Bears of Anza-Borrego Desert State Park
Ancient Bears of Southern California

Bears have been among North America's most successful large mammals for millions of years. The fossil record preserved in Anza-Borrego Desert State Park documents several members of the bear family, including species that no longer exist today. These animals occupied a variety of ecological roles, ranging from omnivorous foragers to some of the largest terrestrial predators ever to inhabit North America.

The fossil deposits of Anza-Borrego preserve evidence of both extinct and modern bear lineages, providing important clues about mammalian evolution, environmental change, and the development of prehistoric ecosystems in southern California.

Bears in Ancient Anza-Borrego
During the Pliocene and Pleistocene, the landscapes of Anza-Borrego were very different from the modern desert. Rivers, woodlands, grasslands, and wetlands supported diverse communities of mammals, including horses, camels, mammoths, ground sloths, and bears. 

Among the most impressive members of the bear family was the giant short-faced bear, Arctodus. This enormous animal was one of the largest mammalian carnivores in North America and may have competed with saber-toothed cats and dire wolves for food resources.

Other bear species represented in the fossil record were more similar to modern bears and likely occupied a variety of ecological niches, feeding on both plant and animal resources.

The Short-Faced Bear
The giant short-faced bear (Arctodus) is one of the most remarkable carnivores known from the Pleistocene of North America. With long legs and a massive body, it was considerably larger than most living bears.

Although scientists continue to debate aspects of its behavior, Arctodus was undoubtedly one of the dominant mammals of Ice Age ecosystems. Its fossils help paleontologists understand predator communities and ecological relationships during the late Cenozoic
The discovery of short-faced bear remains in Anza-Borrego demonstrates that the region once supported large prey populations capable of sustaining major carnivores.

Relatives of Modern Bears
The fossil record also documents members of bear lineages that are more closely related to living species. These fossils provide evidence for the long history of bears in western North America and help scientists trace the evolution and distribution of the family through time.

By comparing fossil and modern bears, researchers can better understand how changing climates and environments influenced mammalian populations during the Pliocene and Pleistocene.

What Bear Fossils Tell Us
Bear fossils help scientists reconstruct:
  • Ancient ecosystems and food webs
  • Predator and scavenger communities
  • Climate and environmental change
  • Mammalian evolution in North America
  • The distribution of large carnivores through time
Because bears occupy important ecological roles, their fossils contribute valuable information about the structure of prehistoric animal communities.
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Explore a Fossil in 3D
Rotate, zoom, and examine this specimen from the Anza-Borrego Desert State Park collections.
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Interactive 3D Model: Tremarctos floridanus
Specimen Information
  • Catalog Number: LACM1454 V4118
  • Element: Dentary
  • Formation: Hueso
  • Epoch: Pleistocene
  • Age: Blancan and/or Irvingtonian
  • Locality: Fish Creek / Vallecito Creek
  • Scanned using Agisoft Metashape
  • Specimen © California State Parks. 3D model produced by the Anza-Borrego Desert State Park Paleontology Society.
Why Anza-Borrego Matters
Anza-Borrego Desert State Park preserves one of the most important late Cenozoic fossil records in North America. Fossil bears are an important part of that record and help document the diversity of large mammals that once inhabited southern California.
Together with fossils of saber-toothed cats, dire wolves, mammoths, camels, and horses, the bear fossils of Anza-Borrego reveal a landscape far richer and more diverse than the desert environment seen today
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The Fossil Record
  • Short-faced bear (Arctodus simus)
  • Florida cave bear (Tremarctos floridanus)

Quick Facts
  • Family: Ursidae
  • Includes: Short-faced bears and relatives of modern bears
  • Famous species: Arctodus
  • Age: Pliocene and Pleistocene
  • Role: Large omnivores, predators, and scavengers
  • Significance: Evidence of Ice Age carnivore communities
  • Location: Anza-Borrego Desert State Park, California
Learn More
Read Chapter 11, "The Large Carnivorans: Wolves, Bears and Big Cats," in Fossil Treasures of the Anza-Borrego Desert for a detailed discussion of fossil bears and their role in the ancient ecosystems of Anza-Borrego Desert State Park.