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Rancho La Brea FAQs
Why are the skeletons on display in the Page Museum brown in color?
The brown color results from the bones becoming saturated with asphalt over thousands of years.
Are the skeletons on display the real bones?
Nearly all of the skeletons on display are real fossils found at the tar pits. They have been mounted using an internal steel and wire armature. Missing bones or parts originally composed of cartilage have been reconstructed with resin or plaster. Only the Shasta ground sloth is 100% plaster, because the bones of this species are rare from Rancho La Brea. In addition, the Columbian mammoth and American mastodon tusks are fiberglass because the original tusks were not completely preserved.
How old is the oldest fossil from Rancho La Brea?
Using the Carbon-14 radiometric dating method, some of the oldest fossils include a dire wolf and a sabertoothed cat from Pit 91 dated at 44,000 years old, a coyote from Pit A dated at 46,800 years old, and wood from Pit 16 dated at 55,000 years old. These dates are estimates based on the amount of carbon 14 isotope remaining in the specimens. The real age of these specimens may be as much as 5,000 years older than the radiocarbon estimates.
When did the animals found at Rancho La Brea live in this region?
The extinct animals discovered at Rancho La Brea were trapped in the asphalt between 11,000 to 50,000 years ago. They may have lived in the Los Angeles region for much of the last 100,000 years but before that time the Los Angeles Basin was covered by the Pacific Ocean.
How many fossils have been removed from Rancho La Brea?
Since 1906, more than one million bones have been recovered representing over 231 species of vertebrates. In addition, 159 species of plants and 234 species of invertebrates have been identified. It is estimated that the collections at the Page Museum contain about three million items. Project 23 is estimated to double this current collection!
What are the most common animal remains found?
Dire wolves are the most common large mammals from Rancho La Brea, with about 4,000 individuals represented in the Page Museum collections. The remains of over 2,000 individuals of sabertoothed cat rank second and coyotes third.
Why are so many fossils found in a single asphalt deposit?
Individual asphalt deposits are the results of entrapment and accumulation over thousands, and in some cases tens of thousands, of years.
How did the animals become trapped?
Asphalt is very sticky, particularly when it is warm. The warm temperatures from late spring to early fall would have provided the optimum conditions for entrapment in asphalt.
Small mammals, birds, and insects inadvertently coming into contact with it would be immobilized as if they were trapped by flypaper. The feet and legs of heavier animals might sink a few inches below the surface. Depending on the time of day or year, strong and healthy animals might have managed to escape, but others would have been held fast until they died of exhaustion, or fell prey to passing predators. A single mired large herbivore might attract the attention of a dozen of hungry carnivorous birds and mammals, some of which would find themselves trapped, providing more food for other carnivores.
This cycle was repeated over the 30,000 years that fossils were accumulating at Rancho La Brea. It has been estimated that one entrapment episode involving ten large mammals every decade would furnish more than enough fossil remains to account for all the large mammal and bird fossils collected since the turn of the twentieth century, over 1 million.
Is entrapment still occurring at Rancho La Brea?
Yes, small mammals and birds sometimes get stuck in the asphalt today.
What was the Ice Age like in the Los Angeles Basin?
Many plant species found in these fossil deposits now only live along the summer fog belt from San Luis Obispo to Oregon and on the Channel Islands. A few species occur today in the southern Sierra Nevada Mountains between 4,000 and 6,000 feet elevation. This suggests that the late Pleistocene maritime climate at Rancho La Brea was cooler and wetter than it is today.