Inside Nature's Giants

Who: herbivore
What: eats grasses and leaves, fruit, bark, roots
Where and When: savannah, daytime

How?

Grasping: The trunk acts like the elephant's hand, grabbing food or water and bringing it to the mouth. The trunk weighs about 113 kg. It has many muscle groups that allow it to bend in many directions, including curling around a plant's stem or branch. The tip of the trunk of an Asian elephant has only one 'finger' like projection (African elephants have two finger-like projections) that allows a pincer-grip for small items (e.g., a peanut). The tusks (actually comprised of ivory because they are teeth - specifically incisors) can also be used to dig up roots or pry bark off trees. About 250 kg of food is eaten daily.

Drinking: Water can be drawn up into the trunk's nasal passageways (two long, hose-like pipes, holding approximately 11 litres volume). Sucking water up the trunk involves use of the very unusual lungs. The water is 'inhaled' into the trunk passively. This is unusual, as in most mammals, inhale actively and exhale passively. Elephants do the reverse! Their lungs are fibrously attached to the ribs, which are compressed to force an exhalation (the way we forcefully exhale out air when blowing out a candle). When the ribs spring out back into place, the air is sucked back into the lungs. The diaphragm plays a much smaller role in inhalation because it cannot be depressed downwards as much as in other mammals due to the enormity of the gut behind it.

Mastication (chewing): The lower jaw teeth move with a backward-forward action against the upper jaw teeth. Food is ground into smaller pieces by unusually large molars, each weighing up to 5 kg in older animals. Each molar gradually advances forward in the jaw as it wears and is replaced by another even larger molar (this replacement occurs up to 6 times). Only two molars are in use on each side of the lower and each side of the upper jaw at any moment (total - 8 molar teeth). After the last molar, there are no more replacements and the elephant is at risk of starving to death.

Stomach: Unlike artiodactyls (cattle, sheep, deer), elephants do not have a four chambered stomach and they do not chew cud. There is relatively minimal processing of food in the stomach compared with the giraffe. The stomach is a simple one chambered organ that mostly stores food while it begins to ferment, and massages the food into smaller units. Digestive juices do some minimal breakdown.

Intestines: Most of the food breakdown occurs in the intestines. The intestines are approximately 18 meters in length. Elephants depend upon bacterial action to break down plant products into nutrients that can be absorbed. A large sac called the cecum is located at the beginning of the colon (large intestine). It is used for storage of food that is fermenting. The remainder of the colon is very large in diameter, and is filled with more fermenting food as well as methane gas from the fermentation (approx. 2000 liters/day is released). The elephant only absorbs nutrients that are relatively easy to extract from the plant food.

Dung: Since most of the food (approx. 60%) is not absorbed, an elephant produces a large quantity of dung – about 100kg/day. The stool is large (roughly the size of two stacked bricks), particularly when compared to giraffe stool (each giraffe stool pellet is slightly smaller than a walnut). Elephants must spend approx. 2/3 day engaged in feeding to acquire an adequate supply of nutrients. The dung is very fibrous and is not much different in appearance from the food that was initially ingested in the mouth. Elephants spend less energy breaking down the difficult to digest components of the plants. Instead, they spend more energy on continuous foraging.