FOOD SUPPLEMENTATION INCREASES MULE DEER (Odocoileus hemionus eremicus) RETENTION AT THE RANCHO SAN HUBERTO WILDLIFE CONSERVATION MANAGEMENT UNIT, SONORA, MEXICO

Abstract

Artificial food and water supplementation programs are common in Wildlife Conservation Management Units (UMAs) in arid northern Mexico to attract and retain mule deer as quality trophies. However, implementing these actions represents a high economic cost, and there is no convincing evidence of their effectiveness. This study evaluated the effect of food and water supplementation by capture-mark-recapture using camera traps at the UMA San Huberto, Sonora, Mexico. During the winter of 2015-2016, male mule deer counts and detection histories were collected at 62 photo-trapping stations spread across four supplementation treatments: 1) water and food, 2) water, 3) food, and 4) no supplementation. In addition, to assess the impact of natural vegetation on trough and feeder utilization on the ranch, the Normalized Difference Vegetation Index was calculated using Landsat 8 satellite images. A log-Poisson regression model for deer counts per photo-trapping station found that food supplementation increased mule deer numbers by 42 % when compared to stations without food supplementation. Vegetation biomass had no effect on the frequency of use of feeders and waterers in any of the treatments. According to the multistate model for detection histories, male mule deer at waterers receiving food-only supplementation are more likely to remain in that treatment than to move to either of the other two treatments (water and feed or water). This finding suggests that food-only supplementation is more effective in retaining male mule deer.