Mammalian Digestive Systems Quiz

Nutritional Ecology: Food Processing Systems

• Mammals have diverse digestive tracts, tailored to their diets.
• Digestive systems vary widely among herbivores, carnivores, and omnivores.
• Different strategies for processing and digesting food include hoarding, caching, and storing.

Mammalian Digestive System: Cavities

• Lips/bills and teeth are crucial for food handling, intake, and processing.
• Taste buds enhance the sense of food quality.
• The tongue aids in manipulating food and swallowing.
• Saliva lubricates food—crucial for swallowing.
• Digestive prep for the stomach is important.
• Herbivores exhibit pronounced buccal cavities.
• Myrmecophagy (anteaters, pangolins, aardvarks) have specialized extreme buccal cavities due to their diet of social insects.
• Their mouths are long tubular structures for feeding.

Mammalian Digestive System: Esophagus

• Transporting food from the buccal cavity to the stomach.

Mammalian Digestive System: Stomach

• Digestion is common in the stomach's simple pH environment.
• The stomach pH in some mammals (not forest animals) is 1-4, and they have hydrochloric acid to help break down food.
• Foregut fermentation in mammals allows anaerobic bacteria to break down cellulose.
• Herbivorous mammals (like monkeys, tree sloths, camels, deer, antelope, hippos, and kangaroos) have anterior portions containing anaerobic bacteria for this process.
• The stomach in deer, antelope, and cattle has four chambers. The abomasum is the fourth or true stomach.
• Ruminant stomachs have rumen fluid with 10 billion bacteria aiding microbial fermentation to extract energy.

Mammalian Digestive System: Cecum

• An elongated tube connecting the small and large intestines.
• Bacterial fermentation of unabsorbed plant fiber occurs in the cecum.
• H2O absorption.
• Food particles are processed to be small.
• Wildebeest, wallabies, rabbits, horses use the cecum for more efficient forestomach fermentation.

Mammalian Digestive System: Small Intestine

• Nutrient absorption into bloodstream happens in the small intestine.
• Length varies based on food habits. Carnivores typically have shorter intestines compared to herbivores who need longer lengths to break down plant materials.

Mammalian Digestive System: Large Intestine

• Located at the posterior end of the small intestine to the rectum.
• Functions similarly to the cecum for water absorption.
• Some mammals (horses, new world monkeys, pigs, and humans) have a colonic portion in their large intestines with microflora for additional fermentation.

Food Hoarding, A Strategy for Mammals

• Hoarding (caching) equals storing food for later.
• Carnivores' hoarding is usually short-term.
• Granivores' and herbivores' hoarding is usually long-term.
• Scatter hoarded food (small amounts) versus larder-hoarded food (large amounts).

Food Hoarding: Protection and Management

• To prevent decomposition (through resistance to microbes and fungi)
• Kangaroo rats use surface pits outside burrows.
• Other animals store in underground chambers
• To protect from green vegetation, pikas, gerbils, and mountain beavers cure plants in haypiles. They also select vegetation high in phenolics (secondary compounds) that are potent antimicrobials.
• Some animals store in rock overhangs.
• Insectivores (short tailed shrews) inject prey with toxins from their submaxillary glands.
• Moles place stolen worms in cool places.
• Some animals nip buds from bulbs to prevent sprouting, like mole rats and voles.
• For white oaks, the acorns are stored but not notched, and some are notched to prevent germination.

Food Hoarding: Relocation of Caches

• Deer mice and seeds are buried 2" deep in peat.
• Grey squirrels have spatial memory relating to hiding spots, but sometimes the exact location is forgotten.
• Niko Tinbergen conducted experiments (1965) involving placing caches for red foxes in which various experiments showed spatial memory in grey squirrels, and the ability of red foxes to locate cached items.