Female rabbits can't exactly tell their owners that they're experiencing morning sickness. They can't pop down to the local store for a pregnancy test either. So it's up to you as an owner to identify the signs of rabbit gestation. A veterinary appointment may confirm your suspicions.
If your female rabbit is usually as sweet as pie, but all of a sudden is a little testy and perhaps even fierce, it could just be an indication that she is indeed "with litter." If your typically mild-mannered and calm bunny gets a little mouthy any time you try to stroke her head, for example, there's a strong chance that she's pregnant. Pregnant rabbits also often seem irritated by the presence of male rabbits. Note, however, that not all pregnant rabbits behave differently.
Nest Construction Preparation
Female rabbits often engage in some pretty conspicuous pregnancy habits, notably tugging on their fur and amassing hay. In doing this they are acquiring materials to construct cozy nests for their upcoming litters. They use fur from their legs and undersides, and bedding material from their cages, for these purposes. You might think this would be a sure sign that your rabbit's in the family way, but does often experience "phantom pregnancies" during which they engage in these same behaviors.
When pregnant rabbits are on the verge of delivery—known as "kindling"—they generally show zero interest in eating. If your rabbit seems especially tired and sluggish—and perhaps is even panting a little—there's a strong chance that her little ones might be making their entrance within a day or so.
Absence of Indications
Many rabbits exhibit absolutely no changes in behavior during their gestational periods, especially if their litters are on the smaller side. Since looking out for the signs isn't always a practical task, a veterinary check is smart if you have your suspicions. Note that typical rabbit pregnancies last for somewhere between 30 and 32 days. Inexperienced rabbit moms might have slightly longer pregnancies—think upward of 34 days. Consult your veterinarian if your rabbit hasn't given birth by the 32nd day. Strangely enough, rabbits carrying fewer youngsters typically stay pregnant longer than those with bigger litters.