Is Carrboro an “Area With Deer Overpopulation”?

This is the second in our series analyzing Carrboro’s Energy and Climate Protection Task Force’s Recommended Deer Cull.

Assertion 2: “Soil studies have shown that the seed stores in areas with deer overpopulation are shifting from native wildflowers and woody plants to invasive plants and grasses. This threatens the ability of our forests to regenerate in a healthy way and continue to serve as diverse ecosystems and significant carbon sinks.” [page 38]

Again, although there are three end notes at the bottom of page 38, none of them references any studies regarding deer and their adverse affect on seed stores or forest regeneration.

The first problem with this assertion is that it starts with a claim about “deer overpopulation” without defining what deer overpopulation is, and without any proof that deer overpopulation is a problem in Carrboro.

So, does Carrboro have a problem with deer overpopulation?

Biologically speaking, overpopulation of a particular species occurs when that species exceeds its biological carrying capacity, or the maximum number of individuals of a species that can exist in a given habitat indefinitely. Factors that affect carrying capacity include the availability of life-sustaining necessities (such as food, water, and cover) and life-threatening situations (such as predators, toxins, and disease).

Deer and other large wild animals rarely exceed their biological carrying capacity. If there is not enough food available to support the population, the weaker individuals will die and the does will absorb some embryos and fewer fawns will be born in the spring.

Is that the situation in Carrboro? No. There is at least one doe in Carrboro who has been crippled since she was very young, either from a pre-natal injury or post-natal injury. This year, that crippled doe delivered and raised a healthy fawn. At least one other doe in Carrboro delivered and raised healthy triplets this year. These are not the signs of overpopulation. These are the signs of a deer population living well within the carrying capacity of the local environment.

What is the biological carrying capacity for deer in urban areas? According to urban wildlife specialist Ricky Lien, “The biological carrying capacity of many of our urban areas can be over 100 deer per square mile.”

The second problem with this assertion is that the deer “overpopulation” causes the spread of invasive species. Yet elsewhere in the Community Climate Action Plan, there is a reference to one of the challenges of the spread of invasive plant species: “Large/big box nurseries often sell few (if any) native species.” Surely, the authors of the plan realize that humans, not deer, are making the purchasing and planting decisions that are the major reason for the spread of invasive species.

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