Julia D. Albright, Christine Calder, and Amy Learn The domestic cat (Felis silvestris catus) remains one of the most popular pets in the United States and throughout much of Europe. Recent survey statistics show that approximately 31.9 million households in the United States are home to more than 58 million cats, with an average of 1.8 cats in each cat‐owning home (American Veterinary Medical Association 2018). These data do not capture the millions of community or feral cats that may live amongst people, yet no one claims to own. The ubiquity of the domestic cat may be rooted in its ability to adapt to almost any environment and human perception of the cat as an affectionate yet self‐sustaining household pet (Bradshaw et al. 2012). Despite their popularity, many aspects of the cat’s normal behavior and cognitive abilities have yet to be explored. Fortunately, the last few decades have seen a rapid rise in research related to human‐cat social interactions, cognitive abilities, and factors that may improve welfare or reduce behavior problems within human homes. 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). 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). 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. 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). 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). 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). 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 conditions and objects within close range. Most notably, whiskers provide important information about the movement of prey, kittens, and other social partners immediately adjacent to the cat. Touch becomes the primary sense at close range due to poor visual acuity at this distance (Bradshaw et al. 2012). The cat’s canine teeth and claws also have pressure receptors to aid in preventing the escape of prey once captured (Byers and Dong 1989). At rest cat facial whiskers are positioned slightly backward, but when moving or aroused, whiskers move forward and away from the head to prepare for gathering information (Beaver 2003). Therefore, whisker position can be a form of conspecific visual communication as well. Conspecific vocal communication is only heard during agonistic, sexual, or mother‐kitten encounters (Kiley‐Worthington 1984). Cats vocalize much more frequently to humans, primarily through the open‐mouthed meow (or miaow) sound, which functions as attention seeking with a learned component. Close‐range affiliative communications include the purr and the trill. The purr is a care‐soliciting behavior heard from kittens when nursing, during friendly interactions, or when the cat is mildly anxious or ill (Crowell‐Davis et al. 2004; Overall 2013). The chirr or trill is a modified, mostly closed‐mouth meow sound used in greeting. The estrus call is also a closed‐mouth vocalization heard from females during courtship and can be similar in character to a type of agonistic male cat call (Overall 2013; Wolski 1982). However, aggressive intercat vocalizations are usually open‐mouthed and include the hiss, spit, growl, snarl, growl, yowl, and shriek (Crowell‐Davis et al. 2004). Urination, defecation, and scratching are behaviors used to disseminate olfactory information (Brown and Bradshaw 2013). Urine, feces, and sebaceous glands, predominantly located on the head, perianal area, and between the digits of the paws, are rich in information about an individual and, therefore, effective forms of olfactory communication. Head rubbing of objects or social targets leaves olfactory signals from sebaceous glands located on the temporal region of the head, under the chin, and around the lips. This head bunting behavior is often accompanied by purring (Crowell‐Davis et al. 2004). Pheromones have been identified from the cheek sebaceous glands (Pageat and Gaultier 2003) and are thought to be a form of conspecific social signaling. Body postures and facial expressions communicate intent and emotional state at a particular moment. Specific behaviors and body positions can have multiple meanings; thus, assessing the entire body, other signals (e.g., vocalizations), and the context is critical when humans are trying to interpret a cat’s emotional state. The vertical “tail up” is one of the most important visual signals (see Figure 2.1). It largely signals the desire to interact amicably. The cat receiving a “tail up” signal may reciprocate with an approach, followed by touching noses; rubbing of the head, neck, and body along the body of another cat; and tail twining (Cafazzo and Natoli 2009). A similar approach and rubbing behavior sequence may be displayed toward an individual of another species, especially human, or an object near the intended receiver (Turner 2017). A stiff, lashing tail indicates aggression, and a tail tucked under the body signifies fear in a non‐resting cat. Piloerection, or hairs stiffened and standing away from the body, indicates strong arousal and is usually accompanied by an upright or arched body, but the tail may be erect or low. A tail wrapped around the body of a sitting cat is thought to communicate ambivalence—the cat is unlikely to show aggression but is not enthusiastic about the interaction (Leyhausen 1979). Figure 2.1 Tail up greeting display. Source: Reproduced with permission from N. Drain. © Natasha Drain. Facial expressions are associated with a range of emotions. A distressed cat’s eyes may blink and pupils dilate, ears lower or flatten to the head, and whiskers move forward. These expressions may be accompanied by hissing or other defensive vocalizations (see Figure 2.2). A very relaxed cat is often lying lateral with the eyes, pupils, and ears in a neutral position. A cat resting in a sternal or sphinx‐like position, often with the tail wrapped around the body, may be slightly more anxious or vigilant about the surroundings (Leyhausen 1979; Bennett et al. 2017; Gourkow et al. 2014). Figure 2.2 Defensive position. Source: Reproduced with permission from K. Watts. © Katie Watts. General Appendix B describes common feline body language characteristics. As a species, cats are extremely adaptable to various environments, but the degree of plasticity is determined by a combination of genetics, prenatal environment, and postnatal experiences, especially those occurring during the socialization development period. Born blind, deaf, and completely dependent on the queen for nourishment, the neurological, musculoskeletal, and cognitive maturation of a kitten from birth to adulthood is a short but complex process. Comparative genetics studies have revealed the domestic cat varies from wildcats at 13 chromosomal loci, many of which code for genes related to neurodevelopment or neurotransmitters known to affect various emotional or motivational states, perhaps revealing the genetic basis for tameness (Montague et al. 2014). Humans have a long history of enhancing certain traits through genetic selection, and this is most evident in the domestic dog, the species with the greatest morphologic diversity on earth. Humans have a much shorter history of selectively breeding domestic cats, and the primary objective has been advancement of desired physical, not functional, traits. Nevertheless, consistent breed predispositions for certain behavioral characteristics seem to exist. Several observational and survey studies have identified differences among purebred cats in terms of aggression, propensity to elimination outside the litterbox, playfulness, shyness, and activity level (Mendl and Harcourt 2000; Wilhelmy et al. 2016; Salonen et al. 2019). Many people believe that coat color and certain personality traits are linked. For example, calico or tortoiseshell color cats are often thought to be more aggressive and anxious (Stelow et al. 2015). While the owner‐queried survey results of Stelow et al. (2015) did indicate some minor increases in aggressive behavior within sex‐linked orange color cats, Wilhelmy et al. (2016) found that differences in behavior among purebred cat coat colors were largely explained by breed alone. Cat personalities seem to be stable and vary along several dimensions of confidence, nervousness, sociability, and activity (Lowe and Bradshaw 2001; Karsten et al. 2017; Litchfield et al. 2017). Personality, like most behavioral phenotypes, is a confluence of environmental and genetic influences. Kittens sired by males with outgoing and friendly personalities were found to show more approach and affiliative behaviors to people, be less stressed by the approach of unfamiliar people, and be more likely to spend time near a novel object (McCune 1995; Reisner et al. 1994). However, handling and socialization provided a protective effect against some fearful and defensive behaviors. Friendly sired but unsocialized kittens behaved in a similar manner to unfriendly sired socialized kittens (McCune 1995). The nutritional status of a dam and her exposure to certain stimuli during the 63‐day gestation period can influence postnatal behavior of her offspring. For instance, kittens show a preference for certain flavors fed to their queen during the prenatal period (Becques et al. 2009). Queens placed on protein‐ or calorie‐restricted diets can produce offspring with elevated emotional reactivity and impairments in social interactions, environmental exploration, and learning (Gallo et al. 1980). Even food restriction limited to the second half of gestation can result in abnormal physical and emotional traits (Smith and Jansen 1977). Studies from other mammalian species indicate offspring born to dams exposed to excessive environmental stressors, such as unpredictable noise stimuli, may suffer from impaired cognitive and neurologic development (Schneider and Moore 2000). Kittens exposed to significant prenatal stress may suffer similar developmental dysfunction. The neonatal period consists of the first two postnatal weeks. The queen encircles the kittens with her body and legs immediately after the birth of all of the kittens. The kittens are suckling within an hour of birth, and a loose teat order is established by 12 hours post‐parturition (Ewer 1960; Houpt 2018). The kittens engage in little other than suckling and sleeping during the neonatal stage. Waste elimination is initiated by the queen via grooming of the perineal region. Neonate kittens do not have the ability to thermoregulate, and thus body temperature is maintained by huddling with their littermates and mother (Jensen et al. 1980; Olmstead et al. 1979). Tactile, thermal, and olfactory stimuli help the kitten orient to the queen and littermates, as the eyes and ears are closed during much of the neonatal period. Orienting to the queen’s abdomen and suckling are highly reflexive behaviors (Raihani et al. 2009), although nursing is largely initiated by the queen during the first two weeks. Purring is observed in nursing kittens and may serve to communicate active suckling to the mother (Bradshaw 2017). The first set of teeth erupt between 2 and 5 weeks of age with adult teeth erupting at approximately 12 weeks. Movement at this age occurs by limb paddling or pulling of the body by the front limbs due to weaker neuromusculature of the hindlimbs in this early stage. Kittens are usually able to hear by the fifth day of life, although the external pinnae do not become erect and the ear canal does not open for another few days. Eyes open during the second week, and several factors can influence the exact timing. The eyes of kittens born to younger mothers tend to open earlier than kittens born to older mothers, female kittens’ eyes are more likely to open prior to males, and excessively dark conditions hasten eye opening. The timing of eye opening is also heritable (Braastad and Heggelund 1984). Vision becomes the kitten’s dominant sensory guide once the eyes are open. Early maternal care is another important environmental factor in healthy kitten behavioral development. Kittens separated from their mother and hand reared by humans from two weeks of age were more fearful and aggressive toward people and other cats, more sensitive to novel stimuli, developed poor social and parenting skills, and did not learn as well as kittens raised by their mother (Mellen 1992). Scruffing is a maternal behavior of grasping the kitten’s loose skin around the neck and shoulders with her teeth. The kitten reflexively goes limp and quiet. This allows the queen to move her kittens to new dens with a lower risk of detection from predators. In free‐roaming situations, a queen typically moves den sites multiple times prior to weaning of the litter. Some cats may retain this limp or trance‐like state reflex into adulthood, but many do not, and scruffing by a human during handling usually induces distress (Moody et al. 2020). First described by Bateson (1979), kittens have an important “sensitive” period when individual life experiences can have lasting effects on behavioral, neurological, and sensory development. The sensitive period for socialization to humans is thought to occur between the ages of two and seven weeks of age in kittens. In one series of studies, kittens handled by humans between the ages of 3 and 14 weeks were more likely to approach humans and accept human handling for a longer duration than kittens who were handled after 7 weeks or never handled before 14 weeks of age. Withholding handling until 7 weeks of age resulted in kittens who seemed unafraid of humans but did not choose to remain in proximity to humans after initial contact (Karsh and Turner 1988). Another study found that even if handling is delayed to 5 weeks of age, kittens can catch up by 6 months of age in terms of sociability with humans to those kittens for whom handling began several weeks earlier (Lowe and Bradshaw 2001, 2002). These studies indicate that exposure to gentle handling from humans by 7 weeks of age is critical for a cat to enjoy human contact. Other studies have focused on the quality of human exposure during the sensitive socialization period. Kittens housed at rescue centers demonstrated significantly fewer signs of fear toward humans when handled for two and five minutes daily from birth to 45 days compared to those kittens who experienced only passive exposure to humans during basic husbandry, such as cage cleaning (Casey and Bradshaw 2008). Kittens handled five minutes daily from birth to 45 days of age were more likely to approach strange toys and unfamiliar people as well as slower to learn avoidance tasks (Wilson et al. 1965). The end of the socialization period (seven weeks) corresponds with further development of the emotional system and fear of novel stimuli. Intraspecific social development has received little research attention, but the timeline presumably parallels that of cat‐human social development (Bradshaw 2017). The socialization development period also corresponds to a time of exponential physical development. Kittens begin running around five weeks of age and have full coordination by seven weeks (Peters 1983). Air righting, or the ability of cats to land on their feet after falling, is first observed between the third and sixth week of life. Kittens produce ultrasonic vocalizations, and the pitch becomes lower with age. Expansion of the vocalization repertoire and avoidance of agonistic vocalizations begins around four weeks of age. Interestingly, the vocalizations of deaf kittens are louder but otherwise almost identical to those of kittens with normal hearing (Houpt 2018). Visual acuity and binocular vision continue to develop during this stage. Cats have been used extensively as models for research into the neurodevelopment of the mammalian visual system. From this research, we know proper sensory development requires environmental stimulation. Deprivation of certain visual stimuli during development creates permanent alterations and deficiencies in the visual cortex. For instance, cats raised in environments with only horizontal lines did not respond to vertical stripes because of degeneration of the neurons responsible for recognizing vertical edges (Blakemore and Cooper 1971). Kittens not allowed to visualize their front paws due to placement in dark conditions or in an Elizabethan collar did not develop fine motor skills needed for placement of the paws (Hein and Held 1967). Socialization with humans may continue to improve into the juvenile period, provided the kitten received some handling from humans in the preceding weeks (Lowe and Bradshaw 2001; McCune 1995). This is assumed to be the case with intercat socialization as well (Bateson 2014). Rapid physical development allows the kitten to become fully independent from the mother during this period. Kittens have well‐developed senses, thermoregulation, movement, and detection of danger by this stage. The weaning process is completed during the juvenile stage, and kittens are fully functioning predators by the early part of the juvenile period. The mother cat initiates weaning by bringing dead prey to the kittens around four weeks of age. As the kittens become more successful at killing prey, she later releases increasingly more mobile prey items near the kittens. Kittens continue to initiate suckling, but the queen gradually decreases the duration of nursing bouts to keep the kittens hungry enough to encourage exploration and hunting behavior. As their motor skills develop, the kittens also follow the dam on hunting trips. Eventually the dam only allows short suckling bouts, presumably for bonding purposes, and weaning of the kittens is usually complete by seven weeks (Bateson 2014). Weaning age appears to have broader impacts on social and abnormal oral behaviors according to a recent survey study (Ahola et al. 2017). Owners of cats weaned before 8 weeks of age were more likely to report behavior problems than owners of cats weaned in the 12–15‐week range. Kittens weaned before 8 weeks were more likely to show aggressive behaviors than those weaned later. Later weaning was a protective factor against aggression toward other cats as well as familiar and unfamiliar people. The prevalence of abnormal oral behaviors like excessive grooming and wool sucking as well as shyness toward novel objects decreased in the kittens weaned after 14 weeks as well (Ahola et al. 2017; Houpt 2018). Overall, owners of cats weaned before 8 weeks of age were more likely to report behavior problems than those weaned in the 12–13‐week range. Aggression, abnormal oral behaviors, and shyness toward novel objects were shown to be inversely correlated to the age of weaning as well (Ahola et al. 2017). The juvenile period ends with sexual maturity. In female cats, this correlates with the first sign of estrus, which can be as early as 3 to 4 months and as late as 12 months of age. Environmental factors such as the time of year born, exposure to mature tomcats, the presence of other female cats in estrus, and increasing periods of light all influence the age of estrus onset. Male domestic cats reach sexual maturity between 9 and 12 months. In free‐ranging cat colonies, however, a male may not become reproductively active until two or three years of age, when full integration into a colony is achieved (Hart and Hart 2014a). Social maturity is the stage of final transition into adult behaviors such as territoriality and aggression and in domestic cats is thought to occur between 36 and 48 months of age (Landsberg et al. 2013). Play is ubiquitous amongst many genera of animals, and cats are no exception. Domestic cat play behaviors are classified as social, locomotor, predatory, or object play (Delgado and Hecht 2019). It has been widely assumed that play is neuromuscular, social, and cognitive preparation for critical adult behaviors (Burghardt 2005). However, research of kittens raised in barren environments provided evidence that play does not seem to be a required precursor for many behaviors, particularly those like predation that are related to survival (Thomas and Schaller 1954). Early experiences can impact the timing and character of play behaviors. Genetics, sex, learning, and characteristics of the queen, litter, and target of play can alter the development of play behaviors in cats (Delgado and Hecht 2019). Figure 2.3 Kitten object play. Source: Reproduced with permission from M. Allison. © Meg Allison. Social interactions begin around 2 to 3 weeks of age in kittens, and social play is apparent by 4 weeks, peaking around 9 to 14 weeks. Social play progresses from chasing and running to stalking and wrestling. Play solicitation behaviors include exposing the belly, pouncing, raising the front paws up, and side stepping (West 1974). As the kitten ages, interest switches from social partners to objects. The first instances of object play coincide with the queen’s provision of prey items to her kittens. Object play is very prevalent by 7 weeks, or the end of weaning, but does not peak until around 18 to 21 weeks of age (Mendoza and Ramirez 1987). Object play in older kittens and adults resembles predatory behaviors such as batting, scooping, pouncing, grasping and biting. Singleton kittens, those weaned early, and those under food restriction tend to display more object play (Guyot et al. 1980; Bateson and Young 1981) (see Figure 2.3). As most cat owners can attest, object play continues into adulthood (Mendoza and Ramirez 1987
2
Introduction to Cat Behavior
2.1 Introduction
2.2 Domestication
2.3 Sensory Perception
2.3.1 Vision
2.3.2 Hearing
2.3.3 Olfaction
2.3.4 Taste
2.3.5 Touch and Balance
2.4 Communication
2.4.1 Vocalization
2.4.2 Scent
2.4.3 Visual Signals
2.5 Behavioral Development
2.5.1 Genetics
2.5.2 Sensitive Periods of Development
2.5.2.1 Prenatal
2.5.2.2 Neonatal (0–14 days)
2.5.2.3 Socialization (Two–Seven Weeks)
2.5.2.4 Juvenile (Seven Weeks–Sexual Maturity)
2.5.2.5 Adult (Sexual and Social Maturity)
2.6 Maintenance Behaviors
2.6.1 Play
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