Tasty Gardens = More Deer + Vehicle Collisions

Car with airbags deployed and a deer jumping infront of it with the text, "Tasty Gardens = More Deer + Vehicle Collisions

Suburban Sprawl Causes More Deer Fatalities

Estimates in 1980 show that around 200,000 deer were killed on roadways. However, in 1991 deer-road kills increased to over 500,000, a conservative estimate. Since the number is increasing, what could be the cause? The short answer is suburban sprawl. Deer are adjusting their patterns because of changing habitat, due to human causes. They are finding that they like the smorgasbord of gardens in all the areas that used to be forest.

With the increase of housing, there is an increase of roadways. In an article published in 2001, it is stated that,

“Approximately 1.5 million deer-vehicle collisions occur annually in the U.S.”

Conover, M. R. “Resolving Human-Wildlife Conflicts.” Lewis, Boca Raton, Florida. 2001.

Why It Is Increasing

The perfect storm of more roads and the close proximity of delicious deer treats mean deer are crossing and living closer to roads more than ever. This in turn makes deer-vehicle collisions more common than ever. A national study from 2008 found that,

“Deer-vehicle collisions (DVCs) are steadily increasing across North America. The increase is particularly pronounced in urban green spaces where deer… populations and road densities are high… DVCs [are] more likely to occur in areas close to water and the combination of high road densities and non-forested vegetation of high productivity within 800 m.”

Ng, J. W., et al. “Landscape and Traffic Factors Influencing Deer–Vehicle Collisions in an Urban Environment.” Human-Wildlife Conflicts, vol. 2, no. 1, 2008, pp. 34–47.

Urbanization

The study shows that in areas where there is a high density of roadways and plants that deer love to eat there are more incidents involving deer-vehicle collisions. Not only does this mean costly damage to cars but also threatens the safety of people in the cars and the deer themselves.

A study done in Alabama on white-tailed deer-vehicle collisions found that urbanization of once forested areas increased these incidents. Similarly to the previously mentioned study, this one comes to pretty much the same conclusion,

“Our results showed that county characteristics, such as (1) having a deer population density (≥31/km²), (2) being part of a metropolitan statistical area, (3) having a high proportion of pasture, urban and other land relative to woodland, and (4) having greater vehicle density per road km were more likely to increase the odds of deer–vehicle collisions.”

Hussain, A., et al. “Land-Use Pattern, Urbanization, and Deer–Vehicle Collisions in Alabama.” Human-Wildlife Conflicts, vol. 1, no. 1, 2007, pp. 89–96.

We can get an equation out of the information so far:

High Deer Populations + Developed Land +Increased Roadways 

= More Deer-Vehicle Collisions.

Changing Habitat Habits

Ultimately, deer are changing their habits to favor urban and suburban environments due to fragmentation of their old stomping grounds. Not only do the deer have less of a choice of where they can live, but they favor the newly created suburbs. Specifically, with these suburban oases the distances between their food sources and roads have shrunk more and more every year. A study out of Illinois in 1999 confirms this,

“A model using only landscape metrics derived from satellite imagery predicted that greater landscape diversity and shorter distances between nearby forest patches increased the probability of a road segment being a high deer/vehicle accident site.”

Finder, R., et al. “Site and landscape conditions at white-tailed deer/vehicle collision locations in Illinois” Landscape and Urban Planning, vol. 44, no. 2-3, 1999, pp. 77-85.

An example of landscape diversity is the area where forest and home landscaping meet. And homes are then connected to roads. Deer now will cross roads to get to other forested areas where they live as well as to get to other yards that are their feeding areas.

The Science Of Putting It all Together

The Rochester Institute of Technology, located in Upstate New York, is a microcosm of the urban/suburban landscape we are talking about. For example, they have densely populated areas, forested land, and agricultural fields along with constant traffic. A study done by scientists from the school found that,

“Faced with shrinking and fragmented natural habitats in many areas, deer populations across the United States are more often adapting to the developed habitat, rather than relocating to areas far removed from human civilization… Deer are moving into urban and suburban areas instead of the more traditional settings of rural and forested areas. This in turn leads to more frequent human/deer interactions, such as deer-vehicle collisions… They primarily feed on the shrubbery planted for landscaping and manicured grass.”

Nau, P., “A Study of the Deer Herd on the RIT Campus and the Relationship of Herd Activity and Habitat to the Incidence of Deer-Vehicle Collisions.” Thesis. Rochester Institute of Technology. 2013.

How To Make A Difference

The way to change the issue of deer-vehicle collisions is to make the lands that deer are now favoring, less favorable. Now nobody is going to empty their lawn of all plants and just have a dirt patch around their house. So how can we go about this without going to that extreme?

Using the equation stated earlier, we can go about this in several ways. An extreme that a lot of people are not in favor of is reducing the deer population. It is off the table. As an individual, you are not going to be able to decrease the amount of roads put in. So the last thing is dealing with favorable habitat for deer now shifting to be home yards.

In fact, the way individuals can help alleviate the problem is by making their landscaping something deer do not find edible. This can be done through planting things that are deer resistant for example. These types of plants are not foolproof however. Nevertheless, if deer are hungry enough, they will eat pretty much anything. So these plantings need to be done in combination with deer repellents. Effective repellents include the use of sprays that are objectionable to deer through taste modification and smells that they dislike. The methods we use at Deer SolutionⓇ are perfect for this.

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