Tag Archives: mammals

Ethereal nature

Around this time of year, I like nothing better than to stand outside at dusk and admire the small local population of bats as they flitter around my head. It really is a wonderful and surprisingly moving experience.

When I say 'small local population', I really do mean small. I seldom see more than two or three bats at any one time—unlike my friend Stense, who counted over 60 bats leaving the roost in her attic recently. Stense also has ospreys nesting outside her window. I am consumed with jealousy.

Yesterday evening, I naively decided to try to photograph the local bats as they hunted for insects above my back garden. Well, naive is probably the wrong word as I knew that my efforts were doomed to failure; I was really just being ridiculously optimistic. So I set my camera's ISO and aperture to maximum and fired away, capturing dozens of photos of empty skies and blurred trees. Bats are fast little buggers.

But I did manage to capture a few images of blurs remotely resembling bats:

Bat above my back garden

A bat flittering above my back garden last night.

Yes, I know the photos are crap, but I rather like their ethereal, crepuscular nature—which pretty much sums up bats, as far as I'm concerned.

Ida: on second viewing

In a barrage of stage-managed publicity, a genuine rock-star has been unveiled to the world. Older than Keith Richards, bonier than Mick Jagger, a better sax player than Clarence Clemons, Ida the fossilised, lemur-monkey creature is already better-known than Pink and Hannah Montana—whoever the hell they are.

If the hype-machine is to be believed, Ida (pronounced Eeda, but more properly pronounced Darwinius masillae) is the biggest event in biology since the Cambrian Explosion: she is the Rosetta Stone, an asteroid hitting the Earth, the greatest fossil find of the century (are we really 8½ years into it already?); Ida is the Second-Coming of the Lord Jesus Christ, Duke Nukem Forever, dark energy, the secret Coke™ formula; she is Catherine Deneuve, Cate Blanchett, Natalie Imbruglia, and Cheryl Ladd in that black bikini (you had the be there, kids) all rolled into one. Above all, Ida is The Missing Link between us primates and the rest of the Animal Kingdom. W00t!!

I watched the TV documentary, of course. Bolstered by several stiff whiskies, I watched and tweeted with like-minded, equally irritated individuals. At the end, I gave the documentary two fully opposable thumbs down.

But was I being fair to the documentary? Had my immense—and, as far as I'm concerned, totally justified—irritation at the media hype surrounding Ida's launch pre-disposed me to dismiss the documentary? This morning, I decided to watch it again, trying to imagine my reaction had I known nothing about the hype.

On second viewing, I don't think the documentary was all that bad. Yes, they should never have used the misleading phrase missing link, and, yes, Sir David Attenborough's script could have been made less misleading in places, and, yes, there were a few subjects conveniently glossed over (such as why was there a need to keep Ida so secret? where did the money to buy her come from? and who was excluded from the dream team which got to examine her?). But, on the whole—well, on 90% of the whole—I think the documentary gave the viewer some interesting insights into the fossil trade, the wonderful Messel Pit, primate evolution, and, in particular, how scientists go about making deductions from fossil evidence.

As to the case made for Ida being an early anthropoid rather than an early prosimian (i.e. on the primate branch of the family tree, rather than on the branch containing lemurs, lorises and tarsiers), I, a total non-expert, think the scientists made some pretty compelling arguments. But I guess we'll have to wait for the peer reviews.

Three things are for certain, though:

  1. media hype only does disservice to science;
  2. Ida is most definitely not a missing link (because there is no such thing as a missing link);
  3. Ida really is very, very beautiful:
Darwinius

Darwinius masillae

Vole piss detection

Kestrel

A kestrel hunting behind my house (More kestrel photos »)

No, not the latest album by The Fall; I've just started reading The Eye: a Natural History by Simon Ings. On page 28, I came across the following fascinating snippet:

Even with their superb visual acuity and excellent colour sense, extending well into the ultraviolet, kestrels find it hard to spot the drab voles which are their favourite food. Happily for the kestrels, however, voles communicate by leaving trails of urine—indeed, they pee almost continuously—and mole urine reflects ultraviolet light. For kestrels, hunting voles is simply a matter of following the arrows.

Amazing.

I must admit, I was initially irked by Ing's use of the word happily to describe what appeared clearly to be a marvellous hunting adaptation evolved by the kestrel. But not so: all birds can see into ultraviolet wavelengths, apparently; so kestrels can't have evolved their ultraviolet vision specifically to hunt voles. The apparent adaptation turns out to be a lucky coincidence, which the kestrel has put to good use—possibly refining it over time.

Ultraviolet mole piss detection isn't so much an adaptation as an exaptation, it would seem.

Kiss me, cat!

BBC: 'Bizarre' new mammal discovered

A new species of mammal has been discovered in the mountains of Tanzania, scientists report. The bizarre-looking creature, dubbed Rhynochocyon udzungwensis, is a type of giant elephant shrew, or sengi.

The cat-sized animal, which is reported in the Journal of Zoology, looks like a cross between a miniature antelope and a small anteater.

Wonderful! A shrew the size of a cat, and nobody's seen one before. Well, no western scientist at least. It's truly marvellous that people are still finding new species like this in this day and age.

One thing, though, BBC: it looks absolutely nothing like a miniature antelope.

Postscript: Oh, apparently, in the same way that elephant shrews aren't elephants, they're not shrews either. Pity.

Darwin's 'rhinoceros'

On this date in 1832, Charles Darwin made a rather important discovery at Punta Alta, near Bahia Blanca, South America. He recorded the find in his Beagle diary:

Sunday Sept: 23rd [1832]

A large party was sent to fish in a creek about 8 miles distant; great numbers of fish were caught. — I walked on to Punta alta to look after fossils; & to my great joy I found the head of some large animal, imbedded in a soft rock. — It took me nearly 3 hours to get it out: As far as I am able to judge, it is allied to the Rhinoceros. — I did not get it on board till some hours after it was dark. —

Megatherium

Megatherium fossil

The bones were eventually shipped back to Blighty, where the great anatomist Richard Owen identified them as belonging to an extinct giant ground sloth, Megatherium.

Megatherium's close relatives, the tree sloths, still live in South America. In later years, Darwin realised that the fact that surviving species were often found in the same locations as closely related extinct ones suggested a geological succession of organic beings. This realisation helped convince him of the concept of descent with modification: a key element of his theory of evolution.

Genetic clock v palaeontology

A few days ago, I wrote about an apparent disagreement between two sets of scientists over the evolution of mammals. I confessed to general confusion as to whether the findings of two different studies actually conflicted with each other. It turns out they did. New Scientist this week contained a short article which nicely summarised the differences:

New Scientist: When did placental and marsupial mammals split?

… According to the fossil record, our ancestors didn't split into modern groups of placental and marsupial mammals until after the dinosaurs bit the dust at the end of the Cretaceous, 65 million years ago. So say John Wible of the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, and colleagues, who have compared late Cretaceous fossils with modern placental groups…

That bolsters the traditional view of palaeontologists, but flies in the face of molecular studies of genetic divergence of living species, which put the origin of placentals 80 to 140 million years ago… "We're in total discord with the molecular dates," Wible says. He thinks genetic clocks fail to account for the post-Cretaceous burst of mammalian evolution.

Are palaeontologists missing fossils, or do bursts of evolutionary diversification throw off molecular clocks? You have to take both sides seriously, says Rich Cifelli of the Oklahoma Museum of Natural History in Norman.

I have to say, I've always had my doubts about the use of so-called genetic clocks to estimate dates of key evolutionary events. It stands to reason that genetic analyses should be able to give us a very good idea of the sequence in which such events happened, but using them to estimate actual dates for these events seems (to this ill-informed outsider at least) hopeful in the extreme.

The very concept of a genetic clock assumes that genetic mutations occur at a constant rate. This may or may not be the case, but to me it seems a bit too convenient. Physicists use radiocarbon dating and potassium-argon dating to give pretty good estimates of the ages of particular samples (although such techniques are not without their problems), but the biological world is far more messy than the physical one with its precise radioactive half-lives. My gut feeling is that using genetic clocks to provide actual dates for evolutionary events is giving in too much to physics-envy.

For the time-being, I'll side with the palaeontologists, who deal with hard—albeit sparse—physical evidence.

But what the hell do I know? If I turn out to be wrong, I will happily stand corrected.

When scientists (apparently) disagree

What on earth is an interested member of the general public supposed to think? I do wish those scientist types would make up their minds. Compare and contrast:

BBC (28-Mar-2007): Mammal rise 'not linked' to dinos

The extinction of the dinosaurs 65 million years ago had little effect on the evolution of mammals, according to a study in the journal Nature…

[A new mammal supertree construction] shows that the placental mammals had already split into [their main] sub-groups by 93 million years ago, long before the space impact and at a time when dinosaurs still ruled the planet.

Reuters (20-Jun-2007): Mammals burst on the scene after dinosaurs' exit

… We wanted to test whether there were any Cretaceous placentals," [John] Wible [of the Carnegie Museum of Natural History in Pittsburgh, whose research appears in the journal Nature] said in a telephone interview. "If the molecular dates are correct, we should be finding things that look like modern placentals in this time period and we are not."

They found that none of these Cretaceous forms of early mammals are related to any living placental mammals. "They are just extinct dead ends," he said.

Wible said his work reinforced the idea that the death of the dinosaurs created an opportunity for explosive growth of modern mammals.

"You've got all of these ecological niches that were occupied by the dinosaurs. They go extinct, and you've got wide open spaces. It's like the Oklahoma land rush," he said.

All joking aside, though, this is a fascinating subject. And, as far as I understand these two studies from the press reports (rather than the original papers), they don't necessarily contradict each other.

… But I could be wrong!

Postscript: It turned out I was wrong: the findings of the two studies are in conflict. More here.

The Easter Bunny

Early this morning, I stepped out into my garden with a mug of tea to admire the view in the unseasonally glorious Easter Sunday weather. I was about to return to the house when I spotted a brown hare (Lepus europaeus) in the adjacent field. I have seen hares on the moors above my house many times, but this was a new one as far as species spotted from my garden was concerned. A good start to the day.

Hare watercolour by Albrecht Durer

Hare watercolour by Albrecht Durer, 1502.

"An Easter Bunny," joked my partner, Jen, when I told her about the hare.

Which got me wondering what on earth the Easter Bunny was all about. It wasn't something I remembered from my childhood. Some silly, new-fangled American 'tradition' like trick or treat and pumpkins at Halloween, I thought. I couldn't have been more wrong:

It turns out that the impressive fecundity of hares (they breed like rabbits), and their famous courtship boxing in early spring, meant they were associated with the Anglo-Saxon goddess of spring, Eostre, whose name and festival was appropriated by the Christians and evolved into Easter. Some European countries still associate Easter with hares and not rabbits.

So Jen was right: I had seen a genuine Easter Bunny.

Link: The British Brown Hare Preservation Society