WEBVTT - Crab Bag, Part 4: For Whom the Crab Tolls 0:00:03.040 --> 0:00:06.760 Welcome to Stuff to Blow Your Mind production of iHeartRadio. 0:00:12.960 --> 0:00:15.160 Hey, welcome to Stuff to Blow Your Mind. My name 0:00:15.160 --> 0:00:16.160 is Robert Lamb. 0:00:16.480 --> 0:00:18.880 And I am Joe McCormick, and we are back with 0:00:18.960 --> 0:00:21.840 the fourth and I think for now final part in 0:00:21.880 --> 0:00:25.320 our crab Bag series. We've been doing episodes on all 0:00:25.400 --> 0:00:28.440 things crab. No real organizing principle except I guess the 0:00:28.800 --> 0:00:33.920 decapod crustacean body plan. In the previous three episodes of 0:00:33.960 --> 0:00:36.879 this series, we have talked about a bunch of stuff. 0:00:36.920 --> 0:00:41.000 We got into the legend of a miracle crab connected 0:00:41.040 --> 0:00:44.839 with the Catholic missionary Saint Francis Xavier and how that 0:00:44.960 --> 0:00:48.120 story connects loosely to a real species known as the 0:00:48.159 --> 0:00:52.640 Crucifix crab, and we got into a bit about questions 0:00:52.640 --> 0:00:56.920 of object carrying behavior in crabs. We talked about the 0:00:56.960 --> 0:01:01.320 family of crabs known as Raninity or FROs, and they's 0:01:01.360 --> 0:01:05.880 somewhat uncrab like. Elongated body shape crabs have a very 0:01:05.959 --> 0:01:10.399 side to side kind of orientation. The Raninity have instead 0:01:10.440 --> 0:01:14.720 specialized for backwards burrowing by somewhat elongating their body front 0:01:14.760 --> 0:01:19.280 to back. We talked about a legendary type of monster 0:01:19.400 --> 0:01:22.640 crab from the traditions of the Lunda people of Zambia. 0:01:22.760 --> 0:01:25.920 A crab with two heads that attacks by eating your 0:01:25.959 --> 0:01:31.080 shadow had some interesting hippopotamus properties as well. We talked 0:01:31.120 --> 0:01:34.600 about the idea of seeing faces in the shells of crabs, 0:01:35.160 --> 0:01:38.600 and in the last episode we read a bizarre and 0:01:38.840 --> 0:01:43.360 interesting eighteen sixty four letter to Scientific American which argued 0:01:43.400 --> 0:01:47.400 that the US Navy should construct a giant biomimetic attack 0:01:47.520 --> 0:01:51.480 submarine based on the model of the Atlantic horseshoe crab. 0:01:52.160 --> 0:01:56.160 The letter writer called this the King Crab Warship, and 0:01:56.240 --> 0:02:00.520 this led into a general discussion about the sort of 0:02:00.600 --> 0:02:05.040 patent fever surrounding the US Civil War and Abraham Lincoln's 0:02:05.200 --> 0:02:10.119 surprising relationship with very eager inventors of every kind, and 0:02:09.800 --> 0:02:13.200 this ran the whole gamut from scammers and cranks to 0:02:13.320 --> 0:02:17.520 real innovators. And in that episode we also talked about 0:02:17.520 --> 0:02:22.040 the cultural significance of crabs in China, including getting into 0:02:22.919 --> 0:02:26.799 a short older report from Fujian of crabs being involved 0:02:26.919 --> 0:02:30.800 in exorcism and protective magic. And then we also talked 0:02:30.800 --> 0:02:34.480 about the more common association in China between crabs and 0:02:34.680 --> 0:02:39.280 good fortune, wealth and luck, and got into a few 0:02:39.280 --> 0:02:42.840 other stories there, like the story of Bajied, the first 0:02:42.880 --> 0:02:45.760 man to eat a crab, which is a great distinction. 0:02:46.040 --> 0:02:50.000 Yeah yeah, yeah, yeah, So a lot of discussion of 0:02:50.720 --> 0:02:54.440 crab iconography, with crabs clutching coins or setting on big 0:02:54.480 --> 0:02:59.720 piles of coins, almost like a Western dragon. So was 0:02:59.760 --> 0:03:02.120 really into that. One thing I wanted to mention You 0:03:02.160 --> 0:03:06.080 were talking about the proposal that the United States needed 0:03:06.720 --> 0:03:12.200 a large crab mech to do its bidding. This reminded 0:03:12.200 --> 0:03:13.680 me of something. I was like, what is it reminding 0:03:13.720 --> 0:03:18.560 me of? And it is the mobile Oppression Palace from Futurama. 0:03:18.680 --> 0:03:22.120 This is an episode in which titled a Taste of Freedom, 0:03:22.480 --> 0:03:26.200 one of my favorites, in which Zoidberg's people end up 0:03:26.720 --> 0:03:32.040 temporarily conquering the earth and they have this giant crab 0:03:32.600 --> 0:03:35.040 mech that also has a sand castle on top of 0:03:35.080 --> 0:03:37.720 it and these big claws for tearing things apart, and 0:03:37.760 --> 0:03:39.480 it is the mobile oppression Palace. 0:03:40.240 --> 0:03:42.840 Does it crawl front to back or side to side. 0:03:43.480 --> 0:03:46.400 A definite side to side movement as I recall, because 0:03:46.440 --> 0:03:48.360 of course Zoidberg does a lot of side to side 0:03:48.400 --> 0:03:51.960 movement from time to time, and the little crab dance. Yeah, 0:03:52.040 --> 0:03:54.040 so yeah, I'm excited to get into more crab topic. 0:03:54.040 --> 0:03:55.640 I was showing you this before him, but I even 0:03:55.680 --> 0:03:58.240 brought out my little crab mini here that I painted 0:03:58.240 --> 0:04:01.280 a while back. Crab folk from Dungeons and Dragons. 0:04:01.680 --> 0:04:04.440 Is this a playable people? Can you make crab folk characters? 0:04:05.280 --> 0:04:08.560 It's it's not one of like the given species that 0:04:08.640 --> 0:04:10.760 you can play, But I think ultimately you can play 0:04:10.760 --> 0:04:14.240 any species you want. There are rules for adapting it, 0:04:14.280 --> 0:04:17.240 and I think really we should all of all of 0:04:17.600 --> 0:04:19.840 all of my fellow Dungeons and Dragons players out there, 0:04:20.120 --> 0:04:22.320 go ahead and mix it up, and in your very 0:04:22.360 --> 0:04:25.920 next session insist that your dungeon master let you play 0:04:25.920 --> 0:04:31.120 a crab folk and insist on lateral movement only when 0:04:31.160 --> 0:04:32.160 you're on the battle map. 0:04:32.560 --> 0:04:36.200 Oh that's yeah, that's good. Uh okay, So are you 0:04:36.240 --> 0:04:38.800 good if I kick things off today with a discussion 0:04:39.000 --> 0:04:40.560 of claw fraud. 0:04:41.400 --> 0:04:44.800 Claw fraud sounds perfect for our crab bag series. Yes, 0:04:44.960 --> 0:04:45.440 let's do it. 0:04:45.520 --> 0:04:48.800 Yeah, okay. So this is a bit of funny biological 0:04:48.839 --> 0:04:51.760 research that I turned up when I was reading about 0:04:51.760 --> 0:04:56.719 our old friends, the Fiddler Crabs. So the term Fiddler 0:04:56.760 --> 0:04:59.960 crabs refers to any one of roughly one hundred species 0:05:00.400 --> 0:05:05.320 in the Brachiurin family, Occipoddy brachurins are the true crabs. 0:05:05.320 --> 0:05:08.279 So unlike some of the other examples we've been talking about, 0:05:08.320 --> 0:05:11.560 like you know, horseshoe crabs are not true crabs. In fact, 0:05:11.720 --> 0:05:13.640 they're not really crabs at all. They're just sort of 0:05:13.680 --> 0:05:19.080 crabs by common naming convention. These are true crabs. They're brachurins. 0:05:19.320 --> 0:05:25.320 The family again, is ossipodidy. Not all occipodity are fiddler crabs, 0:05:25.360 --> 0:05:29.559 but all fiddler crabs are occipodity, and they are known 0:05:29.760 --> 0:05:36.719 for their sexually dimorphic trait of extreme claw asymmetry. So 0:05:37.200 --> 0:05:39.880 even if you've never read much about fiddler crabs before, 0:05:40.120 --> 0:05:42.760 you've probably seen a picture of one of these at 0:05:42.760 --> 0:05:49.039 some point. Among male fiddler crabs, one claw is way 0:05:49.200 --> 0:05:51.960 bigger than the other. It's not just bigger, it is 0:05:52.000 --> 0:05:57.440 often absurdly comically bigger than the other. In extreme cases, 0:05:57.520 --> 0:06:00.600 the bigger claw is up to half of the male's 0:06:00.680 --> 0:06:04.640 total body weight. So for a rough analogy, imagine you 0:06:04.720 --> 0:06:07.560 know an average adult human male and one of his 0:06:07.680 --> 0:06:10.360 hands is normal, but the other hand is about four 0:06:10.360 --> 0:06:13.560 feet wide and weighs like eighty to one hundred pounds. 0:06:13.640 --> 0:06:18.160 Right right oversized and as we'll get into expensive. 0:06:18.760 --> 0:06:22.839 Yes, we explored the biology of the fiddler crab in 0:06:23.120 --> 0:06:24.960 a good bit of detail in a series we did 0:06:24.960 --> 0:06:27.960 a few years back called The Lesser of Two Crab Claws. 0:06:28.000 --> 0:06:30.560 I think that was the title we went with. Those 0:06:30.600 --> 0:06:34.279 episodes were generally about asymmetry in nature, but the male 0:06:34.320 --> 0:06:36.920 fiddler crab is one of the most amazing and bizarre 0:06:36.960 --> 0:06:39.360 examples in the animal kingdom, so it had a kind 0:06:39.400 --> 0:06:43.000 of central place in that series. I guess I'll start 0:06:43.000 --> 0:06:46.320 off by mentioning a few general observations about fiddler crabs 0:06:46.320 --> 0:06:49.640 before we get into the main claw research I wanted 0:06:49.640 --> 0:06:53.480 to talk about today. As I already mentioned, this huge 0:06:53.560 --> 0:06:57.760 asymmetrical claw is a sexually dimorphic trait, so you only 0:06:57.800 --> 0:07:01.960 see it in males. Female fiddler crabs have two smaller, 0:07:02.480 --> 0:07:08.120 matched regular size claws. Fiddler crabs are burrowing crabs, so 0:07:08.160 --> 0:07:11.080 they nest in these little tunnels that they dig in 0:07:11.240 --> 0:07:14.600 the mudflats or in the sandy intertidal areas where they live. 0:07:15.280 --> 0:07:19.520 And exactly how the burrows are used varies between species, 0:07:19.560 --> 0:07:24.160 but usually they're involved in say brooding, you know, laying 0:07:24.200 --> 0:07:29.440 eggs or reproduction in some way, and the quality of 0:07:29.800 --> 0:07:33.400 the burrow defended by a male contributes to the male's 0:07:33.400 --> 0:07:37.240 success in mating. Fiddler crabs have a very interesting way 0:07:37.320 --> 0:07:42.720 of eating. They use their front claws to shovel lumps 0:07:42.760 --> 0:07:46.800 of sand or mud into their mouthparts, and then their 0:07:46.840 --> 0:07:51.240 mouthparts rapidly dig around in this glob of sand or 0:07:51.360 --> 0:07:56.440 mud to find clean and extract any edible material like 0:07:56.560 --> 0:08:01.400 algae or bacteria or bits of dead other detrit us. 0:08:02.440 --> 0:08:06.880 This feeding process creates a very cute waste product. Actually, 0:08:06.920 --> 0:08:09.760 in a couple of sources I was seeing refer to 0:08:09.800 --> 0:08:13.360 this as pseudo feces. I don't know if this technically 0:08:13.480 --> 0:08:17.720 counts as pseudo feces to a zoologist or not, but 0:08:17.760 --> 0:08:22.240 they're little leftover pellets of mud or sand that pile 0:08:22.360 --> 0:08:26.040 up around the fiddler crab's burrow. These are the pellets 0:08:26.080 --> 0:08:29.360 the crab has spit out after extracting food from them, 0:08:29.800 --> 0:08:33.079 to the extent that they are called pseudo feces there. 0:08:33.440 --> 0:08:35.760 This would be because they're not real feces that you know, 0:08:35.800 --> 0:08:39.120 they haven't passed through the animal's whole digestive system. They're 0:08:39.240 --> 0:08:41.920 sort of what gets rejected by the bouncer at the 0:08:42.120 --> 0:08:45.400 entrance of the digestive system rather than what comes out 0:08:45.440 --> 0:08:48.120 at the end, though they do look like and are 0:08:48.120 --> 0:08:50.840 often mistaken for droppings, Hence they would be kind of 0:08:50.880 --> 0:08:53.040 false feces. Rob I've got a picture for you to 0:08:53.080 --> 0:08:54.680 look at in the outline here. I don't know why 0:08:54.720 --> 0:08:56.960 these these little diesel balls are cute to me. 0:08:57.600 --> 0:09:00.760 Yeah, yeah, And it really speaks to the metics nature 0:09:00.960 --> 0:09:04.880 of crab consumption in general, and we as humans we 0:09:04.960 --> 0:09:07.880 might think, oh, gross, you're producing pseudo feces. I think 0:09:07.920 --> 0:09:10.559 the crabs, if they were capable of judging us back, 0:09:10.600 --> 0:09:13.560 would say, it is disgusting that you are not producing 0:09:13.600 --> 0:09:16.720 pseudo feces. You're just saying let it all in, we'll 0:09:16.720 --> 0:09:19.440 work it all out in the truth feces at the end. 0:09:19.640 --> 0:09:22.440 They would probably say disgusting. Yeah. 0:09:22.480 --> 0:09:25.400 I love thinking about their feeding method and trying to 0:09:25.440 --> 0:09:27.880 imagine the human analogy. So it would be like if 0:09:27.880 --> 0:09:31.600 you ate by running around in the yard and scooping 0:09:31.640 --> 0:09:34.600 up handfuls of dirt from the ground, and then you 0:09:34.640 --> 0:09:37.400 put the clod of dirt in your mouth and you 0:09:37.440 --> 0:09:41.679 swish it around until you extract and swallow any earthworms, 0:09:41.920 --> 0:09:47.640 edible roots termite larva like old dorrito as somebody dropped. 0:09:48.280 --> 0:09:50.280 You get all that out of there, you swallow it, 0:09:50.600 --> 0:09:54.120 and then you spit out a tidy little clod of 0:09:54.280 --> 0:09:56.720 soil that is left over, and then you just keep 0:09:56.760 --> 0:09:59.120 doing this over and over all day until you have 0:09:59.160 --> 0:10:02.400 a little mountain of spherical dirt clods piled up around 0:10:02.400 --> 0:10:03.040 your front door. 0:10:03.760 --> 0:10:05.000 I love it. I celebrate it. 0:10:06.440 --> 0:10:09.960 So this actually, this feeding method actually brings us back 0:10:10.000 --> 0:10:13.360 to some interesting things about the claw asymmetry in male 0:10:13.400 --> 0:10:18.040 fiddler crabs. As you might imagine, sifting balls of sand 0:10:18.160 --> 0:10:22.440 and mud through your mouthparts is not the most efficient 0:10:22.480 --> 0:10:25.320 way to find high quality nutrition, so you have to 0:10:25.400 --> 0:10:28.199 do a lot of it. So eating mud is kind 0:10:28.200 --> 0:10:30.640 of a It's a job that requires long hours, it 0:10:31.080 --> 0:10:36.360 takes persistence, and for males it is even worse because 0:10:36.400 --> 0:10:40.240 it turns out that one giant monster claw is pretty 0:10:40.280 --> 0:10:44.080 much completely useless for feeding. So if you watch female 0:10:44.120 --> 0:10:48.520 fiddler crabs eat, they will rapidly shovel mud and sand 0:10:48.600 --> 0:10:53.000 into their mouthparts with both claws in a continuous back 0:10:53.040 --> 0:10:57.880 and forth cycling motion. But because males only have the 0:10:57.960 --> 0:11:01.800 one normal sized claw, their ability to feed themselves is 0:11:01.880 --> 0:11:04.560 basically cut in half. It's like I've just got my 0:11:04.640 --> 0:11:07.320 one good eaten hand and then I've got this big hand, 0:11:07.400 --> 0:11:08.840 but I can't really use it. 0:11:08.840 --> 0:11:10.720 It's like if you went to an Ethiopian restaurant with 0:11:10.760 --> 0:11:14.360 Freddy Krueger, Like, what's he gonna do? The claws just 0:11:14.360 --> 0:11:15.040 got a set there. 0:11:15.440 --> 0:11:17.560 Yeah, so yeah with the with the knives, you can't 0:11:17.559 --> 0:11:20.280 really scoop up with, you know, the delicious food. You've 0:11:20.280 --> 0:11:24.640 only got the one hand to use. So, because they 0:11:24.640 --> 0:11:27.160 only have the one claw that is useful for feeding, 0:11:27.360 --> 0:11:32.520 male fiddler crabs have much lower foraging efficiency than females. 0:11:32.800 --> 0:11:35.560 They might need to spend nearly twice as much time 0:11:35.720 --> 0:11:39.560 eating to extract the same number of calories, so that 0:11:39.679 --> 0:11:42.280 in itself is interesting. You might look at a male 0:11:42.320 --> 0:11:46.640 fiddler crab with this one giant superclaw and you think 0:11:46.760 --> 0:11:49.480 this is a mighty weapon. You know, it makes the 0:11:49.520 --> 0:11:53.040 male that wields it incredibly hardy and healthy and fit. 0:11:53.920 --> 0:11:58.120 And while a big claw might often be a sign 0:11:58.400 --> 0:12:03.280 of underlying fitness, is not the cause of underlying fitness. 0:12:03.320 --> 0:12:07.360 It mainly comes with downsides to the crab's ability to 0:12:07.520 --> 0:12:12.000 survive the daily struggle for food. So not only does 0:12:12.200 --> 0:12:15.520 the claw greatly hamper the mail crab's ability to eat. 0:12:16.240 --> 0:12:21.120 It hugely increases the mail crab's food energy needs. So 0:12:21.160 --> 0:12:23.760 you've got this big old claw. It's a heavy piece 0:12:23.800 --> 0:12:28.760 of tissue, so it increases the crab's based metabolism, and 0:12:28.960 --> 0:12:32.040 it also makes it more energetically expensive for the crab 0:12:32.120 --> 0:12:35.080 to move, to run around and move because it's carrying 0:12:35.160 --> 0:12:38.560 this thing. So you imagine if you had to live 0:12:38.600 --> 0:12:41.800 your life with an eighty pound suitcase surgically attached to 0:12:41.840 --> 0:12:44.040 your hand, that would kind of you would need to 0:12:44.080 --> 0:12:46.199 eat more food. It would just you know, cause a 0:12:46.240 --> 0:12:49.160 lot of trouble for everything else you needed to do well. 0:12:49.160 --> 0:12:53.640 It makes me think too of examples of humans who cultivate, 0:12:53.679 --> 0:12:58.520 say an extreme bodybuilder physique that then comes with its 0:12:58.520 --> 0:13:02.680 own drawbacks, including perhaps having to eat like multiple boiled 0:13:02.760 --> 0:13:03.520 chickens per day. 0:13:03.880 --> 0:13:06.240 Yeah, good thing. This is a funny thing. Actually, if 0:13:06.240 --> 0:13:10.360 you read about like serious bodybuilders, we're trying to maintain 0:13:10.480 --> 0:13:14.319 huge amounts of muscle mass. A hilarious problem they talk 0:13:14.400 --> 0:13:17.320 about is like difficulty eating as much as they need 0:13:17.320 --> 0:13:19.320 to eat. Is like, ah, I got to eat you know, 0:13:19.679 --> 0:13:22.240 fourteen chicken breasts today. I can't eat that much. 0:13:22.559 --> 0:13:25.000 Yeah. Yeah. You hear stories about like pro wrestlers on 0:13:25.040 --> 0:13:26.559 the road and trying to keep up with that kind 0:13:26.559 --> 0:13:28.040 of thing, and it's like, oh, I'm in you know, 0:13:28.120 --> 0:13:31.400 small town Minnesota, and I need to acquire this many 0:13:31.400 --> 0:13:33.319 boiled chickens at the local waffle house. 0:13:33.720 --> 0:13:39.520 Yeah. So anyway, you might think, well, okay, so this 0:13:39.640 --> 0:13:42.439 big crab claw, it comes at a metabolic cost. I 0:13:42.520 --> 0:13:44.920 understand that it's heavy, it's hard to move around, it 0:13:44.960 --> 0:13:49.000 increases your metabolism, but at least it's a big weapon 0:13:49.160 --> 0:13:52.280 and it provides a defense against predators. So you know, 0:13:52.440 --> 0:13:54.240 like something comes to eat you and you can use 0:13:54.280 --> 0:13:58.800 the big claw to fight back. That is not necessarily true. 0:13:58.880 --> 0:14:02.679 It might deter some predators, but research has found that 0:14:03.040 --> 0:14:07.079 birds like grackles, which prey on fiddler crabs, are actually 0:14:07.360 --> 0:14:11.680 more likely to target and attack males with big claws 0:14:11.840 --> 0:14:15.000 than they are to attack females or males with smaller claws. 0:14:15.360 --> 0:14:18.640 So a big claw means you're number one, easier for 0:14:18.679 --> 0:14:22.000 the predators to see, and also you are a more 0:14:22.080 --> 0:14:24.600 valuable prize because there's more meat inside you. 0:14:25.440 --> 0:14:28.400 Hmm yeah. Yeah, So the birds recognize the claw meat 0:14:28.480 --> 0:14:31.120 is good and the claw meat is big in these specimens. 0:14:31.400 --> 0:14:33.800 Yeah, and you're just you're easier to pick out. You know, 0:14:33.840 --> 0:14:36.440 the birds flying above hunting for crabs. You like it 0:14:36.520 --> 0:14:49.800 sees the one with waving the big claw around. So 0:14:49.960 --> 0:14:53.000 if one giant claw comes with all of these tremendous 0:14:53.080 --> 0:14:57.760 downsides to fitness, what is it for? It seems to 0:14:57.800 --> 0:15:02.400 serve a major purpose related to reproduction, and then possibly 0:15:02.440 --> 0:15:06.440 a couple of minor practical purposes. To start with the 0:15:06.480 --> 0:15:10.600 minor practical purposes, I've read that males sometimes use the 0:15:10.680 --> 0:15:13.880 large claw to kind of cover and shield the entrances 0:15:13.880 --> 0:15:17.120 of their burrows, so a large claw may provide extra 0:15:17.240 --> 0:15:21.560 defense in some situations there but by far the most 0:15:21.600 --> 0:15:25.359 widely recognized purpose of the large claw is in sexual 0:15:25.400 --> 0:15:31.840 competition and sexual signaling to appeal to female fiddler crabs 0:15:32.320 --> 0:15:36.800 and to intimidate and fight off rival males, especially in 0:15:37.320 --> 0:15:43.280 competition for access to burrows and the quality of burrows 0:15:43.400 --> 0:15:46.440 is in part what appeals to females who are looking 0:15:46.440 --> 0:15:50.640 to mate. So when it comes time for mating, male 0:15:50.680 --> 0:15:54.720 fiddler crabs engage in a ritualized behavior known as waving, 0:15:54.880 --> 0:15:58.480 where they stake out territory in front of their burrows 0:15:58.560 --> 0:16:00.800 and they wave their big claw up in the air 0:16:00.840 --> 0:16:04.000 for all to see. Each fiddler species has its own 0:16:04.040 --> 0:16:09.520 specific waving pattern, and this waving behavior serves to intimidate 0:16:09.600 --> 0:16:12.040 rival males and drive them away from the area of 0:16:12.120 --> 0:16:15.560 the crabs borough. A big claw so helps with this 0:16:15.640 --> 0:16:17.320 as well, you got a big claw, so it's like, 0:16:17.360 --> 0:16:19.400 oh wow, you know, don't want to mess with that guy. 0:16:20.360 --> 0:16:24.000 And as for appealing to females, the results are in 0:16:24.040 --> 0:16:27.560 and it turns out female fiddler crabs do like big claws, 0:16:27.640 --> 0:16:31.000 that's what they're into. Big claws are often taken as 0:16:31.040 --> 0:16:35.080 an honest signal of genetic fitness, for one thing, because 0:16:35.200 --> 0:16:37.880 they take a lot of energy to grow and sustain, 0:16:38.400 --> 0:16:42.080 so they are evidence that this crab must be eating well, 0:16:42.200 --> 0:16:45.640 it's doing well, it's probably a good mate. And then 0:16:45.920 --> 0:16:50.560 also crabs continue to grow throughout their lives, so that 0:16:50.680 --> 0:16:54.440 means that bigger crabs tend to be older crabs. So 0:16:54.600 --> 0:16:58.480 a bigger claw usually functions as a somewhat honest indication 0:16:58.960 --> 0:17:02.520 that a particular crab is a survivor across many seasons. 0:17:03.040 --> 0:17:04.680 All right, so some good genes there. 0:17:05.000 --> 0:17:08.920 But there is an exception to this honest signaling principle, 0:17:09.040 --> 0:17:11.080 and that's what got me interested in coming back to 0:17:11.119 --> 0:17:14.119 the fiddler crab today. So, as I said earlier, I 0:17:14.160 --> 0:17:17.040 want to talk about claw fraud, and this has to 0:17:17.080 --> 0:17:22.919 do with regenerated limbs, an interesting topic unto itself. My 0:17:23.000 --> 0:17:26.359 main source here is a Royal Society Biological Sciences paper 0:17:26.359 --> 0:17:29.400 from the year two thousand by Patricia Backwell and co 0:17:29.480 --> 0:17:35.120 authors called Dishonest Signaling in a Fiddler Crab. The authors 0:17:35.160 --> 0:17:38.640 of this paper start off by talking about how when 0:17:38.760 --> 0:17:42.639 animals exchange information with one another in situations in all 0:17:42.720 --> 0:17:46.280 kinds of situations like predator prey interactions, make choice and 0:17:46.400 --> 0:17:51.520 competition for resources, you would naturally expect to find some 0:17:53.320 --> 0:17:58.960 evolutionary attempts at dishonest communication. So like, if we're always 0:17:59.000 --> 0:18:01.840 going to compare shoe sizes to decide who gets to 0:18:01.880 --> 0:18:05.160 eat this animal carcass, we both found it would pay 0:18:05.320 --> 0:18:07.720 biologically for me to find a way to make my 0:18:07.840 --> 0:18:13.040 feet seem bigger than they actually are. On the other hand, 0:18:13.520 --> 0:18:17.760 there are some theories in biology that say, you know, 0:18:17.800 --> 0:18:22.399 you can't have too much cheating or dishonesty in information 0:18:22.520 --> 0:18:27.280 exchanges in nature, or the information exchange becomes unstable and 0:18:27.320 --> 0:18:29.199 it just like doesn't really work for this, Like if 0:18:29.240 --> 0:18:34.000 everybody's lying, then the signal just becomes unreliable and it's 0:18:34.040 --> 0:18:36.000 it's no longer useful biologically. 0:18:36.760 --> 0:18:37.640 Yeah, that makes sense. 0:18:38.080 --> 0:18:40.359 So the authors say, even though you would expect to 0:18:40.400 --> 0:18:44.480 find some animals trying to cheat at trying to lie 0:18:44.600 --> 0:18:48.480 at information exchange, they say that at the time of 0:18:48.520 --> 0:18:51.440 this study in the year two thousand, empirical research had 0:18:51.440 --> 0:18:56.440 not found many examples of cheating in sexually selected signals 0:18:56.480 --> 0:18:59.720 in nature. The author is right quote this is not 0:18:59.840 --> 0:19:03.320 so prizing since there are logistic and conceptual problems in 0:19:03.359 --> 0:19:08.159 demonstrating cheating. Cheats are designed to go unnoticed. Even if 0:19:08.200 --> 0:19:12.520 you identify an individual with a disproportionately large signal for 0:19:12.600 --> 0:19:16.520 its underlying quality, it is unclear how you can differentiate 0:19:16.600 --> 0:19:21.199 this from natural variation in the relationship between signal size 0:19:21.240 --> 0:19:26.520 and male quality. However, in the fiddler crab species that 0:19:26.560 --> 0:19:31.800 they call Uca and ulypis now known as Ostrica and Ulypus, 0:19:32.280 --> 0:19:35.560 they argue that it is possible to identify a clear 0:19:35.720 --> 0:19:40.680 example of a dishonest sexually selected signal, and it goes 0:19:40.720 --> 0:19:44.840 like this. When crabs lose a limb, they can often 0:19:45.119 --> 0:19:48.000 grow it back. You know, this is one of the 0:19:48.040 --> 0:19:50.520 advantages of being something like a crab. Mammals or not 0:19:50.680 --> 0:19:53.320 like this. We can regenerate some types of tissue, but 0:19:53.359 --> 0:19:55.560 if we lose a whole limb, it's gone. You know, 0:19:55.720 --> 0:20:00.760 it's not growing back. But crabs frequently lose limp due 0:20:00.760 --> 0:20:04.679 to attacks by predators or fights with rival males, and 0:20:04.960 --> 0:20:09.680 grow new limbs in their place. So, according to the authors, 0:20:09.760 --> 0:20:13.600 when most filler crab species lose a claw, they regenerate 0:20:13.680 --> 0:20:16.280 one that is pretty similar to the original in form, 0:20:16.800 --> 0:20:21.520 But in a few species, including Ostrica and Alypus quote, 0:20:21.640 --> 0:20:26.439 males instead regenerate claws that are lighter, more slender, and 0:20:26.640 --> 0:20:31.680 less robust, which they call leptokilus than the original claus, 0:20:31.920 --> 0:20:36.160 which are called brachikilus. So again, Brachychelus means it's the 0:20:36.200 --> 0:20:40.960 strong claw that the crab had originally. The leptokilis claw 0:20:41.040 --> 0:20:47.360 is the weaker, less muscled regenerated claw, they continue quote. 0:20:47.440 --> 0:20:51.480 For a given claw length, leptokilis claws have a smaller 0:20:51.560 --> 0:20:55.280 muscle mass than do brachykilis claws, and they may thus 0:20:55.359 --> 0:21:00.280 be weaker and less effective weapons. So these regenera did 0:21:00.320 --> 0:21:04.080 leptokilis clause match the original big claw in some ways. 0:21:04.119 --> 0:21:08.280 For example, they sometimes match it in length, but are 0:21:08.520 --> 0:21:12.800 reduced in terms of strength and internal muscle mass. So 0:21:12.840 --> 0:21:16.040 they regrow a claw that looks big, but it is 0:21:16.760 --> 0:21:20.560 literally partially hollow, like, it does have muscles inside, but 0:21:20.640 --> 0:21:23.840 it's got less muscle mass inside than the original claw did. 0:21:24.280 --> 0:21:27.000 So if it actually came down to a real fight, 0:21:27.200 --> 0:21:31.880 this regenerated claw would usually lose. And the authors did 0:21:31.920 --> 0:21:34.960 test this out. They staged some fiddler crab fights to 0:21:35.000 --> 0:21:38.240 make sure, and they indeed found that the Leptokilis males 0:21:38.280 --> 0:21:42.199 were significantly worse at fighting and lost in battle against 0:21:42.240 --> 0:21:43.440 Brackykilis males. 0:21:43.920 --> 0:21:49.240 So it's kind of like imagine a bodybuilder who has 0:21:49.320 --> 0:21:52.879 not maintained the same physique that they previously had, but 0:21:52.960 --> 0:21:57.200 then for their dating profile photo they use some alchemy 0:21:57.440 --> 0:22:02.840 of dishonest photoshoppery or generative AI to make their current 0:22:02.880 --> 0:22:05.760 physique look like their previous physique. So on one level, 0:22:05.760 --> 0:22:08.399 they're saying this is accurate because this is what I 0:22:08.440 --> 0:22:12.680 once had, but in reality it is not packed the 0:22:12.720 --> 0:22:14.840 same strength and it is there is a dishonesty to 0:22:14.920 --> 0:22:15.399 the signal. 0:22:15.720 --> 0:22:18.440 Right, yeah, maybe they're like stuffing fake muscles under their 0:22:18.440 --> 0:22:22.560 shirt or something so like, look, I look pretty big, 0:22:23.240 --> 0:22:25.400 but I don't I can't actually lift as much weight 0:22:25.440 --> 0:22:26.639 as I as I once could. 0:22:27.000 --> 0:22:27.200 Right. 0:22:28.080 --> 0:22:33.080 However, crab competition often does not come down to real fighting, 0:22:33.640 --> 0:22:38.600 and intimidation displays can drive away rivals before a fight begins. 0:22:39.200 --> 0:22:41.120 We've talked about this a lot on the show before. 0:22:41.200 --> 0:22:43.639 This is the case with tons of animal species that 0:22:43.720 --> 0:22:48.600 have aggressive competition for mates. It is in everybody's interest 0:22:48.720 --> 0:22:51.840 to avoid a fight whenever possible, because even if you 0:22:52.080 --> 0:22:57.400 win the fight, actually fighting cost energy, it is risky 0:22:57.560 --> 0:23:00.480 and could lead to injuries which reduce fitness and could 0:23:00.560 --> 0:23:03.960 later kill you. So fighting is just something you want 0:23:04.000 --> 0:23:06.479 to avoid, even if you're probably going to win. So 0:23:06.520 --> 0:23:10.320 it's better for everybody involved if the competing males have 0:23:10.400 --> 0:23:14.159 a way of sizing each other up and deciding who 0:23:14.200 --> 0:23:17.720 would probably win the fight, allowing them to skip the 0:23:17.760 --> 0:23:21.280 fight altogether, so you know the likely loser, they have 0:23:21.400 --> 0:23:23.800 some kind of piece of evidence, you know, maybe horn 0:23:23.960 --> 0:23:27.240 size or in the case of crabs, probably claw size, 0:23:27.600 --> 0:23:30.840 They see the evidence of the likely winner's fitness, and 0:23:30.960 --> 0:23:36.320 the likely loser just retreats before combat starts. Previous research 0:23:36.400 --> 0:23:39.600 in fiddler crabs has found that the main criterion that 0:23:39.680 --> 0:23:43.679 males use to assess each other's fighting ability is big 0:23:43.800 --> 0:23:48.440 claw length, which is not necessarily reduced to the same 0:23:48.480 --> 0:23:51.360 degree in the regenerated claw. The way that other measures 0:23:51.440 --> 0:23:56.040 like strength and internal muscle mass are also appeal to 0:23:56.160 --> 0:24:00.760 females seems related to assessments of claw length. Females of 0:24:00.760 --> 0:24:03.520 this fiddler crab species are looking for males with a 0:24:03.720 --> 0:24:08.919 long claw, so how does this relate to regeneration. The 0:24:08.960 --> 0:24:12.439 authors of the paper set out to investigate whether in 0:24:12.480 --> 0:24:17.880 this species the weaker, partially hollow regenerated clause would serve 0:24:18.000 --> 0:24:22.840 as a dishonest but effective signal to win mating opportunities. 0:24:23.119 --> 0:24:28.080 Could males with these weaker claws bluff their way into 0:24:28.240 --> 0:24:33.000 competitive victory, control of burrows and into sects And the 0:24:33.040 --> 0:24:37.480 answer is basically yes, the bluffing works. So one way 0:24:37.520 --> 0:24:41.600 of assessing the question is if males with strong original 0:24:41.640 --> 0:24:45.719 clause usually win fights against males with the regenerated clause, 0:24:46.520 --> 0:24:50.560 do the males with strong original clause seek out males 0:24:50.600 --> 0:24:54.560 with regenerated clause to dominate in bully or are they 0:24:54.760 --> 0:24:59.080