The white-nosed saki (Chiropotes albinasus) is a species of bearded saki, a type of New World monkey, endemic to the south-central Amazon rainforest in Brazil. Both its scientific and common name were caused by the authors working from dead specimens, where the skin on and around the nose fades to a whitish color. In living individuals, the nose is actually bright pink (though with fine barely visible white hairs). Pelage on the body tends to be black in males and brown to brownish-grey in females. No other species of the genus Chiropotes have a brightly coloured nose. This species is considered to be "medium-sized". They are a primary consumer that eats seeds, fruit, flowers, bark, insects and leaves. They are also a social species that arrange themselves into large groups for many reasons such as sleeping, food gathering and travel arrangements. These social groups are important in situations where they are under attack by a predator as they decide on their anti-predation strategies depending on the number of them available at the time. They are seasonal breeders, only reproducing in specific months during the year. In the 2020 IUCN Red List report, this species was listed as vulnerable with a decreasing population.
Distribution and habitat
Geographical distribution The distribution of this species depends on their ability to survive and adapt to drastic changes in the environment. They are known to be able to handle difficult environmental changes to the point where they can survive for a long period of time before having to move elsewhere. According to research, they are distributed mostly throughout the south-east and south-central regions of the Amazon Rainforest which extends into the country of Brazil. They are dominant in the southern region of the Amazon since they share the eastern part with the Uta Hicks bearded saki which causes problems with food availability. They have also been observed towards the south-western area of the Dos Marmelos River in Brazil.
Habitat preferences As a primary consumer, the white-nosed saki is dependent on habitats with enough food supply. Due to their similarity in diet with other Chiropotes, it is rare to find this species in habitats where they are required to coexist and compete over food supply. They are mainly found in terra firma ecosystems within the Amazon, where their preferred food source of immature seeds is readily available. This species prefers primary terra firma forests which means it has had little to no human disturbance. These forests are known for their "poor soils", but this is not an issue for this species. In fact, they live within this ecosystem because of their ability to easily organise groups for foraging to find their required food source. Although their habitat preference is mainly dependent on food availability, this species also prefers to live within the shaded comfort of upper canopies which are the main characteristic of this particular habitat. These upper canopies are where they have been observed spending most of their day-to-day lives. This species has also been found living and passing through "mountain savanna forests" due to the high elevation; however, this is not as common.
Morphology
Physical characteristics The white-nosed saki has three common physical features including a beard, two "tufts of hair" on its head, and a long "bushy" tail. Its physical characteristics make it easy to identify amongst other species of the genus Chiropotes. Their distinct features include an entirely black, "silky" fur body in contrast with their "reddish-pinkish" noses and lips. In fact, their name can be confusing because although they have 'white' hairs on their noses, the skin of their nose is a brighter mix of red and pink which makes it the more visible colour. Although both the male and female have the same physical features, the female can be distinguished to the male through their shorter and thinner hair within their tufts and beards. Two of their most important body parts include their tail and teeth. The function of their tail changes from when they are young. It is initially used for swinging across canopies, but then becomes "non-prehensile" and used only for balance as they become adults. Regarding balance, this species uses their tail to support them during suspensory behaviours, mostly with feeding. Their teeth on the other hand are described as being of a "canine" appearance and these help them break through the tougher foods they eat e.g., fruits and seeds with harder outer shells.
Body measurements Various research papers have produced similar data which describe this species to be of a medium size. On average, weight measurements were found to be between a minimum of 2.5 kg and a maximum of 3.1 kg, with the female weighing less across all studies. In one of the earlier studies in 1981, José Márcio Ayres found that the female weighed in at 2.52 kg and the male at 3.17 kg. Another study in 1992 found that the female weighed 2.51 kg, while the male weighed 3.02 kg. Then one of the more recent studies in 2009 identified the female weight to be roughly 2.56 kg with the male weighing in at 3.06 kg. In terms of length, the head and body combined measurements for the male and female were measured across two studies. The first measured 39.5 cm for females and 40.2 cm for males, while the other measured females at 41.8 cm and males at 42.7 cm. Generally, their body measurements and weight, in combination with their tails for balance and support, makes them "agile and fast-moving" and "super climbers and leapers".
Behaviours
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