Feline Predatory Behaviour

Prey Selection

Cats most commonly catch prey that is around 1% of their own bodyweight (Pearre & Maas, 1998), with 80% of reported prey caught being <50g in weight according to one study (Brio et al., 2005). In an observational study of feline predatory behaviour in suburban nature preserve in New York, mammals and birds made up 52% and 23% of kills respectively, with an overall success rate for killing of 13% (Kays and DeWan, 2004). Cats show preferences in terms of their predatory targets, and are tolerant of high failure rates in predatory attacks.

The selection of prey target is also influenced by hunger. Although hunger does not appear to affect the rate of hunting behaviour, larger, potentially more dangerous, prey will be targeted when cats are hungry (Biben, 1979). In the same study, hunger was shown to increase the speed of killing behaviour, with satiated cats toying with prey for longer.

Apart from small mammals, birds and rodents, cats will also hunt and consume insects. Evidence for the specific nutritional contribution of insects to the diet of the cat is limited. However, insects (particularly spiders) are rich in taurine (Weisenborn, 2012), an essential amino acid in the cat.

Motivation to Hunt

The motivation to hunt, or at least engage with potential prey, is separate from hunger. Adamec (1976) showed that cats will stop feeding in order to catch and kill a live rat that was introduced to the environment. They would then move the dead prey close to the feeding area and return to eating the meal. Despite having killed the rat, cats showed almost no interest in eating it. The indication is that predatory behaviour is activated by stimuli, such as odour, prey size and movement, that are unrelated to stimuli connected with feeding or hunger.

The amount of time spent searching for food and hunting does vary between pet and feral cats, with feral cats spending twice as much time per day (12 vs. 6 hours) (Turner & Meister, 1988).

Hunting Strategies

Cats employ a variety of strategies when hunting, which are refined through experience. Two approaches predominate; stalking and sit-and-wait. Sit-and-wait is the primary strategy for hunting rodents. These share the common features that they employ stealth and enable the cat to get close enough to its prey that it can make a final brief attack from close range.

Cats appear to identify specific hunting locations where they anticipate a higher probability of encountering vulnerable prey. They move speedily between these locations, rarely deviating to take up unanticipated hunting opportunities. This implies that during an active period of hunting, cats prioritise the catching of prey, rather than the finding new hunting sites. This would make sense, since actual hunting opportunities are time sensitive due to the activity patterns of prey, where as information about potential future hunting sites is available all the time.

At a hunting location the cat will survey the area systematically searching for evidence of the presence of prey. The cat’s hearing extends into the ultrasound, not only enabling the cat to detect scratching sounds and vocalisations of rodents but also to precisely locate prey using hearing alone. When such sounds are heard, active prey seeking is activated. Hunting is activated by movement of anything of around the correct prey size within the cat’s field of vision.

Once the cat finds an area where there are signs of prey, such as the scent of rodent urine close to a hole, then it will withdraw to a distance or area of cover and wait. An attack occurs when prey moves into an open space away from a position of safety, and the cat judges that it will be able to mount a successful attack. During the last phase of a waiting period before an attack, the cat may perform paddling behaviour with its rear feet, which may function to prepare hind leg muscles to deliver maximum out put during a dash and pounce.

If the attack is unsuccessful, then the cat will return to cover or explore the hunting area for another opportunity. If unsuccessful on several occasions, or no further opportunities are detected, then the cat will move on to another hunting area.

Stalking behaviour uses the cover of plants and bushes to move closer to prey, such as birds, that are more mobile and not tied to a burrow or shelter location. Cats will also predate young birds in the nest, dig moles out of their burrows and ambush young rabbits as they leave their burrows. However, the rate of predation of larger species, such as rabbits and squirrels is low in domesticated pet cats compared to the rate of predation of rodents and birds.

Feeding and Elimination

Feral and wild cats use latrine sites that are located in their home range, but not their core territory. Latrine locations are chosen on the basis of location and substrate preference, both of which are learned during development. The natural preference is for a location that is private, where the cat will not be disturbed whilst eliminating and a substrate that is easy to dig, as cats tend to bury urine and faeces unless they are using marking. Cats will tend to choose separate locations to eliminate urine and faeces.

Latrine locations are away from hunting and resting areas, but close enough to those places for the cat to be able to use them without a significant interruption of their other hunting and territory marking routines.

Cats are obligate carnivores, and exhibit a preference for prey that is different from what they have eaten in the past. This is termed a “monotony effect” and is argued to be a way of ensuring and balanced diet (Bradshaw, 1992). Since cats cat hunt independently and catch only small prey that provide a single meal for an individual, they do not share food. Feeding is a solitary activity that carries no social meaning. Cats eat 10-20 small meals each day, according to the availability of prey.

The core territory of domestic cats contains an incompatible arrangement of resources that would not be present in a wild situation. For example, in a study by the author, in 31% of households provided a food bowl near to the litter tray, and the same percentage located a water bowl near the litter tray. From the cat’s perspective, having a latrine location inside the core territory is undesirable. Twenty-seven percent of households placed the litter tray next to the cat door, which might seem an ethologically appropriate choice given that this is the closest possible indoor location to the garden. However, it also means that in multi-cat households, of homes with a plain cat door, the latrine lacks privacy.

In the same study, one third of cat owners fed their cats at specific mealtimes, and 65% indicated that food was not available for the cat all day. This forces cats into close proximity with each other for an activity that is usually solitary. The cat is forced to consume as much food as it can during the periods of food availability.

The Impact of Predation

Felis silvestris is a native species in most of Africa, Europe, central Asia, India, China and Mongolia. In these regions it forms a natural part of local ecology. Due to mutual tolerance between cats and humans, the density of cat populations can be much higher within and around human communities than in rural areas.

Felis silvestris is not a native species in the Americas or Australia, so that the impact it might have on wildlife in those regions may be considered much more serious and intrusive to local ecology. In the USA, it is estimated that free-ranging domestic cats kill 1.4-3.7 billion birds and 6.9-20.7 billion small mammals each year (Loss et al., 2013).

This raises the issue of the impact of pet vs. feral populations. No current estimate of the UK feral cat population could be found, but the total population was estimated at 6 million in 1980, 1.2 million of which were feral (Harris et al., 1995. Tabor, 1981). The current estimate of the UK pet cat population is 8 million, according to the Pet Food Manufacturers Association. This situation can be contrasted with Australia and the USA:

• Australia: 3 million pet cats, 10-20 million feral cats (Jongman and Karland 1996, Dickman and Denny 2010) • USA: 86.4 million pet cats, 60-100 million feral cats (APPA, 2011. Dauphine & Cooper, 2009)

So, whilst in the UK, the feral cat population is perhaps 15% the size of the pet cat population, in the USA these populations are similarly sized and in Australia feral cats outnumber pet cats by a factor of 10-20 to one.

Trap-neuter-return (TNR) programmes have been shown to be effective in a number of studies. Levy et al (2003) showed a 66% reduction in population size over an eleven-year period in one free-roaming population. In the UK, nationwide trap and neuter programmes of this type have been in operation for more than a decade. In the UK and Germany, levels of neutering are generally high, which helps to limit population growth (Heidenburger, 1997).

However, the most significant factors in the maintenance of a large feral population are climate and the availability of prey. The temperate climate of Northern Europe limits kitten survival, compared to the warmer climate of Australia. Australia also has a diverse population of prey species that have evolved in the absence of an equivalent predator to Felis silvestris.

In a study of domestic cat predation in the UK, the estimated mean predation rate was estimated at 18.3 per cat per year, with 65% of households reporting no prey brought back in a given year (falling to 22% when averaged over several seasons (Thomas et al., 2012). The same study found that only 20% of cats returned 4 or more dead prey annually. A retrospective study by the author found an average prey return rate of 3.3 birds and 12 rodents per cat per year for households where cats had outdoor access. 44.6% never returned a bird, and 39.6% never returned a rodent.

The amount of birds observed in a garden correlated significantly with the amount of environmental enrichment provided in a garden (bird feeders, scattered food and nesting boxes), as well as the amount of natural features present (long grass, trees, wild flowers, bushes). Of particular note was a correlation between bird numbers and indicators of active gardening, such as the presence of a greenhouse, vegetable patch and compost heap. However, he number of birds caught did not correlate with scores for the amount of birds observed in the owner’s garden. This is supported by findings from Thomas et al (2012) that reported numbers of five bird species was not correlated with level of their predation. The predation of robins was just significantly correlated with observed numbers (p=0.046). This may relate to some aspect of the vulnerability of this species when feeding and nesting, but the result would also become insignificant when measures are applied to counteract the problem of multiple comparisons.

The study by Thomas also showed a significantly negative correlation between mean annual predation rate, cat population and housing density; the number of prey returned was lower in high residential and cat population density.

In the author’s study, 62% of cat owners indicated an interest in encouraging more cats in the garden, with 48.1% of those giving a positive response also indicating that owning a cat prevented them from doing so. Those who reported that having a cat restricted their ability to attract birds to the garden provided similar numbers of bird tables and hanging feeders, but significantly fewer bird boxes and scatter feeding opportunities for ground feeding birds.

It appears that improving a garden to attract and support bird numbers does not increase the general risk of predation, and cat owners should be encouraged to do so.

Key points

• Felis silvestris is native to Europe, and would exist here without human intervention.
• The impact of this species on wild bird and mammal species must be recognised.
• However, the relative size of the feral population, the impact of climate and public policy responsibilities for TNR programmes should be taken into account when making recommendations to control the activities of pet cats.
• The impact on birds and mammals should not be generalised from countries where Felis silvestris is native to those where it is not, and vice versa.
• Increasing bird numbers by feeding birds and providing an insect and bird friendly garden does not appear to increase predation risk.