The disappearance of large mammals, like bears, represents a significant loss to global biodiversity. Understanding how species vanish provides insights into the delicate balance of nature and the impacts of human activity. This knowledge highlights the importance of preserving remaining populations and their habitats.
Identifying Extinct Bears
Several bear populations have disappeared, including distinct North American and African subspecies. The Mexican Grizzly Bear (Ursus arctos nelsoni) was a smaller brown bear subspecies, known for its distinctive silver-tipped fur, earning it the Spanish name “el oso plateado.” This bear roamed the temperate grasslands and mountain pine forests of northern Mexico, extending into parts of the United States. Its numbers declined significantly by the 1930s, with only about 30 individuals remaining by 1960. The last confirmed killing occurred in 1964, and the subspecies was considered extinct by the late 1960s or early 1970s, despite unconfirmed sightings into the 1980s.
The California Grizzly Bear (Ursus arctos californicus) was a formidable brown bear subspecies, known for its muscular build and silver-tipped fur, earning it the nickname “California golden bear.” These substantial bears often weighed between 300 to 500 kilograms. Before widespread European settlement, an estimated 10,000 California grizzlies inhabited nearly all of California, thriving in diverse environments. The last documented California grizzly was killed in 1922, with the last reported sighting in 1924, leading to its official declaration of extinction that same year.
In North Africa, the Atlas Bear (Ursus arctos crowtheri) was the only native bear species to survive into modern times on the continent. Smaller than other brown bears, it had brown-black fur with reddish-brown underparts and a stocky build, potentially weighing up to 450 kilograms. This subspecies inhabited the forested mountain regions of the Atlas Mountains, from Morocco to Libya. The Atlas Bear faced intense pressure, with the last known specimen believed killed by hunters in the 1870s, leading to its eradication by the late 19th century.
Factors Leading to Extinction
The demise of these bear populations resulted from a combination of human-driven pressures. A primary cause was the extensive loss and fragmentation of their natural habitats. As human settlements expanded, wilderness areas were converted into agricultural land, towns, and cities, reducing available territory for bears. This encroachment diminished their living space and isolated remaining populations, making it difficult for them to find sufficient food and mates.
Overhunting played a substantial role in their decline. Bears were hunted for sport, fur, and meat, and often captured for public spectacles like bear and bull fights. The Atlas Bear, for example, was hunted since the Roman Empire, with its extinction accelerating with modern firearms. Farmers also targeted bears to protect livestock, leading to widespread persecution through trapping, shooting, poisoning, and bounties.
Escalating human-wildlife conflict exacerbated the bears’ precarious situation. As human populations grew and encroached on bear habitats, encounters became more frequent, often resulting in bears preying on livestock. This led to heightened fear and animosity, contributing to systematic eradication campaigns. For the Mexican grizzly, a slow reproductive rate and recurrent droughts further hindered recovery, concentrating populations and increasing conflict.
The Process of Declaring Extinction
Determining when a species is extinct involves a rigorous scientific process, often guided by organizations like the International Union for Conservation of Nature (IUCN). The IUCN Red List of Threatened Species serves as a comprehensive global inventory of species’ conservation status. A species is categorized as “Extinct” (EX) when there is no reasonable doubt that the last individual has died.
A species is presumed extinct after exhaustive surveys across its known and expected habitats fail to record any individuals. These surveys must span a timeframe relevant to the species’ life cycle. While a historical “50-year rule” for no sightings was once a guideline, current protocols emphasize a thorough, data-driven assessment considering population size, geographic range, and habitat degradation.
Beyond “globally extinct,” other classifications describe different degrees of disappearance. A species is “Extinct in the Wild” (EW) if it only survives in captivity, cultivation, or outside its historical range. “Functionally extinct” describes a species whose population is so diminished it no longer plays a significant ecological role. This also applies when remaining individuals cannot reproduce effectively, leading to irreversible decline, even if some are still alive.