Squirrels are diverse rodents with over 200 species worldwide. They live in forests, woodlands, deserts, grasslands, and urban areas. Their omnivorous diet includes nuts, seeds, fruits, insects, fungi, and occasionally eggs or small vertebrates. Most squirrels have cheek pouches for carrying food. They are agile climbers, and some species, like flying squirrels, can glide between trees. Squirrels build nests called dreys high in trees. Some are solitary, while others live in social groups. They are intelligent, with strong problem-solving skills and memory. Certain species hibernate in winter. While many squirrels are abundant, some face threats from habitat loss and the pet trade.