Grass Fights Back Against Grazers

The following is an article in New Scientist this week, who apparently got it from Biology Letters.
Anyway, this is just too wonderful not to quote in full:

Grasses have a secret weapon against grazing that packs a surprisingly powerful punch.

Grass can defend itself using tiny nodules of silica – and a field study of voles suggests that the silica could be causing rodent populations to boom and bust. While predators are known to drive population cycles, the new study suggests that plants can have a similarly drastic effect.

Earlier studies had shown that grasses could form deposits of silica in their leaves, apparently as a response to grazing. Voles seem to dislike eating grasses with these deposits, and the defence gets to them in other ways too – it makes them lose weight, apparently by inhibiting their digestion of proteins in the grass.
Important defence

"People suspected that silica might be an important defense, but didn't think that it was able to drive the population cycles," says study leader Susan Hartley of the University of Sussex, Brighton, UK.

"This is the first evidence from field experiments that silica defence and vole populations might be linked,"she says.

Hartley and colleagues from the University of Aberdeen, UK, have been studying a population of voles (Microtus agrestis) that live in Kielder Forest, in northern England. During the winter, the voles' main food source is tufted hairgrass (Deschampsia caespitosa).

When the number of voles was high, or had been high the previous year, the silica levels in the plants were also high – apparently a response to more grazing, Hartley's team found. But when the voles' numbers had been low before, and grazing was at low levels, the plants had less silica.
Boom and bust

Eating high-silica grass reduced vole body mass by 0.5% per day, an effect that the researchers argue could drive population cycles.

It isn't an instant defence, Hartley says, since it seems to take several months for the grasses to grow the deposits. Nor is it a constant defence.

"It must be quite costly for the plant to extract the silicon from the soil and deposit it [in the leaves]," which would make them less competitive against other grasses not eaten by the voles, Hartley says. "The grass wouldn't want to be on maximum alert all the time."

Other populations of voles may go through booms and busts due to predators, but in England the plants' defence could be driving the cycles.

Journal reference: Biology Letters (DOI: 10.1098/rsbl.2008.0106)

Bind Moggling

April 23 is the birthday of two men, both unquestionably at the highest ranks of literary production. Nabokov, and Shakespeare share this birth date. Shakespeare and another literary giant Miguel de Cervantes both died on the same date, the one in question -- April 23. (Actually though both died in 1616, Spain was using the Gregorian calendar, and England the Julian, and so they did not actually die on the same day.) And though other details could be quibbled about also, these coincidences are interesting.

Character

Few things are less indicative of character than one's attitude toward monogamy.

Is Dolling Up Parody?

In 1994 that the Supreme Court ruled that parody can be protected by the fair use clause of the Copyright Act of 1976. The case arose from a song by the rap group 2 Live Crew, which used elements of the Roy Orbison song from 1964: "Oh Pretty Woman". Among those who argued against the case of 2 Live Crew (being sued for copyright violation by the copyright holders of this song,) was Dolly Parton. The Supreme Court ruled unanimously in favor of 2 Live Crew.

Blue Sky Blue

There is a pigment the Mayans made and used for ceremonial purposes which scientists cannot recreate. This pigment color is called Maya Blue and not only can it not be currently recreated, this pigment has unusual qualities--it is extremely durable and in the words of National Georgraphic (who may have been quoting Antiquity magazine), shows "remarkable ability to resist age, acid, weathering, and even modern chemical solvents." We know about this durability from surviving examples of the pigment on bowls.

2001 SN 263 (a number to remember)

2001 SN 263 is the name of an asteroid which, they just discovered, is actually three bodies orbiting each other. In the words of spaceref news:

First near-Earth triple asteroid discovered by Arecibo Observatory astronomers – a mere 7
million miles from Earth
http://www.spaceref.com/news/viewpr.html?pid=24775

Once considered just your average single asteroid, 2001 SN263 has now been revealed as the
first near-Earth triple asteroid ever found. The asteroid - with three bodies orbiting each other -
was discovered this week by astronomers at the sensitive radar telescope at Cornell University's
Arecibo Observatory in Puerto Rico.

Chocolate Covered Irony

By a lovely coincidence today,February 14, dedicated to lovers, is the birthday of Thomas Malthus (1766) who observed and wrote abstractly of the dynamics of population. The connection is that of microcosm to macrocosm. He was not observant enough, though, as any keeper of a feral cat colony can attest. Population dynamics have a way of demonstrating laws which defy the binary mind of man. After two human generations of spaying and neutering cats, in an effort to shape the population of felines, the result has been that the average litter size (of cats) in the United States has increased from four to six kittens. Tom's own idea was to reduce human population by refusing charitable aid to the poor, so they would die off. He meant people die off, not cats.