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# Plump moose

## You will learn about: cold moose have more fat

Bergmann's rule says that animals living in colder climates tend to be larger in size. Swedish scientists measured the body mass of different moose populations in Sweden and found that the further north you go, the bigger the moose get! Taking their data we can fit a line through it to predict the body mass of a moose at some latitude using the equation $$\text{mass} = a \times \text{latitude} + b$$ where $a = 2.757$ and $b = 16.793$.

Submit some code with a function moose_body_mass(latitude) that returns the expected body mass of a moose living at the input latitude using the equation from above.

Input: Latitude

Output: The expected body mass of a moose living at the input latitude.

Example

Input latitude: 60.5 Output body mass: 183.5915
 Difficulty moose_body_mass(latitude)

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### Notes

• Bergmann's rule is a generalization and so it doesn't apply to every species. In fact many counter-examples to Bergmann's rule exist but it seems to hold true in many cases (Meiri and Dayan, 2003).
• The original explanation given by Bergmann (1847) for why animals are larger in colder climates is due to the need to conserve heat. Since larger animals have a lower surface area to volume ratio, they lose less body heat per unit mass helping to keep them warmer when it's cold. More recent studies don't support this hypothesis though (Ashton et al., 2000).

### References

Sand, Cederlund & Danell (1995), Geographical and latitudinal variation in growth patterns and adult body size of Swedish moose (Alces alces), Oecologia 102, 433–442.
This is where we got the data from.

Bergmann (1847), Über die Verhältnisse der Wärmeökonomie der Thiere zu ihrer Grösse, Göttinger Studien 3(1), 595–708.
This is the original article by Bergmann in German at over a 100 pages long! Google translates the title to English as "About the relation of the heat economy of animals to their size".

Meiri and Dayan (2003), On the validity of Bergmann's rule, Journal of Biogeography 30, 331-351.

Ashton, Tracy, & de Queiroz (2000), Is Bergmann’s Rule Valid for Mammals?, The American Naturalist 156(4), 390-415.

Let us know what you think about this problem! Was it too hard? Difficult to understand? Also feel free to discuss the problem, ask questions, and post cool stuff on Discourse. You should be able see a discussion thread below. Would be nice if you don't post solutions in there but if you do then please organize and document your code well so others can learn from it.