Using GPS to Measure Fine-scale Deer Movements
Knowledge of movement behaviors of white-tailed deer helps us better understand their needs and requirements, and enables us to develop better management strategies for the species. Numerous studies have examined large-scale spatial movements of white-tailed deer using conventional radio telemetry. Behaviors such as home ranging, dispersal and migration are well documented across their range. Few studies have examined fine-scale movements of white-tailed deer.
In a collaborative study with researchers in the Department of Wildlife and Fisheries at Mississippi State University (Dr. Steve Demarais, Stephen Webb, Ph.D. candidate, and Dr. Bronson Strickland), we examined fine-scale movements of white-tailed deer using global positioning system (GPS) technology. The study was conducted on what was the Noble Research Institute Wildlife Unit near Allen, Okla. Over a period of seven years, we collected fine-scale temporal data (15 min/relocation attempt) from 17 female and 15 male white-tailed deer during three seasons. Seasons were defined as: spring (March-May), summer (June-August) and winter (November-February). The objectives of the study were:
- document and compare fine-scale movements of females and males;
- document and compare movements of females during fawning and males during rut;
- determine the effects of moon phase on deer movements; and
- determine the effects of short-term weather patterns on deer movements.
Generally speaking, movements of both sexes were greatest around sunrise and sunset; however, this trend was less prominent for females during the fawning and lactation phases of summer. Average total daily movement of females was greatest from February-April (Figure 1). Female movement sharply declined in May (pre-fawning) and continued to gradually decline until August. Females likely moved less because they were confined to smaller areas due to fawn immobility. This emphasizes the importance of maintaining undisturbed, high quality habitats that provide most requirements in a relatively small area. Average total daily movement of males was greatest in November (corresponding to pre-rut and rut), showing a sharp decline in December, then gradually declining until reaching a low in May (Figure 2). Many hunting seasons correspond to the period of greatest movement which could result in increased vulnerability of bucks to hunters and harvest. Management strategies aimed at improving buck age structure may need to account for this with various harvest restrictions.
We also examined deer movements with respect to time period, moon phase and weather variables. Females moved more during daylight hours than nighttime hours during both spring and summer. Males moved more in daylight hours during spring and nighttime hours during winter. This change in male movement patterns was probably a result of changes in male breeding season behavior and possibly a response to changes in female movement patterns associated with the breeding season. Many people believe that moon phase has a dramatic impact on deer movement; however, the data collected throughout our study indicate that moon phase had no effect on movements of deer of either sex. In general, weather conditions had little effect on deer movements. Of the weather variables tested throughout our study (barometric pressure, precipitation, temperature, wind speed and relative humidity), temperature was the only variable showing any consistent effect on deer movements. While female deer moved less during summer than other seasons, during the summer, they moved greater distances at times with normal to high temperatures and less when temperatures were coolest. Females could have been seeking more favorable thermal habitats during periods of extreme heat, where they could maintain higher rates of movement. Males moved more during winter when temperatures were lowest, possibly to forage more extensively or access more favorable thermal habitats for protection from cold.