Animals and birds all over the world are changing their body weight as part of a survival strategy to deal with global warming, an Israeli professor has discovered.

Birds, foxes and other small mammals are altering their traditional weight patterns in another manifestation of the changes occurring in the world's climate, asserts an Israeli professor.

While some animals are gaining weight, others are losing inches, claims Prof. Yoram Yom-Tov of Tel Aviv University, who says the changes are a strategy for survival as the world heats up.

"This change can be seen as an early indicator of climate change," says the professor from the university's zoology department.

Decades of observations show recent radical change

Yom-Tov has spent decades measuring and monitoring the body sizes of mammals and small birds, and has observed that changes have been happening most rapidly in recent years.

Using data compiled over the years, comparing bones and skulls kept in museums and collections, Yom-Tov studies various features of the animals (including cranial size), and then statistically analyzes how they have evolved.

Among the wildlife populations affected are birds in the UK, small mammals in the arctic, foxes, lynx and otters in cold Scandinavian regions, but Yom-Tov says that plants and wildlife all over the world are seeing significant change: "Climate change is affecting migration patterns and the behavior and growth of birds, mammals, insects, flowers - you name it."

Birds are getting smaller, mammals are getting larger

Those most affected are animals and birds living at higher latitudes, where temperature changes are most radical, says Yom-Tov. Mammals in these regions are growing larger and heavier, while birds are getting smaller, according to most of the species he has examined.

"There is a steady increase of temperatures at higher latitudes, and this effect - whether it's man-made or natural - is having an impact on the animals living in these zones," Yom-Tov explains.

In his most recent study, published in the journal Global Change Biology, Yom-Tov and his colleague Prof. Eli Geffen focus on the declining weight of arctic foxes in Iceland. They surmised that these changes are a result of shifting water currents in the oceans, most likely caused by climate change.

These changing currents affect the foxes' food supply, forcing them to adapt their body weight to the new situation. Smaller bodies allow mammals to cope with warmer temperatures, since a smaller body size gives the body a proportionally increased surface area for the dissipation of heat, he says.

"These animals need to adapt themselves to changing temperatures. In some regions the changes are as large as three to four degrees centigrade [37-39 degrees Fahrenheit],'' says Yom-Tov, adding, "If they don't adapt, their numbers may decline. If they do, their numbers remain stable or even increase... The global warming phenomenon is a fact. What we do with this information may change our world."

(Israel 21C, 09/03/2010)