IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| Gilpin, M.E. | |
| Do hares eat lynx? | |
| 1973 American Naturalist (107): 727-730 | |
To test a recently developed predator-prey model against reality, I chose the well known Canadian hare-lynx system. A measure of the state of this system for the last 200-odd years is available in the fur catch records of the Hudson Bay Company (MacLulich 1937: Elton and Nicholson 1942). Although the accuracy of these data is questionable (see Elton and Nicholson 1942 for a full discussion), they represent the only long-term population record available to ecologists. To perform the test, the derivatives in equations (1a) and (1b) were approximated by the per year changes in lynx and hare densities. Next, the parameters in these equations were adjusted so that the sum of the squares of the error between the observed growth rate and the predicted growth rate (that is, the right hand sides of eqq, (1a) and (1b) with the observed initial values substituted for L and H) is minimized. The methodology and philosophy of this approach are fully explained by Ayals, Gilpin, and Ehremfeld (1973). The idea is not to explain away a real phenomenon. Rather, it is to test the generality and efficiency of a theoretical model. The correlation between the model and the empirical data gives some idea about the general worth of the model. The level of significance of the individual parameters indicates the efficiency of the model. If a model satisfies both of these requirements, and if the parameters have a plausible biological interpretation, then the model may be useful for suggesting additional observations or experimental manipulations. Furthermore, the model would be expected to be of some relevance to similar ecological systems. |
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