Proboscis monkey (swamp forest): largest colobine,
BP + climbing arms overhead, rel.long legs,
gibbonlike locomotion "suspensory",
"walks upright on land", long feet

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Nasalis larvatus (Primates: Colobini)
Lee E Harding 2015
Mammalian Species 47, Issue 926:84–99
doi org/10.1093/mspecies/sev009
... proboscis monkey (the only member of its genus) = largest colobine monkey ... uniquely large nose in males ... folivore in lowland riverine forests, peat swamps & mangrove swamps of Borneo.
It is a strong swimmer, and can swim underwater.
it lives in single-male-multi-female troops or all-male groups, in a multi-level social system. Male dispersal is routine. Females commonly transfer among groups.
... The largest colobine is also the most sexually dimorphic (mean mass of 14 females 10 kg, 13 males 21.2 kg).
Both genders have uniquely large noses: pendulous in mature males, hangs below the mouth, can reach 17.5 cm in length.
N.larvatus is the only cercopithecid in which femur + tibia length is longer than the skeletal trunk ...
habitat along lowland rivers, near-shore islands & coastal mangrove swamps ... large hands & feet, swims well, a useful capability for its riverine & tidal habitats ... an observation of 1 individual swimming submerged for 28 min(?? --mv) to avoid a
hunter in a boat; Bennett & Sebastian (1988) confirm: N.larvatus can swim underwater for up to 20 m to avoid avian predators ... enlarged nose for sex.display, and to amplify vocalizations.
In the odd-nosed colobines (incl.Mesopithecus), several aspects of the scapula (e.g. overall proportions, inclination of glenoid fossa) resemble hylobatids = frequent overhead suspensory locomotion (N.G.Jablonski)?
Youlatos cs (2012:227) classified duoc-langurs, simakobou & Nasalis as “Arboreal Walking/Suspensory” (vs snub-nosed monkeys “Arboreal Walking/Terrestrial”).
Its shoulder morphology “seems to accommodate extended arm movements at the shoulder level, favor a partially extended elbow, and promote frequent forearm prono-supination” (vs the other colobini studied); these movements “occur frequently in
forelimb dominated positional activities: arm swing, brachiation or vertical climb are common”. Suspensory feeding in N.larvatus is common. Napier (1963:187) describes its leap: “its hind-limbs at the moment of take-off are extended at knee & hip
joints. In flight, the forelimbs are extended at the shoulder ...”
N.larvatus walks upright, with the arms raised, when on land & wading (Bennett & Sebastian 1988) ... hands & feet are not “webbed” per se, but the feet have a slight webbing at the base of the phalanges between toes 2 to 5 that may extend as far as
the middle of phalanx 2 (Schultz 1942). The metacarpus & metatarsus are long, absolutely & relative to the digits; these features no doubt give support when walking on soft mangrove swamp mud & in swimming.
... regurgitate & remasticate food ... highly folivorous diet ...
N.larvatus occurs mainly along rivers, coastal deltas & islands, rarely >200 km inland from the coast, usu.at elevations <200 m, max.of c 350 m. Its habitat is mainly riparian or riverine dipterocarp forest & coastal or inland mangrove forest (
dipterocarp forest has taller trees >mangrove, = better predator-avoidance cover, esp.the taller trees used for sleeping) ...
Typical habitat in Sarawak is mangrove-nipa forest along the saline-brackish portions of rivers (Avicennia & Sonneratia close to the river-mouth, upstrea Rhizophora, further upriver Brugiera & Nypa fruticans; further up, where the water is fresh, the
riparian forest is often taller than the surrounding lowland dipterocarp forest) ...
non-territorial, home range sizes mean of 130 ha (25–138 ha) to 221 ha in riverine forest, and 315 ha in coastal mangrove forest with up to 100 % overlap among groups, to 900 ha in mixed mangrove & lowland forests. In good habitat with little
disturbance, home ranges can be much smaller ... Food availability = main determinant of home range size ...
Daily activity e.g. 76.5 % resting, 19.5 % feeding, 3.5% moving ... feeding peaks at 15–17 h, shortly before sleeping (with differences among the seasons & fruit availability) ...
Daily movement ranges from c 500 m, to an average of 910 m ...
Availability of fruit (but not of flowers or young leaves) is the main determinant of daily path length ... In a riverine forest with a max.canopy Ht of 30 m, N.larvatus climbed up to 21 m high - most feeding, resting & traveling were between 10 and 17 m
high ...
These groups occasionally swam across the Kinabatangan River, which might be c 150 m wide at crossing places, but much wider elsewhere, and almost daily across 20–25 m wide tributaries.
Choice of sleeping trees depends on tree size & proximity to the river, not on the tree spp ... near other trees with overlapping branches + good arboreal connectivity for escape ... but at Sungai Tolak, N.larvatus preferred to sleep in large, emergent
trees with few canopy connections located along rivers: less molestation by mosquitoes? reduced potential entry routes for terrestrial predators? ... sleeping sites in tall trees on the river-bank in the angle of bends in the river, and where the river
is narrow, is predator-avoidance strategy?: when danger approaches from land, N.larvatus can leap into the river, and swim across. When the forest is flooded, the predation risk is less = more likely to select interior-forest sleeping sites.
Home range size & daily movement distances are influenced by food (esp.fruit) availability ...
Diet ... e.g. at Kutai Nat.Park: 81.1 % leaves, 8.38 % fruit, 7.68 % flowers, 2.8 % other (bark, insects, crabs)...
On the Kinabatangan River, of the 48 dominant plant spp, 16 had fruits & flowers that N.larvatus did not eat at all: seeds too hard? fruits too big? but orangs & long-tailed macaques ate fruits of at least 5 of those spp ... N.larvatus also consumes bark
of certain trees & nests of an arboreal termite (termites supplement mineral nutrients, absorb toxins, assist digestion, rather than serving as a protein source)...
Leaves from spp consumed are higher in protein, P & K, lower in fiber, Ca & Mg than those available but not consumed (cf other colobine diets that are typically high in protein, and low in protein inhibitors) ...
N.larvatus inhabits riverine forests with higher-quality leaves than other available forest types, incl. primary lowland forest ...
... high Na+ content in their study area (a small patch of mangrove forest adjacent to the ocean, surrounded by a sea of oil palm plantations) vs other dietary studies (limited vegetation heterogeneity).
... an 8.84 kg N.larvatus would consume 900 g fresh Wt (270 g dry Wt) of food/day = 1066 kcal = 120.68 kcal/kg of body-Wt ... leaves, fruits, flowers, seeds eaten are lower in protein, higher in lignin > 9 other colobine spp (poor quality diet?), but
some riparian plant spp’ leaves & aerial roots have higher mineral content than the same plants grown in soil (a nutritional advantage of their habitat?). Certain foods are consumed in small amounts, but contribute a disproportionate amount of
nutrients: high in K, Zn, Ca, Cu: Alophyllus cobbe, R.apiculata flowers, Avicennia officinalis & R.apiculata bark ...
The most frequently heard vocalizations are resonant, drawn-out goose-like calls (female a little softer than the male). Based on multi-parametric analysis, Röper cs identified acoustic features of the 4 most common call types: shrieks, honks, roars,
brays: 3 are “loud calls” (for non-invasive, vocalization-based monitoring). They also described “choruses”: multiple callers produced mixed vocalizations.
During acts of aggression, or when alarmed, they make a very high frequency tonal call (shriek, max.pitch 1.4–6.8 kHz), higher than expected based on a compar.study of large primates = adaptation for predator avoidance (crocodiles) & intra-group
contact in dense vegetation?
...
Nasalis occupies a monophyletic clade of odd-nosed monkeys Rhinopithecini (+ simakobu, duoc-langur, snub-nosed monkey). DNA & mtDNA, Nasalis & snub-nosed monkeys form a sister-clade to duoc-langurs, the odd-nosed group as a whole forms a sister-taxon
with surilis. The odd-nosed clade incl. Nasalis ancestors diverged from the Presbytini (langurs, lutungs, surilis) 7–10 Ma. Age of divergence estimates based on mtDNA: the lineages leading to snub-nosed monkeys, duoc-langur & Nasalis+simakobu
originated late-Miocene c 7.3 Ma,
Nasalis+simakobu split from duoc-langurs 6.3 Ma,
Nasalis & simakobu diverged early-Pleistocene 2.5 to 1.75 Ma.
(cf HP/Gorilla(Lucy...) c 7.5 Ma? Homo/Pan(Taung...) c 5 Ma?? --mv)

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