The mating season often starts on warm days in January, the squirrels chasing each other through the branches. The female red squirrel may produce two litters in a good year, one in the spring (April) and the other in summer (August). There are, on average, three babies in a litter. The breeding drey is usually a little larger than normal with a thick, soft, grassy lining. The young are born blind and naked. If she is disturbed, she will carry the babies in her mouth, one by one, to another nest, which is sometimes quite a distance away.
As the young develop, the female spends more and more time away from the drey, and by the time they are three weeks old she may leave them for several hours at a time. The male takes no part in rearing the young.
At seven weeks the young begin to venture away from the nest and at eight to ten weeks they are weaned and become independent. Their fluffy, darker baby coats change into the adult colour.
The success of the breeding season i.e. the numbers of babies born and raised, depends on the seed crop of the main trees where they live. Where there are plenty of acorns, pine cones etc. squirrels build up a lot of body fat and many survive the winter in good condition. This means they will start breeding early in the next year and rear many babies. In a year when there is a shortage of tree seeds, the squirrels do not put on much fat and they may die from starvation or disease during the winter. Most of the survivors are not fit enough to breed successfully.Read More: Threats to the Red Squirrel