City of Austin - White Tail Deer

White-tailed deer have become a common sight in neighborhoods on the preserve's edge as well as in parks and other wooded areas. While some may still feel the thrill of seeing these wild animals, many others bemoan their effects on landscaping and the danger they represent on area roadways. Biologists view them as a species that has grown beyond the carrying capacity of the habitat resulting in damage to the woodland communities where other species, including our local endangered species, try to survive. Once a species exceeds its carrying capacity, damage to the resources will impact the ability of future generations of deer to survive in the same area.

History
In our area, white-tailed deer were historically prey animals for larger carnivores such as wolves and mountain lions. The high reproductive rate seen in white-tailed deer is typical of animals that are prey species. Under natural circumstances, this high birth rate would be necessary to maintain their numbers in the face of constant loss to predation and variation in food supply. When their predators are absent, however, this high birth rate results in overpopulation and results in their population controls being disease, starvation and car impacts.

Native Americans used deer for meat and met many of their daily needs for tools and other items with hides, bones and other parts of the deer. Each may have used as many as two to three deer annually. European settlers also hunted deer but at much higher rates, and also extirpated their predators and began to clear the woodlands. While the screw worm fly, specifically its larvae, had always been a natural factor limiting the expansion of deer herds in the southern states, deer populations dropped to extremely low numbers in the late nineteenth century due to the addition of uncontrolled hunting and habitat loss. Many states outlawed deer hunting and set aside preserves. This low point was temporary. Deer populations recovered and swelled to today's high numbers due to several factors.

Deer Density and the Habitat
White-tailed deer prefer to eat forbs, or broad-leaved herbaceous plants, but will also eat leaves and twigs from shrubs and trees, called browse, and the nuts and fruits from plants such as acorns, called mast. Deer eat little grasses as opposed to other hoofed animals, or ungulates, such as goats, sheep and cows that routinely graze on grass. Even in favorable habitats, deer populations will find an upper limit, or carrying capacity, beyond which they compete with each other for food and can pass diseases through more frequent contact. In addition to the health of the deer, the health of the ecosystem begins to suffer. Crowding creates browsing pressure on the vegetation as deer begin to eat many plants they would avoid in less crowded conditions. They will also return to browse again and again on root-sprouting trees until the root reserves of the tree are gone and it dies.

A sure sign of deer overpopulation is the presence of a clearly demarcated "browse line" or leafless vegetation from about five feet high down to the ground. The lower layer of vegetation below this browse line is the woodlands' understory. It provides habitat needed by smaller brush-dwelling animals such as rabbits, certain birds and many others. The understory also protects new hardwood and brushy seedlings and saplings. When the understory disappears, young oaks and many other seedlings are exposed then eaten by white-tailed deer resulting in a lack of stand replacement over time. Because Ashe juniper (cedar) plants are among white-tailed deer's least preferred food plants, they are one of the very few plant species which survive in these areas. The long-term result is a shift toward an Ashe juniper monoculture, sometime called a cedar brake, that supports a limited range of plants and animals.

Deer and Humans
Large urban deer populations affect people and communities in surprising ways. Homeowners annually spend thousands of dollars replacing landscapes destroyed by hungry deer. Deer also damage crops which may not be a local problem but can show up in the cost of produce. Even more costly is the hazard of deer on roadways that endanger lives and damage automobiles. Municipalities incur expenses hauling deer carcasses from roadsides. In a November 2005 report on auto-deer collisions, the auto insurer State Farm estimates that there are 1.5 million deer-vehicle collisions each year, resulting in 150 human deaths and $1.1 billion in vehicle damages, and ranks Texas ninth in the nation for number of collisions with deer. (Source: http://money.cnn.com/2005/11/04/news/newsmakers/deer, "Worst 10 States for Auto-Deer Collisions"). Less measurable is the community ill will generated by the inevitable conflict between those who continue to feed deer and those who wish to reduce their numbers.

For more information on white-tailed deer, visit Texas Parks & Wildlife's website that provide species information and downloadable brochures on the topic.

Managing Deer
On specific program lands, the Wildland Conservation Division uses a combination of lethal means to reduce the density of white-tailed deer and the installation of game fencing to prohibit movement of deer back into those areas. Deer removed from the land are processed and donated to the Capital Area Food Bank through the statewide Hunters for the Hungry program.