Modelling habitat suitability for black-tailed deer ( Odocoileus hemionus columbianus) in heterogeneous landscapes

Abstract

The California Wildlife Habitat Relationships (CWHR) System is a set of standardized procedures including an information system describing the management status, distribution, life history, and habitat requirements of 643 species of terrestrial vertebrates regularly occurring in California. The original CWHR Database consisted of a series of non-spatial, matrix models, including one for black-tailed deer. A series of second-generation models incorporates explicit spatial relations for use within a geographic information system. These models were designed for landscapes larger than 60 000 ha with a minimum mapping unit of 0.8 ha. As part of our development of a third-generation model applicable to landscape depictions with a minimum mapping unit of 0.06 ha, we assessed the utility of a measure of landscape composition, and an interspersion index, both based on feeding and cover habitat suitability classes found within deer home ranges. General linear model analysis indicated that the percentage of the home rang comprised by each class and the interspersion index were correlated ( P < 0.05) with feeding-cover class, site, the interaction between feeding-cover class and site, and the interaction between home range type (actual or random) and site. The percentage of home ranges comprised by feeding-cover class and the level of interspersion within home ranges differed significantly by suitability class. We detected differences between actual deer home ranges and random home ranges of similar size only within the site that had significant separation in the composition of classes and the interspersion of classes. This suggests that landscape representations resulting in classes with similar composition levels and similar levels of interspersion at the scale of the animal's home range may hinder the assessment of habitat use within home ranges by promoting Type II errors. We demonstrated that organism-centered specifications for extent and grain can be defined from a generic structural representation of the landscape using functional-based models. Spatial extent was defined using the adaptive kernel home range estimator. Within this extent, habitat suitability classed based on feeding and cover produced the grain size for black-tailed deer (mean 0.44 ha, range 0.06–7.79 ha). Furthermore, this approach portrayed the low feeding-high cover matrix class exerting the dominant influence within home ranges. Thus, we suggest measures of landscape composition and interspersion may be useful for characterizing landscapes when assessing habitat use by deer. They may also be of value to natural resource managers attempting to predict the response of deer to proposed changes in land use.