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Estimating the Location of the Focal Center in Red Squirrel Home Ranges
Author(s) -
Lair Helene
Publication year - 1987
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1938381
Subject(s) - center (category theory) , bivariate analysis , harmonic mean , statistics , mathematics , harmonic , geodesy , geography , physics , chemistry , crystallography , quantum mechanics
I attempted to evaluate the relative usefulness of three statistical estimates of focal center location in red squirrel (Tamiasciurus hudsonicus) activity fields (defined as the distribution of an animal's time as a function of location). The statistics compared were the bivariate arithmetic mean center, the bivariate median, and the harmonic mean center. The arithmetic mean center, the classical center of activity, was an unsatisfactory estimate of focal center location; the median center was closer to the point of greatest activity in 77 of 81 cases, but still did not coincide with it; the harmonic mean center was a good estimate of focal center by definition, and it coincided with the behavior focal center whenever the latter could be identified from direct observation. Because the harmonic mean center usually did not coincide with either the arithmetic mean or the median centers, I recommend the use of the harmonic mean center to field biologists wanting to estimate the location of an animal's point of greatest activity from the geographical distribution of its active time, and I discuss its possible biological interpretation.