New Worlds: Lizards weigh heavily on the ecological scales

Methods to better predict which communities of animals will shrink, grow or adapt after massive environmental disasters.

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September 25, 2010 23:39
4 minute read.
The aftermath of an oil spill [file]

Oil Spill Lizard311. (photo credit: Heidi Hatre)

 
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How much does a lizard weigh? Most people couldn’t care less. But Tel Aviv University zoologists say the amphibians are an important indicator for understanding the condition of specific ecosystems. Their body weight is a crucial index for evaluating species health, but lizards are seldom weighed, perhaps because they lose their tails spontaneously under stress.

Now TAU researcher Dr. Shai Meiri claims to have an improved tool for translating lizard body length to weight. The new equations calculate this valuable morphological feature to estimate the weight of a lizard species in a variety of different ecosystems.

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“Body shape and body size are hugely important for the understanding of multiple ecological phenomena, but there is a need for a common metric to compare a multitude of different species,” he says. In a study published recently in the Journal of Zoology, Meiri evaluated hundreds of lizard species – long-bodied, legless species and stout, long-legged species; some that sit and wait for prey, others that are active foragers. Based on empirical evidence, such as well-established behavioral traits, he built a statistical model that could predict weights of lizards in a reliable, standardized manner, for use in the field or at the lab.

For the study, the zoologist looked at a large sample – 900 lizard species in 28 families – and generated a dataset of weights, using this dataset to develop formulas that derive body weight from the most commonly used size index for lizards (the length of the head and body, or “snout-vent length”). He then applied a species-level evolutionary hypothesis to examine the ecological factors that affect variation in weight-length relationships.

This standardized metric can protect the environment by helping predict how lizard species will react to major shifts in the availability of food due to climactic changes, he says.

In the future, zoologists will be able to use the method to better predict which communities of animals will shrink, grow or adapt after massive environmental disasters like the recent Gulf of Mexico oil spill.

DECISIONMAKING BOOSTED BY VIDEOGAMES

It might be worth equipping decisionmakers at the Israeli/Palestinian peace talks with video games. Cognitive scientists from the University of Rochester in New York State have discovered that playing action video games trains people to make correct decisions faster. They found that video game players develop a heightened sensitivity to what is going on around them, and this benefit doesn’t just make them better at video games, but improves a wide variety of skills that can help with everyday activities like multitasking, driving, reading small print, keeping track of friends in a crowd and navigating around town.



In a study published in the journal Current Biology, authors Daphne Bavelier, Alexandre Pouget, and Shawn Green report that video games could provide a potent training regimen for many types of real-life situations.

Video games have grown in popularity to the point where 68% of US households and uncounted numbers of Israeli children and adults play them.

The researchers tested dozens of 18- to 25-year-olds who were not ordinarily video game players and split them into two groups. One played 50 hours of the fastpaced action video games Call of Duty 2 and Unreal Tournament, while the other group played 50 hours of the slow-moving strategy game The Sims 2. After this training period, all the subjects were asked to make quick decisions in several tasks designed by the researchers. The participants had to look at a screen, analyze what was going on and answer a simple question about the action as quickly as possible (such as whether a clump of erratically moving dots was migrating right or left on average). To ensure that the effect wasn’t limited to just visual perception, participants were also asked to complete an analogous task that was purely auditory.

The action game players were up to 25% faster at coming to a conclusion, and answered just as many questions correctly as their strategy-game playing peers.

“It’s not the case that the action-game players are triggerhappy and less accurate: They are just as accurate and also faster,” Bavelier said. “Action-game players make more correct decisions per unit time. If you are a surgeon or are in a battlefield, that can make all the difference.”

The authors’ neural simulations shed light on why action gamers have augmented decision-making capabilities. People make decisions based on probabilities that they are constantly calculating and refining, Bavelier explains. The process is called probabilistic inference. The brain continuously accumulates small pieces of visual or auditory information as a person surveys a scene, eventually gathering enough for the person to make what they perceive to be an accurate decision. “Decisions are never black and white,” she said. “The brain is always computing probabilities. As you drive, for instance, you may see a movement on your right, estimate whether you are on a collision course and, based on that probability, make a binary decision – brake or don’t brake.”

Action-video game players’ brains are more efficient collectors of visual and auditory information, and therefore arrive at the necessary threshold of information much faster than non gamers, the researchers found.

The new study builds on previous work by Bavelier and colleagues that showed video games improve vision by making players more sensitive to slightly different shades of color.

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