Allen's Swamp Monkey

Allenopithecus nigroviridis

A stocky, greenish-gray monkey from the swamp forests of central Africa that forages in trees and shallow water.

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About the Allen's Swamp Monkey

Allen's swamp monkeys have bodies up to 18 inches long and tails even longer. Males can weigh more than 13 pounds, while females weigh about 7.5 pounds. They live in swamp forests of the Congo basin in central Africa and often sleep near water. They eat fruit, seeds, leaves, insects, fish, shrimp and snails, searching on the ground and in shallow water.^[1]

Quick facts

Scientific name: Allenopithecus nigroviridis^[1]
Size: Body up to 18 inches; tail over 19 inches.^[1]
Weight: Males over 13 pounds; females about 7.5 pounds.^[1]
Lifespan: About 28 years.^[1]
Diet: Omnivore. Fruits, seeds, leaves, insects, fish, shrimp and snails.^[1]
Habitat: Swamp forests.^[1]
Where it lives: Central Africa's Congo basin, including Cameroon, Congo and the Democratic Republic of the Congo.^[1]
Group life: Troops of 40 or more. Active during the day.^[1]
Babies: Usually one baby, rarely twins, after a 5- to 6-month pregnancy.^[1]
Conservation status: Least Concern (IUCN Red List, assessed 2018).^[2]

Fun facts

Allen's swamp monkeys find food in shallow water as well as in trees.^[1]
Their calls include warning chirps, deep croaks and grunts.^[1]
Their tails are usually longer than their bodies.^[1]

Vocabulary

troop: A group of monkeys that live together.
swamp: A wet, spongy area of land often covered with water and trees.
arboreal: Living mostly in trees.
omnivore: An animal that eats both plants and other animals.
least concern: A conservation label meaning a species is widespread and not at risk of dying out soon.

See it in person

Smithsonian's National ZooWashington, D.C. · PrimatesSee this animal on the zoo's website ↗

These zoos had this animal when we gathered our information, but animals sometimes move. Check the zoo's website or contact the zoo before you visit.

Sources

[1] Smithsonian's National Zoo & Conservation Biology Institute. “Allen's swamp monkey.” https://nationalzoo.si.edu/animals/allens-swamp-monkey (accessed 2026-10-08)
[2] IUCN Red List of Threatened Species. “Allenopithecus nigroviridis (Allen's Swamp Monkey).” https://www.iucnredlist.org/species/865/166606573 (accessed 2026-10-08)