Animals all feed on organic matter, but their diets and way of obtaining food vary enormously. Some animals are omnivores, meaning that they are capable of surviving on a very wide range of foods.
Feeding Adaptations.
Animals all feed on organic matter, but their diets and way of obtaining food vary enormously. Some animals are omnivores, meaning that they are capable of surviving on a very wide range of foods.
Many other animals, from giant pandas to fleas, have extremely precise requirements and cannot deviate from their highly specialized diet.
Carnivores in general eat other animals, or the remains of living things. Plant-eaters, or herbivores, often do not have to search far to find things to eat, and in some cases-for example wood-boring insects-they are entirely surrounded by their food.
The disadvantage of a plant-based diet is that it can be difficult to digest and is often low in nutrients. To overcome the first of these problems, most herbivores have tough mouthparts for chewing and grinding their food. Many plant-eating animals, from termites to cattle, have complex digestive systems containing microorganisms that break down cellulose and other indigestible plant substances, turning them into nutrients that the animals can absorb. The second problem- due to lack of nutrients-is harder to sidestep, particularly in a diet made up largely of leaves. As a result, leaf-eaters often have to feed for many hours each day to obtain the nutrients that they need.
Carnivores live on flesh from other animals that is often nutrient-rich and easy to digest but difficult to obtain. Finding and capturing this kind of food calls for keen senses. But even though a hunter has acute vision or a highly developed sense of smell, a large proportion of a hunter's victims manage to escape. If this happens too often, a predator quickly starves. Some mammalian predators, such as the lion and wolf, increase their chances of success by hunting in groups. While this strategy enables them to tackle larger prey, a successful kill has to be shared ...
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Carnivores live on flesh from other animals that is often nutrient-rich and easy to digest but difficult to obtain. Finding and capturing this kind of food calls for keen senses. But even though a hunter has acute vision or a highly developed sense of smell, a large proportion of a hunter's victims manage to escape. If this happens too often, a predator quickly starves. Some mammalian predators, such as the lion and wolf, increase their chances of success by hunting in groups. While this strategy enables them to tackle larger prey, a successful kill has to be shared among members of the group.
But in the animal world as a whole, many other predators adopt a less energy-intensive approach to catching their food. Instead of actively searching out their prey, they position themselves in a suitable location and wait for their prey to come within striking distance. In this method of hunting, camouflage and other forms of deception play a prominent role.
Most animals that use a lie-and-wait strategy blend in with their surroundings, but a few use lures to entice their prey within range. A typical example is the snapping turtle of North America, which waves a ribbon of pink flesh on its tongue that resembles a worm. Any fish venturing toward it is swallowed whole. In predatory animals, teeth or other mouthparts often play a part in catching and subduing food as well as in preparing it for digestion. These mouthparts include canine teeth in carnivorous mammals, venomous fangs in snakes, and poisonous "harpoons" in some marine molluscs. These harpoons can impale and kill small fish. Each harpoon is used just once, and afterwards it is expelled and another is formed in its place. Other Feeding Strategies Most predators hunt the largest animals that they can catch without putting themselves unduly at risk. However, some animals concentrate on food items that are much too small to be worth collecting one by one. Instead of catching food individually, they have special feeding adaptations for sweeping it up in bulk. On land, these animals include insect-eating mammals, such as anteaters and pangolins. Using their long and sticky tongues, they lick up ants and termites and can consume over 20,000 insects a day.
In water, this kind of feeding strategy is mirrored by animals called filter feeders, which sieve small animals or food particles from their surroundings. Many of these filter feeders are sessile animals that sieve food from the water immediately around them.
Others, such as some whales, scoop up their food while on the move and filter it out in their mouths, using specialized gills or plates of a fibrous material called baleen. This feeding technique is extremely efficient, allowing whales to grow to an immense size.
In another feeding technique, predators seek out sources of food that are much larger than themselves but only eat part of their prey-usually its blood. This way of life is has been pursued with great success by several groups of flying insects, such as mosquitoes and horseflies.
But in the animal world as a whole, fluid diets are much more common in animals that feed on plants. Aphids, cicadas, and other true bugs use piercing mouthparts to suck sap from plant stems. Many different animals, including moths, butterflies, hummingbirds, and bats, use probing beaks and tongues to reach nectar in flowers. To avoid the need to track down food, some animals use a highly specialized feeding strategy, called parasitism (see Parasite). A parasite lives on or inside other animals and simply siphons off some of its host's food or, more commonly, feeds on the host itself.
External parasites, such as fleas, have well-developed senses and adaptations that enable them to cling to their hosts. Internal parasites, such as tapeworms and liver flukes, are highly modified for a life inside their hosts. The sense organs of internal parasites are rudimentary or absent because they do not need to find food or avoid enemies. Instead, they devote their time entirely to the twin tasks of feeding and reproduction.
