Climate change is creating shape-shifting animals

Climate change isn't just making some species extinct, but forcing others to "shape shift" in order to better handle rising global temperatures. While the vast majority of experts warn that, unless humans tackle factors like emissions and fossil fuel use, Earth's environment will be irreversibly altered, new research suggests the animal kingdom is turning to new physical characteristics in order to better deal with excess heat.

While physical features like birds' beaks and mammals' ears have obvious roles in eating and hearing, they also serve secondary purposes for heat regulation. Beaks, fleshy appendages such as tailed, and other similar surfaces can be used by animals to dissipate excess body heat and control internal temperature.

Research into the use of such body parts has been around for centuries. The so-called Allen's rule, for example, holds that animals in warmer climates have larger appendages for more efficient heat exchange, and is named after Joel Asaph Allen who worked on the theory in the late 19th century. A new study by a team at Deakin University in Australia and Brock University in Canada, however, indicates the differences are becoming more marked.

Their paper, "Shape-shifting: changing animal morphologies as a response to climatic warming" published in Cell: Trends in Ecology & Evolution this week, looks at around 30 different species, and how those warm-blooded animals have changed. The researchers looked at approximately 100 different prior studies, encompassing lab experiments, field research, and analysis of museum specimens, allowing them to track physiological trends over time.

In Australian parrots, for example, they discovered that beak surface area has increased by as much as 10-percent since 1871. Masked shrews saw tail and leg size increases, while the European rabbit found in Australia had larger ears.

One of the challenges, the researchers say, is that temperature-based explanations of why animal morphology has been altering often come second to other, more obvious possibilities. "Additionally, climatic warming is not always discussed even when temperature is the focus," the researchers point out. "Studies looking to verify Allen's rule can, while verifying the link to temperature, leave out the temporal trend associated with climate change, despite data spanning meaningful time frames of several decades." Instead, reasons of diet and other factors are more commonly cited.

The reality, the researchers say, is that more research is needed to figure out just how much this is happening worldwide, and in what other ways that may not be so readily captured by the longstanding measurements currently used. "As we reckon with the effects of current anthropogenic climate change, the capacity to predict the future is crucial," the team points out. In short, while we may not be able to count on animals being able to shape-shift their way out of harm's way, understanding what changes they can and can't make might help give a more accurate timeline for climate change's overall impact.