WEBVTT 00:00:30.912 --> 00:00:32.725 Blue whales are the largest animals 00:00:32.725 --> 00:00:34.644 that have ever roamed the planet. 00:00:34.644 --> 00:00:37.785 They're at least two times as big as the biggest dinosaurs, 00:00:38.954 --> 00:00:40.275 "That's big!" 00:00:40.275 --> 00:00:41.736 the length of a basketball court, 00:00:41.736 --> 00:00:44.781 and as heavy as 40 African elephants. 00:00:44.781 --> 00:00:46.579 If that's not enough to make you marvel, 00:00:46.579 --> 00:00:48.659 here's something that will. 00:00:48.659 --> 00:00:50.367 They're grown to this enormous size 00:00:50.367 --> 00:00:54.705 by feeding exclusively on tiny shrimp-like creatures called krill 00:00:58.333 --> 00:01:00.568 that are no bigger than your little finger. 00:01:00.568 --> 00:01:02.559 In many ways, the sheer size of krill 00:01:02.559 --> 00:01:05.940 seems to have driven the evolution of the blue whale. 00:01:08.032 --> 00:01:10.093 See, krill are so small 00:01:10.093 --> 00:01:12.132 but are found in dense patches. 00:01:12.132 --> 00:01:13.133 For increased efficiency, 00:01:13.133 --> 00:01:14.467 blue whales have evolved 00:01:14.467 --> 00:01:15.715 to use a feeding strategy 00:01:15.715 --> 00:01:17.596 called lunge feeding. 00:01:17.596 --> 00:01:20.846 Basically, the whale accelerates towards a prey patch 00:01:20.846 --> 00:01:22.900 and opens its mouth wide. 00:01:22.900 --> 00:01:26.062 To increase the capacity, its mouth expands. 00:01:26.062 --> 00:01:28.178 The special, accordion-like blubber layer 00:01:28.178 --> 00:01:30.441 that extends from its snout to its belly button 00:01:30.441 --> 00:01:32.944 enables the whale to engulf large quantities 00:01:32.944 --> 00:01:35.176 of prey-laden water. 00:01:42.836 --> 00:01:44.376 With each giant gulp, 00:01:44.376 --> 00:01:48.129 the whale takes in 125% of its body weight 00:01:48.129 --> 00:01:50.300 in water and krill. 00:01:50.300 --> 00:01:51.968 The whale must then expel the water 00:01:51.968 --> 00:01:54.227 while retaining the yummy krill. 00:01:54.227 --> 00:01:56.446 To do this, it uses its baleen, 00:01:56.446 --> 00:01:58.272 the comb-like structure made of the same stuff 00:01:58.272 --> 00:02:00.884 our nails and hair are made of, 00:02:00.884 --> 00:02:02.616 and its tongue. 00:02:08.599 --> 00:02:10.909 It's pretty crazy that the blue whale's heart 00:02:10.909 --> 00:02:12.674 is as big as a small car, 00:02:12.674 --> 00:02:15.139 a child could crawl through its arteries, 00:02:15.139 --> 00:02:17.255 its tongue weighs as much as an elephant, 00:02:17.255 --> 00:02:20.051 but its esophagus is so small, 00:02:20.051 --> 00:02:23.263 the whale could choke on a loaf of bread. 00:02:23.263 --> 00:02:24.844 These whales are really not designed 00:02:24.844 --> 00:02:27.415 to feed on anything larger than krill. 00:02:31.459 --> 00:02:35.629 It's estimated that blue whales eat four tons of krill per day. 00:02:35.629 --> 00:02:36.889 Because of the incredible design, 00:02:36.889 --> 00:02:38.541 each dive provides the blue whale 00:02:38.541 --> 00:02:42.181 with 90 times as much energy as is used. 00:02:42.181 --> 00:02:46.937 Every mouthful of krill provides almost 480,000 calories, 00:02:46.937 --> 00:02:52.160 the same amount you get from eating 1,900 hamburgers. 00:02:54.780 --> 00:02:57.680 But, why are blue whales so big? 00:02:57.680 --> 00:02:59.186 Blue whales are considerably larger 00:02:59.186 --> 00:03:02.047 than the largest living land animal, the elephant. 00:03:02.047 --> 00:03:03.691 The heavier an animal is, 00:03:03.691 --> 00:03:06.204 the greater its relative surface area. 00:03:06.204 --> 00:03:07.519 As weight increases, 00:03:07.519 --> 00:03:09.680 there's a point at which the legs of that animal 00:03:09.680 --> 00:03:12.421 would simply collapse. 00:03:12.421 --> 00:03:14.263 That explains why elephants don't stand 00:03:14.263 --> 00:03:17.179 on the delicate legs of a horse. 00:03:17.179 --> 00:03:19.181 They need legs shaped like stout pedestals 00:03:19.181 --> 00:03:22.341 to hold their bodies up against gravity. 00:03:25.234 --> 00:03:28.032 In water, the situation is quite different. 00:03:28.032 --> 00:03:30.705 Buoyancy counteracts the gravitational pull on the body 00:03:30.705 --> 00:03:33.243 and their great bulk is therefore partially supported 00:03:33.243 --> 00:03:35.080 by the water. 00:03:35.080 --> 00:03:37.164 So, the ocean is a great place for species 00:03:37.164 --> 00:03:39.499 that want to grow bigger. 00:03:39.499 --> 00:03:42.333 The other secret to their size is their diet. 00:03:42.333 --> 00:03:44.045 By evolving such a huge mouth, 00:03:44.045 --> 00:03:46.640 the whale's have specialized to catch enormous quantities 00:03:46.640 --> 00:03:49.267 of highly abundant and nutritious prey, 00:03:49.267 --> 00:03:53.427 which provides the energy needed to grow so big. 00:03:56.063 --> 00:03:58.178 But, now maybe you're wondering 00:03:58.178 --> 00:04:00.771 why blue whales aren't any bigger? 00:04:00.771 --> 00:04:02.869 After all, the ocean sounds like nirvana 00:04:02.869 --> 00:04:04.447 for any growing beast. 00:04:04.447 --> 00:04:07.179 Well, while lunge feeding may have allowed blue whales 00:04:07.179 --> 00:04:08.640 to become the biggest animal 00:04:08.640 --> 00:04:10.337 to have ever roamed the planet, 00:04:10.337 --> 00:04:13.819 by enabling them to feed efficiently in dense prey patches, 00:04:13.819 --> 00:04:15.656 it isn't cost free. 00:04:15.656 --> 00:04:18.776 Scientists compared all the costs involved with lunge feeding 00:04:18.776 --> 00:04:21.459 to the energy gained from the krill they eat. 00:04:21.459 --> 00:04:24.832 What they found is that when the whale's body increases in size, 00:04:24.832 --> 00:04:27.375 the energy that body demands rises faster 00:04:27.375 --> 00:04:31.495 than the extra energy they get from their food. 00:04:31.495 --> 00:04:35.592 Feeding whales needs 15 times the energy required to remain still 00:04:35.592 --> 00:04:39.556 and 5 times more energy than used when swimming. 00:04:39.556 --> 00:04:40.959 Calculations show 00:04:40.959 --> 00:04:44.782 that the largest a lunge feeder can grow is 33 meters, 00:04:44.782 --> 00:04:47.313 pretty much blue whale size. 00:04:47.313 --> 00:04:49.780 Turns out blue whales have a lot to thank krill for: 00:04:49.780 --> 00:04:51.406 neat, evolutionary adaptations 00:04:51.406 --> 00:04:54.872 that would not have been possible if krill were not so small. 00:04:54.872 --> 00:04:56.924 It's incredible that these tiny creatures 00:04:56.924 --> 00:04:59.739 have allowed blue whales to really push the limits 00:04:59.739 --> 00:05:01.557 of size on our planet. 00:05:01.557 --> 00:05:03.671 Makes you wonder if that old adage, 00:05:03.671 --> 00:05:05.518 "You are what you eat," 00:05:05.518 --> 00:05:09.131 really does apply in blue whale world.