Angel Island

Angel Island, off the coast of California, had a healthy deer population in a state park. Hunting was prohibited, and the number of deer in the park increased beyond what the habitat could support. The California Department of Fish & Game suggested that biologists shoot excess deer to reduce deer numbers. The public was opposed to the idea, and 203 animals were instead live-trapped and released in another part of the state.

Some of the deer that were released had a radio “collar” put around their necks. The collar would tell biologists where the deer were, and it would help them study how the deer would survive in their new habitat. At the end of the first year, 85% of the deer were dead in their new habitat. More than one-half died within the first three months.

The live-trapping and transplanting cost $3,000 per deer…and it really didn’t help increase deer populations in other parts of the state.

The carrying capacity image (shown previously) and the story about Angel Island help explain why we cannot simply capture and release wildlife into new areas. Biologists say that all habitats have a fixed carrying capacity. The carrying capacity of a habitat is the number of animals that the habitat can support throughout the year without damaging the habitat. The habitat pail image shown previously can hold only a fixed amount of wildlife. If we add more wildlife without increasing the size of the pail, the extra animals will consume more food and water and may damage the habitat for all animals. We can’t add new animals to an area unless we know there is enough good habitat.

The carrying capacity of a habitat can change for better or for worse. Forest fires, for example, are often helpful to big game. The new vegetation that grows after a forest fire offers a ready source of food to many big game species. With enough cover and water in the right arrangement, a forest fire actually can help expand the carrying capacity of a habitat over time.

What about a new housing development that transforms 100 acres of woodlands into new homes and streets? This is an example of reducing the carrying capacity of a given habitat. Most wildlife using that 100 acres will be forced into other areas.

Sometimes biologists do live-trap wild animals and release them into new areas. For example, this occurred in Washington during the past few years with the mountain goat and the wild turkey populations.