Macaque

Macaques are mainly vegetarian, although some species have been observed feeding on insects. In natural habitats, they have been observed to consume certain parts of over one hundred species of plants including the buds, fruit, young leaves, bark, roots, and flowers. When macaques live amongst people, they raid agricultural crops such as wheat, rice, or sugarcane; and garden crops like tomatoes, bananas, melons, mangos, or papayas.[10] In human settings, they also rely heavily on direct handouts from people. This includes peanuts, rice, legumes, or even prepared food.

Macaques live in established social groups that can range from a few individuals to several hundred; as they are social animals. A typical social group possess between 20 and 50 individuals of all ages and of both sexes. Typical composition consists of 15% adult males, 35% adult females, 20% infants, and 30% juveniles, though there exists variation in structure and size of groups across populations.[9]

The premotor cortex of macaques is widely studied.[11]

Macaques have a very intricate social structure and hierarchy. If a macaque of a lower level in the social chain has eaten berries and none are left for a higher-ranking macaque, then the one higher in status can, within this social organization, remove the berries from the other monkey's mouth.[12]

The reproductive potential of each species differs. Populations of the rhesus macaque can grow at rates of 10% to 15% per year if the environmental conditions are favorable. However, some forest-dwelling species are endangered with much lower reproductive rates.[9] After one year of age, macaques move from being dependent on their mother during infancy, to the juvenile stage, where they begin to associate more with other juveniles through rough tumble and playing activities. They sexually mature between three and five years of age. Females will usually stay with the social group in which they were born; however, young adult males tend to disperse and attempt to enter other social groups. Not all males succeed in joining other groups and may become solitary, attempting to join other social groups for many years.[9] Macaques have a typical lifespan of 20 to 30 years.

M. fascicularis on a scooter at Ko Chang, Thailand

Certain species under the genus Macaca have become invasive in certain parts of the world, while others that survive in forest habitats remain threatened. The long-tailed macaque (M. fascicularis) is listed as a threat and invasive alien species in Mauritius, along with the rhesus macaques (M. mulatta) in Florida.[13]

The long-tailed macaque causes severe damage to parts of its range where it has been introduced because the populations grow unchecked due to a lack of predators.[14] On the island Mauritius, they have created serious conservation concerns for other endemic species. They consume seeds of native plants and aid in the spread of exotic weeds throughout the forests. This changes the composition of the habitats and allows them to be rapidly overrun by invasive plants.

Long-tailed macaques are also responsible for the near extinction of several bird species on Mauritius by destroying the nests of the birds as they move through their native ranges and eat the eggs of critically endangered species, such as the pink pigeon and Mauritian green parrot.[15] They can be serious agricultural pests because they raid crops and gardens and humans often shoot the monkeys which can eliminate entire local populations.

In Florida, a group of rhesus macaques inhabit Silver Springs State Park. Humans often feed them, which may alter their movement and keep them close to the river on weekends where high human traffic is present.[13] The monkeys can become aggressive toward humans, and also carry potentially fatal human diseases, including the herpes B virus.[16]

Management techniques have historically been controversial, and public disapproval can hinder control efforts. Previously, efforts to remove macaque individuals were met with public resistance.[13] One management strategy that is currently being explored is that of sterilization. Natural resource managers are being educated by scientific studies in the proposed strategy. Effectiveness of this strategy is estimated to succeed in keeping populations in check. For example, if 80% of females are sterilized every five years, or 50% every two years, it could effectively reduce the population.[13] Other control strategies include planting specific trees to provide protection to native birds from macaque predation, live trapping, and the vaccine porcine zona pellucida (PZP), which causes infertility in females.[15]

In January 2018, scientists in China reported in the journal Cell the first creation of two crab-eating macaque clones, named Zhong Zhong and Hua Hua, using somatic cell nuclear transfer – the same method that produced Dolly the sheep.[19][20][21][22]