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 en
