Қоян тұқымдастары және олардың сипаттамасы

Family of rodents
the squirrel family (Sciuridae) as a whole

Squirrels are members of the family Sciuridae (/s//I//'//j//u://r//I//d//eI//, // //d//i:/), a family that includes small or medium sized rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squirrels are indigenous to the Americas, Eurasia, and Africa, and were introduced by humans to Australia. The earliest known fossilized squirrels date from the Eocene epoch, and among other living rodent families, the squirrels are most closely related to the mountain beaver and to the dormice.

The word squirrel, first attested in 1327, comes from the Anglo Norman esquirel which is from the Old French escurel, the reflex of a Latin word sciurus, which was taken from the Ancient Greek word σκίουρος (skiouros; from σκία ουρος) 'shadow tailed', referring to the long bushy tail which many of its members have. The native Old English word for the squirrel, ācweorna, only survived into Middle English (as aquerne) before being replaced. The Old English word is of Common Germanic origin, cognates of which are still used in other Germanic languages, including the German Eichhörnchen (diminutive of Eichhorn, which is not as frequently used); the Norwegian ikorn/ekorn; the Dutch eekhoorn; the Swedish ekorre and the Danish egern. A group of squirrels is called a "dray" or a "scurry".

Squirrels mate either once or twice a year and, following a gestation period of three to six weeks, give birth to a number of offspring that varies by species. The young are altricial, being born naked, toothless, and blind. In most species of squirrel, the female alone looks after the young, which are weaned at six to ten weeks and become sexually mature by the end of their first year. In general, the ground dwelling squirrel species are social, often living in well developed colonies, while the tree dwelling species are more solitary. while the flying squirrels tend to be nocturnal—except for lactating flying squirrels and their young, which have a period of diurnality during the summer. During hot periods, squirrels have been documented to sploot, or lay their stomachs down on cool surfaces. Squirrels, like other rodents, employ species specific strategies to store food, buffering against periods of scarcity. In temperate regions, squirrels commonly cache nuts beneath leaf litter, inside hollow trees, or underground. However, in subtropical and humid environments, traditional caching can lead to mold growth, decomposition, or premature germination. To counteract these challenges, some squirrels, particularly in subtropical zones, hang nuts or mushrooms on tree branches. This behavior, believed to minimize fungal infections and reduce the risk of food loss, also inadvertently aids certain trees, like Cyclobalanopsis, in expanding their range, with forgotten or dislodged nuts sprouting in new locations, influencing forest ecology. Two species of flying squrrirel, the particolored flying squirrel and Hainan flying squirrel aid such cacheing by carving grooves into the nuts to fix the nuts tightly between small intersecting twigs, akin to the mortise tenon joint in carpentry.

Because squirrels cannot digest cellulose, they must rely on foods rich in protein, carbohydrates, and fats. In temperate regions, early spring is the hardest time of year for squirrels because the nuts they buried are beginning to sprout (and thus are no longer available to eat), while many of the usual food sources are not yet available. During these times, squirrels rely heavily on tree buds. Squirrels, being primarily herbivores, eat a wide variety of plants, as well as nuts, seeds, conifer cones, fruits, fungi, and green vegetation. Some squirrels, however, also consume meat, especially when faced with hunger. Squirrels have been known to eat small birds, young snakes, and smaller rodents, as well as bird eggs and insects. Some tropical squirrel species have shifted almost entirely to a diet of insects. Squirrels, like pigeons and other fauna, are synanthropes, in that they benefit and thrive from their interaction in human environments. This gradual process of successful interaction is called synurbanization, wherein squirrels lose their inherent fear of humans in an urban environment. When squirrels were almost completely eradicated during the Industrial Revolution in New York, they were later re introduced to "entertain and remind" humans of nature. The squirrel blended into the urban environment so efficiently that when synanthropic behavior stops (i. e. people do not leave trash outside during particularly cold winters), they can become aggressive in their search for food. Aggression and predatory behavior has been observed in various species of ground squirrels, in particular the thirteen lined ground squirrel. For example, Bernard Bailey, a scientist in the 1920s, observed a thirteen lined ground squirrel preying upon a young chicken. Wistrand reported seeing this same species eating a freshly killed snake. There has also been at least one report of squirrels preying on atypical animals, such as an incident in 2005 where a pack of black squirrels killed and ate a large stray dog in Lazo, Russia. Squirrel attacks on humans are exceedingly rare, but do occur. Whitaker examined the stomachs of 139 thirteen lined ground squirrels and found bird flesh in four of the specimens and the remains of a short tailed shrew in one; Bradley, examining the stomachs of white tailed antelope squirrels, found at least 10% of his 609 specimens' stomachs contained some type of vertebrate, mostly lizards and rodents. Morgart observed a white tailed antelope squirrel capturing and eating a silky pocket mouse.

The living squirrels are divided into five subfamilies, with about 58 genera and some 285 species. The oldest squirrel fossil, Hesperopetes, dates back to the Chadronian (late Eocene, about 40–35 million years ago) and is similar to modern flying squirrels. A variety of fossil squirrels, from the latest Eocene to the Miocene, have not been assigned with certainty to any living lineage. At least some of these probably were variants of the oldest basal "protosquirrels" (in the sense that they lacked the full range of living squirrels' autapomorphies). The distribution and diversity of such ancient and ancestral forms suggest the squirrels as a group may have originated in North America. Apart from these sometimes little known fossil forms, the phylogeny of the living squirrels is fairly straightforward. The three main lineages are the Ratufinae (Oriental giant squirrels), Sciurillinae and all other subfamilies. The Ratufinae contain a mere handful of living species in tropical Asia. The neotropical pygmy squirrel of tropical South America is the sole living member of the Sciurillinae. The third lineage, by far the largest, has a near cosmopolitan distribution. This further supports the hypothesis that the common ancestor of all squirrels, living and fossil, lived in North America, as these three most ancient lineages seem to have radiated from there; if squirrels had originated in Eurasia, for example, one would expect quite ancient lineages in Africa, but African squirrels seem to be of more recent origin. Sciurillinae, a single South American species; and Xerinae, which includes three tribes of mostly terrestrial squirrels, including the Marmotini (marmots, chipmunks, prairie dogs, and other Holarctic ground squirrels), Xerini (African and some Eurasian ground squirrels), and Protoxerini (African tree squirrels).

Squirrels have been kept as pets in Western society at least until the 19th century. Because of their small size and tame nature, they were especially popular with women and the clergy. Squirrels are a cause for concern because they often cause electrical disruptions. It has been hypothesized that the threat to the internet, infrastructure and services posed by squirrels may exceed that posed by cyber attacks. This idea was first presented by Joshua Corman and Brian Martin (Jericho) at BruCon in 2012. Subsequently, Cris Thomas (Space Rogue), along with others, did further work on the topic in the form of aggregating animal related service outages around the world in a project named CyberSquirrel1. Squirrels have been reported to be "successfully trained" in Chongqing, China to sniff out illicit drugs and in 2023, a team of six Eurasian red squirrels had become part of a sub unit within the Chongqing city police dog brigade. According to Chongqing police department, their small size and agility are beneficial as they are able to help the police detect drugs through "tiny spaces" in warehouses and storage units that dogs are unable to reach. Yin Jin, a police dog handler, who had been assigned to train these squirrels told The Paper that "these squirrels have an acute sense of smell. But in the past, our training problems for small rodents was not developed enough to attempt a program like this" and that her team of squirrels have so far done an "excellent job" in drug detection exercises, but are not yet ready to be deployed.