Читать книгу Animal Behavior for Shelter Veterinarians and Staff - Группа авторов - Страница 49

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.