2.2 Domestication
Cats and humans have a long and somewhat complicated history. Mitochondrial DNA evidence suggests the Felis genus of small cats diverged from other larger members of the Felidae family about 6.2 million years ago. The domestication of cats likely started as a commensal process around the Fertile Crescent approximately 10,000 years ago (Driscoll, Macdonald et al. 2009). Stores of grain created by early agricultural villages attracted mice, which in turn provided an excellent source of food for wildcats (Hu et al. 2014). Individuals with minimal fear of humans would have best survived in close contact with villages, placing more confident cats in proximity to breed and produce offspring with a genetic predisposition for bolder temperaments (Driscoll, Clutton‐Brock et al. 2009; Driscoll, Macdonald et al. 2009).
The practice of taming individuals of various Felis wildcat species, presumably for their usefulness as rodent hunters, appears to have been commonplace throughout many cultures prior to domestication of the cat (Hu et al. 2014; Serpell 2014). The first archeological evidence of a cat‐human relationship dates back almost 10,000 years to a cat skeleton in a Cypriot human grave (Vigne et al. 2016). The success of cats in human cultures, however, cannot be solely attributed to their mousing skills. Appealing juvenile traits like large eyes and a small mouth also likely enticed humans to keep cats as objects of affection, gaining an advantage over other animals, such as those in the weasel family, that were arguably even more efficient vermin exterminators (Serpell 2014). Although many Felis species seemed to be feasible candidates for domestication, genetic evidence clearly indicates the sole ancestral species is Felis silvestrus lybica, or the African wildcat subspecies (Driscoll, Macdonald et al. 2009).
The perception of cats in human culture has had its highs and lows over the centuries. Cats were revered by some ancient cultures and then demonized in parts of Christian‐dominated Europe due to this association with paganism starting in the Middle Ages. The negative connotations spread to the United States, and even today we can see lingering effects, particularly with black cats, in superstitious folklore and literature. Although many countries and cultures never lost their respect for the cat and its usefulness in agrarian society, a more affectionate outlook toward the cat began starting in the eighteenth century. Many consider domestication of the cat as fully achieved during Victorian England, at which time humans began purposefully breeding cats for specific physical traits rather than behavior or function (Montague et al. 2014). The past 150 years has seen the recognition of approximately 50 different cat breeds (Cat Fanciers Association 2020), although purebred cats make up only 6–8% of the total US cat population today (Bradshaw et al. 2012).
2.3 Sensory Perception
The sensory systems of the domestic cat, which are almost identical to other Felis wildcats, have evolved to allow these species to become efficient hunters under a variety of environmental conditions. Perception also dictates the manner by which cats communicate with one another and with humans (Brown and Bradshaw 2013).
2.3.1 Vision
Small rodents are typically active at dawn and dusk, and cats have evolved features to enhance low‐light vision for crepuscular hunting. Cats have large eyes, and their pupils greatly expand in dark conditions, allowing increased light transmission to the retina. The pupil can narrow to a very thin slit to protect the retina in bright lighting. The tapetum is a reflective layer of tissue in the choroid of the eye. In addition to creating the “eye shine” observed when passing a light across the eyes of a cat (and many other species) at night, this structure also allows any light entering the eye to be reflected and amplified (Houpt 2018). The cat’s retina contains about three times more rods than cones. Rods are photoreceptor cells responsible for night vision, but the sacrifice in cone density results in lower visual acuity and color perception. Cats probably have a dichromatic spectrum of mainly blues and greens (Bradshaw et al. 2012). Color is unlikely to be an important factor in a cat’s sensory world. Cats have binocular vision but may not be able to focus well on an object within a foot from the eyes. Caged cats are nearsighted compared to outdoor cats (Belkin et al. 1977). Excellent motion detection due to specialized neurocircuitry in the visual cortex is yet another sensory capability that greatly enhances predatory success.
2.3.2 Hearing
Cats are able to detect sounds between 45 and 64,000 Hz, including 10.5 octaves, which is one of the broadest hearing ranges of any mammalian species (Fay and Popper 1994). The high‐frequency, even ultrasonic sound perception is likely helpful for the detection of prey and possibly kitten communication, but the evolutionary function for detecting very low‐frequency sounds remains a mystery (Bradshaw et al. 2012). The pinnae, or external parts of the ear, are highly moveable, amplify sounds, and allow the cat to more easily pinpoint the location of the source. Additionally, the pinnae position can be used to visually communicate emotional information to a conspecific (Leyhausen 1979; Overall 2013).
2.3.3 Olfaction
The importance of olfactory signals in hunting and conspecific communication has not been well studied. Cats seem to rely less on smell to locate prey compared to dogs (Montague et al. 2014); nevertheless, cats have a relatively robust sense of smell based on the numbers of olfactory receptors (Shreve and Udell 2017). Olfaction in cats, as in most non‐human animals, is composed of both the main and accessory systems. The main olfactory system is responsible for scent detection, whereas the distinct secondary system identifies socially relevant chemicals, such as pheromones. At the center of the accessory system is the vomeronasal organ, a cluster of specialized sensory cells that sit above the nasopalatine bone and connect to both oral and nasal passages, allowing evaluation of both airborne and fluid‐borne molecules (Brown and Bradshaw 2013). The information is relayed to the emotional centers of the brain, which can permit the animal to physiologically and behaviorally prepare for the appropriate action, usually without any conscious awareness (Mills 2005). A cat using the accessory olfactory system can be observed holding the mouth slightly agape, during which the flicking tongue draws salient molecules into the incisive duct, then up to the vomeronasal organ. The flehmen or “gaping” behavior is most commonly seen when a cat smells a strange cat’s urine (Hart and Leedy 1987; Houpt 2018).
2.3.4 Taste
Cats are obligate carnivores and must consume prey animals to obtain essential compounds (Montague et al. 2014). Cats have relatively few taste buds and no ability to taste sweet substances, perhaps because cats have little need to detect plant‐based sugars as an energy source. Recent research has shown that cats do have bitter taste receptors, which may provide a means of toxin detection and avoidance (Lei et al. 2015).
2.3.5 Touch and Balance
Balance is due to an integration of information from the visual, vestibular, central, and peripheral nervous systems. Cats are famous for the ability to right themselves during a fall by reflexively twisting the head and spine to land on their feet. This righting reflex relies primarily on the fluid in the bony labyrinth and semicircular canals of the vestibular system (Cremieux et al. 1984).
Whiskers, or vibrissae, are richly innervated specialized hairs with follicles originating from deep in the subcutaneous skin layer on the face, head, and carpi of a cat (Dyce et al. 2010). Mechanical stimulation of the whiskers transmits information to the sensory cortex of the brain and allows the cat to gain information about environmental