Jetz et al. 2004 by T. Hawkins

The Scaling of Animal Space Use

By Walter Jetz, Chris Carbone, Jenny Fulford, and James Brown

Blog by Tanner Hawkins

Energetics and metabolism have a lot of explanatory power in ecology at the individual and population level. It explains body and population size very neatly, from an empirical and theoretical standpoint. However, it’s not entirely sure whether energetics can explain other population traits, or if interspecific interaction muddle these effects. The impetus behind Jetz et al. writing this paper is if home range can be well described as a function of metabolic rate.

The short version is… not really. While phenomena such as population density generally agrees with the metabolic theory put forth by West et al. and Damuth’s description of population dynamics as a function of energy, they don’t explain home range as well. The key reason why is defensibility. As body and population size reach a certain point, the amount of resources needed to maintain it requires such a large amount of resources, that a population has to be mobile to get enough resources, and once a population becomes mobile, it makes having exclusive resources that much harder to defend from neighboring populations. This can be shown empirically, as the home range and metabolism become less correlated as body size increases.

While I understand that there’s a pragmatic reason why, it’s interesting that in these mechanism papers they test whether the final model is true, but never the intermediate steps. The authors may have gotten the end result correctly, but for the wrong reasons, and we may never know for sure. Is there an alternative mechanism that others have put forward to explain this data?