These Mice Grow Bigger on One Side of Their Mountain Home. Now We Know Why

Mice from the same species are growing bigger on the western side of the mountains compared to the eastern side.

There is a new study suggesting a solution.

The mice on the western slopes have more food to eat due to the rain shadow effect, which causes clouds to push higher as they pass over the mountains.

The rain shadow effect is a common phenomenon that leaves one side less wet than the other.

Scientists are still learning how this affects the environment.

There are a lot of ecogeographic rules that scientists use to explain trends that we see in nature.

The rain shadow effect can change the size and shape of mammals.

The team analyzed 450 mouse skulls and found that there were differences in size between males and females.

They looked at correlations between size and latitude, altitude, temperature, and precipitation.

The variations in size were related to the location of the mice. The researchers almost had their answer when they added in the resource rule, which says that more resources tend to lead to bigger animals.

There was one question left, why there were more resources to the west.

The team thought it was the rain shadow. As the air rises it gets colder as water is picked up from the ocean. It can mean a lot on one side of the mountain range.

De la Sancha says that one side of the mountain will be wet and the other will be cold.

The difference on some mountains is very large. One face can be a tropical rainforest, and the other can be a desert.

This is a natural rule. Bergmann's rule links larger animals in the same species with colder environments if they have a thicker body.

Climate change is brought with it new concerns. Scientists now know that temperature and precipitation levels can affect the appearance of mice and possibly other animals. The amount of food available to be eaten could be affected by the weather.

While the future remains unclear, it's important to gather as much data as possible so we can understand the current and potential implications of climate change.

De la Sancha says that it could be something that's more universal. It may be more of a rule than an exception. It would be a good idea to test it on a lot of different taxa.

The journal of biogeography has published the research.