Mexican Grizzlies (Ursus arctos nelsoni) at the Field Columbian Museum, 1919.From: “The grizzly, our greatest wild animal” by Enos Abijah Mills (1870-1922)

Scientific name:  Ursus arctos nelsoni (Clinton Hart Merriam, 1914)

Description:  Smaller than the brown bears of the northern USA and Canada.  Male bears weighed up to around 315 kgs, with females being smaller.  Length was around 180 cms.  Colour varied from pale buff-yellow to a grizzled grey or white which would appear silver in bright sunlight, hence the bear’s Mexican name of “el oso plateado” (the silver bear).

Range:  The Mexican grizzly bear was found in the northern territories of Mexico, particularly in the northern savannah and mountain forests, and northwards into New Mexico and Arizona in the USA.

Historic grizzly range c1850 (light green), remaining range c1920 (dark green), & approximate dates of local extirpations, where known.  Probable extent of Mexican grizzly range edged in red.  (D. Mattson, unpublished data, edging Bear Conservation)

Habitat:  Temperate grasslands and mountain pine forests but also adapted to survive the arid conditions of the Sonoran Desert and canyonlands.

Life span:  Probably a natural lifespan of around twenty five years in the wild.

Food:  In common with other brown bears the Mexican grizzly was an omnivore eating plants, fruits, insects, small mammals and carrion.

Behaviour:  It seems unlikely that the bears would have hibernated although they may have spent some time in winter dens.  Females produced one to three cubs which would remain with them for around two and a half years, during which time the mother would not become pregnant again.  Except during mating and for mothers with cubs the bears were solitary.

Reasons for extinction:  With the expansion of cattle farming within the Mexican brown bear’s range the animals increasingly came to be considered by cattle farmers as pests and were trapped, shot and poisoned.  The situation deteriorated rapidly in the early twentieth century and the subspecies was rare by the 1930s.  Ultimately their range was reduced to the isolated mountains of Cerro Campano, Santa Clara and Sierra del Nido and by 1960 it was believed that only thirty bears or less remained.  Although the bears were protected illegal hunting and persecution continued.  By 1969, probably sooner, the subspecies was extinct.  From time to time there have been rumoured sightings of lone animals and in 1980 Trevino & Jonkel published a report indicating that grizzly bears might still be present in Mexico (see “More Information” below).  There have been no further substantiated sightings.


“Do grizzly bears still live in Mexico?” (Trevino & Jonkel, 1980).  Click here for pdf of report.

Page updated 15 September 2017