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Posts Tagged animal behaviour

‘slow life’ – corals and anemones strut their stuff Alison Campbell Mar 29

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When I was a kid we used to go to the beaches of the Mahia peninsula most weekends. (Well, memory says 'most weekends' – it might not have been that often!). Sometimes we'd stop at the sweeping sandy shores of Blue Bay, but on other days we'd go round to the exposed rocky coast & spend happy hours messing around in the rock pools. I used to love floating my fingers past the sea anemones & feeling the tiny tugs as we touched (at the time, of course, I had no idea that those tiny tugs were the anemones discharging nematocysts into my fingers!) And to me it seemed that these intriguing little animals, which retracted into blobs of jelly when touched less gently, didn't really seem to do much.

Similarly corals – when we've snorkelled around corals I've been amazed by the forms they take and – in living corals – by their colours. But it's hard to see much actually happening.

But tonight a friend of mine posted this video – "Slow Life" – on their Facebook page. It's gorgeous, visually stunning – and it shows the hidden life of cnidarians in glorious technicolour. Best on the big screen, I think; I'm looking forward to showing it to my first-year class next week.

Enjoy!

it’s not all fun & games being a crocodile, you know Alison Campbell Mar 09

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Crocodiles (& their relatives, alligators) are generally viewed as top predators. They're 'ambush' hunters1, lunging up out of the water to snatch at their prey at the last moment.

But sometimes, they come off second-best. Check out this video on the National Geographic site, of a jaguar stalking, catching, & killing a caiman.

And how about these images of a rather large boa chowing down on a metre-long crocodile? Or an otter, eating a juvenile alligator?  Yep, it's not all fun & games being a crocodile.

 

1 Having said that, when I was writing this post I came across the intriguing suggestion that some crocodilians use sticks to lure birds within lunging distance ie that they use tools. They've been observed doing this only during the birds' breeding season, when their feathery cousins2 are looking around for sticks to use in nest-building.

2 Taxonomically speaking, crocs and birds are both archosaurs. Early crocodilians – the pseudosuchians – were a predatory force to be reckoned with & it's possible that the pseudosuchians' demise, in the mass extinction that marked the end of the Triassic, was a factor that opened things up for the expansion of the dinosaur lineages.

of whale poo, wolves, and spiny s*x Alison Campbell Feb 20

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Whales – competing with us for food, or helping to sustain the phytoplankton production on which most life in the oceans depends? The story and video at this link make a good case for the latter.

Then there’s the wolves – their return to Yellowstone Park in the US has led to a whole cascade of environmental changes: changes that are very much for the better. Because the wolves keep the elk population moving around & to some degree under control in terms of population size, the vegetation has had a chance to recover from overgrazing. Forest regrowth along the riverbanks has stabilised those banks and contributed to an improvement in water quality. Beaver populations have bounced back & their activity has further altered the landscape in ways that have seen other species return or recover. The wolves have benefited the park’s ecosystem in ways that nobody had predicted.

As for the final topic, well… I have occasionally been asked by much younger, smaller persons how hedgehogs “do it” (the answer being, “carefully!”). In fact Nanny Ogg had a hum’rous song on that very topic. Brian Switek discusses the issue as it might relate to stegasaurs in My Beloved Brontosaurus. And then there are porcupines, animals for whom it seems all coitus must be consensual (unlike ducks, bedbugs, & dolphins, to name just three). Because anything else really wouldn’t work…

selecting for maladaptive behaviour Alison Campbell Dec 13

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One of the questions that often comes up in my first-year bio classes relates to natural selection and human evolution. Does the fact that modern medical science keeps alive people who in previous centuries might have died, mean that we’re countering the effects of natural selection? As you can imagine, this generates quite a lot of interesting discussion that spans ethical issues as well as the obvious biological ones.

Next year I think I’ll give the class a new paper to read: one that examines such a question in the context of the Chatham Island black robins (Petroica traversi) (Massaro et al, 2013).

As many New Zealand biology students may know, by 1980 the breeding population of this little bird was reduced to a single pair, in a total population of seven. Things were not looking good, but dedicated conservation workers – led by the late Don Merton (there’s a lovely obituary for him here) – managed to turn things around by careful management of the population, including fostering the robin’s first clutches under another species (thus inducing the robins to lay again), and translocating the small population from Little Mangere Island to the better habitat on Mangere Island. However, it seems that at the same time, the conservationists were also unwittingly selecting for a distinctly maladaptive behaviour – that of laying eggs that were left teetering on the very brim of the nest.

After that initial bottleneck event the population slowly started to recover. However, the researchers working with them noticed that in 1984 one of the five breeding females laid a sinlge egg were laid at the edge of her nest, with more females following suit in subsequent years. Left alone the eggs didn’t hatch, mainly because they weren’t incubated (although I suspect some could simply fall off the edge). The obvious thing to do was to reposition the eggs in the nest, & this resulted in an increased in chicks hatched & subsequently fledged. However, Massaro & her colleagues report that by 1989 18 of the 35 females (51%) were ‘edge-layers’, a behaviour that would leave the population completely reliant on human intervention if edge-laying continued to spread.

The research team suspected that this was an example of inherited rather than learned behaviour, and hypothesised that

[if] rim-laying [had] a genetic basis, and its spread [had] been facilitated by human intervention through egg repositioning, the frequency of this trait would be predicted to decrease following cessation of intervention.
Conservation workers stopped moving rim eggs in 1990, which then meant that the researchers could subsequently compare data sets:
we therefore compared egg-laying data from three years before cessation of repositioning (1987–89) with a three year period almost two decades after management stopped (2007–09)

and found that the number of rim eggs being laid decreased significantly between those two periods. They next looked at the many years’ worth of data to see if the ‘rim-laying’ behaviour had any effect on individuals’ evolutionary fitness, and discovered that

[when] rim eggs were not repositioned, females that laid rim eggs had significantly reduced clutch sizes (i.e. number of eggs laid inside nests that were incubated), and decreased hatching and breeding success compared to normal-laying females, demonstrating that rim laying substantially reduces fitness.
The final step was to confirm that this maladaptive behaviour did have a genetic underpinning. This part of the study was aided by the fact that there’s an extensive genetic pedigree available for this closely-studied species. Examining that pedigree, Massaro & her co-workers found that a) the behaviour first showed up in the grand-daughters of the ‘founding’ female, ‘Old Blue’; and b) that the population was highly inbred. A detailed analysis of the pedigree led them to determine that the rim-laying trait was an autosomal dominant trait that’s inherited in a Mendelian manner (ie no evidence of sex-linkage). Their final message:
This episode yields an important lesson for conservation biology: fixation of maladaptive traits could render small threatened populations completely dependent on humans for reproduction, irreversibly compromising the long term viability of populations humanity seeks to conserve.

 

You’ll also find information on the study here on the University of Canterbury website.

Massaro M., Sainudiin, R., Merton, D., Briskie JV, Poole, AM, Hale ML (2013) Human-Assisted Spread of a Maladaptive Behavior in a Critically Endangered Bird. PLoS ONE 8(12): e79066. doi: 10.1371/journal.pone.0079066

 

why did the pigeon cross the road? Alison Campbell Nov 19

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if I lived in Hawkes Bay I’d be keen to attend this Royal Society public lecture, & I’ll certainly be watching the video, which will be available after. It looks like being of interest & value to senior Biology teachers.

The ninth lecture in the 10X10 series

Why did the pigeon cross the road?

Dr Claire Postlethwaite

Napier | 7.30 Tuesday 19 November | Hawke’s Bay Holt Planetarium | View Livestream

In this lecture, Dr Claire Postlethwaite  (University of Auckland) will talk about using mathematical models to understand animal behaviour, using examples from homing pigeons,  possums, bees and electric fish.

The lecture is being livestreamed courtesy of i-film NZ Science. You can watch the lecture live or watch it afterwards. You can also skip back and see earlier parts of the talk while it is livestreaming. 

Visit our website for full details of the 10X10 Lecture Series, including audio and video recordings of previous speakers in the series.
View Livestream

 

The lecture is free and open to the general public. Enquiries: 04 472 7421 or 

 

a creeping assassin Alison Campbell Nov 04

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The daughter & her friends play Assassin’s Creed from time to time. This little arachnid would fit right in:

Photo: Jeremy Miller

For this is an assassin spider, one of a number of species (in the superfamily Palpiamanoidea) that prey on other spiders.

The assassin spiders have a long history: a combination of fossil & DNA evidence suggests that they go to before the supercontinent Gondwana began to break up under the slow but irresistable influence of plate tectonics. While there’s one fossil found in what’s now the northern hemisphere, all living species are found south of the equator, in Madagascar, South Africa, and Australia.

These strange little creatures are only a couple of millimetres long, but have a set of adaptations that allow them to strike their prey from a (reasonably!) safe distance. Their fang-tipped jaws are enormous – in the image above, the jaws holding the spider’s meal are about the length of the animal’s abdomen. The long ‘neck’ is an extension of the cephalothorax – the first of the 2 major sections of a spider’s body (the other is the abdomen, or opisthoma). The combination of neck & jaws means an assassin spider can impale another spider before the latter is within range to strike back. That’s after they’ve found their prospective dinner by following lines of thread it’s left behind, using their very long forelegs (which may also be used to lure the prey closer.

Which is probably quite enough for those of you who aren’t fond of spiders, not even itsy little 2mm-long spiders. But for those who want to find out more, try this video:

a beautiful nightmare Alison Campbell Sep 10

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A few weeks back I briefly mentioned the ‘bobbit worm’ – a rather large polychaete worm of scary appearance (a friend said ‘nightmarish’ was closer to the mark) and predatory habits. I’ve noticed on Facebook how interest in any particular subject seems to come in waves, and so it is with this creature.

For via FB I’ve come to Matt Simon’s interesting article – with Jenny Huang’s rather lovely photo – on wiredscience.

File:Eunice aphroditois.jpg

Image by Jenny Huang,via Wikimedia

A beautiful nightmare, then.

Apparently there’s not a lot known about them in the wild, but these worms can be a right pain in the proverbial for aquarium keepers: bring in some coral for your tropical marine tank, & it’s possible there’s a little bobbit worm hiding in there, ready to come out & pick off your fish when it’s feeling peckish. And growing bigger… up to 3 metres or more in length.

It’s possible that, like other similar polychaetes, bobbit worms reproduce in a distinctly odd manner: at certain times of year the rear part of each worms body, packed with gametes, breaks off and swims upwards to the surface in a massive, mass mating swarm. Which leaves Simon with the opportunity for a truly excellent punch-line for his story:

Hate to leave you with the image of a beautiful tropical ocean swarming with sex-crazed 10-foot-long worms with hair-trigger jaws, but that’s totally happening now.

"the only memory of the bee is a painting by a dying flower" Alison Campbell Sep 09

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The image below is of the bee orchid, Ophrys apifera. I know I’m ‘seeing’ something – the ‘face’ – that isn’t really there (an example of pareidolia), but still, that’s one happy-looking flower!

File:Ophrys apifera (flower).jpg

Image courtesy of Hans Hillewaert, from wikimedia.

Actually, the flower looks quite a bit like a bee sitting on on a blossom. This suggests that the plant is pollinated by at least one species of bee, with male bees attempting to copulate with something that looks to them like a potential mate. This is well-known in orchids, and indeed some species also produce pheromones mimicking those of a female wasp.

However, it turns out that over much of the range of O.apifera there is no longer any pollinator. Instead, in many regions the orchid self-pollinates, relying on the wind to blow the flowers dangling pollen sacs (‘pollinia’) against its sticky stigma, which seems a little hit-&-miss.

While one pollinator does still exist in one part of the orchid’s range, this cartoon from xkcd is nonetheless rather poignant:

Bee Orchid

 

 

is this a coat of many colours? Alison Campbell Aug 21

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I had to look twice at this undersea Liberace-lookalike before recognising it as an octopus (more precisely, a blanket octopus, Tremoctopus sp.) These beautiful creatures live in the open ocean where they grow up to 2m long. The female in this image (thanks, Science Alert) has unfurled a sort of cape (called a ‘web’ in this Scientific American article) that may function in deterring potential predators – after all, you’d have to be fairly big to take on something of this apparent size. The web can be shed in sections, presumably acting as a distractor if the octopus is threatened by something large & hungry.

Interestingly, it’s only the females who can put on this impressive display (the cape’s rolled up when not in use), for the males are much smaller.  So small, in fact, that it was some time before one of the 2.4cm males was even identified. That’s a pretty extreme example of sexual dimorphism; in terms of the orders of magnitude between the size of the two sexes it must give some of the deep-sea angler fish a run for their money.

But also – it seems that small blanket octopuses (ie males & young females) use tentacles from Portuguese man-o-war jellyfish as defensive/offensive weapons, something that was first reported on back in 1963 (there’s an image here on the ToLWeb site). Presumably these cephalopods are immune to the jellyfishes’ stings.

bicep-flexing & s*xual selection Alison Campbell Aug 09

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When I was a kid, we’d all look forward to Friday evenings – because Dad & Grandma would come back from town with the weekly supply of comics. The ads in the back were almost as good as the cartoons, although we were very disappointed to find out that sea monkeys were definitely not as advertised! I also remember regular ads featuring a poor weedy guy who, having had sand kicked in his face by various over-muscled bullies, followed the instructions of various manly authorities and ended up developing his own set of biceps, triceps, washboard abs & all the rest: all the better to impress the girls at the beach.

I was reminded of all this earlier this week when I noticed a Facebook report on bicep-flexing in male kangaroos, based on this 2013 paper in the Biological Journal of the Linnaean Society. (It’s behind a paywall, alas, but you should be able to read the abstract.)

As Darwin recognised, at least some of the physical differences between males and females may be the result of competition: think showy male peacocks and their relatively dowdy mates, for example. This competition may be directly between males, as they try to gain access to females – an example of this would be elephant seals, where the males battle each other to become ‘beach-masters’, and the winners gain access to females coming ashore on their beaches. In this case, selection favours male strength. In other cases females select males to mate with on the basis of some attribute – perhaps the brightest plumage, or the loudest song.

As Warburton & her colleagues point out, these different forms of sexual selection are not mutually exclusive, & it’s sometimes hard to tease out which has the greatest impact on a species’ characteristics. They decided to investigate sexual selection in a large species of marsupial, the western grey kangaroo (Macropus fuliginosa), a polygynous species where males tend to have greater development of the chest & arm muscles. It’s fairly clear that in large kangaroos & wallabies, male reproductive success is linked to body size, which in turn is linked to social status: “the large males… gain an exclusive consort relationship with oestrous females”. Larger males have larger home ranges and so may have more chance to find and mate with females, and in addition genetic data suggest that

alpha males may be able to outcompete and exclude smaller males from access to females.

But how to tell if the larger arm & chest musculature of males is down to sexual selection, or simply a factor of differences in overall body size? You measure some kangaroos (in this case, purchased from pet food manufacturers. Poor Skippy!) This allowed the research team to look at the slope of trait size (eg bicep size) against body size:

When the slope of a trait size against body size is ‘isometric’, the relative trait size is constant across a range of body sizes. Where the trait size decreases with body size, the slope shows ‘negative allometry’ and where the trait size increases with body size the slope shows positive allometry. A trait that is positively allometric is therefore relatively larger, in proportion to body size, in larger individuals. If this relationship differs between the sexes, then it can be interpreted that there is differential selective pressure acting on males and females as they grow larger.

While the numbers involved were fairly low (13 males and 15 females), the team ensured they had a range of body sizes. (I’m guessing the fact that that body mass was estimated from measurements of the thigh bone rather than directly, by weighing, reflects a lack of scales big enough to plonk an entire kangaroo corpse onto.)

The results? Male kangaroos had larger (“more exaggerated”) forelimbs, and more variability in muscle mass, than females. Both of these suggest that sexual selection might be acting on forelimb size, and it’s likely to be through male-male competition. This is because male kangaroos use their forelimbs to push or wrestle with their opponents as they fight to determine their place in the social hierarchy. There’s also a suggestion that the larger male muscles

may also be an important aspect of visual signalling (presumably of potential fighting ability) and dominant males will frequently adopt poses which best display their muscularity and size.

So perhaps there’s also potentially an element of female choice: those exaggerated biceps may attract admiring female glances (or at least, allow them to appraise a male’s genetic quality), rather than being simply a part of the roo equivalent of sand-kicking.

N.M.Warburton, P.W.Bateman & P.A.Fleming (2013) Sexual selection on forelimb muscles of western grey kangaroos (Skippy was clearly a female). Biological Journal of the Linnean Society 109(4): 923-931

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