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Spatial Ecology of the Giant Kangaroo Rat (Dipodomys ingens): A Test of Species Distribution Models as Ecological Revealers


Monitoring a species' distribution and abundance is a critical component in both applied and theoretical ecology. Wildlife managers demand effective and efficient methods for monitoring species of concern. Theoretical ecologists, as well, need accurate estimates of species' distributions and abundance, and measures of the quality of habitat that determines these parameters. Recent advances in species distribution models have suggested an inexpensive and robust way forward for estimating habitat suitability, but these models have rarely addressed species distributions at ecologically relevant spatial or temporal scales. Further, few studies have examined the relationship between habitat suitability, as estimated from species distribution models, and habitat quality, a better predictor of long-term population persistence. In this study, I (1) test current methods for monitoring giant kangaroo rat population extent and abundance; (2) create novel species distribution models that incorporate primary productivity as an ecological predictor for giant kangaroo rat distribution; and (3) test whether these models are actually related to independent measures of habitat quality. Aerial surveys are shown to be a reliable estimator for giant kangaroo rat population extent. Burrow counts may be a reliable index of long-term population size, but are inadequate to detecting short-term changes in size or growth. Distribution models that incorporate ecologically relevant variables on annual time scales are shown to better predict giant kangaroo rat distribution than static models that assume the species is at equilibrium. Finally, species distribution models perform well at measuring long-term giant kangaroo rat abundance, and temporally explicit models predict short-term abundance, but species distribution models are generally incapable of adequately distinguishing between high and low quality habitat as measured by survival or body condition.

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