Howler Monkey
Howler monkeys are large New World primates famed for their extremely loud, low-frequency calls produced by an enlarged hyoid (throat) chamber, audible for kilometers through forest. They are primarily arboreal folivores that move deliberately in small territorial groups and use a prehensile tail as a fifth limb.
Scientific Name
Genus Alouatta
Behavior
Howlers are diurnal and highly arboreal, spending most of the day feeding, resting, and moving slowly through the canopy. Their hallmark loud vocalizations (male-dominant roaring/howling) are used to defend territory and space between groups; otherwise social life centers on grooming, close affiliative bonds, and coordinated travel within a home range. Group size and social structure vary by species and habitat, commonly forming small multimale–multifemale groups or single-male groups with year-round cohesion.
Breeding
Reproduction timing varies regionally with food availability; many populations show seasonal peaks tied to rainfall. Females produce a single offspring after a gestation of roughly 5–7 months; infants are carried and nursed by mothers, begin solid food later, and are typically weaned by around one year. Sexual maturity occurs after a few years (often 3–4 years), and interbirth intervals are influenced by nutrition and social stress, commonly 1.5–2.5 years.
Characteristics
Howler monkeys have robust bodies (size and weight vary by species), long prehensile tails with a bare gripping patch, and broad skulls housing an expanded hyoid bone that amplifies calls. Their digestive system is adapted for a leaf-rich diet—enlarged gut and microbial fermentation—leading to lower activity levels and slower metabolism compared with more frugivorous primates. Sexual dimorphism exists in size and sometimes pelage; males often produce the loudest calls.
History
Howlers evolved in the Neotropics and have long occupied lowland and montane forests from Mexico through Central America into South America. Indigenous peoples knew and sometimes hunted them; since European colonization their ranges have been altered by deforestation, agriculture and roadbuilding, which fragmented populations and changed local ecology.
Current Status
Conservation status varies by species—from Least Concern for many widespread howlers to Vulnerable or Endangered for range-restricted species (threats include habitat loss and fragmentation, hunting, and road mortality). Conservation measures emphasize habitat protection and corridor creation, local community engagement to reduce hunting, and monitoring of populations and disease impacts.