Thesis

Habitat suitability analysis of the Coast Horned Lizard (Phrynosoma coronatum blainvillii) in the Santa Monica Mountain National Recreation Area

The Coast Horned Lizard (Phrynosoma coronatum blainvillii) is a native species of special concern in California. One of the major threats to Coast Horned Lizards, particularly in southern California, is habitat loss and fragmentation. Studies have suggested that the Coast Horned Lizard selects habitats in chaparral and coastal sage scrub vegetation with friable sandy soils and low to moderate slope percent rise. The Santa Monica Mountains National Recreation Area (SMMNRA), located in Los Angeles and Ventura counties, is within the known range of Coast Horned Lizard inhabitation. Due to ecologically disruptive human activity in and around the SMMNRA, potential Coast Horned Lizard highly suitable habitat may be at risk of fragmentation, decrease in suitability and/or complete loss of habitat. This study identifies areas of high Coast Horned Lizard suitability so that these areas may be further studied in regards to actual species presence and human impact. Habitat suitability models and landscape pattern were analyzed to investigate the extent to which the SMMNRA is suitable for Coast Horned Lizard inhabitation. First, three habitat suitability models were used to classify the habitat suitability of areas in the SMMNRA depending on designated habitat needs such as slope, soil type, and vegetation cover. Then landscape metrics were used to measure habitat fragmentation, particularly for highly suitable areas. In the SMMNRA, 70% of the total land area was found to meet the majority of the habitat suitability criteria (high suitability, HSA) or some of these requirements (high-medium suitability, HMSA) for the Coast Horned Lizard. HMSAs covered from 59% to 66% of the SMMNRA, depending on the model's weighting. Similarities in percent areas were observed between the results for model 1 and model 3. Model 2 showed significantly higher HSA percent (11%) than other models (3%) due to increased vegetation weighting. The landscape patterns and metrics of the SMMNRA showed that most of the area is at least HMSA for Coast Horned Lizards. Fragmentation occurred in areas of human impact but did not prevent the connection of suitable habitats within the interior mountain range. Other factors of suitability should be explored in respect to the SMMNRA to gain a more accurate assessment of Coast Horned Lizard habitat. In addition, field surveys would be needed to confirm actual Coast Horned Lizard presence.

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