Using Radio Telemetry to Monitor Deer Population on Bald Head Island

Radio Telemetry is a very versatile method that is used with many different species ranging from small to large in size. BHI Conservancy uses it to keep track of the deer on Bald Head Island. The Village of BHI and the Conservancy have used immunocontraception to manage the White Tailed Deer population since 2015.  When the deer are caught and given the contraceptive they are also given a radio tracking collar so that they can be tracked through time. These collars are designed so that they will fall off eventually with everyday wear and tear. The data that we are collecting now is also related to understanding the size of the home ranges of the deer on the Island. A study conducted by Brandon Sherrill looked at where the deer preferred to live and how large their home ranges are. It was found that the deer prefer maritime forest/shrub habitat over any other and have an average home range size of 60.73 ha (0.24 square miles).

When conducting a radio telemetry survey we use a receiver and an antenna so that you can listen for the transmitters that are attached to the deer and put off signals at unique frequencies. The sites that we visit to listen for the deer are based on the home ranges that have been established. When we get to a site we turn on the receiver which is already attached to the antenna, lift the antenna in the air, rotate in a circle slowly and listen for a slow beeping sound. When listening for the beeping we need to figure out what direction the sound is the loudest. This is typically the direction the deer is in. Once that has been determined we take out a compass and read the bearing. We write this information down on the data sheet and move on to the next site. You may have seen us on the side of the road holding what looks like a lightning rod in the air!

When a collar is dropped and has been in the same place for 24 hours it starts to give off a “mortality signal,” which is a quicker and higher pitched signal. When this happens we go out and find the dropped collar. We use a technique called triangulation which is where we go around to the home range of the deer that dropped the collar and get bearings from all directions to zero in on a location that the collar would be found. Once it is found we bring it back to the lab where we deactivate the signal with magnets to stop it from giving off a signal anymore. This is a super fun project and it is always like a scavenger hunt whether it is just listening for the signal or locating a dropped collar. The deer are a fan favorite on the Island and we love being able to keep up with them and their effects on our beautiful island. 

Citations:

Sherrill, Brandon & Snider, Anthony & DePerno, Christopher. (2010) White-tailed Deer on a Barrier Island: Implications for Preserving an Ecologically Important Maritime Forest. . Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies. 64. 38-43.