Why do shrews shrink in the winter?

Why do shrews shrink in the winter?

Background: Shrews are tiny mammals that weigh only a few grams. They are found in cold climates like Canada, northern Europe, and Russia, despite their small size. These little critters have extremely high metabolisms requiring them to eat every couple of hours. This means they cannot hibernate through the winter. Rather than putting on fat in the winter like bears, they actually lose body mass.

The graph below shows a scatter plot of shrew body mass verses metabolic rate. Metabolic rate is a measure of how much energy an animal uses to stay alive and go about its daily activities.  The dark dots show shrews that were measured in the summer, and the light dots are ones measured in the winter.

Data Source: https://mjmerrick.wordpress.com/2013/01/13/shrews-just-have-to-be-differ...

Questions: 

1.  Describe what the graph shows about how shrew body mass relates to metabolic rate.

2. Why do you think the shrews tend to have smaller bodies in the winter than the summer? 

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