Читать книгу Animal Behavior for Shelter Veterinarians and Staff - Группа авторов - Страница 29

Dogs are known for their noses and with good reason. Compared to microsmatic, or “poor smelling,” animals like humans, dogs have physiological structures that prioritize smelling and can detect and discriminate a large number of, what are for humans, imperceptible odors (Horowitz 2009b). Scent particles enter the dog’s nose both by sniffing and regular breathing (Neuhaus 1981). These particles then enter the nasal cavity, where a mucus lining covers the olfactory epithelium and mediates olfaction—smelling (Furton and Myers 2001). Considerably more genes code for olfactory receptors in dogs than in humans (Quignon et al. 2003).

Compared to humans, dogs seek out and access a much wider set of contextual and social information through smell, and olfaction is a major part of dog intra‐ and interspecific social encounters. Dogs, like many mammals, have a secondary molecule‐detection organ, the vomeronasal organ (VNO), that is directly involved in social communication and pheromone assessment (Adams and Wiekamp 1984). Distinct from the main olfactory epithelium, the VNO is located below the nasal cavity, and its receptors also carry information to the olfactory bulb. This chemosensory organ is ordinarily viewed as responsible for pheromone detection in urine, feces, and saliva as well as glands in the anogenital region, mouth, and face. Using odor cues, dogs can discriminate conspecifics as well as identify something unique about themselves compared to other odors (Bekoff 2001; Horowitz 2017). Horowitz (2020) also found that dogs can distinguish their owner’s odor from that of a stranger. Additionally, dogs appear to take note of human odors associated with fear or happiness (D’Aniello et al. 2018).

Dog social encounters are marked by close olfactory inspection, particularly of the head and anogenital area. Body sniffing is common between dogs when they first meet, either on or off leash (Bradshaw and Lea 1992; Westgarth et al. 2010). Initial encounters are typically short, and dogs often explore the environment instead of furthering the interaction, a phenomenon that has been described in free‐ranging dogs and at dog parks (Howse et al. 2018; Ward 2020). In the samples studied, often self‐selected groups at dog parks or open spaces, post‐greeting aggression and even play were relatively rare. Direct encounters between dogs at shelters may be rare, and dogs tend to be on leash (or in kennels), and interactions might be thwarted due to shelter operational protocols. Without the opportunity for direct olfactory investigation, these dogs might experience tension, restraint, or frustration upon seeing other dogs, which could affect subsequent intraspecific interactions.

Olfaction also plays a role in dog interactions with people. For example, the anogential and thigh areas of unfamiliar people are investigated more than those areas of the owner, who is already known to the dog (Filiatre et al. 1991). Unfortunately, humans may thwart olfactory investigation, for example, reaching out or descending a hand on top of a dog’s head, instead of allowing the dog to approach and sniff.

Communication via scents is common by depositing secretions and excretions in the environment. Urination is more than waste expulsion; canids gain valuable social information by attending to these splatterings and pay considerable attention to unfamiliar urine (Lisberg and Snowdon 2009). Scent marking can even be performed differently between dogs of the same sex. Small male dogs have been found to mark higher than they are tall; hypotheses for why they do this have not yet been tested (McGuire et al. 2018). Depending on the surface, scent marks could be visual, olfactory, or even, possibly, auditory (Bekoff 1979).

Olfaction is essential to the dog umwelt, or perceptual world (Horowitz 2009b). Providing dogs with opportunities to actively use their noses—for instance, through nosework—can enhance well‐being. Duranton and Horowitz (2019) found that dogs who participated in nosework for two weeks displayed a more optimistic outlook—measured via cognitive bias test—when compared to dogs who participated in heelwork practice. Engaging in sniffing is good for dogs. Humans’ jobs, as their observers and caretakers, is to know that the dog's nose is constantly engaged, to actively provide them with smelling opportunities, and to not discourage them from using their nose in species‐typical ways.