Monday, February 2, 2009

Ask the Experts: Why did the animals die?

A shift in climate approximately 11,000 years ago ended the Ice Age and resulted in the extinction of the animals seen in our exhibits.

In the Diamond Valley Lake area the fossil record supports the notion that large Ice Age animals died not from a sudden catastrophic event, but as a result of a gradual climate change. This change began to melt the ice sheets and decrease the amount of open landscapes. These changes drastically affected rainfall and growing cycles, changing once-green grasslands and forests into drier chapparal and deserts, and ultimately affecting the entire ecosystem. The change in the weather decreased the amount of plants in the area, and so created greater competition for both plant-eating animals (like mammoths) and, in turn, the predators (like saber tooth cats) that hunted them.

The climate shift also created new environments for bacteria and disease. The microorganisms thrived due to warmer temperatures, as well as new available animal hosts. The slow metabolism of many of the large animals, such as ground sloths, could not fight off these new diseases that flourished in the warmer temperatures.

In other Ice Age sites, fossils have been found indicating large mammals died, at least in part, from being over hunted by humans. At the Diamond Valley Lake sites, though, a gap of 2,000 years exists between the last large mammal fossils and the earliest human archaeological remains, indicating that this was not the case for the mammals in our area.

The combination of restricted food and water supplies, warmer weather, and increased competition and disease all contributed to the death of Ice Age animals. The Ice Age mammal’s inability to adapt to the changes in their environment eventually lead to their extinction.


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