How did the animals become entrapped?
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 two or three inches below its surface. Depending on the time of day or year, strong and healthy animals may have managed to escape, but others would have been held fast until they died of exhaustion, or fell prey to passing predators. Under the right conditions, a single mired large herbivore would attract the attention of a dozen or more hungry carnivorous birds and mammals, some of which would find themselves trapped, providing more food for other carnivores. This cycle repeated during the 30,000 years that fossils were accumulating at Rancho La Brea. It is estimated that one entrapment episode involving ten large mammals every deca
