Plecturocebus donacophilus (d'Orbigny, 1836)

Common Name and Size Class

Plecturocebus donacophilus, commonly called the white-eared titi, is a medium-sized primate.

Sexual Dimorphism and Body Length

This species has no sexual dimorphism: average male head-and-body length is 311 millimetres (12.2 in), while average female head-and-body length is 340 millimetres (13 in).

Body Weight

Females are generally slightly lighter in body weight, which ranges from 800 to 1,200 grams (1.8 to 2.6 lb) overall.

Pelage Characteristics

The white-eared titi has grey to orange pelage, with thick fur.

Body Coloration

Its dorsal side and limbs range in color from grey agouti to orange agouti, it has an orange underside, and distinct white ear tufts.

Tail Morphology

Its fluffy tail is longer than the combined length of its head and body.

Dental Formula

It has a dental formula of 2.1.3.3/2.1.3.3 × 2 = 36: on each side of each jaw, it has two incisors, one canine tooth, three premolars, and three molar teeth.

Canine Tooth Size

Compared to other New World monkeys, its canine teeth are relatively short.

Lifespan

Captive white-eared titis have been recorded living over 25 years.

Habitat Preference Humidity

The white-eared titi inhabits tropical humid forests, and actually prefers drier regions over more humid ones.

Habitat Types

It occurs in riparian zones and gallery forests, and is strongly associated with open habitats such as grasslands and swampy grasslands.

Vegetation Preference

It prefers areas with dense vegetation, and often lives in the thickest parts of the forest.

Disturbance Tolerance

The species shows notable tolerance to habitat disturbance.

Geographic Distribution

Its distribution covers parts of Bolivia and Brazil: in Bolivia, it lives in the upper basins of the Mamoré, Grande, and San Miguel rivers, east of the Manique River in Beni, and in the forests surrounding Santa Cruz de la Sierra; its range extends north into southern Rondônia, Brazil.

Research Status

Relatively little is known about the ecology of the white-eared titi, or even titi monkeys as a whole, with few studies focused specifically on this species.

Activity Pattern

It is diurnal: it becomes active around sunrise and remains active until sunset.

Food Availability and Activity Timing

Food availability can alter its activity times: when food is abundant during warmer fruiting months, it may start activity earlier, while when food is scarce, it may stay at its feeding tree into the evening.

Daily Activity Structure

It typically rests during the middle of the day, has two main feeding periods in the morning and afternoon, and has an extended feeding period towards the end of the day.

Daily Activity Duration

On average, it is active for 11.5 hours total each day, 2.7 hours of which are spent feeding.

Sleeping Site Height

It sleeps on branches at least 15 metres (49 ft) above the ground.

Sleeping Behavior

Like when resting during the day, sleeping white-eared titis huddle together and twine their tails.

General Titi Diet

While there is little published research specifically on the white-eared titi's diet, titi monkeys overall are omnivores that eat fruit, leaves, insects, and seeds.

Leaf Consumption and Digestion

They feed mostly on leaves, particularly young leaves and leaf buds that are high in protein, so they spend a large portion of the day resting to digest the cellulose in these leaves.

Plant Food Diversity

In total, they consume food from over 100 different plant species.

Animal Prey

They also eat small insects including ants, moths, butterflies and their cocoons, as well as spiders, and can catch flying prey that comes near their position.

Seasonal Diet Variation

Feeding time spent on leaves increases during the dry season, and it is thought that insect consumption increases during lactation to boost the protein content of the diet.

Daily Travel and Home Range

The white-eared titi travels between 425 and 1,152 m (1,394 and 3,780 ft) each day, and maintains a home range of 0.005 to 0.14 km² (0.0019 to 0.0541 sq mi).

Dry Season Travel Distance

During the dry season, less fruit is available, so the species does not need to travel as far; its daily travel distance in the dry season is often only one third of its usual distance.

Sympatric Primate Species

The white-eared titi often shares its home range with other primate species, including marmosets, squirrel monkeys, capuchins, owl monkeys, howler monkeys, and spider monkeys.

Interspecific Interactions

Larger primate species will sometimes chase it away from feeding sites, and the white-eared titi generally tries to avoid other primates.