Anyone who has a cat knows this – during the winter, their hair increases in mass and volumeparticularly in cat breeds with longer, thicker hair. This is a normal process which allows the cat to replace old and damaged hair and replace them with new ones when the seasons change, and is activated by changes in living conditions lighting And temperature. In winter it’s actually cats’ fur it grows more slowly, but also falls lessallowing longer hairs to stay attached longer and form thicker fur. In summer, however, they fall more often: they don’t have time to stretch and are therefore shorter. As with most felines, the seasonal change in cats’ fur is a thermal regulation mechanisman evolutionary legacy dating back to before domestication when these animals lived mainly outdoors.
The accumulation of fur during the winter
In cats they typically have two layers of fur: i guard hairs external, which act as protection, and the undercoatmade from dense, soft and insulating hair. Based on the genetic mutations artificially selected by us humans, the basic length of these layers can vary greatly depending on the breed: the Siberian cat, with very thick fur, has an intermediate layer of fur, while the sphinx cat, with its hairless appearance, has none.
As temperature and lighting conditions change, the rate of growth and replacement of these two layers also changes, increasing in summer and decreasing in winter. In fact, cats seem to have more fur in winter not because their fur grows more than in summer, but because it falls out less and it is not replaced frequently. By falling out less often, individual hairs grow more and their density increases, giving the cat fur more voluminous and weatherproof. As the hot season arrives, the replacement rate and fall rate increaseand the hairs that remain on the fur are consequently shorter.
When they shed their winter fur and how much it grows during the seasons
Depending on the breed, the length of cat fur varies from 25-12 mm in summer to 30-15 mm in winter. THE’follicle activity of fur reaches its maximum peak towards the end of summer (when the fur is shed more frequently) and its minimum during late winter. During the summer approximately 70% of the outer layer and 50% of the inner layer are active – although affected by the season the replacement is therefore gradual and does not involve the entire surface of the fur at the same time.
The variation is influenced not only by temperature but also bydiet: the cat must have a sufficient supply of amino acids to replace its hair. A New Zealand study quantified the growth variation in terms of weight: the maximum is 289 micrograms of hair per square centimeter (μg/cm2) per day in summer, and a minimum of 62 μg/cm2 to the winter day. In total, a typical short-haired cat annually produces approximately 32 grams of hair for every kilo of weight.
A mass of hair that is not without consequences for our domestic environment: the extra hair released around can cause quite a few problems for allergy sufferers. Regularly capturing this excess hair by brushing your feline with special combs is therefore advisable to prevent it from being scattered around the house, and strengthens the emotional bond mutual with your cat.
Fur variations in felines
Seasonal hair growth is a evolutionary legacy of a pre-domestication era, when putting on winter or summer fur increased the chances of survival. Today, domestic cats are used to living in an environment where drastic changes in temperature no longer exist: for this reason, variations in fur are much less pronounced in more domestic cats, which tend to shed and shed hair constantly throughout the year.
Even in wild cat species, the extent of fur variations is determined by environmental conditions. For example, for those who live in the warm tropical environments (leopards, caracals…), where the temperature does not vary much from season to season, the fur tends to remain short all year round and performs a camouflage function, as well as a protective one. Much more drastic variations are instead recorded in the Amur Tiger or Siberian Tiger, a population of Panthera tigris tigris located on the border between Russia and north-eastern China. With temperatures reaching 30°C in summer and can drop to lows of -60°C in winter, the temperature range in Siberia requires a drastic adaptation of fur. In winter, the Siberian tiger’s fur grows in length and density: denser hair is better able to trap air and create a protective layer from the cold. The fur on the legs, in particular, becomes thicker, almost as if the animal were wearing the equivalent of ski boots, and a sort of mane also forms, where individual hairs reach up to 10 cm in length. The color takes on duller tones such as straw yellow, less evident on the snow cover. In summer, however, all this additional fur would be a hindrance: the length is greatly reduced and the color becomes more vibrantto better camouflage in the strong chiaroscuro of summer forests.
