2009 Science News of the Year: Life

Breeding records for sheep on Hirta offer an unusual opportunity to study inheritance. Image Credit: Arpat Ozgul
Breeding records for sheep on Hirta offer an unusual opportunity to study inheritance. Image Credit: Arpat Ozgul

Gentler winters shrink sheep
Warming has trumped the benefits of fat to shrink sheep on the remote North Atlantic island of Hirta, a new analytical approach has revealed (SN: 8/1/09, p. 12). Weights for wild female Soay sheep dropped about 5 percent during the past two decades, says Tim Coulson of Imperial College London’s campus in Berkshire. He and his colleagues teased apart the causes by incorporating detailed annual data into the basic equations that population biologists use to describe how traits change over time. The researchers combined the equations to create a type of bookkeeper’s ledger of influences on size. The trait is partly inherited, and researchers found that evolutionary forces tend to favor bigger body size; sheep draw on fat reserves in winter and larger youngsters are more likely to survive than smaller ones. Milder winters have swamped that trend, though, as an increasing number of small, weak youngsters survive.

Honey, I unshrunk the fish
A lab test raises hope that over generations fish could recover some of their former size if people stopped catching just the big ones. That practice has been blamed for creating evolutionary pressures for small-bodied populations (SN: 3/28/09, p. 9).

Chimps get AIDS
Chimps naturally infected with a nonhuman version of HIV do get sick (SN: 8/15/09, p. 5).

Animal toolkits
Wild chimps employ as many as five homemade tools to collect honey (SN: 6/20/09, p. 9). Crows in captivity also use sticks and stones in sophisticated ways, without training, to obtain food (SN: 8/29/09, p. 5).

Tied to land
Fossils of ancient whales — including a pregnant female — suggest that at least one species gave birth on land (SN: 2/28/09, p. 5).

As the ocean churns
Small creatures such as krill drag enough water with them to contribute to ocean mixing (SN: 8/29/09, p. 14).

A roughly 14-million-year-old fossil reveals that North America once had a native honeybee (SN: 8/15/09, p. 13).

Birds in decline
Nearly a third of the United States’ 800 bird species are endangered, threatened or in significant decline, reports the first U.S. State of the Birds review (SN Online: 3/19/09). A study also finds that a majority of Sierra Nevada bird species have shifted ranges as climate has changed (SN Online: 9/14/09).

Wings reshaped
Logging may have driven birds in mature boreal forests toward pointier wings, while reforestation has led to rounder wings (SN: 9/12/09, p. 7). Other work finds that German birds spending winters at U.K. feeders look different from birds of the same species that go to Spain (SN: 1/2/10, p. 12).

Fancy resin
Ancient plants made amber chemically similar to today’s flowering plant resin (SN: 10/24/09, p. 5).

Mosquito wooing
Male and female Aedes aegypti mosquitoes, carriers of dengue and yellow fever, sing courtship duets with matching harmonics (SN: 1/31/09, p. 10).

Don’t blame climate
An analysis of fungal spores suggests that climate change didn’t cause the megafaunal extinctions at the end of the last ice age (SN: 12/19/09, p. 5).

Confusion spurs red tides
The underwater version of wind shear may disorient phytoplankton, explaining why they form thin layers that can cause red tides (SN: 3/14/09, p. 8).

Humpbacks change tune
Studying humpbacks with methods adapted from bird research has uncovered evidence that whales respond musically to each other’s songs (SN: 11/7/09, p. 5).

Hot trade-offs
The hottest chili peppers are protected from fungus but are more vulnerable to droughts and ants (SN: 7/18/09, p. 12).

Push back
A fossilized steroid molecule bumps back compelling evidence of animal life to at least 635 million years ago (SN: 2/28/09, p. 13).

Living fertilizer
In the fungus farms of leaf-cutter ants, previously overlooked bacteria fix nitrogen, helping to sustain millions of worker ants (SN: 12/19/09, p. 8).

Weapon as weakness
Fire ant venom attracts parasitic phorid flies that deposit eggs, which hatch into larvae and devour the ant from the inside (SN Online: 9/18/09).

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