What is Non-Human Primate (NHP)?


The term ‘Primate” often refers to the type of mammal constituting the taxonomic order Primates, whereas the term ‘Non-Human Primate’ or ‘NHP’ is simply the same taxonomic order excluding ‘Human (genus homo)’, or in a more routine way to say, us, the only existing species Homo Sapiens. Since around 85–55 million years ago, the first primate species arose from jungle forests, typical environmental-adaptive traits started to present such as large brains, visual acuity, colored vision, large degree of movement in the shoulder joint, and dextrous hands, as strategies to survive in this environment, where many of the traits had eventually inherited by human.

Nowadays, there are about up to 522 species of primates (NHP) living on this planet, ranging from the tiniest Madame Berthe's mouse lemur, which weighs 30g, to the largest eastern gorilla, weighing over 200kg. A ‘super’-briefed classification of existing primate species is as following:

Primates:

1.       the strepsirrhines ('twisted-nostriled')

a)       lemurs

b)       galagos

c)       lorisids

2.       the haplorhines ('simple-noses')

a)       the tarsiers

b)       the simians ('snub-noses', ‘monkeys and apes’).

                     i.            the platyrrhines ('flat-noses'), or New World monkeys

Ø  capuchins

Ø  howlers

Ø  squirrel monkeys

                   ii.            the catarrhines ('narrow-noses'), or Old World monkeys

Ø  baboons

Ø  macaques

                  iii.            the apes (including humans)

Ø  gibbons

Ø  great apes

Old World Monkeys


Being the largest primate family, the Old World Monkeys now has over 24 genera and over 138 species recognized by humans. Native to Africa and Asia, these monkeys now inhabit numerous environments such as tropical regions, savannas, and both arboreal (‘tree-living’) and terrestrial species are existing. Despite being Omnivorous, the majority of food component of Old World Monkeys are plant- or grain-based.

Most species of Old World monkeys are large in size but there are also small species, such as the talapoin, being the smallest among all with a 34–37 cm length, and 0.7-1.3kg in weight. In contrast the mandrill is about 70 cm in length, and up to 50 kg in weight. The common distinction of Old World Monkeys from New Old Monkeys is the structure of the rhinarium (nose), due to the fact that Primates generally tend to present an evolutionary trend towards a reduced snout. Because of the same reason, it is the arrangement of dentition (teeth shaped differently) that distinct Old World Monkeys form the apes.

Like humans, births from Old World monkeys are usually single and occasionally twins, following a Gestation period from five to seven months, differed by each species. The infants are born relatively well-developed, and lactation can often end around 3-8 months after birth. It takes a while before the monkey grown into sexually matured individuals, with three to six years being typical of most species. In many species, only a single adult male lives or dominate the entire cohort, expelling all rivals, establishing hierarchical relationships between dominant and other individuals. Group sizes are highly variable, even within species, depending on the availability of food and other resources.

Cynomolgus macaque

Cynomolgus macaque (Macaca fascicularis), also named long-tailed macaque and referred to as the cynomolgus monkey in laboratories, inhabit in South East Asian territories and is a member of the macaque family. The crab-eating macaque has a long history alongside humans, and in some languages the species is also called ‘crab-eating macaque’, due to that it is believed to be found initially on the beachside while foraging crabs. Cynomolgus macaque has been recorded using tools as a measure to obtain food, and each have a cheek pouch to store food while foraging. Inter-species conflicting with human and other mammals has been documented in the history, due to the great overlap in habitat and resources. 

When reached adulthood when about 4-5 years old, typical male could have varied body lengths of 38–55 cm (15–22 in), and body weights of 5–9 kg, depending on the subspecies and nutrient condition. In contrast, adult females have smaller body weight of 3–6 kg. The dark-brown colored fur covers most part of the body, except for the abdomen which most likely to be white or light grey. Black skin on the feet and ears, pink skin around the snout, and swollen red bottoms during the mate season. Typical infantile cynomolgus macaque is born after an around 6-7 months’ gestation, and the weight at birth is about 300-400 g. Usually only one newborn is found and rarely twins. The infant spends most of the times staying with its mother and become more peripheral to the group when growing older. At puberty the males will leave the group and seek to join other groups. Young females, on the other hand, stay with the group which they were born.

A social group of cynomolgus macaque is usually composed of one alpha male, none, or few other males, and 5-20 females, and the offspring. that contain three to 20 females, their offspring, and one or many males. The form the social groups are usually matrilines where a clear and stable dominance hierarchy is seen among females. In addition, male dominance rankings also exist as alpha males have a higher frequency of mating, and less dominant individuals lose to a higher-ranking individual when conflict arises. Interestingly in almost all groups, grooming and support among the individuals is a measure of conflict mitigation and increasing mating opportunities.

As a commonly species for medical experiments, cynomolgus monkeys have been used extensively in the fields of neuroscience and disease research. Due to the close phylogeny and similar physiology to humans, preclinical studies with cynomolgus monkeys present huge advantages in the evaluation of drug safety, metabolic, efficacy, and translational research for new drug research and development. – this will be elaborated in detail in the section ‘What is a NHP study’.


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