Terrestrial Habitat Preferences of Adult Arroyo Southwestern Toads

Abstract

Using an external belt attachment system, we attached 1.8-g radiotransmitters to arroyo southwestern toads (Bufo microscaphus californicus). We tracked 83 arroyo southwestern toads over an average period of 30.9 days (SD = 29.0) in 1998. Male calling activity began at the study site on 6 March and ended on 29 July. We observed arroyo toad activity in upland habitats throughout the study. We examined the habitat preferences of arroyo toads by comparing land cover within a minimum convex polygon estimate home range for each animal to the study site subarea where each toad occurred. We also compared substrate, vegetation, and vegetation structure use to availability within each minimum convex polygon area. We found significant between-sex differences in land use and vegetation-type preferences during the study, but not for substrate or vegetation-structure preferences. Female arroyo southwestern toads preferred terrace and channel habitats to campground, agricultural, or upland habitats.During the breeding season, male arroyo southwestern toad preference for channel habitats was significantly greater than for all other habitat types. Toads preferred sands for burrowing substrate, but no substrate type was preferred for surface activity. Differences in preference rank for vegetation type were weak. Male use of agricultural lands adjacent to breeding sites increased after the breeding season. Dense, tall vegetation structures were least preferred by arroyo southwestern toads for burrows. Arroyo southwestern toads may forage and disperse through many vegetation types that are common in riparian and upland habitats of southern California.