Impact Assessment of a Trap-Neuter-Return Program on Selected Features of Auburn, Alabama Feral Cat Colonies

Abstract

Feral cats (Felis catus) are defined here as offspring of domestic cats raised without human socialization or cats that were previously owned that have reverted to a wild state not trusting humans. A feral cat colony consists of a group of cats that regularly reside in a particular area which includes a food source and shelter. A non-lethal approach to feral cat control known as Trap-Neuter-Return (TNR) has been used with increasing frequency over the past decade. TNR involves trapping all cats at a location for surgical sterilization and subsequently returning them to their respective colony site. This investigation’s main focus was to determine what effects TNR has on feral cats located on Auburn University’s campus located in Auburn, Alabama. Specifically, the influence of TNR on population size, home range size and habitat use of 7 colonies of feral cats was evaluated. Population parameters were measured for 1 year before and 1 year after initiating treatment to determine the effects of TNR on the Auburn feral cat colonies. Seven box-style feeding stations were established at 7 pre-existing unmanaged feral cat colonies (Graywood, Jennings, Mack’s, Thach Hall, Ingram Hall, Horticulture and Theta Xi). Photographic sampling using infrared-triggered cameras from inside each feeding box was conducted once every two weeks. During the two-year study, 4,924 photographs were produced and analyzed. A total of 99 individual cats were identified in photographs from the 7 colonies. Total cats identified per colony ranged from 7-30 cats. The Chapman model for mark-recapture used a 95% confidence interval to analyze data in 3-month intervals. The Chapman model was successful for estimating 4 of the 7 colony populations due to their larger colony size (n=5-21). Photographic sampling results from the 3 smaller colonies (Ingram Hall, Horticulture, and Theta Xi) periodically resulted in only 1 cat photographed for weeks at a time. With only 1 cat sited the Chapman model produced a population outcome of n=0. Therefore, the smaller colonies were not analyzed further. Graywood feral cat colony grew significantly larger (p=0.002) from pre-TNR (X=9.2, SD=2.2, n=4) and post-TNR initiation (X=15.5, SD=1.1, n=4) treatment. Thach Hall had a similar outcome although not significant (p=0.49). Jennings and Mack’s had a decrease from pre-TNR to post-TNR initiation however neither difference was significant (p=0.34 and p=0.49). Photographic sampling was an accurate and reliable way to census these colonies of feral cats. Longer study duration is recommended to determine possible impact of TNR on the population size of feral cat colonies. The mean home ranges were calculated as minimum convex polygons or (MCP) and then categorized by sex and TNR status. The MCPs were compared using the proc_glm ANOVA with Tukey’s multiple comparison test. Overall the model was not significant (F=2.67) with p=0.0668. There were differences among male (X=8.5 pre-TNR and X=3.6 post-TNR initiation) and female (X=2.5 pre-TNR and X=2.2. post-TNR initiation) home ranges, but due to a small sample size and high variability the results were not significant. Lawn, hardscape and structures composed over 65% of the study area with roadway, landscaping, woods, scrub, and water composing the other portion of study area. The most common habitats in the pre-TNR and post-TNR MCP were hardscape, structures, and landscaping. Within the MCP both pre-TNR and post-TNR initiation feral cats significantly preferred woods over other habitat types.