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0:29
When we look at animals in the wild, we are mesmerized by their behaviors.
0:35
But defining a behavior is not as easy as recognizing them in action. What is a behavior? Is it movement?
0:48
Many behaviors involve being as still as possible, such as hiding from predators. Is it interacting with the environment?
0:57
A leaf interacts with the wind, but is that a behavior? Is it a feature that is unique to animals?
1:07
All forms of life, whether they're bacteria or plants, may feed and reproduce and even move around actively. So, no, it's not an animal trait exclusively.
1:19
Over the years, animal behavior biologists or ethologists as we used to call them have tried to come up with a lasting definition of a behavior. Although there are many variations on the details, most of them say that a behavior is any observable change in the internal or external environment. So, for example, if we see a bird eating a worm, well, that would be a behavior because we observed a change in its external environment seeing a tasty worm.
1:48
Likewise, if my face were to turn red from embarrassment
1:56
well, not... not that red...
2:00
that's more like it. So you see blushing is a behavior too, because it's an observable response to my internal environment. Meaning the psychological effect of the embarrassment itself. So in either case, these behaviors might serve different functions in one instance, feeding a bird, for example, and in the other communicating important social information to my human peers. But in both instances, they serve the animal in important ways that are relevant to its species. Prior to the 1860s,
2:31
any animal behaviors were thought to be quirks of the species and were given names like habits, manners and instincts.
2:40
But the publication of Charles Darwin's book On The Origin of Species in 1859 brought behaviors into the realm of biology and explained them as adapted traits like all others.
2:54
In this new evolutionary light, behaviors were able to be seen as adaptive features that contribute to the survival and or reproduction of animals known together as the fitness of the adaptive trait.
3:09
These two elements are seen as the main driving forces behind evolution by natural selection.
3:15
Because behaviors have evolved through adaptive selection, they must be linked to the genes in order to be heritable. And by consequence, the genetic variation inherent to populations may lead to differences in the adaptive value of those behaviors when performed. The adaptive value is the contribution of a behavior to an animal's fitness, whether positive or negative. And will be subjected to natural selection. Determining both the animal and its genes outcome
3:48
because behaviors can be rooted in the genes, we will find that many animal behaviors are paradoxical in nature and don't seem to benefit the individual. Despite having been obviously selected for over evolutionary time because of their prevalence, many self-sacrificing behaviors for example, seem to harm the individual's fitness, and yet they keep doing it
4:13
The worker bees, wasps and ants of the social insect group, the Hymenoptera, all work for the benefit of only a few sisters that will get to be future queens for themselves, and each devoted worker will die without personally having reproduced and disallowed to continue their own family line.
4:33
As we shall see, the evolutionary explanation for these extremely altruistic behaviors can be found at the genetic level. And the passing along of large amounts of identical genes, regardless of which individual gets to be the one to reproduce.
4:49
In other cases of individual self-sacrifice, we find that the benefactors are at a higher level of organization, that of the group.
4:59
When a monarch butterfly is eaten by a naive bird trying one for its first time. The toxic cardiac glycosides chemicals in its body will certainly deter the bird from eating another monarch but that first dead one cannot possibly benefit from the distasteful message that it sent to the bird and any of its compatriots that saw the whole process
5:22
How, then, can these toxic chemical defenses evolve to protect the monarch butterfly if it must die for them to work
5:31
The answer lies in the common warning colors that the species wears that quickly becomes an easily recognizable color scheme for predators to learn to avoid when monarchs and other insects display these warning or aposematic colors, They're using behaviors that benefit the whole group, despite the occasional requirement to sacrifice an individual from time to time. To reinforce the message among the inexperienced predators out there.
6:03
Because of the biological lens needed to view animal behavior, biologists have decided that there are four main ways to study it. These are often posed as questions.
6:15
Firstly, what is the mechanism behind this behavior?
6:20
That is what are the components and processes involved inside the animal and without that are involved in the production of the behavior
6:31
The second question is to ask How does it develop? How does the behavior change over the life of the animal? Does it happen on its own, or is there a requirement for learning? Does the behavior occur in certain situations and not others?
6:50
The third question is to ask What is the behavior for? Or What is its evolutionary purpose? And How does the behavior impact the fitness of the animal or its survival and reproductive consequences?
7:06
Lastly, we could ask where did this behavior come from over evolutionary time?
7:14
As the behavior existed among common animals for long periods of time? Or is it a more recent adaptation in just a few animal groups
7:25
You may note that the first of these two questions about the mechanism and the development are on somewhat of a different order of magnitude from the other two about its function and its evolutionary history. Indeed, these two different ways of viewing animal behavior can be said to occur at the proximate level, which focuses more on the immediate causes of the behaviors or at the ultimate level which focuses on the evolutionary origins. These four levels of biological analysis provide
7:56
many interesting things for biologists to study about animal behaviors.
8:01
Some sample the gene activity of bees at various times over their short lives. Others may study the development of different parts of a bird's brain.
8:11
Field biologists are often asking why the animals are behaving the way that they do, such as trying to figure out the adaptive value of social bonds in primate groups. Lastly, evolutionary biologists may compare fossil species to modern ones and try to recreate the origin of behaviors like parental care in vertebrates. Did it evolve once long ago? Or several times throughout the vertebrates evolutionary history
8:40
Of course, these lines of inquiry are not mutually exclusive from one another. In fact, the most comprehensive understanding of an animal behavior will involve knowledge of both the proximate and ultimate causes of that behavior.
8:59
Let's take the example of songbirds singing.
9:07
In human culture, songbirds have a long association with love and courtship. Ancient Greek poets wrote verses about the songs of swallows and bards of the medieval and Renaissance era were particularly taken with the romance of bird songs. Including William Shakespeare, who, in As You Like It, wrote "When Birds do sing, hey ding-a-ding-ding. Sweet lovers love the spring."
9:37
Unfortunately, there are no remaining records of the Late Renaissance Hey Ding-a-Ding-Ding bird, but apparently it was quite inspiring.
9:48
Many classical composers have also copied the songs of birds in their music, including Ludwig van Beethoven, who actually transcribed the calls of a number of songbirds for his Sixth Symphony, "Pastoral"
10:12
And of course, movies, television shows and commercials often add the songs of birds singing to heighten the effect of romantic moments,
10:22
although they often add the songs of birds that don't actually live in the places they're showing. But that's another story.
10:36
By now, we are familiar enough with this behavior to know that it is male birds that sing and that they're probably doing it to announce themselves in their territory and to hopefully be persuasive to the females who are looking for a nesting mate. These intricate and melodic songs are species specific, meaning that each species has their own song, which allows them to recognize each other and have sing off competitions with the right species of rivals
11:05
because there are as many songbirds songs as there are species, ornithologists have come up with a number of mnemonic phrases that help us humans remember which species is saying what.
11:17
For example, sometimes a phrase is used to mimic their song, such as the Red-Eyed Vireo that says, "Here I am, where are you?"
11:32
Or the White Throated Sparrow, who says "Old John Peabody, Peabody Peabody" "Old John Peabody, Peabody Peabody"
11:52
In other cases, the name of the bird was given to them based on their song, such as the Black-Capped Chickadee, who says “Chickadee-dee- dee, Chickadee-dee-dee”
12:05
or the Eastern Wood Pewee, who enthusiastically sings his own name. “Pee-wee!”
12:26
Regardless of the details of the species songs as animal behavior biologists, we should be starting to have a lot of questions about this particular behavior. That is so unique to just some species of male birds.
12:40
At the proximate level, we could ask where such a behavior would be rooted in the makeup of the birds themselves. Which genes are involved, and where is the behavior controlled from or produced, for example?
12:55
Given that male and female birds do differ at the genetic level, perhaps those genes that only males have would be good candidates to study
13:04
At the physiological level, we could ask where in the brains of the male birds does the song production area exist?
13:12
Neurophysiologist have done a pretty good job of mapping out the bird brain and note a series of structures that are all linked to one another as well as to the syrinx, which is the sound producing organ in birds.
13:26
Among those structures is one known as the Higher Vocal Centre (or HVC) which seems to be integral to the song learning and production process because it only increases in size in males and only when they're exposed to the sounds of their species song during early development at about three to six weeks of age.
13:48
Interestingly, the HVC does not grow in male birds that are prevented from hearing the sound of their species song during this critical developmental window. So the interaction with the environment and the ability to learn the behavior also seem to be very important in its development.
14:07
When the activity of specific genes in the specific areas of male birds brains are monitored, we see clearly that some genes are active at some points and inactive at others and vice versa for other genes.
14:22
It seems that the genes are involved in many aspects of the behavior from its mechanism and the timing of events that are important for its proper development.
14:33
As you can see, we can use these proximate levels of analysis to begin to decipher the nature of this behavior and to have an idea of how it is made by the male birds who sing songs
14:47
Now, you don't need to be a third year biology student to know that the songs themselves also play a communication function for the male birds. They clearly seem to be announcing their presence in a territory, and we presume that the end game is to court and woo a willing female to engage in some reproduction together
15:08
While common knowledge often contains much truth to it. The scientific process begs of us to attempt to demonstrate what is going on and to try to confirm or deny our suspicions
15:21
The first explanation for the functional role of the male bird song is what is known as the species identification hypothesis, in which the singing males are in part singing to other males of their own species and saying, "I'm a male of your bird species, and I'm setting up shop here in this here, Hemlock Grove So don't even think about trying to do the same, or else there will be trouble for you!"
15:48
Yes, there can be a lot of information transmitted in just a few little whistles.
15:56
If this species identification were a true function of the singing behavior, the songs would have a repelling effect on incoming males looking for a vacant territory.
16:14
Field ornithologists tested this by removing some resident singing male birds from their territories and replacing just some of them with a speaker that continued to sing a song in those other territories with no speakers and where no songs were being played. Many more males came in and attempted to claim it as their own, whereas the territories with songs coming out of them remained unchallenged. So it does seem that the males are singing
16:42
some important information to their rival males in the neighborhood, and that those males are paying attention in such a way as to help themselves find their own territories without needing to fight for them.
16:55
The second explanation for the functional role of a male bird' s song, not mutually exclusive from the first is that they're also singing to the females in an attempt to seduce them through courtship displays.
17:08
This mate attraction hypothesis implies that the song also contains info intended for the females that says, "I'm pretty sure that I'm the male that you will find to be the most attractive around these parts, so please come and check me out, ladies!"
17:26
in this case, we should expect that the songs of male birds will attract females of their own species and not those of other species of birds.
17:36
Field biologists have also tested out this hypothesis by again removing resident male birds from their territories and replacing them with speakers that either continue to sing his song in his absence. Or to sing the song of another species of male bird. Perhaps unsurprisingly, the territory with the original male's song coming out of it attracted more female birds of his species than the territories with other species songs in them.
18:05
This then confirms that the males are also singing to the females of their species and that these females are listening and paying attention
18:15
But how do the females decide which male to choose as a partner? It turns out that there are many ways to distinguish between the high quality males and those runners up looking to score a good mating partner
18:31
Firstly, the quality of his habitat is a good indicator of the quality of that male
18:36
because good habitats with optimal nesting sites and good access to food resources will be very important to the success of their nestling chicks,
18:47
but also because those males that can actually keep hold of a good habitat in the face of intruding and challenging other males must have something good going for them.
18:58
And that would be of interest to the females who are considering the kinds of genes that their offspring would end up having too.
19:08
Secondly, it turns out that the females are also paying close attention to the complexity and quality of the song that he sings. They are more impressed by difficult and challenging songs than the simpler, more basic versions What possible benefit would there be to the females to choose a male mate that can sing more complex songs than the others?
19:33
It turns out that the ability of a male to sing a complex song is an honest reflection of his health status and a genetic contributor to her offspring. Bird songs are difficult behaviors to master because they require specific environmental contexts in which to develop, and they're tricky to produce without a healthy and vigorous specimen of a male behind its production.
19:58
This has been confirmed experimentally when male birds that were reared under stressed conditions of poor nutritional quality were allowed to court females as adults by singing next to other males that were raised under ideal health conditions
20:14
The songs produced by these two groups of healthy versus unhealthy males differed markedly in the quality and complexity and the females invariably preferred the strong singing by the healthy males. This would be an evolutionarily stable strategy for females who are shopping around for male suitors based on the visual and auditory quality of their displays.
20:40
It turns out that when it comes to bird songs, you can indeed judge a book by its cover or its soundtrack. At least
20:49
as we have seen, these male birds are seeing an awful lot through their songs. They are announcing their vigor, strength and status to their rivals, all while advertising their health, romantic devotion and reproductive prowess to their female interests.
21:06
It is probably no coincidence that these are also the same themes that are often sung about in human music
21:14
whether it is a young fit and virile pop singer dancing across the stage in athletic and titillating routines That make clear their attractiveness and sex appeal or a group of hip hop rap musicians showing off their bling resources and bragging about their social status or a country or R&B song about love and devotion.
21:39
It appears that music is a communication code that transcends species boundaries. and speaks to us at our most primordial levels.
21:48
Is there any wonder that so much of society is built around a mutual love and admiration of successful musicians?
21:59
In conclusion, our analysis of male birdsong allow us to note that animal behaviors involve a continuum between proximate and ultimate factors. Certainly there need to be genes that code for nerves and tissues and muscles and hormone schedules that allow behaviors to happen in the first place. But the proximate factors do not exist in a vacuum. They're constantly interacting with the environment, and external stimuli are dictating how behaviors will develop and when to operate
22:29
in the proper contexts. So these individual differences in the bird's gene environment interactions will have implications for their fitness, whereas it will affect the survivorship and or the reproductive success of the various birds in the population. Of course, that will have effects on which genes make their way into the next generation. And then we find ourselves back at the beginning again with the new series of proximate factors, a bunch of new genes interacting with their new environment
22:56
The end result of our behavioral analysis leads us to confirm that animal behaviors must, in fact be adaptive traits that have evolved over evolutionary time to contribute to the fitness of the animals that are performing them, and that a full expression of a behavior can only occur when an animal is interacting with its environment
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