The effect of collar weight and capture frequency on bodyweight in feral cats (Felis catus).

Context: Animal-borne devices can affect animal survival, reproduction, and behaviour through both the addition of weight and bulk and the direct effects of initial and subsequent capture. Researchers commonly employ a general rule of thumb that weight of the device must be less than 5% of bodyweight for terrestrial animals; however, this threshold has little empirical basis. Aims: We evaluated the effects of environmental variables, repeated capture, and weight of animal-borne devices on bodyweight in free-ranging feral cats. Methods: We recaptured feral cats at varying frequencies, wearing GPS and/or VHF collars that ranged from 0.29% to 4.88% of bodyweight, and recorded change in cat weight over time. Key results: Collar weight as a percentage of bodyweight was not a significant predictor of feral cat weight change. Rather, change in bodyweight was best described by a negative relationship with an increasing temperature and number of captures, and a positive relationship with time since collar attachment. Conclusions: Capture had a significant influence on feral cat weight but collar weights up to 5% of bodyweight did not significantly contribute to weight loss. However, the absence of control cats without collars hindered definitive conclusions on the effect of collar weight on cat weight change. Implications: Researchers should space capture and handling events more than 30 days apart to reduce effects of weight loss from capture and handling. Researchers should also consider increasing collar weight and reducing frequency of capture (where collars are less than 5% of bodyweight), particularly if cat bodyweight is a parameter of interest. Feral cats are one of the most harmful invasive species in Australia, and are often caught and collared as part of scientific study to investigate their impacts and inform management. We evaluated the impacts of this process on feral cats. Even though collar weight had no impact, repeated recaptures reduced cat weight. Researchers should consider prioritising fewer capture and handling events over collar-weight reductions, or offset the effect of repeated capture by allowing recovery time greater than 30 days before subsequent recapture attempts. Photograph by Darcy Whittaker. [ABSTRACT FROM AUTHOR]