What triggers cats to grow a winter coat?
Most pet owners will notice that their cat’s coat grows thicker during the cooler months and once spring arrives, the coat sheds, leaving behind a much thinner. Scientists have found that growth of the winter coat is triggered by shortening daylight hours, and not a drop in temperature.
Once daylight hours begin to shorten, information is relayed via the retinohypothalamic tract to a master clock known as suprachiasmatic nucleus (SCN) in the hypothalamus which encodes these signals and disseminates them throughout the cat to drive the circadian and circannual changes in physiology. At the pineal gland, the SCN signal affects melatonin secretion (a hormone that modulates hair growth) and the length of daylight hours is proportional to the duration of melatonin production. Melatonin suppresses prolactin secretion, which regulates the hair follicle cycle. Increased production of the melatonin and declining prolactin trigger winter coat growth in cats. As days become longer in spring, melatonin production declines and prolactin increases, leading to shedding.
