Are deer in West Seneca overpopulated?

How many deer can an area support? This may sound like a simple question, but the answer is often anything but simple. In wildlife science, the term carrying capacity refers to the number of individuals of a species that a particular area can support. However, there are three different ways to define carrying capacity, and therefore three different carrying capacities for any location.

Biological Carrying Capacity (BCC) is the maximum number of deer that the habitat can support on a continuous, long-term basis. When a population grows above this size, it is susceptible to density-dependent effects, such as starvation (which can result in low reproductive rates and death) or disease spread. BCC is extremely difficult to measure. Indications of a population above this density might include large numbers of emaciated deer, low reproductive rate, low fawn survival, and high numbers of “winter kill” – deer that die of starvation during the winter season. It is important to note that some winter kill happens in any population, and deer regularly die of old age or illness. The most definitive way to assess if deer are suffering from starvation is to examine the bone marrow of deer found deceased in winter.

Ecological Carrying Capacity (ECC) is the maximum number of deer that allows for natural habitat succession and regeneration of native plants. When the population grows beyond this, deer feeding activities may negatively impact native plant growth, in turn impacting other wildlife that depends on those plants for food or other habitat needs. ECC is most often measured by examining the growth rates of certain indicator plants. It is important to note that this measure refers to native plants. Damage to garden plants would be considered an issue of Social Carrying Capacity.

Social Carrying Capacity (SCC) (also called Social-cultural or Cultural Carrying Capacity) is the maximum number of deer at which the local human population is able to tolerate or accept the issues associated with sharing space with deer. When the population grows beyond this, local stakeholders experience significant concerns about issues such as deer-vehicle collisions, property damage, or disease. SCC is more about the comfort and safety perceived by humans in an area than it is about any biological or ecological measure of deer health or impacts. SCC is most commonly measured though resident surveys, deer-vehicle collision rates, and local disease case rates (such as Lyme disease).

So how does this all relate to deer in West Seneca?

One of the first tasks required for making decisions about the West Seneca deer herd is to understand which of these definitions of carrying capacity best defines the issue. In many cases, biological carrying capacity is actually higher for deer in urban and suburban areas because of the large number of food sources available. Deer are well-adapted to edge habitats, and the mix of developed and undeveloped land in suburban locations create an ideal situation for deer. This makes it unlikely that West Seneca deer have exceeded their biological carrying capacity. Ecological carrying capacity is an option that the town may choose to investigate through plant surveys at local parks and other green spaces. However, social carrying capacity is most often the definition that is used in making decisions about suburban deer populations. Even if a population is well below biological or ecological carrying capacity, it may still exceed the social tolerance levels of the community. The West Seneca Deer Task Force has been exploring issues of social carrying capacity through surveys of local residents and taxpayers to gauge community attitudes towards the deer herd, and assess the level of impact that residents are experiencing.

The short answer to this question is that from a biological perspective, deer are most likely not "overpopulated" in West Seneca. However, resident surveys and deer-vehicle collision rates indicate that the deer population may be too high for residents to tolerate.

References:

Bowman, J.L. 2011. Managing White-tailed Deer: Exurban, Suburban, and Urban Environments. In, Hewitt, D. G. (ed.), 2011. Biology and Management of White-tailed Deer. CRC Press, Boca Raton, Fl. pp. 599-620

Decker, D.J. and K.G. Purdy. 1988. Toward a Concept of Wildlife Acceptance Capacity in in Wildlife Management. Wildlife Society Bulletin 16 (1): 53-57

Deer Ecology and Management Lab, Mississippi State University, 2019. Deer Habitat Carrying Capacity. Accessed at https://www.msudeer.msstate.edu/deer-habitat-carrying-capacity.php

Human Wildlife Conflicts Working Group. 2018. Methods for Managing Deer in Populated Areas. Association of Fish and Wildlife Agencies. Accessed at https://www.fishwildlife.org/application/files/7315/3745/9637/AFWA_Deer_Mngmt_Pop_Areas_August_31_2018_version.pdf

Sullivan, K.L., P.J. Smallidge, and P.D. Curtis. 2020. AVID: Assessing Vegetation Impacts from Deer. Cornell Cooperative Extension and NYS Department of Environmental Conservation. Accessed at https://aviddeer.com/files/AVID_Manual_2020.pdf