San Joaquin Kit Fox Habitat Model - Santa Clara County, California

The habitat distribution model for San Joaquin kit fox used in the Santa Clara County Regional Conservation Investment Strategy (Santa Clara County RCIS). This habitat distribution model was developed on a regional scale using regional data. This habitat distribution model is intended to be used only for planning purposes at the scale of the Santa Clara County RCIS area. The use of this model is voluntary. The model imposes no regulatory requirements. If used for site planning, the model should be only used as a guide. All habitat and occurrences should be verified in the field. Occurrence data are incomplete and limited by where field surveys have been conducted. Some occurrence points may also be geographically general or inaccurate.

The precision of the habitat distribution models is limited by several factors, including minimum mapping units of the underlying land cover datasets (see below). Areas of suitable habitat smaller than the mapping thresholds were not mapped and could therefore not be incorporated into the models.

The habitat distribution model was limited to distinguishing habitat uses based on key life history requirements. The land cover data do not allow further distinctions of habitat quality on a regional scale. To account for these limitations, conservative estimates of habitat parameters were used. This approach tends to overestimate the actual extent of suitable or required habitat for this species, but is consistent with current conservation planning practices when data are limited.

The habitat distribution model was created using the land cover dataset assembled for the Santa Clara County RCIS. The Santa Clara County RCIS did not create new data to develop the land cover dataset and the habitat model. All data were compiled from existing datasets. See Chapter 2, Environmental Setting, Section 2.3.4.1, Methods and Data Sources for a description of the methods and data sources used to compile the land cover dataset used to create this habitat model.

Following is a summary of the description of the methods used to develop habitat distribution models for the Santa Clara County RCIS from Section 2.3, Habitat Distribution Models.

Habitat distribution models were developed for most focal plant and wildlife species to predict where they could occur, based on known habitat requirements and previously documented occurrences. Habitat distribution models were used to aid the development of the conservation strategy, including the conservation objectives and conservation actions for focal species (e.g., to protect a certain amount of habitat for a focal species).

This habitat distribution model was developed to be consistent with the Santa Clara Valley HCP/NCCP’s (Habitat Plan; ICF International 2012) habitat distribution models for this species.

Model Structure and Development Methods

The habitat distribution model was designed to estimate the extent and location of key habitat characteristics of each species and to be repeatable and scientifically defensible, while remaining as simple as possible. The model is a spatially explicit, GIS-based “expert opinion models” based on identification of suitable land cover types in the Santa Clara County RCIS area and location of known species occurrences. Land cover types are the basic unit of evaluation for habitat modeling and developing conservation strategies for the focal species. Land cover types were identified as suitable habitat based on the known or presumed habitat requirements and use patterns of each species. When supported by appropriate data, the mode may incorporate physical parameters, including the elevation limits of known occurrences or soil type. In some cases, perimeter zones that were used to designate habitat are defined by a certain distance from a suitable land cover type.

Habitats for San Joaquin kit fox were designated according to type of habitat use, such as breeding, foraging, aestivation, and movement habitat. Determination of suitable land cover types and additional physical parameters were based on available data from peer-reviewed scientific literature. When data were inconclusive or contradictory, conservative values were used in estimating suitable habitat. Overall, the habitat distribution model likely overestimates the actual extent of suitable habitat because some important habitat features cannot be spatially mapped at the scale of the Santa Clara County RCIS area, or such mapping was beyond the scope of the Santa Clara County RCIS, and because species do not occupy all of their suitable habitat.

Location Data

Documented occurrences of focal species within the Santa Clara County RCIS area were used to visually evaluate and refine the habitat distribution models. The data used to identify locations of occurrence of focal species, and to inform the development of the focal species’ habitat models come primarily from the CNDDB (California Natural Diversity Database 2016), with some additional data from the USGS’s Biodiversity Information Serving Our Nation (BISON) database (U.S. Geological Survey 2016). These occurrence records are also displayed in the habitat distribution map. In addition, occurrence data specific to the Habitat Plan (i.e., from a source other than CNDDB) were reviewed to identify suitable land cover types for the focal species’ habitat models, but were not included on the habitat distribution maps. See Section 2. 3.5.2 Habitat Distribution Models , Focal Species Locations for data sources and criteria and methods used for

Occurrences that fell outside of a model’s predicted habitat distribution were evaluated to determine whether they indicated flaws in the model or were an anomalous or erroneous location point. Erroneous points were deleted; anomalous points (e.g., those that occur in unsuitable habitat, or beyond the expected range of the species), were retained but were not used to adjust the model results. Aerial photographs were examined to assess the significance of extreme outliers.

Model Parameters

Model parameters for San Joaquin kit fox were developed to capture movement and foraging habitat and low-use habitat. Movement and foraging habitat includes all grassland land cover types and seasonal wetlands that are adjacent to grasslands. Valley oak forest and woodland, blue oak woodland, and coast live oak forest and woodland within 500-feet of suitable grasslands were also modeled as movement and foraging habitat (ICF International 2012). . Low-use habitat includes areas that San Joaquin kit fox may use occasionally for movement, including all cultivated agriculture types except vineyards and shrublands that are connected to (i.e., adjacent to) movement and foraging habitat described above. These areas represent land that individuals might pass through while moving between other more suitable habitat types (ICF International 2012). The model was limited to watersheds currently thought to have potential to support kit fox movement and dispersal (U.S. Fish and Wildlife Service 1998a, U.S. Fish and Wildlife Service 2006, ICF International 2012, California Natural Diversity Database 2016).