SCIENCE BEHIND TYPICAL ANIMALS BEHAVIOR

• Animal behavior includes all the ways animals interact with other organisms and the physical environment.

• Behavior can also be defined as a change in the activity of an organism in response to a stimulus, an external or internal cue or combo of cues.

• To fully understand a behavior, we want to know what causes it, how it develops in an individual, how it benefits an organism, and how it evolved.

• Some behaviors are innate, or genetically hardwired, while others are learned, or developed through experience. In many cases, behaviors have both an innate component and a learned component.

• Behavior is shaped by natural selection. Many behaviors directly increase an organism’s fitness, that is, they help it survive and reproduce.

Introduction

Do the squirrels in your neighborhood bury acorns underground? Does your cat start meowing around the time you usually feed her? Do you start hanging around the kitchen when it’s close to dinnertime?

If you’ve noticed any of these things, congratulations—you’ve made your first observations in behavioral biology! These are all examples of animal behaviors. Yep, you and I count as animals too. In fact, these behaviors are just a tiny sampling of the amazing and diverse behaviors we can see in nature.

We could ask what behavior is used for, but it might be better to ask, what isn’tit used for? Animals have behaviors for almost every imaginable aspect of life, from finding food to wooing mates, from fighting off rivals to raising offspring. Some of these behaviors are innate, or hardwired, in an organism’s genes. For instance, this is true of the squirrel and its acorn

Broadly speaking, animal behavior includes all the ways animals interact with other members of their species, with organisms of other species, and with their environment.

Behavior can also be defined more narrowly as a change in the activity of an organism in response to a stimulus, an external or internal cue or combination of cues.

For example, your dog might start drooling—a change in activity—in response to the sight of food—a stimulus.

One type of instinctual behavior is fixed action patterns, which are behaviors the animal is compelled to engage in. For instance, some birds will raise the chicks of other birds if the eggs are put in their nests during nesting season, because caring for an egg is a fixed action pattern. Another instinctual behavior is imprinting, wherein a baby animal accepts a person, or even an item, as a surrogate mother. Sexual behavior is also instinctual, bolstered by play, which helps animals learn courtship and mating skills. Many of these behaviors are dictated by specific body systems, like the nervous system, which responds to stimuli in the environment.

Learned behavior is important both for wild animals, who must learn specific and new ways to survive, and for domestic animals that we seek to train. Animals can learn to anticipate that an action will have a predictable outcome through trial and error, such as dog learning to sit for a treat. This is called operant conditioning. They can also learn that one event precedes another, such as the sound of a metal food bowl being moved signaling food being served, which is known as associative learning. Animals also learn a lot through watching others and mimicry. All of these behaviors allow an animal to adapt to new situations and problems.

Identifying behavior patterns enables people to determine when animals are behaving abnormally. These abnormal behaviors might simply be annoying to animal owners; however, in other instances they may also be dangerous for the animal and others or even threaten their very survival. For example, inappropriately aggressive dogs, which might be suffering from disease or trauma, are potentially dangerous to themselves and others. The behavior may be addressed if it is identified as abnormal and normal behavior is reestablished. More important to species survival are mating and raising offspring, and in these cases abnormal behavior that leads to failure to mate or care for offspring can present a threat to the animal’s long-term survival.

Nikolaas (Niko) Tinbergen was a Dutch ornithologist, or bird biologist, who studied behavior and is now considered one of the founders of the field of ethology. Based on his own research, Tinbergen proposed four basic questions helpful in understanding any animal behavior.

Let’s look at these questions, using the production of song by the zebra finch—a common songbird—as an example.

1. Causation—What causes the behavior? What triggers the behavior, and what body parts, functions, and molecules are involved in carrying it out?

Example: Singing is triggered in zebra finches by social cues, such as the proximity of a potential mate, as well as the appropriate hormonal state. The ability to produce songs is influenced by male hormones and occurs mainly in male birds. Songs are produced when air flows from air sacs in the bronchii through an organ called the syrinx. Certain parts of the brain control song production and are well-developed in male zebra finches.

2. Development—How does the behavior develop? Is the behavior present early in life? Does it change over the course of the organism’s lifetime? What experiences are necessary for its development?

Example: Young male zebra finches first listen to the songs of nearby males of their species, particularly their fathers. Then, they start to practice singing. By adulthood, male zebra finches have learned to produce their own songs, which are unique but often have similarities to those of their fathers. Once a finch has perfected its song, the song remains fixed for life.

3. Function/adaptive value—How does the behavior affect fitness? How does the behavior affect an organism’s chances of survival and reproduction?

Example: Singing helps male zebra finches attract mates, increasing the chances that they will reproduce. Singing is part of an elaborate courtship ritual that entices the female to choose the male.

4. Phylogeny—How did the behavior evolve? How does the behavior compare to those of related species? Why might it have evolved as it did?

Example: Almost all species of birds can make vocal sounds, but only those in the suborder Passeri are songbirds. Relative to the zebra finch, other songbird species differ in the timing of their listening and practicing phases, the plasticity of song over their lifetimes, the extent to which the song is similar among individuals of the species, and the way that singing is used—for example, for defense of territory vs. courtship of mates.

At its core, an animal behavior is a response to an internal or external cue. Through behavior, animals can act on the information they receive in ways that will, hopefully, favor their survival and reproductive success.

What kinds of cues can trigger behavior? In some cases, the cue is largely external:

• In hibernation, an animal goes into a den or burrow, reduces its metabolic rate, and enters a state of inactivity during the winter, conserving resources while conditions are harsh and food is scarce. Environmental cues often trigger hibernation behavior. For instance, brown bears enter their den and hibernate when temperature drops to 0C and snowfall begins

• Estivation is similar to hibernation, but it occurs during the summer months. Some desert animals estivate in response to dry conditions. This shift helps them survive the harshest months of the year

• The snails in the photo below climb to the tops of fence posts to estivate.

• Migration is a behavior in which animals move from one location to another in a seasonal pattern. For instance, monarch butterflies living in the northern and central United States migrate to Mexico in the autumn, where they spend the winter. Environmental cues that trigger the autumn migration include air temperature, day length, and food availability

In other cases, the cue for a behavior may be internal. For instance, some behaviors occur with a circadian rhythm, meaning that they are triggered by the animal’s internal body clock. You, for example, tend to wake up and become active at roughly the same time each day. As you may have discovered if you’ve ever taken a long flight, your body’s alarm clock will still “go off” at the same time even if the external cues change, which is what causes jet lag!

It’s also common for behaviors to be triggered by a combination of internal and external cues interacting. For instance, mating behaviors may be triggered in an animal only when it’s in the right hormonal state, an internal cue, and when it sees a member of the opposite sex, an external cue

When we are trying to understand how a behavior develops and how it arose evolutionarily, one important question is whether the behavior is genetically preprogrammed or acquired through experience. Let’s consider some vocab:

• Innate behaviors are genetically hardwired and are inherited by an organism from its parents.

• Learned behaviors are not inherited. They develop during an organism’s lifetime as the result of experience and environmental influence.

Behavioral biologists have found that many behaviors have both an innate and a learned component. So, it’s generally most accurate for us to ask to what extent a behavior is innate or learned.

There are some examples of behaviors that are really and truly hardwired. These behaviors take place in a highly predictable way in response to the right stimulus, even if the organism has never before encountered that stimulus.

For example, an adult salamander will swim perfectly if it’s placed in water, even if it never saw water when it was young and has never watched another salamander swim In this case, the behavior of swimming can only be explained as something genetically preprogrammed in the salamander.

Similarly, you—or any human—will rapidly jerk your hand away if you touch a very hot object. This response is a reflex that’s hardwired in the circuits of your sensory and motor neurons and doesn’t even involve your brain

Partly innate, partly learned behaviors

In other cases, an organism is genetically programmed to develop a behavior, but the form the behavior takes depends on the individual’s experience.

One example is the learning of a song by a zebra finch or other songbird, as we saw above. All male zebra finches will begin listening to and learning song at about the same age and practicing and producing song at a slightly later age. Although this pattern is genetically determined, the exact features of the song a bird sings will depend on the songs it hears during its learning period.

Another, more familiar example is language acquisition in humans. Babies are preprogrammed for language learning, but which language they learn depends on what they’re exposed to during their plastic, or formative, period.

Mostly learned behaviors

In other cases, behaviors are largely dependent on experience—they’re learned—and can’t be fully explained by genetic preprogramming.

For instance, if a rat receives a food reward each time it pushes a lever, it will quickly learn to push the lever in order to get the food. Similarly, if a cow gets an electric shock each time it brushes up against an electric fence, like the one below, it will rapidly learn to avoid the fence. Pushing a lever to get a reward and avoiding electric fences are not hardwired in rats and cows but are, instead, learned behaviors the animals develop through experience.

If a behavior is learned rather than innate, it isn’t directly inherited. But it does still depend on genes. For instance, not all types of animals could learn to push a lever to get a reward. The rat’s capacity to learn this behavior depends on how its brain is wired, and the construction, maintenance, and function of a rat brain are all determined by genes in the rat genome.

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To the extent that a behavior is genetically determined or relies on genes, it’s subject to evolutionary forces, such as natural selection. In many cases, we can see how a behavior gives a survival or reproduction benefit to an animal that performs it—in other words, the behavior increases fitness.

Here are some examples of behaviors that clearly increase fitness:

• Baby birds of many species instinctively open their mouths for food when the mother returns to the nest Birds with this heritable behavior will tend to get fed more—and thus survive to adulthood more—than those that don’t.

• Mother greylag geese instinctively roll eggs back into the nest if they fall out

• Geese with this heritable behavior will tend to have more offspring that survive to hatch than geese without the behavior.

• Zebra finch males learn songs while they are juveniles, young birds, and they use these songs in courtship rituals. Birds with the heritable tendency to learn a song will obtain a mate more often than those that don’t.

An important point from the last example is that natural selection can act even when the behavior itself is not inherited. A zebra finch doesn’t inherit its song directly—it has to learn the song. But its capacity and tendency to learn a song are genetically determined, so they can be subject to natural selection.