I remember thinking about this classic problem with my friends back in school and tried to work through it again from a physics point of view. It turned out that it is more complicated that I thought:
Why do smaller animals survive falls from larger heights?
I would specifically like to know how physical scaling laws affect the chance of survival of an animal, i.e. we suppose the animals can be modeled as the same shape but every length scaled by a factor $k$. There are two biological factors one has to assume, namely that animals have roughly equal density and the force a muscle can apply scales according to the cross-sectional area it has ($\propto k^2$). I think apart from that one should be able to get away with making reasonable physics approximations. So maybe to reformulate what I mean by the "why" in the question above: can the phenomenon that smaller animals survive falls from larger heights be explained by physical scaling laws?
Best Answer
I can't claim to know the full answer, but it's amusing to note that this question has a fairly long history in biology. Way back in 1928, J.B.S. Haldane (my great-great uncle) wrote a popular-science article called "On being the right size", about the importance of scaling laws for biological anatomy. The following passage is relevant for the question at hand:
Haldane claimed (without offering direct evidence) that the difference could be explained because of air resistance. The force of air resistance scales as $f_r \propto L^2$, where $L$ is a characteristic linear dimension of the animal. However, the force due to gravity scales as $f_g\propto L^3$ (assuming fixed density). The ratio of these quantities scales as $$\frac{f_r}{f_g} \propto L^{-1}, $$ meaning that smaller animals are buoyed up more effectively by air resistance as they fall.
I expect that there is probably more to the story than this, however, as noted in the comments, these sorts of experiments are tricky to get funding for...