Angel Island, the largest island in the San Francisco Bay, is 740 acres in area and is 788 feet at its highest point, Mt. Livermore. Located one mile south of the Tiburon Peninsula, it stands as a shining example of the limiting factors environments place upon populations. It clearly illustrates the biological principle of carrying capacity and how human interference with the environment can throw the ecosystem out of balance.

Deer were introduced to Angel Island during the early twentieth century by humans. Angel Island, which had not previously been populated by deer, proved to be a welcoming habitat for its new deer population. The deer population growth, left unchecked by a lack of any sort of predator, soon reached a point where the island's florae was no longer a sufficent source of energy for the deer.

The population of deer had gone over the carrying capacity of the island. Meaning that, there were more deer than the island could naturally support.

Confounding the problem were the efforts of several well-intentioned picnickers. These individuals saw the deer, many of which were starving. They began to bring food for the deer. However, despite these picnicker's good intentions, they were really making the problem go from bad to worse. The already over-inflated deer population grew even further.

It was begining to look bad for Angel Island. The deer were litterally stripping the island of all its vegetation. The deer mainly ate the native and imported European grasses, but they also ate other types of vegetation such as elderberry bushes, sagebrush, coyote brush, madrone, oak, and bay trees. This was even more of a problem than it first seems. The vegetation had many roots, when the vegetation died, so did the roots. The roots of the plants were the only thing keeping the soil from eroding during heavy rains. Something had to be done to save the island.

In order to prevent this, the game managers of Angel Island offered the plan of bringing in expert hunters to kill off some of the herd. This plan was protested as being too cruel by the public. An alternate plan was drawn. It called for the importation of coyotes to prey upon the deer and thin the herd. This too, was deemed too cruel.

Eventually, it was decided that 200 of the over 300 deer would be relocated to other locations in California. Shipped and tagged with electronic markers for tracking, many of the deer died. Used to an envrionment of no predators and domesticated by humans that fed them, they were ill-suited to life off the island. Many were soon killed by cars, coyotes, and the like.

Through the history of Angel Island, we can see two main biological concepts, the first being carrying capacity. Carrying capactiy is the maximum number of organisms that can be supported by the environment. At the same time we can see carrying capacity in this history, we notice human interference. We notice how humans introduce deer to an environment without predators, causing the deer population to skyrocket above the carrying capacity of the island. As many of the deer naturally starve, we note further interference by humans; the humans feed the deer. This causes the population to over-inflate even more, and the deer become more and more domesticated. In the end, the deer strip away much of Angel Island's vegetation and become ill-suited for their natural environment due to domestication.


Dr. Steven J. Wolf. Introduction to Ecology. California State University. April 5, 2004.

Cecie Starr and Ralph Taggart. Biology: The Unity and Diversity of Life. United States of America: Brooks/Cole, 2001.

Angel Island Stat Park. California Department of Parks and Recreation. April 6, 2004

Vistor Information. California Department of Parks and Recreation. April 6, 2004

Visitor Information. California Department of Parks and Recreation. April 6, 2004.