Animal behavior발음듣기
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Animal behavior
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My cat Cameo is now responding to both an external stimulus, the sound of a bag of treats, and an internal stimulus, her hunger, or at least her insatiable desire for treats.발음듣기
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But if you look closely enough you can see how all behavior serves a purpose to help an animal mate, eat, avoid predators, and raise young.발음듣기
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And since behaviors can come with advantages like these, natural selection acts on them, just as it acts on physical traits ensuring the success of animals who engage in beneficial behaviors while weeding out those that do stupid, dangerous, or otherwise unhelpful stuff.발음듣기
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The most beneficial behaviors are those that make an animal better at doing the only two things in the world that matter. Eating and sexing.발음듣기
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Morphology or the physical structure of an animal and physiology or the function of that morphology.발음듣기
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For example, Cameo does not have opposable thumbs, so as much as she would like to get into the treat bag by herself, she cannot. This limitation is strictly hereditary.발음듣기
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It's the same way that a penguin can't fly to escape a predator, or a gazelle can't reach the same leaves as a giraffe can.발음듣기
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This is because of her physiology, everything from her teeth to her digestive system are geared for eating meat and if she pounced on and ate every blade of grass she came across, let's just say I would not want to be in charge of that litter box.발음듣기
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The traits that make up an animal's morphology and physiology are often heritable so we generally talk about selection acting on those traits.발음듣기
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It's the use of the trait, using wings and feathers to escape predators, or using a long neck to reach leaves that provides the evolutionary advantage.발음듣기
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Some behaviors are learned and even for animals that learn how to do things, natural selection has favored brain structures that are capable of learning.발음듣기
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So one way or another most behaviors have some genetic underpinning and we call those behaviors adaptive.발음듣기
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The problem is it's not always obvious what the evolutionary advantages are for some of the nutty things that animals do.발음듣기
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To answer questions like those we have to figure out one, what stimulus causes these behaviors, and two, what functions the behaviors serve.발음듣기
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To do this I'm going to need the help of one of the first animal behavior scientists ever or ethologists, Niko Tinbergen.발음듣기
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The questions focus on how a behavior occurs and why natural selection has favored this particular behavior.발음듣기
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One, what stimulus causes it? And two, what does the animals body do in response to that stimulus?발음듣기
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In the case of the male Siberian hamster the stimulus is a delicious smelling pheromone that the sexy female hamster releases when she's ready to mate.발음듣기
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The male hamster's response, of course, is to scuttle surprisingly quickly over several miles, if necessary, to find and mate with her.발음듣기
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So, the proximate cause of this behavior was that the girl hamster signaled that she was ready to knock boots and the male ran like crazy to get to the boot knocking.발음듣기
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Asking the more complex question of why natural selection has favored this behavior requires asking two more questions.발음듣기
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These as you can tell are bigger picture questions and they show us the ultimate causes of the behavior.발음듣기
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The answer to the first question, of course, is that the ability of a male hamster to detect and respond to the pheromones of an ovulating female is directly linked to his reproductive success.발음듣기
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As for the the second question you can also see that male hamsters with superior pheromone detectors will be able to find females more successfully than other male hamsters and thereby produce more offspring.발음듣기
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So natural selection has honed this particular physical ability and behavior over generations of hamsters.발음듣기
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And where is my chair? (piano music) Niko Tinbergen was one-third of a trifecta of revolutionary ethologists in the 20th century.발음듣기
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Along with Austrains Karl Von Frisch and Konrad Lorenz, he provided a foundation for studying animal behavior and applied these ideas to the study of specific behaviors and for that all three shared the Nobel Prize in 1973.발음듣기
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You may have seen the famous photos of young greylag geese following obediently in line behind a man.발음듣기
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That was Lorenz and his experiments first conducted in the 1930's introduced the world to imprinting.발음듣기
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The formation of social bonds in infant animals and the behavior that includes both learned and innate components.발음듣기
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When he observed newly hatched ducklings and geese, he discovered that waterfowl in particular had no innate recognition of their mothers.발음듣기
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In the case of greylag geese he found the imprinting stimulus to be any nearby object moving away from the young.발음듣기
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So when incubator hatched gosslings spent their first hours with Lorenz, not only did they follow him, but they showed no recognition of their real mother or other adult in their species.발음듣기
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Unfortunately, Lorenz was also a member of the Nazi party from 1938 to 1943 and in response to some of his studies on degenerative features that arose in hybrid geese, Lorenz warned that it took only a small amount of tainted blood to have an influence on a pure blooded race.발음듣기
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Unsurprisingly, Nazi party leaders were quick to draw some insane conclusions from Lorenz's behavioral studies and the cause of what they called race hygiene.발음듣기
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Lorenz never denied his Nazi affiliation, but spent years trying to distance himself from the party and apologizing for getting caught up in that evil.발음듣기
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That's where we turn to those two types of behavior that are the only things in the world that matter, eating and sex having.발음듣기
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Behavior associated with finding and eating food is known as foraging, which you've heard of.발음듣기
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And natural selection can act on behaviors that allow animals to exploit food sources while using the least amount of energy possible.발음듣기
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Rather than running around hunting down its prey, it simply sits in the water and food comes to him.발음듣기
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So the alligator snapping turtle has a long pink tongue, divided into two segments, making it look like a tasty worm to a passing fish.발음듣기
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Natural selection has, over many generations, acted not only on turtles with pinker and more wiggly tongues to catch more fish, it's also acted on those that best know how and when to wiggle those tongues to get the most food.발음듣기
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Well, how about sex? As we saw with our friend the horny Siberian hamster, some behaviors and their associated physical features are adapted to allow an animal to reproduce more, simply by being better at finding mates.발음듣기
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Many times animals of the same species live close together or in groups and determining who in what group gets to mate creates some interesting behaviors and features.발음듣기
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Often males of the species will find and defend a desirable habitat to raise young in and females will choose a male based on their territory.발음듣기
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But what about those species, and there are many of them, where the female picks a male not because of that, but because of how he dances, or even weirder, how much junk he's collected? Take the male bowerbird.발음듣기
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He builds an elaborate hut or bower out of twigs and bits of grass and then spends an enormous amount of time collecting stuff.발음듣기
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Ethologists believe that he is collecting the stuff to attract the female to check out his elaborate house.발음듣기
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Once the female has been enticed to take a closer look, the male starts to sing songs and dance around, often mimicking other species, inside of his little house for her.발음듣기
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Now doing more complex dances and having more blue objects in your bower scores bigger with females.발음듣기
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And ethologists have shown that a higher level of problem solving or intelligence in males correlates to both of these activities.발음듣기
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So, yeah it took some brawn to build that bower and collect all that junk, but chicks also dig nerds who can learn dances, so the bowerbird's brain is evolving in response to sexual selection by females.발음듣기
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This intelligence likely also translates into other helpful behaviors, like avoiding predators.발음듣기
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So thanks to the evolution of behavior, we're really good at taking care of our nutritional and sexual needs, but what's confused scientists for a long time is why animals often look after others' needs.발음듣기
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For instance vampire bats in South America will literally regurgitate blood into the mouths of members of its clan who didn't get a meal that night.발음듣기
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We actually did a whole side show episode on this very subject, but basically we can thank British scientist William Hamilton for coming up with an equation to explain how natural selection can simultaneously make animals fit and allow for the evolution of altruism.발음듣기
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Hamilton found that the evolution of altruism was best understood at the level of larger communities, especially extended animal families.발음듣기
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Basically altruism can evolve if the benefit of a behavior is greater than its cost on an individual, because it helped the individual's relatives enough to make it worth it.발음듣기
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Hamilton called this inclusive fitness, expanding Darwin's definition of fitness, which is basically how many babies somebody is making, to include the offspring of relatives.발음듣기
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Now I guess the only question left is if I forget to feed you two, who's going to regurgitate blood into the other one's mouth?발음듣기
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