Alouatta pigra Lawrence, 1933

Taxonomic Naming and Size Status

The Yucatán black howler, scientifically named Alouatta pigra Lawrence, 1933, is the largest howler monkey species and one of the largest New World monkeys. Males of this species are larger than males of any other Central American monkey species.

Body Mass

On average, males weigh 11.4 kg (25 lb) and females weigh 6.4 kg (14 lb).

Body and Tail Length

Excluding the tail, body length ranges from 521 to 639 mm (20.5 to 25.2 in), and the tail itself is between 590 and 690 mm (23 to 27 in) long.

Pelage and Distinguishing Markings

Adult individuals of both sexes have long, black hair and a prehensile tail, while infant Yucatán black howlers have brown fur. Males older than four months have white scrotums.

Diet Adaptations

Like other howler monkey species, the Yucatán black howler has several adaptations that support its folivorous diet, which consists mostly of leaves. Its molars have high shearing crests to help process leaves.

Vocal Adaptation

Males of the species have an enlarged hyoid bone near the vocal cords that amplifies their howling calls. This adaptation lets males locate other males without expending much energy, which is important because leaves are a low-energy food source.

Howling Behavior

Howling activity happens primarily at dawn and dusk.

Activity Pattern

The Yucatán black howler is diurnal and arboreal.

Group Composition

It typically lives in groups containing one or two adult males, with an average ratio of about 1.3 females per male. Most groups have between 2 and 10 members (including juveniles), though groups as large as 16 members have been studied.

Home Range

The home range of a group is between 3 and 25 hectares.

Population Density

In the Community Baboon Sanctuary in Belize, population density can exceed 250 monkeys per square kilometer.

Diet Composition

The diet of the Yucatán black howler is mostly made up of leaves and fruit, with flowers making up a small portion of its food intake. During some seasons, the breadnut tree can provide up to 86% of the monkey's total diet.

Daily Activity Budget

Like other howler monkey species, the Yucatán black howler spends most of its day resting. Eating accounts for around a quarter of its daily activity, moving accounts for around 10% of the day, and the remaining time is spent on socializing and other activities.

Sexual Maturity

Females reach sexual maturity at 4 years old, while males reach sexual maturity between 6 and 8 years old.

Natal Dispersal

Upon reaching sexual maturity, males leave their natal group, while females generally stay in their natal group.

Lifespan

Yucatán black howlers can live up to 20 years.