. However, more species will continue to disappear unless the level of conservation management is seriously increased to address threats, including those posed by macaques.

Vincent Florens, Associate Professor, Department of Biosciences at the Faculty of Science, University of Mauritius.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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