Body Size and Bite Force of Stray and Feral Cats-Are Bigger or Older Cats Taking the Largest or More Difficult-to-Handle Prey?

Abstract

Simple SummaryPredation by cats (Felis catus) threatens Australian wildlife. As they rely on their jaws to hold and subdue prey, their body size, skull shape and bite force can reflect an individual’s prey handling ability. Prey less than 100 g are the usual prey of F. catus but they have frequently been recorded to take larger prey, and previous studies have suggested that large male cats represent a disproportionate risk to threatened and translocated native wildlife populations. We tested whether a cat’s sex, age, body mass, body condition, and bite force determined the size of the prey they took (prey body mass) especially for those prey that might be ‘dangerous’ or difficult to handle (our subjective assessment of whether animals would be capable of fighting back and would therefore require skill to subdue). Large male cats do indeed represent the greatest risk in that they have greater body mass and bite force that would allow them to handle a greater range of prey. However even small cats were active hunters, and many had taken large or dangerous prey species. The strongest predictor of prey size was the age of the cat, with older cats taking the largest prey.As carnivorans rely heavily on their head and jaws for prey capture and handling, skull morphology and bite force can therefore reflect their ability to take larger or more difficult-to-handle prey. For 568 feral and stray cats (Felis catus), we recorded their demographics (sex and age), source location (feral or stray) and morphological measures (body mass, body condition); we estimated potential bite force from skull measurements for n = 268 of these cats, and quantified diet composition from stomach contents for n = 358. We compared skull measurements to estimate their bite force and determine how it varied with sex, age, body mass, body condition. Body mass had the strongest influence of bite force. In our sample, males were 36.2% heavier and had 20.0% greater estimated bite force (206.2 ± 44.7 Newtons, n = 168) than females (171.9 ± 29.3 Newtons, n = 120). However, cat age was the strongest predictor of the size of prey that they had taken, with older cats taking larger prey. The predictive power of this relationship was poor though (r2 < 0.038, p < 0.003), because even small cats ate large prey and some of the largest cats ate small prey, such as invertebrates. Cats are opportunistic, generalist carnivores taking a broad range of prey. Their ability to handle larger prey increases as the cats grow, increasing their jaw strength, and improving their hunting skills, but even the smallest cats in our sample had tackled and consumed large and potentially ‘dangerous’ prey that would likely have put up a defence.