Density-Dependent Habitat Selection: A Tool for More Effective Population Management
Habitats vary in quality and individuals choose them accordingly. Some species distribute themselves non-randomly among habitats so as to equalize the net reproductive rates of individuals in different habitats (Ideal Free Distribution). Habitat selectivity is greatest when population sizes are small.
Determining habitat preferences may be done in the laboratory or the field. The latter may be accomplished by studying the covariance of census and habitat qualities, or by studying the non-randomness of population distribution among habitats. All methods have confirmed the density-dependence of habitat selectivity.
Density-sensitive habitat distributions may be used to reduce the cost of regular censuses. In some cases, they may make it practical to replace censuses and yield limits with habitat reserves.
When populations decline greatly, they are supported by the most favored habitats. Substantial fractions of some populations may depend on such cradle habitats. Pest populations may be controlled most cheaply by concentrating on their cradle habitats, although natural selection might interfere.
Managers will have to take cognizance of habitat selection in order to achieve maximum sustainable yields. Sometimes, harvesting should be concentrated in habitats where death rates are naturally high or birth rates naturally low. But long-term considerations in cases where some individuals dominate others may complicate achieving maximum sustainable yields.
KeywordsBiomass Migration Covariance Gravel Fishing
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