Andean Bear

About the Andean bear

The Andean bear, also known as the spectacled bear, is the only bear species native to South America and the last surviving member of the short-faced bear subfamily, Tremarctinae — a group that also once included the North American Tremarctos floridanus and the fellow short-faced bears Arctodus and Arctotherium, both of which went extinct around 12,000 years ago at the end of the Pleistocene. Unlike most bears, which are omnivorous, the Andean bear's diet is mostly herbivorous, a distinction that sets its ecology apart from relatives like the American black bear or brown bear.

The name "spectacled bear" comes from the light, beige or ginger-colored markings that some individuals carry across the face and upper chest, which can resemble spectacles. Not every bear has this patterning, though, and the shape and extent of the markings differ from one animal to the next, making individuals distinguishable by their facial patterns alone. The rest of the coat is blackish, ranging from jet black to dark brown or even reddish. The species is also known locally as jukumari or ukumari in Aymara and Quechua, names that translate roughly to "hole bear," a reference to the way the pale facial markings can make the eyes look like dark holes.

Genetically, tremarctine bears diverged from other living bears around 5.7 million years ago, and the group underwent a burst of diversification near the end of the Miocene as grasslands spread and the climate cooled sharply. The Andean bear itself doesn't show up in the South American fossil record until the Holocene, and researchers believe it descends from a distinct, later wave of bears that dispersed south from North America, possibly after other short-faced bears in South America, such as Arctotherium, had died out. Its skull differs from those of other living bears in several ways: it has taller, shorter skulls with well-developed zygomatic arches, larger and more rounded eye sockets, and bigger molars relative to its size.

Andean bears show striking size differences between the sexes. Males are about a third larger than females and sometimes twice their weight, ranging from 100 to 200 kg (220 to 440 lb) and averaging around 115 kg (254 lb); one obese captive male weighed 222.5 kg (491 lb). Females run from 35 to 82 kg (77 to 181 lb), averaging about 65 kg (143 lb) — a level of sexual dimorphism rivaled among living bears only by the polar bear. Shoulder height ranges from 70 to 90 cm (27.5 to 35.5 in), the tail is a short 10 cm (3.9 in), and head-and-body length runs from 1.2 to 2 m (4 to 6.5 ft), with mature males measuring at least 150 cm (4.9 ft).

Behavior and diet

The Andean bear is one of only four living bear species that are habitually arboreal, alongside the American black bear, the Asian black bear, and the sun bear. In the Andean cloud forests that make up its core habitat, it can be active during both the day and night; in the Peruvian desert, by contrast, individuals tend to bed down under cover during daylight hours. Climbing ability has been key to the species' survival alongside expanding human settlement — bears typically retreat from people by heading up a tree, and once there, they sometimes build a platform, likely useful for concealment as well as for resting and storing food.

Andean bears are solitary and generally keep their distance from one another to avoid competition, but they are not territorial, and have even been recorded feeding together in small groups where food is unusually abundant. Males range more widely than the setting suggests for a mid-sized bear: an average of 23 km2 (8.9 sq mi) during the wet season, expanding to 27 km2 (10 sq mi) in the dry season. The species also has an unusually acute sense of smell — sensitive enough to detect from the ground when a tree overhead is loaded with ripe fruit — which compensates for hearing that is only moderate and eyesight that is comparatively short.

Range and habitat

Andean bears are found almost entirely within the Andes Mountains, ranging through Venezuela, Colombia, Ecuador, Peru, western Bolivia, and northwestern Argentina, with occasional spillover into eastern Panama. The range is a narrow, elongated band — only 200 to 650 km (120 to 400 mi) wide but stretching more than 4,600 km (2,900 mi) along the mountain chain.

Before the last 500 years fragmented its populations, the species had a reputation for adaptability, turning up in cloud forests, high-altitude grasslands known as páramo, dry forests, and scrub deserts. The best habitat for Andean bears is humid to very humid montane cloud forest, typically occupying an elevational band of 500 to 1,000 m (1,640 to 3,280 ft) somewhere within the broader range of 1,000 to 2,700 m (3,280 to 8,860 ft), depending on latitude — generally, the wetter the forest, the more food it can support. Bears occasionally range as low as 250 m (820 ft) but are rarely found below 1,900 m (6,230 ft) in the foothills, and can climb as high as the mountain snow line, above 5,000 m (16,400 ft), in elevation.

Conservation status

The Andean bear is classified as Vulnerable by the IUCN, primarily because of habitat loss across its Andean range. Populations have become fragmented over the last 500 years, in contrast to the species' earlier reputation for adaptability across a wide range of forest and grassland habitats.