OFFICIAL1 What is the main topic of the lecture?

[00:00.00]Narrator: Listen to part of a lecture in a biology class.
[00:05.10]FEMALE PROFESSOR: For today's discussion, we'll review the case study on how some animals have behaviorally adapted to their environments. [00:12.54]Now, you had to read about two animal species: the eastern marmot and the Olympic marmot.
[00:17.98]Marmots are rodents... [00:19.68]they're large ground squirrels about the size of an average house cat, [00:23.20]and they live in a variety of habitats. [00:25.40]And even though they spend a significant portion of the year hibernating, according to this case study, marmots are still considered excellent subjects for animal behavioral studies. [00:35.65]Why is that?
[00:36.96]MALE STUDENT: Well, when they're not hibernating, you can find them in open areas, [00:41.88]and they're pretty active during the day, which makes them easy to observe, right? 
[00:46.02]FEMALE PROFESSOR: Uh huh. So, first let's discuss the eastern marmots. [00:50.51]They reside throughout the eastern region of North America where there's a temperate climate, where the growing season lasts for at least five months of the year... which is when they do all their mating, playing, and eating.
[01:01.79]MALE STUDENT: Oh, I see... [01:02.95]at first, I wasn't sure what 'growing season' meant just from the reading, but now I get it. [01:08.38]It's the amount of time it takes for them to grow, right? [01:11.34]So, it'd be five months?
[01:13.38]FEMALE PROFESSOR: Hm? Ohh, I'm sorry but no, [01:16.20]it has nothing to do with that. [01:17.68]It's not about the time it takes for eastern marmots to grow, [01:21.24]it's when the food is available. [01:23.53]That is--when it's not covered in snow and there's no frost covering the grass, and um vegetative parts of uh, plants, herbs, and the flowers that marmots like to eat.  [01:33.26]So, 'growing season' refers to the availability of the food they eat. Ok? [01:38.41]So now, how would you describe the eastern marmots' social habits?
[01:43.28]FEMALE STUDENT: Well, they're really territorial and loners and just so aggressive even with other eastern marmots. [01:51.71]And their mating ritual is just so... impersonal.
[01:55.51]FEMALE PROFESSOR: Uh huh. Now, when they emerge in the spring from hibernation, the mating process begins. [02:02.13]For them, well, they come together to mate and then they go their separate ways. [02:07.16]Then, about six to eight weeks after birth, the offspring leave their mothers.
[02:11.78]FEMALE STUDENT: Really, just six weeks? [02:14.17]Is it possible for the offspring to make it on their own so young? 
[02:18.14]FEMALE PROFESSOR: Well, it's not as if they aren't ready for the real world... because they are.  [02:23.15]Remember, they mature quickly and the weather's nice. [02:26.34]Also, they live in open fields where there's lots of edible vegetation. [02:30.26]So roughly six weeks after birth, eastern marmots are just old enough to take their chances of surviving in a temperate environment.  [02:37.98]So, how does this relate to their behavior?
[02:42.06]FEMALE STUDENT: Oh, I get it. [02:44.38]Since, the climate's not too bad, the eastern marmots don't have to rely on each other too much and they really don't need to stay together as a family to survive either.
[02:53.91]FEMALE PROFESSOR: Uh huh. [02:54.79]And in contrast... the Olympic marmots... [02:57.73]what about them?
[02:59.27]FEMALE STUDENT: Well, they live together as a family and take care of their young until they're at least two years old. [03:05.17]They're really friendly with each other, [03:07.52]and what I really like is that they even have greeting ceremonies [03:12.13]and they're not at all aggressive and territorial like the eastern marmots.  [03:16.11]So, um, their social behavior's so different from the eastern marmots' because of the climate where they live? [03:22.79]That seems so bizarre!
[03:24.66]FEMALE PROFESSOR: Well, the Olympic marmots inhabit meadows high in the Olympic Mountains where the weather conditions are much harsher [03:31.70]so there's a lot more wind and snow. [03:33.80]The growing season only lasts about two to three months. [03:37.27]So, in that much shorter period of time, all of the Olympic marmots, male and female, eat, play, work, and nurture the young together.
[03:45.55]Because the climate is so harsh, cooperation increases the survival rate of the Olympic marmots. [03:51.76]They keep their young at home until they're physically able to survive on their own. [03:56.07]This could explain why the social behavior of the Olympic marmots is so unlike that of the eastern marmots.