Eating strategies in animals

Read the text to find out about a) different ways of digesting the food b) examples of carnivores, herbivores, or omnivores. Complete the table below.

Animals have different ways of digesting the food they eat. According to their eating strategies, they can be carnivores, herbivores, or omnivores. Their teeth and digestive systems are adapted to their diet.

Herbivores are animals that get their energy from eating plants. These animals have evolved digestive systems capable of digesting large amounts of plant material. Many herbivores do not have upper incisors (the teeth on the top jaw in the very front that cut food), and they cut the plants with their lips instead. However, all herbivores need their molars (the big flat teeth at the back of the mouth) for grinding the mouthfuls of food. Herbivore’s molars are big and have ridges for better grinding. Herbivore skulls have spaces for big muscles to move their jaws for so much chewing. The plants are high in fiber and starch, which provide the main energy source in their diet. Since some parts of plant materials, such as cellulose, are hard to digest, the digestive tract of herbivores is adapted so that food may be digested properly. Many large herbivores have symbiotic bacteria within their guts to assist with the breakdown of cellulose. They have long and complex digestive tracts to allow enough space and time for microbial fermentation to occur. Examples of herbivores include vertebrates like deer, koalas, and some bird species, as well as invertebrates such as crickets and caterpillars.

Carnivores are animals that eat meat. Carnivores get more nutrients from their food, so they do not need to spend as much time eating as herbivores do. Their digestive system is shorter than that of herbivores for the same reason. Because of the amount of nutrition they get, carnivores can go for several days without food. Carnivore’s teeth are different from herbivore’s because of the different food.

Carnivores need long canine teeth (the teeth at the corners of the mouth) so they can grip and kill prey quickly. Their incisors strip flesh from bones. They don’t need molars for grinding food, so they have teeth that slice meat – these are called carnassial teeth, not molars. Carnivores have a shorter jaw than herbivores because that helps give them a powerful bite. Wild cats, such as lions and tigers, are examples of vertebrate carnivores, as are snakes and sharks, while invertebrate carnivores include sea stars, spiders, and ladybugs. Obligate carnivores are those that rely entirely on animal flesh to obtain their nutrients; examples of obligate carnivores are members of the cat family. Facultative carnivores are those that also eat non-animal food in addition to animal food. Note, that there is no clear line, that differentiates obligate carnivores and facultative carnivores.

Omnivores are animals that eat both plant- and animal food. Although the Latin term omnivore literally means "eater of everything", omnivores cannot really eat everything that other animals eat. For example, most omnivores cannot live by grazing, nor are they able to eat some hard-shelled animals or successfully hunt large or fast prey. Humans, bears, and chickens are examples of vertebrate omnivores; invertebrate omnivores include cockroaches and crayfish.
Omnivores lack the specialized teeth. Their digestive system is similar to that of carnivores.

Exercise 1. Expand the given statements using the information from the text.
1. The teeth and digestive systems are adapted to a diet of animals.
2. The herbivores have evolved digestive systems capable of digesting large amounts of plant material.
3. Carnivores get more nutrients from their food, so they do not need to spend as much time eating as herbivores do.
4. Carnivores don’t need molars for grinding food, so they have teeth that slice meat.
5. Although the Latin term omnivore literally means "eater of everything", omnivores cannot really eat everything that other animals eat.
6. There are obligate carnivores and facultative carnivores.