WEBVTT 00:00:00.000 --> 00:00:02.520 align:middle line:84% The following content is provided under a Creative 00:00:02.520 --> 00:00:04.030 align:middle line:90% Commons license. 00:00:04.030 --> 00:00:06.370 align:middle line:84% Your support will help MIT OpenCourseWare 00:00:06.370 --> 00:00:10.740 align:middle line:84% continue to offer high quality educational resources for free. 00:00:10.740 --> 00:00:13.360 align:middle line:84% To make a donation or view additional materials 00:00:13.360 --> 00:00:17.258 align:middle line:84% from hundreds of MIT courses, visit MIT OpenCourseWare 00:00:17.258 --> 00:00:17.883 align:middle line:90% at ocw.mit.edu. 00:00:17.883 --> 00:00:22.670 align:middle line:90% 00:00:22.670 --> 00:00:25.160 align:middle line:84% PROFESSOR: We have just this topic 00:00:25.160 --> 00:00:28.250 align:middle line:84% to cover before the midterm exam. 00:00:28.250 --> 00:00:31.780 align:middle line:84% So we'll probably have a little bit of it to cover on Friday, 00:00:31.780 --> 00:00:33.940 align:middle line:84% but I'm working on a review for you. 00:00:33.940 --> 00:00:37.670 align:middle line:84% And I won't answer everything on the review, of course. 00:00:37.670 --> 00:00:38.870 align:middle line:90% We won't have time for that. 00:00:38.870 --> 00:00:42.730 align:middle line:84% But I will try to go over some of the points 00:00:42.730 --> 00:00:45.980 align:middle line:84% that students have asked me about in the past 00:00:45.980 --> 00:00:50.830 align:middle line:84% before the midterm, points that seem to cause more confusion. 00:00:50.830 --> 00:00:52.700 align:middle line:84% And I'll give you a few clues to the kind 00:00:52.700 --> 00:00:54.320 align:middle line:90% of things I put on the exam. 00:00:54.320 --> 00:00:56.267 align:middle line:84% But it's basically a short-answer exam. 00:00:56.267 --> 00:00:57.475 align:middle line:90% There might be some matching. 00:00:57.475 --> 00:01:01.570 align:middle line:90% 00:01:01.570 --> 00:01:07.660 align:middle line:84% We got started with this last time, 00:01:07.660 --> 00:01:11.816 align:middle line:84% primary and secondary defense mechanisms. 00:01:11.816 --> 00:01:14.450 align:middle line:90% 00:01:14.450 --> 00:01:17.410 align:middle line:84% We talked a little bit about countershading in camouflage. 00:01:17.410 --> 00:01:23.850 align:middle line:90% 00:01:23.850 --> 00:01:25.570 align:middle line:90% And this is where we left. 00:01:25.570 --> 00:01:30.260 align:middle line:84% Many predators developed search images by perceptual learning, 00:01:30.260 --> 00:01:35.250 align:middle line:84% and then they learn to search for their prey, 00:01:35.250 --> 00:01:37.865 align:middle line:84% remembering what they've been successful with in the past. 00:01:37.865 --> 00:01:40.990 align:middle line:90% 00:01:40.990 --> 00:01:44.200 align:middle line:84% And I asked what octopus and squid do. 00:01:44.200 --> 00:01:49.060 align:middle line:84% And for that, I would like to show a video. 00:01:49.060 --> 00:01:51.190 align:middle line:90% Let me see if I'm online here. 00:01:51.190 --> 00:01:54.790 align:middle line:90% 00:01:54.790 --> 00:01:58.812 align:middle line:84% Some of you may not be familiar with this. 00:01:58.812 --> 00:02:02.177 align:middle line:90% The mimic octopus. 00:02:02.177 --> 00:02:03.635 align:middle line:84% I'll only take a couple of minutes. 00:02:03.635 --> 00:02:06.250 align:middle line:90% 00:02:06.250 --> 00:02:10.169 align:middle line:84% This content has been removed due to copyright restrictions 00:02:10.169 --> 00:02:13.080 align:middle line:84% see the readings and feelings page for information 00:02:13.080 --> 00:02:18.660 align:middle line:90% about this material 00:02:18.660 --> 00:02:21.690 align:middle line:84% PROFESSOR: Anyway, you can find a little more 00:02:21.690 --> 00:02:22.770 align:middle line:90% online if you want. 00:02:22.770 --> 00:02:30.510 align:middle line:90% 00:02:30.510 --> 00:02:34.430 align:middle line:84% So that behavior of the octopus-- 00:02:34.430 --> 00:02:36.510 align:middle line:84% and there's another example right here 00:02:36.510 --> 00:02:37.840 align:middle line:90% in the cover of your book-- 00:02:37.840 --> 00:02:40.780 align:middle line:90% 00:02:40.780 --> 00:02:46.330 align:middle line:84% another octopus that can change color patterns on its surface. 00:02:46.330 --> 00:02:48.060 align:middle line:90% It can mimic predators. 00:02:48.060 --> 00:02:51.390 align:middle line:84% Actually, this animal can create a thing that 00:02:51.390 --> 00:02:53.705 align:middle line:84% looks like two big eyes facing you, 00:02:53.705 --> 00:02:55.770 align:middle line:90% so it looks like a predator. 00:02:55.770 --> 00:02:58.630 align:middle line:84% Most predators have forward-facing eyes. 00:02:58.630 --> 00:03:01.230 align:middle line:90% 00:03:01.230 --> 00:03:04.690 align:middle line:84% It's related to mimicry, and I want 00:03:04.690 --> 00:03:07.220 align:middle line:84% to talk here about the different kinds of mimicry. 00:03:07.220 --> 00:03:11.170 align:middle line:84% There's two kinds: Mullerian and Batesian. 00:03:11.170 --> 00:03:18.780 align:middle line:84% With Mullerian, different species that are all poisonous 00:03:18.780 --> 00:03:20.930 align:middle line:84% evolved to look similar to each other, 00:03:20.930 --> 00:03:24.430 align:middle line:84% because then they all benefit, like the vespid wasps. 00:03:24.430 --> 00:03:31.335 align:middle line:84% So, an animal learns by trying to eat one vespid wasp. 00:03:31.335 --> 00:03:31.960 align:middle line:90% They taste bad. 00:03:31.960 --> 00:03:34.270 align:middle line:90% They're poisonous. 00:03:34.270 --> 00:03:37.330 align:middle line:84% The animal, the predator, learns to avoid 00:03:37.330 --> 00:03:40.070 align:middle line:84% not just at one species, but other vespids, 00:03:40.070 --> 00:03:42.070 align:middle line:84% too, because they look fairly similar. 00:03:42.070 --> 00:03:44.270 align:middle line:90% They all have the bands-- 00:03:44.270 --> 00:03:48.030 align:middle line:84% yellow and black bands-- on her abdomen. 00:03:48.030 --> 00:03:55.130 align:middle line:84% And that's the evolution of Mullerian mimicry. 00:03:55.130 --> 00:03:59.680 align:middle line:84% With Batesian mimicry, animals that are not poisonous 00:03:59.680 --> 00:04:02.670 align:middle line:84% will evolve to look like a poisonous one. 00:04:02.670 --> 00:04:05.980 align:middle line:84% The best-known is the monarch butterfly, which 00:04:05.980 --> 00:04:08.990 align:middle line:90% is poisonous and bad tasting. 00:04:08.990 --> 00:04:11.970 align:middle line:90% Animals learn to avoid it. 00:04:11.970 --> 00:04:15.740 align:middle line:84% Birds will generally not attack monarchs. 00:04:15.740 --> 00:04:17.529 align:middle line:84% And this is an example right here 00:04:17.529 --> 00:04:19.870 align:middle line:84% the viceroy butterfly that's evolved to look 00:04:19.870 --> 00:04:21.399 align:middle line:90% very much like the monarch. 00:04:21.399 --> 00:04:24.120 align:middle line:90% Here's a female monarch. 00:04:24.120 --> 00:04:27.990 align:middle line:90% Here's a male monarch butterfly. 00:04:27.990 --> 00:04:29.945 align:middle line:84% And there's several species that have 00:04:29.945 --> 00:04:31.335 align:middle line:90% evolved to look like a monarch. 00:04:31.335 --> 00:04:34.580 align:middle line:90% 00:04:34.580 --> 00:04:38.040 align:middle line:84% Now, let's talk about other ways to avoid predation. 00:04:38.040 --> 00:04:43.970 align:middle line:84% The ground-nesting birds: why do some birds nest in the open, 00:04:43.970 --> 00:04:46.050 align:middle line:90% on the ground? 00:04:46.050 --> 00:04:48.620 align:middle line:90% They must have some advantages. 00:04:48.620 --> 00:04:51.610 align:middle line:84% And you can see one clear advantage: 00:04:51.610 --> 00:04:54.330 align:middle line:84% they can see any approaching predator, 00:04:54.330 --> 00:04:57.070 align:middle line:90% because there's no concealment. 00:04:57.070 --> 00:05:00.020 align:middle line:84% But, of course, their nest isn't all that well concealed, 00:05:00.020 --> 00:05:01.700 align:middle line:90% either. 00:05:01.700 --> 00:05:07.820 align:middle line:84% So, what do they do to protect their nests 00:05:07.820 --> 00:05:12.530 align:middle line:84% from an approaching predator, like a fox or a polecat? 00:05:12.530 --> 00:05:17.080 align:middle line:84% And one of the best known examples that's usually cited 00:05:17.080 --> 00:05:20.500 align:middle line:90% is the way the plovers behave. 00:05:20.500 --> 00:05:23.460 align:middle line:84% Here's a couple: the black-headed plover 00:05:23.460 --> 00:05:25.550 align:middle line:90% and a Piping Plover. 00:05:25.550 --> 00:05:29.350 align:middle line:84% They both nest on the ground, so they have that problem: what 00:05:29.350 --> 00:05:32.720 align:middle line:90% to do if there is a predator. 00:05:32.720 --> 00:05:36.790 align:middle line:90% They want to protect their eggs. 00:05:36.790 --> 00:05:38.680 align:middle line:84% They, of course, can flay away, but that 00:05:38.680 --> 00:05:39.885 align:middle line:90% leaves the eggs unprotected. 00:05:39.885 --> 00:05:43.900 align:middle line:90% 00:05:43.900 --> 00:05:47.650 align:middle line:84% One of the things they do is reminiscent of what 00:05:47.650 --> 00:05:50.330 align:middle line:84% we saw in that very first video we showed 00:05:50.330 --> 00:05:53.020 align:middle line:90% in class of the stickleback. 00:05:53.020 --> 00:05:55.620 align:middle line:84% Remember, the male stickleback can 00:05:55.620 --> 00:05:58.290 align:middle line:84% have his nest attacked by female sticklebacks, 00:05:58.290 --> 00:06:03.060 align:middle line:84% and he'll behave like he's got a nest some other place. 00:06:03.060 --> 00:06:06.276 align:middle line:84% He creates a false nest, and he attracts them to that. 00:06:06.276 --> 00:06:09.530 align:middle line:90% 00:06:09.530 --> 00:06:12.660 align:middle line:84% So they, then, are led away from his real nest. 00:06:12.660 --> 00:06:16.400 align:middle line:90% And that's what these birds do. 00:06:16.400 --> 00:06:20.270 align:middle line:84% They'll pretend they're nesting in the wrong place, 00:06:20.270 --> 00:06:24.130 align:middle line:84% attract the predator, and, of course, they fly away, 00:06:24.130 --> 00:06:28.090 align:middle line:84% and then the predator doesn't get their eggs. 00:06:28.090 --> 00:06:32.540 align:middle line:84% Another method is to approach the predator, if there's 00:06:32.540 --> 00:06:36.650 align:middle line:90% tall grass where he can do it. 00:06:36.650 --> 00:06:38.800 align:middle line:84% And then, suddenly, they'll duck down, 00:06:38.800 --> 00:06:41.570 align:middle line:84% so they're hidden in the grass, and they'll scurry away, 00:06:41.570 --> 00:06:44.020 align:middle line:90% squeaking like a rodent. 00:06:44.020 --> 00:06:46.410 align:middle line:84% And the predator finds that irresistible. 00:06:46.410 --> 00:06:48.200 align:middle line:90% He chases after the rodent. 00:06:48.200 --> 00:06:51.970 align:middle line:90% 00:06:51.970 --> 00:06:56.720 align:middle line:84% And, of course, that rodent mimic, 00:06:56.720 --> 00:07:01.910 align:middle line:84% the Plover is leading the animal away from their nest. 00:07:01.910 --> 00:07:06.070 align:middle line:84% And there's another couple of methods they can use. 00:07:06.070 --> 00:07:08.375 align:middle line:84% Especially if the predator's already pretty close, 00:07:08.375 --> 00:07:10.040 align:middle line:90% they can run directly at it. 00:07:10.040 --> 00:07:12.570 align:middle line:90% They can run or fly towards it. 00:07:12.570 --> 00:07:13.870 align:middle line:90% They'll call very loudly. 00:07:13.870 --> 00:07:18.230 align:middle line:84% They turn away the last second, and move away from the nest. 00:07:18.230 --> 00:07:22.760 align:middle line:84% That way, they attract the predator to attack them. 00:07:22.760 --> 00:07:26.920 align:middle line:84% But they're quite able to get away. 00:07:26.920 --> 00:07:30.120 align:middle line:84% Another well known one-- and a few of you may have 00:07:30.120 --> 00:07:33.720 align:middle line:84% occasionally seen this in the wild-- 00:07:33.720 --> 00:07:36.920 align:middle line:84% if you like to observe birds' nests, the broken-wing display. 00:07:36.920 --> 00:07:39.510 align:middle line:84% This animal that's being attacked 00:07:39.510 --> 00:07:44.550 align:middle line:84% can flee along the ground, acting 00:07:44.550 --> 00:07:47.500 align:middle line:84% like he can't fly, looking exactly 00:07:47.500 --> 00:07:49.960 align:middle line:90% like he's got an injured wing. 00:07:49.960 --> 00:07:53.550 align:middle line:84% And, again, predators can't resist that. 00:07:53.550 --> 00:07:59.170 align:middle line:84% An injured bird is their best chance, catching a bird. 00:07:59.170 --> 00:08:00.890 align:middle line:84% Normally, they can't catch birds, 00:08:00.890 --> 00:08:04.340 align:middle line:84% but they can catch them if they're injured. 00:08:04.340 --> 00:08:07.750 align:middle line:84% That way, the plover can lead the animal away 00:08:07.750 --> 00:08:08.485 align:middle line:90% from their nest. 00:08:08.485 --> 00:08:11.080 align:middle line:90% 00:08:11.080 --> 00:08:13.710 align:middle line:84% So all of that's kind of secondary defense: 00:08:13.710 --> 00:08:21.620 align:middle line:84% reduces the success of an attack, 00:08:21.620 --> 00:08:23.990 align:middle line:84% reducing the probability of attack. 00:08:23.990 --> 00:08:25.960 align:middle line:90% Its, sorry, primary. 00:08:25.960 --> 00:08:30.510 align:middle line:84% Now, secondary defense is when an animal is actually 00:08:30.510 --> 00:08:32.409 align:middle line:90% caught by the predator. 00:08:32.409 --> 00:08:35.169 align:middle line:84% What does he do to reduce the chances 00:08:35.169 --> 00:08:37.190 align:middle line:90% he's going to be killed? 00:08:37.190 --> 00:08:39.779 align:middle line:84% They're not totally helpless, even if they're caught. 00:08:39.779 --> 00:08:43.570 align:middle line:90% 00:08:43.570 --> 00:08:46.840 align:middle line:84% Scott describes the behavior of a chick. 00:08:46.840 --> 00:08:52.790 align:middle line:84% Chicks, of course, are a lot less able than adult chickens. 00:08:52.790 --> 00:08:56.700 align:middle line:90% They can't fly yet. 00:08:56.700 --> 00:08:58.530 align:middle line:90% They can't even run very fast. 00:08:58.530 --> 00:09:00.380 align:middle line:84% They're much more likely to get caught 00:09:00.380 --> 00:09:01.910 align:middle line:90% in the jaws of a predator. 00:09:01.910 --> 00:09:03.920 align:middle line:90% What do they do? 00:09:03.920 --> 00:09:08.537 align:middle line:84% Well, they have this physiological change 00:09:08.537 --> 00:09:09.120 align:middle line:90% in their body. 00:09:09.120 --> 00:09:11.970 align:middle line:90% It's called tonic immobility. 00:09:11.970 --> 00:09:15.340 align:middle line:90% We call it "playing dead." 00:09:15.340 --> 00:09:19.350 align:middle line:84% But it's a physiological response. 00:09:19.350 --> 00:09:20.920 align:middle line:90% It's a fixed action pattern. 00:09:20.920 --> 00:09:23.470 align:middle line:90% 00:09:23.470 --> 00:09:26.390 align:middle line:84% Other animals, I ask here whether mammals 00:09:26.390 --> 00:09:29.640 align:middle line:84% have such response, and many small mammals do. 00:09:29.640 --> 00:09:32.860 align:middle line:90% 00:09:32.860 --> 00:09:36.410 align:middle line:84% I still remember, when I was keeping 00:09:36.410 --> 00:09:38.840 align:middle line:90% hamsters in a basement-- 00:09:38.840 --> 00:09:42.566 align:middle line:84% I kept pet hamsters for awhile before I started studying them 00:09:42.566 --> 00:09:43.780 align:middle line:90% in a lab-- 00:09:43.780 --> 00:09:45.420 align:middle line:84% and I remember coming down there, 00:09:45.420 --> 00:09:52.610 align:middle line:84% and a female had gotten out of the nest, or the cage 00:09:52.610 --> 00:09:55.270 align:middle line:90% that I had. 00:09:55.270 --> 00:09:57.090 align:middle line:84% But when I turned the light on and made 00:09:57.090 --> 00:10:03.910 align:middle line:84% movement, that animal just froze, became totally immobile. 00:10:03.910 --> 00:10:06.490 align:middle line:84% And I thought, as soon as I walk over here, 00:10:06.490 --> 00:10:08.050 align:middle line:84% she's just gonna run and get away. 00:10:08.050 --> 00:10:13.410 align:middle line:84% I'm gonna have to trap her with food or something, or water. 00:10:13.410 --> 00:10:16.320 align:middle line:84% And if you know these animals well, that's fairly easy to do, 00:10:16.320 --> 00:10:17.460 align:middle line:90% but it takes a lot of time. 00:10:17.460 --> 00:10:22.130 align:middle line:84% But instead, the animal was totally immobile. 00:10:22.130 --> 00:10:24.950 align:middle line:84% I could even touch the animal and move a limb, 00:10:24.950 --> 00:10:27.960 align:middle line:90% and it would just stay that way. 00:10:27.960 --> 00:10:30.580 align:middle line:84% It was a tonic immobility response, 00:10:30.580 --> 00:10:35.140 align:middle line:84% and they maintain it for quite a few minutes. 00:10:35.140 --> 00:10:39.810 align:middle line:84% Hamsters also have that as a response to specific odors. 00:10:39.810 --> 00:10:42.440 align:middle line:84% For example, polecat-like animals 00:10:42.440 --> 00:10:45.180 align:middle line:90% and certain species of dog. 00:10:45.180 --> 00:10:49.160 align:middle line:84% I had it happen with visitors who had dog, 00:10:49.160 --> 00:10:53.090 align:middle line:84% but all dogs didn't elicit that, just certain ones. 00:10:53.090 --> 00:10:55.960 align:middle line:84% And I never tracked down exactly which 00:10:55.960 --> 00:11:01.760 align:middle line:84% ones were more related to the polecat, their odor. 00:11:01.760 --> 00:11:04.660 align:middle line:84% But anyway, these chicks are responding 00:11:04.660 --> 00:11:09.610 align:middle line:84% to the vision of those two predator eyes facing 'em. 00:11:09.610 --> 00:11:11.475 align:middle line:84% That triggers the tonic immobility. 00:11:11.475 --> 00:11:15.830 align:middle line:90% 00:11:15.830 --> 00:11:20.480 align:middle line:84% said Generally, the predator, if he doesn't struggle and doesn't 00:11:20.480 --> 00:11:26.870 align:middle line:84% move, just keeps him in its nest area, 00:11:26.870 --> 00:11:29.410 align:middle line:84% and doesn't immediately kill them. 00:11:29.410 --> 00:11:33.660 align:middle line:84% I, mean he doesn't need to, unless he's 00:11:33.660 --> 00:11:37.240 align:middle line:84% competing with other animals, in which case he might. 00:11:37.240 --> 00:11:40.300 align:middle line:84% This method doesn't always work for the chick. 00:11:40.300 --> 00:11:42.790 align:middle line:84% But the chick lying there will occasionally 00:11:42.790 --> 00:11:45.580 align:middle line:84% peek to find out if the predator is still there. 00:11:45.580 --> 00:11:49.810 align:middle line:84% And it looks, and it still gets that stimulus, 00:11:49.810 --> 00:11:55.480 align:middle line:84% he'll continue in that state of tonic immobility. 00:11:55.480 --> 00:11:57.790 align:middle line:90% But if it doesn't see the eyes-- 00:11:57.790 --> 00:12:02.130 align:middle line:84% so the innate releasing mechanism is missing-- 00:12:02.130 --> 00:12:05.180 align:middle line:84% he will lose the tonic immobility, and run away. 00:12:05.180 --> 00:12:08.560 align:middle line:90% 00:12:08.560 --> 00:12:12.650 align:middle line:84% Now, we know the opossum does something similar there. 00:12:12.650 --> 00:12:14.570 align:middle line:84% We talk about opossums playing dead. 00:12:14.570 --> 00:12:18.830 align:middle line:84% You don't hear about hamsters, but I can assure you, 00:12:18.830 --> 00:12:20.950 align:middle line:90% they also can do that. 00:12:20.950 --> 00:12:24.470 align:middle line:84% And many other small mammals with certain kinds 00:12:24.470 --> 00:12:25.770 align:middle line:90% of stimulation-- 00:12:25.770 --> 00:12:28.500 align:middle line:84% rabbits, for example-- can enter that state. 00:12:28.500 --> 00:12:31.670 align:middle line:90% 00:12:31.670 --> 00:12:34.890 align:middle line:84% We talked about anti-predator benefits of group foraging 00:12:34.890 --> 00:12:37.850 align:middle line:90% by birds before. 00:12:37.850 --> 00:12:41.310 align:middle line:84% You should be able to tell what the major benefits are, 00:12:41.310 --> 00:12:43.220 align:middle line:90% and the costs. 00:12:43.220 --> 00:12:45.800 align:middle line:84% I can count at least three benefits. 00:12:45.800 --> 00:12:48.400 align:middle line:90% One is dilution effect. 00:12:48.400 --> 00:12:51.350 align:middle line:90% We call it the selfish herd. 00:12:51.350 --> 00:12:55.660 align:middle line:84% The more animals are there, the less chance that any one 00:12:55.660 --> 00:12:56.880 align:middle line:90% animal's going to be caught. 00:12:56.880 --> 00:13:00.300 align:middle line:84% And for that reason, in the period of reproduction, 00:13:00.300 --> 00:13:03.220 align:middle line:84% many animals reproduce in a colony, 00:13:03.220 --> 00:13:05.440 align:middle line:84% because if the colonies attacked, 00:13:05.440 --> 00:13:08.920 align:middle line:84% the chances that it will be their nest and their young that 00:13:08.920 --> 00:13:11.630 align:middle line:90% are attacked are reduced. 00:13:11.630 --> 00:13:14.860 align:middle line:84% It also, of course, reduces the demands 00:13:14.860 --> 00:13:18.500 align:middle line:84% for vigilance on an individual, because there's many more eyes 00:13:18.500 --> 00:13:20.030 align:middle line:90% to see the predator. 00:13:20.030 --> 00:13:22.290 align:middle line:84% So the chances of their detecting a predator 00:13:22.290 --> 00:13:23.650 align:middle line:90% are much greater. 00:13:23.650 --> 00:13:27.000 align:middle line:84% As one animal responds, it's quickly 00:13:27.000 --> 00:13:29.290 align:middle line:84% communicated to all of them, either because they fly, 00:13:29.290 --> 00:13:33.470 align:middle line:84% or they emit alarm calls, or both. 00:13:33.470 --> 00:13:37.690 align:middle line:84% And, of course, if they all fly up at once, 00:13:37.690 --> 00:13:40.550 align:middle line:84% it confuses the predator, and very often the predator 00:13:40.550 --> 00:13:44.000 align:middle line:90% doesn't get any of them. 00:13:44.000 --> 00:13:47.570 align:middle line:90% It has costs, of course. 00:13:47.570 --> 00:13:50.550 align:middle line:84% You're competing with a lot of other animals for food. 00:13:50.550 --> 00:13:54.675 align:middle line:90% 00:13:54.675 --> 00:13:56.660 align:middle line:84% Other animals that are interfering 00:13:56.660 --> 00:13:58.720 align:middle line:84% can interfere with your activities. 00:13:58.720 --> 00:14:01.230 align:middle line:84% It's, of course, a lot worse if you're not 00:14:01.230 --> 00:14:07.025 align:middle line:84% a dominant individual in the flock. 00:14:07.025 --> 00:14:09.610 align:middle line:90% 00:14:09.610 --> 00:14:12.110 align:middle line:84% We talked about the optimal group size, 00:14:12.110 --> 00:14:15.400 align:middle line:84% which was not specifically rated related to predation, 00:14:15.400 --> 00:14:18.460 align:middle line:90% but to food gathering ability. 00:14:18.460 --> 00:14:21.250 align:middle line:84% So I won't go back over that now. 00:14:21.250 --> 00:14:23.940 align:middle line:90% I will mention mobbing here. 00:14:23.940 --> 00:14:29.820 align:middle line:84% We've talked about mobbing in jackdaws and in geese. 00:14:29.820 --> 00:14:34.050 align:middle line:84% You saw examples of that, of the geese in the video. 00:14:34.050 --> 00:14:38.110 align:middle line:84% You read about it in Lawrence's description of jackdaws. 00:14:38.110 --> 00:14:43.960 align:middle line:84% We saw it in the meerkat video, as well. 00:14:43.960 --> 00:14:48.120 align:middle line:84% Scott discusses the black-headed gulls, which 00:14:48.120 --> 00:14:50.450 align:middle line:90% will show mobbing of predators. 00:14:50.450 --> 00:14:54.390 align:middle line:84% And he cites data from a study where 00:14:54.390 --> 00:14:59.460 align:middle line:84% they looked at colony-nesting gulls, 00:14:59.460 --> 00:15:02.500 align:middle line:84% and how frequently they engaged in mobbing 00:15:02.500 --> 00:15:06.210 align:middle line:84% as a function of where their nest was in the colony. 00:15:06.210 --> 00:15:08.680 align:middle line:84% If they were near the center of the colony, 00:15:08.680 --> 00:15:12.950 align:middle line:84% the rate of mobbing in most animals in most nests 00:15:12.950 --> 00:15:15.290 align:middle line:90% was the highest. 00:15:15.290 --> 00:15:20.840 align:middle line:84% The rate at which they lost eggs to a predator was the lowest. 00:15:20.840 --> 00:15:24.950 align:middle line:84% And then, if you went to the edge of the colony, further 00:15:24.950 --> 00:15:29.120 align:middle line:84% he got from the center, then they 00:15:29.120 --> 00:15:33.120 align:middle line:84% were less likely to engage in the mobbing behavior, 00:15:33.120 --> 00:15:37.890 align:middle line:84% but they were much more likely to have their nests predated, 00:15:37.890 --> 00:15:39.220 align:middle line:90% and they would lose eggs. 00:15:39.220 --> 00:15:42.020 align:middle line:90% 00:15:42.020 --> 00:15:47.400 align:middle line:84% So mobbing is an effective kind of anti-predator behavior. 00:15:47.400 --> 00:15:51.270 align:middle line:84% So what they do besides these kinds of behaviors, 00:15:51.270 --> 00:15:53.700 align:middle line:90% or just running away? 00:15:53.700 --> 00:15:56.900 align:middle line:84% Of course, that's the main defense an animal has. 00:15:56.900 --> 00:15:59.640 align:middle line:84% If he's by himself, he's attacked by a predator, 00:15:59.640 --> 00:16:01.285 align:middle line:90% he has to run. 00:16:01.285 --> 00:16:04.230 align:middle line:90% 00:16:04.230 --> 00:16:06.455 align:middle line:84% And the trick is simply not getting caught. 00:16:06.455 --> 00:16:09.450 align:middle line:90% 00:16:09.450 --> 00:16:11.100 align:middle line:84% But they can do other things, too. 00:16:11.100 --> 00:16:17.880 align:middle line:84% For example, some mollusks, they have these tentacles. 00:16:17.880 --> 00:16:20.280 align:middle line:84% Some of these chemicals are actually are pretty meaty, 00:16:20.280 --> 00:16:22.840 align:middle line:84% and animals will often-- because they're moving-- 00:16:22.840 --> 00:16:26.390 align:middle line:84% are more likely to attack that part of the mollusk. 00:16:26.390 --> 00:16:30.010 align:middle line:90% But these things can be shed. 00:16:30.010 --> 00:16:33.070 align:middle line:90% Similarly, lizards. 00:16:33.070 --> 00:16:34.513 align:middle line:84% They'll move their tail much more 00:16:34.513 --> 00:16:35.680 align:middle line:90% than the rest of their body. 00:16:35.680 --> 00:16:40.220 align:middle line:84% And they will do that purposely, because if the animal attacks 00:16:40.220 --> 00:16:45.600 align:middle line:84% them, grabs the tail, the lizard just sheds the tail, 00:16:45.600 --> 00:16:49.550 align:middle line:84% and the tailless lizard will get away. 00:16:49.550 --> 00:16:51.610 align:middle line:84% And, sometimes, the tail will be shed 00:16:51.610 --> 00:16:53.080 align:middle line:84% and it keeps wiggling and wiggling 00:16:53.080 --> 00:16:55.267 align:middle line:84% and the predator keeps going after it. 00:16:55.267 --> 00:16:58.070 align:middle line:90% 00:16:58.070 --> 00:17:00.445 align:middle line:84% The movement is irresistible to the predator. 00:17:00.445 --> 00:17:04.089 align:middle line:90% 00:17:04.089 --> 00:17:06.910 align:middle line:84% We talked about this a little bit, about alarm calls. 00:17:06.910 --> 00:17:10.859 align:middle line:84% You should know that there's both altruistic and selfish 00:17:10.859 --> 00:17:13.410 align:middle line:90% uses of alarm calls. 00:17:13.410 --> 00:17:17.060 align:middle line:84% We know it can be altruistic, it can help others. 00:17:17.060 --> 00:17:19.240 align:middle line:84% But, of course, the animal doing the calling, 00:17:19.240 --> 00:17:22.290 align:middle line:84% his position is betrayed to the predator. 00:17:22.290 --> 00:17:23.194 align:middle line:90% So that's a cost. 00:17:23.194 --> 00:17:26.260 align:middle line:90% 00:17:26.260 --> 00:17:30.390 align:middle line:84% And of course, the animal can elicit a mass escape 00:17:30.390 --> 00:17:34.020 align:middle line:84% and benefit from the dilution and confusion effects, 00:17:34.020 --> 00:17:35.120 align:middle line:90% and he can do that. 00:17:35.120 --> 00:17:42.420 align:middle line:84% He's benefiting perhaps more than others, because they head 00:17:42.420 --> 00:17:44.650 align:middle line:90% start he gets. 00:17:44.650 --> 00:17:47.680 align:middle line:84% And, sometimes, he will do that even if there's not a predator, 00:17:47.680 --> 00:17:49.670 align:middle line:90% just so he gets access to food. 00:17:49.670 --> 00:17:52.570 align:middle line:84% So that's another selfish use of the alarm calls. 00:17:52.570 --> 00:17:56.120 align:middle line:90% 00:17:56.120 --> 00:18:00.170 align:middle line:84% [? Cresswell ?] in '94 is reviewed by Scott. 00:18:00.170 --> 00:18:02.940 align:middle line:84% Collected data on that, these animals 00:18:02.940 --> 00:18:04.620 align:middle line:84% that wade around the shallow water 00:18:04.620 --> 00:18:09.645 align:middle line:84% and eat fat worms that they find in the bottom of the ponds. 00:18:09.645 --> 00:18:13.570 align:middle line:90% 00:18:13.570 --> 00:18:20.860 align:middle line:84% He found that the ones that didn't call, 00:18:20.860 --> 00:18:25.620 align:middle line:84% and the ones that flew up the latest, were the most likely 00:18:25.620 --> 00:18:26.750 align:middle line:90% to be attacked. 00:18:26.750 --> 00:18:28.950 align:middle line:84% So those animals that were doing the calling 00:18:28.950 --> 00:18:31.350 align:middle line:84% weren't the most likely to be caught, even though they 00:18:31.350 --> 00:18:34.170 align:middle line:90% did betray their position. 00:18:34.170 --> 00:18:38.200 align:middle line:84% The calling might attract the predator to the region, 00:18:38.200 --> 00:18:41.580 align:middle line:84% but it doesn't make him select the animal to attack. 00:18:41.580 --> 00:18:43.410 align:middle line:84% In fact, if the animal's calling, 00:18:43.410 --> 00:18:45.430 align:middle line:84% he's probably the one you don't want to attack, 00:18:45.430 --> 00:18:48.550 align:middle line:84% because he's the vigilant one that saw you first. 00:18:48.550 --> 00:18:50.670 align:middle line:84% They want to attack an animal that's less aware, 00:18:50.670 --> 00:18:53.600 align:middle line:90% and that's exactly what they do. 00:18:53.600 --> 00:18:56.160 align:middle line:84% The late-flyers and the non-callers 00:18:56.160 --> 00:18:57.670 align:middle line:84% were the most likely to be attacked. 00:18:57.670 --> 00:19:00.400 align:middle line:90% 00:19:00.400 --> 00:19:02.620 align:middle line:84% And, of course, I mention here at the end 00:19:02.620 --> 00:19:05.550 align:middle line:84% that alarm calls can also attract 00:19:05.550 --> 00:19:08.530 align:middle line:90% predators of the predator. 00:19:08.530 --> 00:19:13.075 align:middle line:84% So it's another occasional benefit of the calling. 00:19:13.075 --> 00:19:17.520 align:middle line:90% 00:19:17.520 --> 00:19:23.220 align:middle line:84% Redshanks actually have two distinct ways of escaping. 00:19:23.220 --> 00:19:28.120 align:middle line:84% Some animals even have very distinct calls. 00:19:28.120 --> 00:19:30.350 align:middle line:84% It gives away which way they're going to escape, 00:19:30.350 --> 00:19:35.850 align:middle line:84% and that's because they can be attacked in different ways. 00:19:35.850 --> 00:19:42.330 align:middle line:84% And for the redshanks, they have two major predators. 00:19:42.330 --> 00:19:45.810 align:middle line:84% The peregrine falcons attack from above, 00:19:45.810 --> 00:19:49.760 align:middle line:84% in a rapid-diving attack, so they 00:19:49.760 --> 00:19:53.080 align:middle line:84% need to crouch low and remain still, 00:19:53.080 --> 00:19:58.700 align:middle line:84% so they're not attracting the vision of that falcon. 00:19:58.700 --> 00:20:01.780 align:middle line:84% Whereas the sparrow hawk attacks flying 00:20:01.780 --> 00:20:05.030 align:middle line:90% in just above the ground, low. 00:20:05.030 --> 00:20:07.590 align:middle line:84% So their best bet-- if he's already been detected 00:20:07.590 --> 00:20:10.580 align:middle line:84% and that hawk is coming towards him-- the best thing he can do 00:20:10.580 --> 00:20:12.980 align:middle line:90% is fly up. 00:20:12.980 --> 00:20:16.930 align:middle line:84% Those are two very distinct methods of escape, 00:20:16.930 --> 00:20:21.530 align:middle line:84% and they each work best for one these predators. 00:20:21.530 --> 00:20:24.250 align:middle line:90% 00:20:24.250 --> 00:20:28.270 align:middle line:84% And then we come to a really weird one: stotting behavior. 00:20:28.270 --> 00:20:31.490 align:middle line:84% It's caused a lot of confusion in studies of animal behavior. 00:20:31.490 --> 00:20:33.110 align:middle line:90% Do know what it is? 00:20:33.110 --> 00:20:37.860 align:middle line:84% These little gazelles will be fleeing from a predator, 00:20:37.860 --> 00:20:43.780 align:middle line:84% and as they flee, they're using extra energy and extra time 00:20:43.780 --> 00:20:47.380 align:middle line:84% to leap up high so they can be seen. 00:20:47.380 --> 00:20:50.710 align:middle line:84% They make themselves visible to the predator. 00:20:50.710 --> 00:20:52.630 align:middle line:84% And this is the way they look like. 00:20:52.630 --> 00:20:57.100 align:middle line:84% And when you're looking at them, as you see in the drawing here, 00:20:57.100 --> 00:21:01.580 align:middle line:84% here's a cheetah pursuing one of these Thomson's gazelle. 00:21:01.580 --> 00:21:05.450 align:middle line:84% And the cheetah sees him from behind, and what he sees 00:21:05.450 --> 00:21:10.220 align:middle line:84% is this, like a white flag, every time 00:21:10.220 --> 00:21:12.010 align:middle line:90% the gazelle leaps up. 00:21:12.010 --> 00:21:12.970 align:middle line:90% Why would they do that? 00:21:12.970 --> 00:21:16.050 align:middle line:90% 00:21:16.050 --> 00:21:18.306 align:middle line:84% There's been multiple hypotheses. 00:21:18.306 --> 00:21:21.720 align:middle line:90% 00:21:21.720 --> 00:21:26.490 align:middle line:84% The book mentions that there are 11 different hypotheses. 00:21:26.490 --> 00:21:29.790 align:middle line:90% 00:21:29.790 --> 00:21:31.870 align:middle line:84% He summarizes just three of them, 00:21:31.870 --> 00:21:34.830 align:middle line:90% and uses data from Carrol. 00:21:34.830 --> 00:21:38.320 align:middle line:90% This is from 1986. 00:21:38.320 --> 00:21:44.340 align:middle line:84% He found that attacks by cheetahs 00:21:44.340 --> 00:21:46.820 align:middle line:84% appeared to be deterred by the stotting. 00:21:46.820 --> 00:21:51.360 align:middle line:84% It does work, and the interpretation 00:21:51.360 --> 00:21:53.990 align:middle line:84% is that it's communicating this: I'm 00:21:53.990 --> 00:21:57.480 align:middle line:84% far enough away that I have a high probability of escape, 00:21:57.480 --> 00:21:59.720 align:middle line:84% so why waste your time and energy? 00:21:59.720 --> 00:22:03.635 align:middle line:84% And, of course, if it does deter the attack of the cheetah, then 00:22:03.635 --> 00:22:08.060 align:middle line:84% the animal himself will use less energy. 00:22:08.060 --> 00:22:11.720 align:middle line:84% He will not have to flee as long. 00:22:11.720 --> 00:22:14.970 align:middle line:84% And, in fact, they've collected data that is summarized 00:22:14.970 --> 00:22:19.310 align:middle line:84% in the book about the frequency of success of these attacks 00:22:19.310 --> 00:22:22.270 align:middle line:84% in animals that engage in stotting and those that don't. 00:22:22.270 --> 00:22:25.880 align:middle line:84% And those that show the stotting behavior 00:22:25.880 --> 00:22:29.655 align:middle line:90% are not caught as often. 00:22:29.655 --> 00:22:34.850 align:middle line:90% 00:22:34.850 --> 00:22:40.700 align:middle line:84% So, I want to show this video called Great Escapes. 00:22:40.700 --> 00:22:42.580 align:middle line:84% Some of you have seen Marty Stouffer 00:22:42.580 --> 00:22:45.000 align:middle line:90% on the TV and public television. 00:22:45.000 --> 00:22:48.930 align:middle line:90% 00:22:48.930 --> 00:22:51.350 align:middle line:84% I don't know if I'll show all of these things, 00:22:51.350 --> 00:22:53.380 align:middle line:84% but this is a summary of a number 00:22:53.380 --> 00:22:59.480 align:middle line:84% of the things in the earlier part of the video. 00:22:59.480 --> 00:23:01.190 align:middle line:90% So let me pull up here. 00:23:01.190 --> 00:23:20.150 align:middle line:90% 00:23:20.150 --> 00:23:26.170 align:middle line:84% It'll start out with a bobcat, the most common big cat 00:23:26.170 --> 00:23:29.310 align:middle line:90% in the USA. 00:23:29.310 --> 00:23:33.390 align:middle line:84% Not a real huge cat, but a common predator. 00:23:33.390 --> 00:23:39.880 align:middle line:90% 00:23:39.880 --> 00:23:43.800 align:middle line:84% This content has been removed due to copyright restrictions 00:23:43.800 --> 00:23:46.672 align:middle line:84% see the Readings and Viewings page for information 00:23:46.672 --> 00:23:47.505 align:middle line:90% about this material. 00:23:47.505 --> 00:23:54.692 align:middle line:90% 00:23:54.692 --> 00:23:56.400 align:middle line:84% PROFESSOR: Why didn't the bobcat kill it? 00:23:56.400 --> 00:23:59.560 align:middle line:90% 00:23:59.560 --> 00:24:02.000 align:middle line:84% We've met this before, when we talked 00:24:02.000 --> 00:24:07.135 align:middle line:84% about predatory behavior and the work of Layhuasen and Lawrence. 00:24:07.135 --> 00:24:10.060 align:middle line:90% 00:24:10.060 --> 00:24:12.330 align:middle line:90% What's your interpretation? 00:24:12.330 --> 00:24:15.230 align:middle line:90% Good exam question. 00:24:15.230 --> 00:24:17.524 align:middle line:84% Interpret what just happened there. 00:24:17.524 --> 00:24:23.460 align:middle line:90% 00:24:23.460 --> 00:24:23.960 align:middle line:90% Yes. 00:24:23.960 --> 00:24:33.280 align:middle line:90% AUDIENCE: [INAUDIBLE] 00:24:33.280 --> 00:24:35.120 align:middle line:84% PROFESSOR: If I'm hearing you right, 00:24:35.120 --> 00:24:37.710 align:middle line:84% I think you what you said is correct. 00:24:37.710 --> 00:24:43.370 align:middle line:84% He had exercised his killing by pretty recently, 00:24:43.370 --> 00:24:45.110 align:middle line:90% and killed prey. 00:24:45.110 --> 00:24:48.540 align:middle line:84% His motivation for executing the killing bite 00:24:48.540 --> 00:24:52.970 align:middle line:84% was reduced below the level where it could be triggered 00:24:52.970 --> 00:24:55.030 align:middle line:90% by that prairie chicken. 00:24:55.030 --> 00:24:59.090 align:middle line:84% But his motivation to stalk, and even attack, 00:24:59.090 --> 00:25:03.430 align:middle line:84% was still high enough that when the stimulus was strong, 00:25:03.430 --> 00:25:09.440 align:middle line:84% like that prairie chicken taking off, it elicited the attack. 00:25:09.440 --> 00:25:11.630 align:middle line:84% But he wasn't sufficiently motivated 00:25:11.630 --> 00:25:15.530 align:middle line:84% to finish that last step, because 00:25:15.530 --> 00:25:18.800 align:middle line:84% the action-specific potential, the motivation 00:25:18.800 --> 00:25:23.620 align:middle line:84% to do the killing bite, doesn't build up as fast 00:25:23.620 --> 00:25:25.810 align:middle line:84% as the motivation for those earlier 00:25:25.810 --> 00:25:27.615 align:middle line:90% parts of predatory behavior. 00:25:27.615 --> 00:25:30.320 align:middle line:90% 00:25:30.320 --> 00:25:35.300 align:middle line:84% So there's other examples of that in the work of Leyhausen. 00:25:35.300 --> 00:25:38.880 align:middle line:84% He wasn't playing with it, but that 00:25:38.880 --> 00:25:40.450 align:middle line:90% seems to be what it amounts to. 00:25:40.450 --> 00:25:43.170 align:middle line:84% And in fact, these big cats will do 00:25:43.170 --> 00:25:48.380 align:middle line:84% that when they themselves have killed and eaten and so forth. 00:25:48.380 --> 00:25:52.710 align:middle line:84% They will still actually catch prey without killing it, 00:25:52.710 --> 00:25:56.195 align:middle line:84% and bring it to their young, which then can practice. 00:25:56.195 --> 00:26:02.610 align:middle line:90% 00:26:02.610 --> 00:26:03.790 align:middle line:90% We're going to see a coyote. 00:26:03.790 --> 00:26:06.960 align:middle line:90% 00:26:06.960 --> 00:26:10.870 align:middle line:84% This content has been removed due to copyright restrictions 00:26:10.870 --> 00:26:13.702 align:middle line:84% see the Readings and Viewings page for information 00:26:13.702 --> 00:26:14.535 align:middle line:90% about this material. 00:26:14.535 --> 00:26:20.912 align:middle line:90% 00:26:20.912 --> 00:26:23.370 align:middle line:84% PROFESSOR: There was only one other thing I could show you. 00:26:23.370 --> 00:26:25.540 align:middle line:84% It's just a bobcat attacking a lizard, 00:26:25.540 --> 00:26:30.770 align:middle line:84% and the bobcat ends up chasing a tail. 00:26:30.770 --> 00:26:33.970 align:middle line:90% OK, so I will see you on Friday. 00:26:33.970 --> 00:26:35.870 align:middle line:84% And we will just have a little bit more 00:26:35.870 --> 00:26:37.660 align:middle line:84% on anti-predator behavior, and then we'll 00:26:37.660 --> 00:26:39.840 align:middle line:90% do us some reviewing. 00:26:39.840 --> 00:26:41.734 align:middle line:90%