1. Rabbits Mainly Eat Grass, Not Carrots
Although the image of "rabbits and carrots" is strong, care guides show that carrots are not the center of their diet. A pamphlet from Osaka Prefecture states that the basic diet for rabbits consists of three things: hay, pellets, and fresh water [7]. Pellets are feed made by compressing grass and other ingredients into granules. It is recommended that hay be available at all times for free eating, and for adult rabbits over 7 months old, grass-family Timothy hay is commonly used [7]. Vegetables have high water content and can cause diarrhea if given too much. The sugar in fruits is explained as a cause of obesity [7]. Rabbits are herbivores that live on the ground and mainly eat grass, sometimes young tree bark [1]. The domestic rabbit kept at home is a domesticated version of the European rabbit, which lives in central and southern Europe and northern Africa, and eats grass, leaves, bark, and roots [1]. If eating hard grass alone is enough to provide necessary nutrients, why do rabbits have this surprising habit?
2. Rabbits Produce Two Types of Droppings: Hard and Soft
There are two types of rabbit droppings. One is a round, hard dropping, which is simply expelled from the body [2]. The other is a soft dropping. Rabbits catch this with their mouths directly as it comes from the anus and eat it [2]. About half of the soft droppings are bacteria, containing high-quality protein and many water-soluble vitamins [2]. They are said to be rich in Vitamin B12 and help maintain health [1]. The time when they start eating varies depending on the source. A document from the United Nations Food and Agriculture Organization (FAO) states that if food amount is fixed, they eat 8 to 12 hours after feeding, and if food is free-choice, they eat after the peak of eating [2]. Since this changes based on how they are kept or studied, it is safer not to assume it happens "only at night." It is safe to treat the timing as a rough range with some variation.
3. How the Large Intestine Sorts Food Residue into Two Types of Droppings
In the middle of the large intestine, food residue is sorted by particle size [3]. Small particles (roughly smaller than 0.1 mm) and dissolved components are pushed back into the cecum. Large fiber particles move forward to become hard droppings [2]. This sorting is explained as being due to the movement of pouches (haustra) in the intestinal wall. The movement of these pouches returns dissolved components and small particles toward the cecum [4]. The figure of 0.1 mm is a rough guide, not a strict boundary. The cecum is large among animals relative to body size, reaching about 40 cm in length, according to a commentary in the Journal of the Japanese Society of Agricultural Chemistry [4]. This commentary also introduces an interesting experiment. In a 1955 experiment, rabbits survived healthily even after their cecum was removed, and the digestion rate of fiber did not change much, but they stopped eating droppings [4]. This result is difficult to explain with the simple view that the cecum is just a dedicated bag for breaking down fiber.
4. Cows Chew Their Food Again, While Rabbits Eat Their Soft Droppings Again
Cows bring swallowed grass back to their mouths and chew it again. This is called rumination. Rabbits do not ruminate, but they expel material that has passed through the stomach once in the form of droppings and eat it again [5]. A commentary from a Japanese animal hospital states that rabbits eat large amounts of grass, return to their nest, and after a while, produce crumbly granular droppings, which they eat slowly [5]. This commentary explains this as an action equivalent to cow rumination. However, the mechanism is not exactly the same. The first record of rabbits selectively eating only soft droppings is attributed to C. Morot in 1882 [4]. Up to this point, the path by which rabbits turn grass into nutrients has become visible. The entrance to this path is the mouth and teeth that chew grass.
5. How Chewing Grass Keeps Rabbits' Ever-Growing Teeth in Shape
Rabbit teeth grow throughout their lives. It is usually said that they grow about 1 cm per month, but the speed differs by tooth type, so consider this a rough guide [6]. As long as they keep growing, they must be worn down continuously. Wild rabbits wear down their teeth by chewing grass and roots all day long [6]. Pellets are granular and not long fibers. American animal hospital materials explain that long-fiber hay is necessary to wear down the back teeth by rubbing them together [6]. The Osaka Prefecture pamphlet also states that eating hay every day prevents dental diseases like malocclusion (a condition where teeth grow faster than they wear down, causing poor alignment) and gastrointestinal diseases [7]. Connecting the story so far, the mouth that chews grass, the intestines that sort material, and the action of re-eating droppings appear as one continuous flow.
6. What to Watch For When Observing a Rabbit Eat
If there are rabbits in school animal care facilities or at home, ask to see how they eat. Are they moving their mouths while eating hay? Just watch; ask an adult before touching. The behavior of eating droppings may or may not be observed. At zoos or pet shops, look at whether there is more hay or pellets in the food container. Do not give food on your own. The Osaka Prefecture pamphlet lists foods that should not be given to rabbits. Onions, green onions, chives, garlic, avocado, raw beans, and potato sprouts and skins are said to have the risk of poisoning [7].