Posts Tagged ‘cetaceans’
a bonobo world 62: more species, and then back to the point of it all
male aggression – it’s everywhere
Canto: Okay, let’s look at other cetaceans. There are 89 species, so we can’t cover them all. There are toothed and baleen types, but all dolphins and porpoises are toothed. There are river dolphins and oceanic dolphins, and in terms of size, cetaceans range widely, so that we have names like northern right whale dolphin, southern right whale dolphin, false killer whale, pygmy killer whale and various types of humpback dolphin as well the humpback whale. So it might be that they’re as culturally various as humans. I’ll limit my examination, then, to four or five well-known species, with no pretence that any of them typify the whole.
Jacinta: Yes, when we talked about dolphins before, it was the common bottle-nose dolphin, right?
Canto: Essentially yes, and I’ll pick some of the best known cetaceans, avoiding those most endangered, because they’ll probably be the least studied in the wild. First, the humpback whale, which is a rorqual. Rorquals represent the largest group of baleen whales, and of course humpback whales are an iconic and fairly well researched species, as whales go. And one immediately interesting fact is that the females are on average slightly larger than the males.
Jacinta: Size usually matters.
Canto: And they can live up to 100 years. But let’s talk about sex, or courtship as the Wikipedia article on humpbacks charmingly describes it. You’ll be happy to know that humpbacks are polyandrous – that’s to say, females mate with many males during their breeding season. This is generally seen as the opposite of polygyny – one male mating with many females. In fact polyandry is more often seen in insects than in any other life forms. Humpbacks have even been known to have it off with other species. Wikipedia calls it hybridisation. There’s apparently a humpback-blue whale hybrid out there.
Jacinta: I assure you that when females rule the world – in nevereverland – any attempt to employ ‘euphemisms’ for fucking will be punished by instant castration.
Canto: Well you’ll also be amused to know that males fight over females.
Jacinta: How very unsurprising. But at least they sing, which almost compensates.
Canto: Yes, males and females vocalise, but the long, complex and very loud songs are produced by males. It’s believed that they help to produce estrus in the females.
Jacinta: The correct term is fuck-readiness.
Canto: In fact, researchers only think that because only males produce the complex songs. It’s a reasonable inference, but it could be wrong. Some think that the songs might be used to prove the male’s virility to the female, to make him more attractive. This supposedly happens with birdsong too.
Jacinta: Trying to think of human equivalents. Rocks in the jocks?
Canto: Oh no, too chafing. Being a good cook helps, I’ve found. But what with the obesity epidemic, that’s a balancing act. Anyway, those humpback boys put a lot of energy into their songs, which sometimes last for over 24 hours. Animals of one population, which can be very large, sing the same culturally transmitted song, which slowly changes over time. All interesting, but probably not much of a model for us. I can barely swim.
Jacinta: Well yes, it’s hardly sing or swim for us, but let’s turn to other cetaceans. What about blue whales?
Canto: Well it’s interesting to find that most websites don’t even mention their social life – it’s all about their ginormity, their big hearts, and their feeding and digestion. It took me a while to discover that they’re solitary creatures, which I suppose is common sense. Hard to imagine a superpod of blue whales out in search of a collective meal. They do sometimes gather in small groups, presumably for sex, and of course there’s a mother-calf relationship until maturity. As with humpbacks, the females are a bit larger than the males. What would that be about?
Jacinta: Well, some researchers (see link below) have discovered that male humpbacks favour the largest females, so there’s presumably sexual selection going on. And of course, they fight over the biggest females.
Canto: Well you can’t blame them for being macho. It be nature, and what do please gods.
Jacinta: Oh no, let’s not go there. Anyway, the largest females produce the largest and presumably healthiest offspring. They also found that the older females make the best mothers, which I’m sure is generally the case in humans too, mutatis mutandis.
Canto: So in conclusion, these mostly solitary creatures, whether they be cetaceans or primates, can’t be said to be patriarchal or matriarchal, but the males still manage to be more violent, or at least more cross with each other, than the females.
Jacinta: But it doesn’t have to be that way, hence bonobos.
Canto: Yes, but that makes me think. I hear that bonobos use sex to ‘ease tensions’, among other things. Tensions hints of violence, or at least anger. I’m wondering if that anger comes mostly from the males, and if the use of sex to dissipate that anger comes mostly from the females.
Jacinta: That’s a good question. There’s a site, linked below, which sort of looks at that question. It cites research showing that female bonobos gang up on male aggressors. The researchers found an absence of female-on-female aggression (perhaps less so than in the human world). According to this site – which may not be wholly reliable, as it’s really about humans and nightlife behaviour – female bonobos bond in small groups for the specific purpose of keeping males in line. How do they know that? They might be arguing from girl nightlife behaviour. I mean, who’s zoomin who?
Canto: The general point though is that among bonobos, males are more aggressive than females. Which isn’t to say that females can’t be aggressive, and not just in a defensive way.
Jacinta: This website also mentions something which is the general point of all our conversations on bonobos and humans and sex and well-being. It’s worth quoting in full:
Anthropological data analyzed by neuropsychologist James Prescott suggests societies that are more sexually open are also less likely to be violent. The key to understanding this correlation, however, is that it’s the society as a whole that is more sexually open and not just a small percentage of individuals.
Canto: That’s a good quote to get us back to humans. We need to look at this matter more closely next time. And the next and the next.
References
https://en.wikipedia.org/wiki/List_of_cetaceans
https://www.nbcnews.com/id/wbna29187881
a bonobo world 61 or so: some more species
Gibbons – beautiful and imperilled
Canto: So if only we could quicken the modern world, which is so fast leaving behind the benefits of brute strength and embracing the strength of collaborative smarts… Well, maybe not that fast… We’d experience ourselves the loving fruits of bonobo-humanism.
Jacinta: Yeah, too bad. So let’s look more closely at other female dominated species, like elephants. They tend to value experience, so their family units have a female head.
Canto: Except that, they split into female and male groups, don’t they?
Jacinta: Well, they have these female family units, ranging from 3 to 25 members. The males presumably have their groupings, but sometimes they come together to form large herds or herd aggregations – huge numbers. Males can also be solitary, which virtually never happens with females. Of course it’s the females who raise the young, but there can be a lot of group solidarity.
Canto: It seems that the grouping changes more or less perpetually, seasonally, daily, hourly.
Jacinta: Yes, that’s a fission-fusion society, common among primates too – such as Homo sapiens at work, school, uni etc. But over time, the matriarch becomes more important, and presides over a wider network as she gets older. They play follow the leader as she has accumulated knowledge on the best watering holes, the paths of least resistance.
Canto: So elephants have it all worked out. What about those orangutans, what’s going on there?
Jacinta: Well apart from imminent extinction, there’s little to say. They’re solitary, though the Sumatran orang-utans are a little less so than those in Borneo, due to more food being available. The males exhibit hostility to each other and try to avoid each other, though they’re not territorial. They only hang out with females until they get their end away, and the females raise the offspring until they’re old enough to go solo.
Canto: So I wonder why the males are so much bigger than the females?
Jacinta: Yes they can be well over twice the size of the females. I haven’t found any explanation for it. They don’t have a harem of females to prove their rugged manliness. Apparently those big cheek pads help to attract the girls, but their huge bulk seems a bit superfluous.
Canto: Maybe it’s like whales – they grow big because they can. But then, the more you grow, the more you have to eat, presumably. A bit of a mug’s game.
Jacinta: Tell that to the elephants. Or those old ginorosauruses. Basically, if you’re as huge as an elephant, who else is going to attack you or compete with you? Apart from blokes with guns. But we were talking about sex. Or at least gender. Gorillas are proving a lot more complex than originally thought in their social structure – quite multilayered, not quite the chest-beating alpha male and his harem, more like human extended families. Matriarchies within patriarchies perhaps.
Canto: And what about gibbons – just to round out the primates. I know nothing about them.
Jacinta: Well, apparently these South-East Asian apes are monogamous, unlike other primates (except maybe humans, but I’m reluctant to rule on that). In fact only 3% of mammals are monogamous, according to a fact sheet I found (linked below). So that makes for family groups of two to six, just like our nuclear family, unless you’re a Catholic. Gibbons are considered as ‘lesser apes’, family Hylobatidae, unlike we great apes, family Hominidae. Physically, they’re by far the smallest of the apes, depending on particular species, but weighing at most about 12 kgs. These small family groups defend their territory aggressively – none of this fission-fusion stuff. They’re quite good at bipedalism, and present a good model for bipedalism in humans, but they’re also fantastically acrobatic tree-swingers, with the longest arms in relation to their bodies of any of the primates. They also have a nice healthy herbivorous diet.
Canto: They sound like a good human model all-round, and maybe a model for gender equality?
Jacinta: Well, yes, but I do prefer female supremacy. Gibbons are apparently the least studied of all the apes. There are 12 species of them, but many species are very near extinction, a fact not much known by the general public. Orangutans clearly get much more attention.
Canto: Okay so let’s look further afield – before coming back to human cultures to see if there are any matriarchies worth emulating. What more do we know about dolphins and other cetaceans?
Jacinta: Well, as you know dolphins live together in pods of up to 30, though sometimes where there’s an abundant food source they can form massive superpods of over 1000. And as we’ve learned, they engage in sex for fun.
Canto: I suppose also they could form superpods in the face of predators, like schools of fish.
Jacinta: Yes, possibly, though they wouldn’t have too many predators, unlike small fish. Interestingly these superpods can be made up of different cetacean species, so this would obviously benefit the smaller species. And individual dolphins can switch from pod to pod quite freely. Something like fission-fusion, but with greater flexibility. Researchers find this flexibility a sign of high intelligence.
Canto: Ahh, so that accounts for the stupidity of conservatives.
Jacinta: Some dolphin species are a bit more hierarchical than others, and you can see plenty of bite marks on bottlenose dolphins, evidence of fights for dominance.
Canto: And I recall a big hubbub a few years ago when those delightful creatures were discovered torturing and killing some of their own. But then, they are male-dominated, aren’t they?
Jacinta: They are, sadly. Males of all species are largely arseholes (well, not literally). But they certainly engage in a lot of play, I mean dolphins generally. Maybe they’ll evolve one day into a higher form of female-dominated life, but I doubt it. They’ll have to realise how fucked-up they are as a species to do that, like some humans have realised – but not enough.
Canto: Okay, so dolphins are out as a model. What about other cetaceans? I somehow suspect that orcas won’t fit the bill.
Jacinta: Next time. And we’ll look at some human models, if we can find them.
References
https://www.independent.co.uk/voices/comment/six-facts-about-elephant-families-9015298.html
https://seaworld.org/animals/all-about/orangutans/behavior/
http://www.gibbons.de/main2/08teachtext/factgibbons/gibbonfact.html
how did blue whales get so big?
a baby blue
Cetaceans came into being when a group of mammals left the land some 55 million years ago, to return to the oceans (creatures first left the oceans for the land some 375 million years ago). The closest land species to whales are the artiodactyls or even-toed ungulates, a large group which includes sheep, goats, cattle, giraffes, camels, llamas, pigs and deer, but another artiodactyl species, the hippo, is most closely related to cetaceans. But, of course, since returning to the oceans, the creatures who finally evolved into cetaceans were able to become ‘super-sized’. The blue whale, likely the largest creature ever to exist on this planet, can tip the scales at over 170 tonnes, and can measure well over 30 metres. The largest dinosaur unearthed so far, Argentinosaurus, a titanosaur sauropod (that’s to say a really effing big dino – named for the ancient mythical titans – with a long neck and tail and a comparatively small head, like the brontosaurus of my youth, now sadly out of favour) weighed around 75 tonnes.
Cetaceans have managed to fill a diverse range of ecological niches. Some of the best-known are the blue whale (a filter-feeding baleen whale or rorqual), the orca (often called a killer whale, but in fact it’s the largest species of dolphin) and the sperm whale, the largest of the toothed whales. Their success, and especially that of rorquals, may owe much to the abundance of krill in the oceans. Some researchers have also attributed the great growth spurt of the blue whale over the past few million years to this ready supply of food. It’s been estimated that, in the southern oceans alone, the krill biomass may be as much as 500 million tonnes, twice the biomass of humans on the planet.
Of course the behaviour of humans has had a massive impact on blue whales, especially in the century of so before 1966, when they came under international protection. The Antarctic population before whaling has been estimated at between 200,000 and 300,000, possibly as much as ten times the current population, though numbers are difficult to determine. You can’t help but wonder what would have happened to whale – and krill – populations without human depredations.
Researchers and analysts point to two main and perhaps complementary reasons for whale ginormity; the abundance of food, and the lack of restraint on size in an oceanic medium. I’ll focus on the second reason first. This presumably has to do with physics, my weakest subject, so I want to get it straight in my mind.
Allometry is the study of the size of organisms and what it means in terms of growth, behaviour, environment and other constraints and factors. Allometry helps explain how a large oxygen-breathing mammal can survive in and transport itself through its chosen medium. Whales are ‘neutrally buoyant’ – that’s to say, their body’s density is equal to the density of the water around them. This means that they don’t have to expend the energy that land animals have to in counteracting the effects of gravity – scuba divers have to learn the correct breathing underwater to achieve this neutral buoyancy. Every step we landlubbers take involves a lifting up of our bodies against the gravitational force pinning us to the earth. The endless gentle push of gravity is what makes us wrinkle and sag over our lifetime. Okay, let’s not think about that anymore. Locomotion in the water has much to do with allometric scaling, because the rate of oxygen consumption per gram body size decreases consistently with increasing body size. Other factors include shape and type of movement, which influence the laminar or turbulent flow around the organism. All of this is very complicated and can be worked out with equations – the Reynolds equation, which relates turbulence to velocity, being of prime importance, though hard to work out in nature, especially with cetaceans, who seem to break all the rules. That’s to say, there’s much about their physiology and how it’s adapted to water that we still don’t know.
Of course, aquatic mammals have to pump blood around their bodies and get air into their lungs just like land mammals. Interestingly, mammals have much the same heart-body mass ratio, whether they’re mice or elephants, land or aquatic. That of course means that the blue whale has the biggest heart of any mammal, and that also goes for a number of other organs. Scaling is much the same, for example, for lungs, and for lung capacity, and for blood, which represents around 5.5% of body mass. So, for mammals of similar form, larger ones can travel more quickly, because it requires the same expenditure of energy to move a body length. The large body length of a blue whale enables it to move great distances in search of food or for other purposes at less metabolic expense. It also enables them to dive for much longer than other cetaceans. Whales have a lower heart rate and can carry more oxygen through their bloodstream than smaller marine mammals. These are just some of the advantages of size in the oceans.
Of course, greater mass requires greater volumes of food to sustain it, but krill seems to have provided just about all a blue whale needs in that department, though it’s also partial to a class of small crustaceans called copepods, and it’s happy, too, to consume any other stray crustaceans and little fishes it catches up in its lunge dives through the krill – described recently as ‘the largest biomechenical event on earth’. Its feeding system and technique is adapted to these small but vastly numerous life forms. For all its size, a blue whale’s throat opening won’t allow it to swallow anything larger than a beach ball, yet it can eat up to 40 million krill a day. It’s jawline is huge, extending over halfway down its body, and the jaws can open to almost a ninety degree angle during lunge diving, allowing it to scoop up about 100 tonnes of krill-infested water in about ten seconds. The water is then squeezed out through the baleen with the help of its ventral pouch and massive tongue.
So it’s understandable why the blue whale has grown to this size, which raises the question – has it ended its growth spurt? There’s a bit of an argument going on about this. Obviously the present moment is but a snapshot, and we can never be certain about where evolution is heading, but often growth spurts in species occur at a rapid clip, and then things stabilize. The blue whales are relatively recent, judged as having split from an ancestor at around 10-15 million years ago, but it may be that they grew to their present size quickly after the split. We have no way of knowing as yet, unless we find a massive blue whale fossil dating back more than 10 million years, which is unlikely. However, other ways of knowing might crop up. There’s also an argument that these rorquals have reached their limit due to feeding limitations and oxygen supply limitations. Lots of interesting research questions to ponder over.