Crab-eating macaque

This monkey has a very long tail.

The tail is as long as its body and head. It lives in many places. It lives in forests and near the sea. It can also live near people. These monkeys are very smart. They can use stones as tools to find food. They also like to eat fruit and crabs. Some monkeys live in big groups. These groups can have up to 85 monkeys. They are very busy animals.

The crab-eating macaque is a smart monkey from Southeast Asia.

People call it the long-tailed macaque. This is because its tail is very long. The tail is the same length as its body and head.

These monkeys live in many places. They live in rainforests and near the sea. They also live close to humans.

These monkeys eat many things. They eat fruit and crabs. They are very clever. They are the only old-world monkeys that use stone tools. They use stones to help them find food.

They live in groups led by females. A group can have 10 to 85 monkeys. Males leave their home group when they grow up. Today, these monkeys face many threats. They are listed as Endangered. This means they might disappear soon. Many monkeys are used in scientific research. Others are seen as pests by people. We must learn more to help them.

The crab-eating macaque is a clever primate from Southeast Asia.

People also call them long-tailed macaques or cynomolgus macaques. They are very good at living in different places. You might find them in thick rainforests or near the coast. They even live very close to human towns. Because they live near people, they are called synanthropic. This means they thrive in places where humans live.

They are very important to study because they are so adaptive.

These monkeys have a very interesting way of living. They are omnivorous, which means they eat both plants and animals. They love to eat fruit, but they also forage for crabs on beaches. They are also the only old-world monkeys known to use stone tools for food. They live in groups led by females. These groups can have between 10 and 85 members. When males reach puberty, they leave their home group to find new ones. This social structure is called female philopatry.

Humans have many different views of these monkeys. Some people see them as smart and sacred animals. Others see them as pests or vermin because they live near farms.

In some places, they are even seen as invasive species. For example, on the island of Mauritius, they are thought to compete with native animals. However, many experts say the biggest problem for birds is actually habitat loss caused by humans. This shows how complicated it is to understand how monkeys affect nature.

Scientists have studied these monkeys for a long time. Sir Thomas Raffles gave them their scientific name in 1821. The name *Macaca* comes from a word in the Ibinda language.

The specific name *fascicularis* is Latin for a small band or stripe. Today, they are very important in biomedical research. Because of this and other threats, they were listed as Endangered in 2022. This means their numbers are dropping quickly.

It is amazing to see how these monkeys fit into our world. They are one of the few mammals that cross the Wallace line. This is a famous boundary that separates different groups of animals. They can be found in many places like Indonesia, Malaysia, and the Philippines. Whether they are using a stone to crack a nut or living near a temple, they are truly remarkable. They remind us how much life can change depending on where it lives.

The crab-eating macaque, known scientifically as *Macaca fascicularis*, is a highly adaptive primate native to Southeast Asia.

They are also frequently called long-tailed macaques or cynomolgus macaques. These primates are classified as synanthropic, meaning they thrive in environments close to human settlements. This ability to live near people allows them to inhabit diverse areas like primary rainforests, secondary forests, and coastal mangroves. Because they are so versatile, they play many different roles in human society. They are seen as sacred animals in some cultures, while others view them as pests or vermin.

Socially, these macaques live in organized matrilineal groups. These groups can range in size from 10 to 85 individuals. The species exhibits female philopatry, which means females stay within their birth groups for their entire lives. In contrast, males undergo emigration at puberty, leaving their natal groups to find new ones. Their diet is both omnivorous and frugivorous, meaning they eat both animals and fruit. They are famous for foraging for crabs on beaches. Remarkably, they are the only old-world monkeys known to use stone tools for daily foraging. In certain tourist areas, they even display complex behaviors like robbing and bartering with humans.

The physical appearance of the crab-eating macaque is quite distinct. They are sexually dimorphic, meaning males and females look different. Adult males typically weigh between 7 and 12 kilograms, while females are smaller, weighing between 3 and 6 kilograms. Their height ranges from 40 to 65 centimeters for males and 30 to 50 centimeters for females. Their most notable feature is a tail that is as long as their head and body combined. Their fur, or pelage, is usually greyish or brownish with a white underbelly.

Most adults have beards around their faces, though older females often have fuller beards than males.

Taxonomically, the species has a complex history of subspecies. While there were once ten recognized subspecies, the status of the Philippine long-tailed macaque is currently under dispute. The most widespread is *M. f. fascicularis*, found in Indonesia, Malaysia, the Philippines, and several other nations. Other subspecies are isolated on various islands. For example, *M. f. aurea* is found in Myanmar, Laos, and Thailand. Some subspecies, like *M. f. umbrosa*, live on deep-water fringing islands, while others, like *M. f. karimondjiwae*, inhabit shallow-water islands.

The evolutionary history of the macaque genus began in northeastern Africa about 7 million years ago. The *fascicularis* group likely shared a common ancestor with other species about 2.5 million years ago. Scientists believe the group originated from ancient hybridization between the *sinica* and *silenus* lineages roughly 3.5 million years ago. This happened during periods of changing sea levels in the early Pleistocene. Fossil evidence shows they inhabited the Sunda Shelf at least 1 million years ago. They are unique because they are one of the few terrestrial mammals to cross the Wallace line, reaching the Lesser Sunda Islands.

Human interaction has significantly impacted the species. In 2000, the crab-eating macaque was included on a list of the 100 most invasive species. On the island of Mauritius, they are considered an invasive alien species. Some argue they compete with native species like the Mauritian flying fox or spread invasive plant seeds. However, many researchers argue that human-driven habitat destruction is the primary cause of bird extinctions on the island.

The perception of them as "weeds" or pests is often used to justify their use in biomedical research. Currently, they are the most traded primate species and the most popular species used in scientific studies.

Due to these various pressures, the crab-eating macaque faces serious survival challenges. In 2022, the IUCN Red List officially classified them as Endangered. Their survival is tied to the balance between their natural habitats and the expanding human world. Whether they are being studied in a lab or foraging in a mangrove forest, they remain a vital part of the Southeast Asian ecosystem. Their ability to adapt to human presence makes them a central figure in discussions about biodiversity and conservation.