Why do female rabbits pull out their fur?

Female rabbits typically pull out their fur due to an increase of estrogen levels during pseudopregnancy, prompting them to carry out maternal behaviors such as building a nest. This stage of the pseudopregnancy (release of ova prior to gestation), which usually occurs between 15 and 18 days after ovulation, is accompanied by a loosening of fur.

The loosening of fur makes it easier for female rabbits to pull it out, generally from the abdominal and shoulder areas within reach.

During this nest-building period, female rabbits will tend to collect whatever materials are available and carry them to a nesting point. These might include hay, paper and even fur.