If you find an "abandoned" bunny nest, the first thing to do is not disturb it. Many people do not know that mother rabbits only attend to their bunnies once a day during the early hours of the morning.
If you are observing a nest, and never see the mother, don't assume that the bunnies are abandoned, chances are you just were not present when the mother came to nurse the bunnies. If you are observing a nest, and the bunnies are in a "Bunny Pile", then they are being properly cared for by the mother. If the bunnies are scattered in the nest, then the chances increase that they have been truly abandoned. Avoid disturbing the nest to look inside, however, because disrupted nests can cause the mother to abandon the babies. Other causes for abandonment include: agalactia (doe with no milk), mastitis (doe with an infection of the mammary glands), and hypothermia (chilling) of the young.
If you find bunnies that need to be fostered (for example if you ran over a bunny nest with your lawn mower), you should be aware that it is rarely a rewarding experience. Most wild rabbits do not survive if they are not being cared for by a mother rabbit. If possible, putting orphaned bunnies with a doe nursing her own litter, will increase their chance of survival. Does are more likely to adopt bunnies from a different litter if the bunnies are less then 2 weeks of age, and within 2 days of the age of the litter belonging to the foster doe. A drop of perfume or pine oil-type scent applied to the nose of the foster doe helps to prevent rejection of the orphaned bunnies.
If you cannot find a surrogate mother for the bunnies, then you will need to care for them. Bunnies under 3 weeks of age should be fed milk replacer (see formula below). (Note: Determining how old bunnies are can be difficult, as a general rule, bunnies with their eyes still closed are less then 2 weeks of age and need to be feed formula. Bunnies with their eyes open, should be offered both formula and adult food.) Give the formula to the bunnies slowly 2-3 times a day. Up to 5cc (1 teaspoon), can be given in the first few days. The volume is increased slowly to 15cc (1 tablespoon) the second week, and 25cc (nearly 1 ounce) the third week. The anal area should be gently swabbed with a warm water-soaked cotton ball to stimulate defecation and urination. This is very important, because bunnies will not go to the bathroom on their own if not stimulated. The nest should be kept at 95-98 degrees for the first 2 weeks, then lower the temperature 3-5 degrees a day until it is at room temperature.
When the bunnies are 2-3 weeks old, you can start to introduce rolled oats, and at 30 days, you can start them on commercial pellets. It is important to slowly switch rabbits to oats and pellets or you can cause enterotoxemia, a type of intestinal infection with a high mortality rate.
MILK FORMULA FOR ORPHANED BUNNIES
1 egg yolk,
8 oz. (240cc) of canned evaporated milk
8 oz. (240cc) of bottled water
1 teaspoon (5cc) honey
1 teaspoon (5cc) pediatric vitamin/mineral supplement
You can refrigerate this formula and warm up just what you need.