Posts

Showing posts from January, 2017

Making the Science of Animal Space Use Less Soft

Image
A provocative headline is a double-edged sword. Why do I indicate that one of the most rapidly developing fields of animal ecology should still be regarded as a soft science? When it comes to individual space use rest assured that I’m thrilled by the substantial leaps forward in some parts of the theory of animal whereabouts. On the other hand, I also have critical comments. In my view there is still too strong disconnection between some general properties of movement-related animal behaviour and theoretical representations of this behaviour in models.


Both in my book and in previous blog posts I have repeatedly pointed out the unfortunate fact that contemporary models in the field often referred to as “movement ecology” have matured into two quite distinct premise foundations. On one hand we see a broadened recognition of scale-free movement as a quite general property and on the other hand also a broadened recognition that spatial memory is influencing movement under common ecologi…

Statistical Independence in Space Use Data?

Image
Already from the early days of statistical analysis of home range data one particular property has received particular attention, the degree of serial autocorrelation of the individual’s positions during a period of sampling. In short, if a data series is autocorrelated (due to high frequency sampling of fixes), one is advised to use methods involving path analysis. If data is non-autocorrelated, one should use methods involving a study of locally varying fix density (like classic use-availability analysis). In the latter case, verification of non-significant serial autocorrelation is assumed to imply that each fix can be treated as an independent representation of visits to this particular part of the home range. However, this assumption is in fact deeply erroneous, and it continues to hamper progress in statistical analysis of animal space use.

The Schoener’s ratio (t2/r2) (Shoener 1981) or other methods can easily be applied to test for serial independency in space use data. The ‘…