Deer Monitoring at Pea Ridge National Military Park in Arkansas, 2023

White-tailed Deer

Deer are one of the more charismatic creatures you can find at Pea Ridge National Military Park. It's hard to imagine that white-tailed deer were almost extinct in the early 1900s from overhunting and clearing of forests. Hunting regulations and removal of most of their natural predators has now led to unprecedented deer population growth. Without natural predators, deer can become overpopulated and die of disease and starvation. Scientists from the Heartland Inventory and Monitoring Network monitor deer at Pea Ridge National Military Park to better understand how their populations may be changing over time.

White-tailed deer at Pea Ridge National Military Park.

NPS

Why Do We Monitor Deer?

Restoration of the oak savanna and oak forest vegetation that were present at the time of the Civil War battle is a primary focus at Pea Ridge National Military Park. Deer love to browse tree saplings and other native vegetation. When the deer population gets too large, overbrowsing of native plant species can impact restoration efforts and promote exotic, invasive plants. Deer also disperse ticks that can spread diseases to other animals and humans, and it becomes more difficult to manage these diseases when there are too many deer. Increasing deer-vehicle collisions are another risk when deer populations are high. Monitoring information helps park staff make informed management decisions that protect deer, other park wildlife, park habitats, and people.

How Do We Monitor Deer?

We began monitoring deer on the park in 2005 to determine yearly changes and long-term trends in their populations and to map their locations. Each year in winter, we use bright spotlights at night to count deer along the main tour road that makes a 10-kilometer loop through the park. We conduct these surveys during a four-week period between January and mid-March.

White-tailed deer at Pea Ridge National Military Park

NPS

Monitoring Highlights
(2005–2023)

Over 19 years of monitoring, we have observed rapid declines and recoveries in the deer population at Pea Ridge National Military Park. The deer population ranged from a low of about 15 individuals/km² in 2007, after a two-year hemorrhagic disease outbreak, to about 63 individuals/km² in 2023.

Overall, deer on the park increased moderately over time (3.2% per year increase on average) despite the rapid die-off from 2005 to 2007. An analysis of deer harvesting and monitoring data suggests that things other than hunting are driving annual changes in the deer population at Pea Ridge National Military Park. We will continue to monitor deer on the park to help the park manage deer and to better understand the factors affecting deer populations.

Map of deer locations in 2023 on the main tour road that makes a loop in Pea Ridge National Military Park. Also shown is the visible area that was surveyed. Surveys take place from vehicles as we drive slowly around the loop road.

NPS

A white-tailed deer with shining eyes.

NPS

Why Do Deer Eyes Glow?

When a bright light is pointed at deer, their eyes glow. This is not unique to deer. Many animals have this eyeshine, including dogs, cats, cattle, horses, and even some reptiles, amphibians, fish, birds, and insects! There is a special, reflective membrane called the tapetum lucidum behind the retina in the eyes of these animals. Tapetum lucidum is Latin for “tapestry of light” or “shining layer.” The reason deer and other animals have the reflective membrane in their eyes is to help them see in the dark. While deer can be active in the day or night, they are called crepuscular, which means they are most active at dawn and dusk when it is dim to dark outside. The reflective eye membrane along with large pupils make it easier for deer to navigate these low-light conditions.

We count deer using a big spotlight to make their eyes glow so we can see them. The pupil of the deer is fully dilated when it is dark. When the light beam hits their eyes, they freeze until their eyes can adjust. This explains the old saying, “like a deer in headlights” to describe someone who is so surprised, confused, or afraid that they can’t move. Luckily, the spotlight is painless for the deer and allows us to monitor them, so we can protect deer populations and park ecosystems.

For More Information

Read the full report.

Web article created by the Heartland Inventory and Monitoring Network.