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Intro to animal behavior

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What exactly counts as behavior? What triggers behaviors? Are they hard-wired in animals' genes, or learned based on experience?

Key points

  • 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't it 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.start superscript, 1, end superscript Other behaviors are learned, such as your tendency to hang around the kitchen at dinnertime or your ability to read the words on this screen.
In this article, we’ll take a closer look at animal behavior—how it’s studied, how it evolves, and how it can run the gamut from hardwired to learned.

What is behavior?

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.
Image credit: Eye on the prize by Kae Yen Wong, CC BY-SA 2.0
Behavioral biology is the study of the biological and evolutionary bases for behavior. Modern behavioral biology draws on work from the related but distinct disciplines of ethology and comparative psychology.
  • Ethology is a field of basic biology, like ecology or genetics. It focuses on the behaviors of diverse organisms in their natural environment.
  • Comparative psychology is an extension of work done in human psychology. It focuses largely on a few species studied in a lab setting.
Behavioral biology also draws on many related areas of biology, including genetics, anatomy, physiology, evolutionary biology, and, of course, neurobiology—which traces the neural circuits that underlie animal behavior.

Four questions to understand a behavior

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.
Image credit: Taeniopygia guttata by Keith Gerstung, CC BY 2.0
  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.
    Image credit: modified from Songbird species recognition by Petra Deane, CC BY 1.0
  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.

Cues that trigger behavior

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 0start superscript, start text, o, end text, end superscriptC and snowfall begins.squared
  • 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.cubed The snails in the photo below climb to the tops of fence posts to estivate.
    Image credit: Kadina snails climb fence by Vladimir Menkov, CC BY-SA 4.0
  • 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.start superscript, 4, end superscript
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.start superscript, 5, end superscript

Innate vs. learned behaviors

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.

Mostly innate behaviors

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.start superscript, 5, end superscript 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.start superscript, 5, end superscript

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.start superscript, 6, end superscript 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.
Image credit: Cow by Joi Ito, CC BY 2.0
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.

Check your understanding

Beach mice dig burrows in the sand when they are living in their natural environment. A beach mouse burrow has a specific shape with a long escape tunnel that is different from the burrows of closely related mouse species.
A young beach mouse is raised in captivity, without any access to dirt or sand or any chance to observe burrowing adults. When given access to dirt, it immediately digs a burrow with the normal shape for its species.start superscript, 7, end superscript
What type of behavior is burrow digging in the beach mouse?
Choose 1 answer:
Choose 1 answer:


Natural selection shapes behavior.

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.start superscript, 8, end superscript 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.start superscript, 8, end superscript 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.

Want to join the conversation?

  • primosaur seedling style avatar for user Cameron
    Do humans exhibit any signs of hibernation, estivation, or migration in response to cues?
    (28 votes)
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  • female robot grace style avatar for user Trash Panda
    What are barnacles? Do they count as estivation?
    (7 votes)
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    • leafers sapling style avatar for user katherine
      barnacles are a type of arthropod, relating closely to crabs, lobsters, and shrimps. they are often hermaphrodites, meaning they have both female and male sex organs within their bodies, allowing them to be both carriers and distributors in the reproduction process. barnacles don't survive by estivation, as they don't necessarily face the need to hibernate during the day, they just secrete a sticky "glue" and stick themselves to something or the other, and hitch rides until they die.
      (3 votes)
  • area 52 blue style avatar for user Ariel
    How does environment exactly influence innate behaviours? Is there a moment where a learned behaviour affects genes and become innate? Or do they come from random mutations and natural selection?
    (4 votes)
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  • aqualine sapling style avatar for user grace.brandenburg
    what is something humans do
    (1 vote)
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  • boggle green style avatar for user yibo
    Scientists have this theory that we evolved from apes. If it is true, have humans developed some innate behaviors that apes get? If we don't have them all, doesn't that mean we grew out of habits that were hardwired in our brains. In your opinion, do you think animals will grow out of those behaviors as we go into the future?
    (3 votes)
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    • male robot hal style avatar for user Charles LaCour
      Keep in mind that the species that humans evolved from no longer exist, both modern apes and humans (humans are technically still under the classification of ape) evolved from a common ancestor.

      So there may well be innate traits shared between humans and other ape species but they would have been inherited from that common ancestor not each other.
      (2 votes)
  • duskpin seedling style avatar for user NavahaS
    When people started Natural Selection how did those traits and DNA come to mix and Them learn traits from eachother and pass it on from diffrent learned traits and how did they cope?
    (1 vote)
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    • male robot hal style avatar for user Charles LaCour
      DNA is where the information about how specific biological features or processes are encoded. For example the trait of fur color is controlled by the pigment proteins that specific genes in the DNA code for. The fur color can help the animal hide or attract a mate. The better or worse the fur color is at allowing hiding or getting a mate will affect how well the animal is able to have offspring to carry its DNA into later generations.

      For things like learned learned actions it is not the learned actions that are encoded into DNA and passed on but the organisms ability to learn an adapt, this is indirectly the trait that natural selection acts on.
      (3 votes)
  • boggle green style avatar for user yibo
    So, the mother cukcoo bird puts the her egg in some other birds nest, and the bird grows up with a totally different parent. Is it an innate behavior for all cukcoo birds to do that or, when they grow up do they see other birds that look like them doing it. This always confused me. :/ (I read an article on it and I thought it was best to ask the question here.)
    (2 votes)
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  • blobby green style avatar for user Jen Barrett
    If a Zebra Finch was raised in captivity but the person who raised it played music would the bird learn to sing a song that is related to the music that was played as it grew up?
    (1 vote)
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    • marcimus purple style avatar for user Stoichiometry
      Hi There

      That is an interesting question. I'm not sure if there really is a wrong or right answer for this question as the hypothesis would have to be thoroughly tested before one could undoubtedly give an answer. Since Zebra Finches' songs are partly innate and partly learned, I think it would have to depend on the music as well as many environmental factors. For example, if pop or rock music were to be played to it, I doubt any of music would be implemented into its song and it could have affect the birds mental health (and certainly not in a good way). On the other hand, many birds enjoy listening to classical music (which has positive effects on the brain), and parrots specifically, either imitate or show they enjoy it. Although the Zebra Finch would not imitate it exactly, there is the possibility that it would use patterns from the song. I'm honestly not 100% sure though as to whether or not it would use patterns found in the music.
      That said, picture a Zebra Finch which has been raised by humans who acquired it whilst it was still inside the egg. This little Zebra Finch never heard music and it was not was exposed to any other avians. The bird would not have learnt any specific songs, but without doubt, the bird would still sing, creating its own song/s and using different patterns. Likewise, there is a strong possibility that it would not relate its song to the music.

      Hope this helps! :)
      (3 votes)
  • boggle blue style avatar for user x.asper
    How would you classify a fish that does dances for mates?
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  • starky seedling style avatar for user Grayjay07
    do all mammals hibernate? and why did humans stop hibernating? did we grow out of our genetic traits?
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