Mantled HowlerAlouatta palliataWhere and when to see them

The mantled howler is one of Central America’s most recognizable forest mammals, known for calls that can carry far beyond the animal producing them. Mostly black fur contrasts with a fringe of longer golden-brown hair along the flanks. In Costa Rica, groups occupy both extensive forests and some wooded fragments. Their tolerance of disturbed habitat does not remove their dependence on connected trees and reliable food supplies.

Size

45–65 cm head-body length

Weight

3–9 kg

Lifespan

15–25 years

Status

Vulnerable

Mantled howlers spend much of the day resting, an energy-saving strategy suited to a leaf-rich diet. Groups travel through the canopy in relatively short feeding movements, using a prehensile tail for support. Loud bouts of calling, particularly around dawn, advertise presence to neighboring groups. Social groups may contain several adults of both sexes, while grooming, play and close resting help maintain relationships within the group. The guttural roars are primarily used by males to defend territory and communicate group location, reducing the need for direct confrontation. Group size can vary widely, typically ranging from 10 to 20 individuals, including multiple adult males and females.

• An enlarged hyoid bone helps amplify its resonant calls.
• A bare gripping pad beneath the tail tip improves its hold on branches.
• Leaf fermentation helps it extract energy from fibrous plant food.
• Both males and females can leave their birth group.

Howlers are resident and can be observed year-round in Costa Rica. December through April often makes Pacific forest visits easier, and reduced foliage may improve visibility in dry forest. Early morning is usually more useful than choosing a particular month. While generally active at dawn, howlers can also be heard calling throughout the day, especially if groups are interacting or disturbed. Binoculars are essential for observing their often-still forms high in the canopy.

They inhabit tropical dry forest, humid lowland forest, riverine woodland and some secondary growth. Coastal forests can support groups where canopy connections remain intact. Roads, power lines and cleared gaps create hazards, even where monkeys persist near settlements and farms. They are often found in fragmented forests and can adapt to human-modified landscapes if sufficient tree cover and connectivity remain. Their preference for tall trees with strong branches allows them to navigate the canopy safely.

Young leaves are important, supplemented by fruit, flowers and other plant material. Food choices change with seasonal availability and tree species. Microbial fermentation helps process fibrous leaves, but digestion is slow, contributing to long resting periods between bouts of feeding. In addition to leaves, they consume petioles, bark, and even soil, likely to obtain minerals or detoxify plant compounds. Their specialized digestive system allows them to subsist on a relatively low-quality diet, which is a key to their wide distribution.

Common name

Mantled Howler

Scientific name

Alouatta palliata

Animal group

Mammals

Size

45–65 cm head-body length

Weight

3–9 kg

Lifespan

15–25 years

Status

Vulnerable

Identification

The black coat with golden-brown flank fringes and heavy throat distinguishes it from Costa Rica’s slimmer spider monkeys and pale-faced capuchins. Infants and juveniles share the adult's dark coat but may have less developed golden fringing on their flanks. Adult males are generally larger and have a more prominent throat sac compared to females.