CONCEPTS IN BIOLOGY

PART IV. EVOLUTION AND ECOLOGY

18. Evolutionary and Ecological Aspects of Behavior

18.5. Instinct and Learning in the Same Animal

It is important to recognize that all animals have both learned and instinctive behaviors, and that a single behavior pattern can include both instinctive and learned elements. For example, biologists have raised young song sparrows in the absence of any adult birds, so that there was no song for the young birds to imitate. These isolated birds sang a series of notes similar to the normal song of the species, but not exactly correct. Birds from the same nest that were raised with their parents developed a song nearly identical to that of their parents. If birdsongs were totally instinctive, there would be no difference between these two groups. It appears that all these birds inherited the ability to produce appropriate notes but the refinements of the song’s melody came from experience. Therefore, the characteristic song of that species is partly learned behavior (a change in behavior as a result of experience) and partly unlearned (instinctive). This is probably true of the behavior of many organisms; they show complex behaviors that are a combination of instinct and learning. It is important to note that many kinds of birds learn most of their songs with very few innate components. Mockingbirds are very good at imitating the songs of a wide variety of bird species in their region. They even imitate the sounds made by inanimate objects, such as the screeching of a rusty hinge.

This mixture of learned and instinctive behavior is not the same for all species. Many invertebrate animals rely on instinct for most of their behavior patterns, whereas many of the vertebrates (particularly birds and mammals) make use of a great deal of learning (figure 18.10).

FIGURE 18.10. The Distribution of Learned and Instinctive Behaviors

Different groups of animals show different proportions of instinctive and learned behaviors in their behavior patterns.

When a behavior pattern has both instinctive and learned components, typically the learned components have particular value for the animal’s survival. For example, most of a honeybee’s behavior is instinctive; however, when it finds a new food source, it can remember the route between the hive and the food source. A bird’s style of nest is instinctive, but the skill with which it builds may improve with experience. Birds’ food-searching behavior is probably instinctive, but the ability to modify the behavior to exploit unusual food sources, such as bird feeders, is learned. On the other hand, honeybees cannot be taught to make products other than honey and beeswax, a robin will not build a nest in a birdhouse, and most insect-eating birds will not learn to visit bird feeders.

18.5. CONCEPT REVIEW

15. Which one of the following animals—goose, shark, or grasshopper—is likely to have the highest proportion of learning in its behavior? List two reasons for your answer.