Scientia Pro Publica 21!

GrrlScientist hosts the most recent Scientia Pro Publica carnival. Check it out for links to some great science, medicine, and nature writing!

Links for the week of 2/8/2010

Physical sciences:
Scientists from the Weizmann Institute of Science in Rehovot, Israel figure out how to get water to freeze at different temperatures by modifying the electric charge on the surface it is sitting on. (ScienceNews)

Plastic water? misc.ience describes how scientists are able to make hydrogels that retain their shape, but are made almost entirely out of water.

Biology:
Researchers at the University of Maryland shed light on how Egyptian bats track their prey. Rather than firing sound waves directly at it, they shoot to either side. This makes them less likely to locate prey, but once they have found it, they can follow it more accurately. (EcoTone)

Beware mussels bearing "gifts": Neuroskeptic describes a study of amnesia caused by toxins in shellfish.

It's now fairly common knowledge that bees dance to tell other bees where to find food. But a recent study in Current Biology shows that they also use short buzzes to tell each other not to go to a dangerous location. Ed Yong at Not Exactly Rocket Science describes the study.

Female crickets can apparently warn their young of environmental dangers: baby crickets born to mothers hunted by wolf spiders are more likely to freeze and hide when they detect the spiders. (Not Exactly Rocket Science)

Sociology/human psychology:
Also from Neuroskeptic: A study of whether antipsychotic medication can reduce psychotic experiences in marijuana users.

If you want to encourage altruism, lead by example...and cleaning that bathroom might not hurt, either. A recent study suggests that watching other people perform good deeds increases the observer's altruistic tendencies. Interestingly, smells associated with cleaning also seem to increase altruism. (Psych Central; Not Exactly Rocket Science)

Daniel Hawes at Ingenious Monkey-20 two 5 has an excellent pair of posts on factors affecting girls' success in math.

A number of bloggers have written about Inuk, an ancient Greenlander whose entire genome was recently sequenced. Gene Expression describes the genetic relationships between Inuk's people (which anthropologists call the Saqqaq) and other human groups. Ed Yong describes what we know about his appearance, and how we know it.

John Tierney of The New York Times describes a sociological study conducted using the Times' own records. As it turns out, articles that inspire awe and those that deal with complex topics are the most likely to be forwarded on. (I wonder if there might be selection bias--perhaps readers of The New York Times are more likely to be interested in complex or awesome topics?)

Is religion necessary for morality? A common belief (for lack of a better word) is that religions originally developed to provide a basis for morality--i.e., to give the members of the society rules to follow to keep the society functioning. A recent analysis of studies in moral psychology, however, suggest that religious training and beliefs do not affect how people make moral decisions. Instead, the authors suggest, religion may have filled other needs in early society, such as the need to feel in control of one's surroundings. (björn brembs blog)

Links for the week of 2/1/2010

Since I don't seem able to put together a daily links post, maybe weekly will be more manageable. Within each group, links are posted in approximately reverse chronological order (most recent first). (Yes, I know some of these are from before Feb. 1. I never said what the error bars were on that date.)

First, DINOSAURS!:
Fossil Feather Colors Really ARE Written in Stone (Living the Scientific Life)
The renaissance of technicolour dinosaurs continues (and the gloves come off...) (Not Exactly Rocket Science)
Oldest feathered dino shows its colors (Science News)
Newly Described Bird-Like Dinosaur Predates Archaeopteryx by 15-20 Million Years (Living the Scientific Life)

Next: Running...ur doin it rong...(maybe):
Evo. Anthro. Study Suggests You Might Be Running Wrong (Laelaps)
New Nature Magazine Cover Story Shines More Light on Barefootin' (Runner's World Peak Performance)

How to not be annoying at the gym, courtesy of Peter at Obesity Panacea:
Appropriate Gym Etiquette
Annoying Gym Personalities
What to Wear


And finally, assorted other interesting things:
Seven habits of highly successful toads (Not Exactly Rocket Science)
Friday Weird Science: Preserving the Species (Neurotopia)
Un-Natural Disasters (In Terra Veritas)
Backyard Chickens: An Art, A Science, A Social Movement (Food Politics)
Dave Munger (formerly of the Cognitive Daily) has launched a new blog, The Daily Monthly. It's awesome.
Bees can learn to discriminate human faces (Arthropoda)
Playing to Learn (NYTimes Op/Ed)
Looking inside the structure of the Yellowstone caldera (Eruptions)
Power source for a light saber (Dot Physics)

Why migrate?

Growing up in New Hampshire, I took the yearly migration of ducks, geese, and (less obviously, but more impressively) Monarch butterflies pretty much for granted. It never really occurred to me to ask why all of these animals migrate. If I had been asked, I probably would have made the (common) anthropomorphic fallacy and said that they migrate because they "want to," or because they "like it better" at their ultimate destination.

Think about it: migration--especially very long-distance migration, such as that performed by some shorebirds, which can migrate from the southern tip of Africa all the way to the Arctic--is incredibly resource-intensive. It takes a long time, requires enormous amounts of energy, and is pretty dangerous. For a behavior like that to survive and develop in a population, it must provide significant survival or reproductive benefits. There are three main hypothesis about what those benefits might be:

1. Increases in food resources. For example, migrating south might allow birds to avoid competing for the limited food available in New England in the winter.
2. Reduction in parasite load. For example, migrating out of an area during a parasite's main breeding season might allow a bird to avoid infestation by the parasite.
3. Reduction in predation pressure. For example, migrating to different areas during different times of year might allow birds (or their eggs or hatchlings) to avoid attacks by predators that are common during those times.

It's possible to test these different hypotheses by looking at exactly where different populations migrate to. For example, consider those shorebirds I just mentioned. They migrate to high northern latitudes from the southern parts of Africa. The range of latitudes to which they migrate is wide; some stop just below the Arctic circle, but others keep going nearly to the North Pole. Previous studies have shown increased food availability and reduced parasite loads at these high latitudes. However, until now, there have been few studies that produced quantitative data on how migration site affects predation risk. In the 15 January issue of Science, Gilg and Yoccoz and McKinnon et al offer substantial evidence to support the idea that migrating to high latitudes offers significant benefits in terms of avoiding predators.

McKinnon et al placed more than 1500 artificial shorebird nests at various locations in northern Canada, over a latitude range of about 3350 km. They monitored the nests for two or more summers and recorded how well they survived predation.

The result? For every one degree further northward a nest was placed, the risk of predation on the nest decreased by about 3.6%. Over the range of latitudes they studied, that translates to 65% lower predation on the northernmost sites than on the southernmost sites. This is a significant reduction, and suggests that predation may indeed play an important role in driving bird migration.

However, other studies of predation risk at different latitudes didn't show such a clear trend. McKinnon et al suggest that this might be because those other studies used real nests, which vary in size, health, etc. In other words, previous trials were not as well controlled as was this investigation. By using artificial nests, the researchers reduced other potentially confounding factors.

Gilg and Yoccoz add to the story by suggesting that an important factor influencing predation on the nests is the distribution of another common prey species, the lemming. Lemmings and shorebirds (and shorebird eggs) are common prey for the Arctic fox. By comparing the distributions of the lemmings and the shorebirds, Gilg and Yoccoz show that the shorebirds most commonly hunted by foxes are typically common only where lemmings also occur. They hypothesize that, in areas without lemming populations, the predation pressure on the shorebirds is too high for their populations to survive.

Together, these two articles indicate that there are many more factors influencing bird migration patterns than simply "because the birds like it better there."

Gilg, O., & Yoccoz, N. (2010). Explaining Bird Migration Science, 327 (5963), 276-277 DOI: 10.1126/science.1184964

McKinnon, L., Smith, P., Nol, E., Martin, J., Doyle, F., Abraham, K., Gilchrist, H., Morrison, R., & Bety, J. (2010). Lower Predation Risk for Migratory Birds at High Latitudes Science, 327 (5963), 326-327 DOI: 10.1126/science.1183010