This species occurs in the Central Valley and bordering foothills of California and along the Coast Ranges (south of San Francisco Bay) in the USA, southward into north-western Baja California, Mexico. It is found from near sea level to 1,363m asl (Zeiner et al. (eds.) 1988, cited by Jennings and Hayes 1994), but usually below 910m asl (Stebbins 1985b).
Habitat and Ecology
It lives in a wide range of habitats, from lowlands to foothills, in grasslands, open chaparral and pine-oak woodlands. It is fossorial, and breeds in temporary rain pools and slow-moving streams (for example, in areas flooded by intermittent streams). It also breeds in stock tanks and other artificial water bodies as long as the surrounding habitat is not developed for human settlement or irrigated agriculture.
Jennings and Hayes (1994) mapped several dozen localities with extant populations. The total adult population size is unknown but is likely to be at least many thousands. Since the 1950s, substantial declines have been noted in the Central Valley and southern California. In southern California, more than 80% of the previously occupied habitat has been developed or converted to incompatible uses; more than 30% has been similarly affected in northern and central California (Jennings and Hayes 1994). In both the US and Mexican portions of its range, this species is still common where appropriate habitat exists.
The main threat to this species is the development and conversion of habitat to incompatible uses such as human settlement and irrigated agriculture, which destroy the terrestrial habitat and change the hydroperiod of temporary pools. Recruitment may be unsuccessful in pools with bullfrogs (Rana catesbeiana) or introduced fish (for example, at least historically, those containing mosquitofish (Gambusia) used for mosquito abatement).
This species is protected in a few small Nature Conservancy preserves, some US Department of Defence, Department of Energy, and Bureau of Land Management lands, some National Monuments, and some National Wildlife Refuges. It also occurs within the University of California's Natural Reserve System. This species is also covered in some US federal Habitat Conservation Plans, but is is not listed by US state or federal agencies.
Spea multiplicata formerly was included in this species, which is frequently considered a synonym of S. multiplicata.
Georgina Santos-Barrera, Geoffrey Hammerson, Steven Morey 2004. Spea hammondii. In: IUCN 2014