Western Spadefoot Toad

Like many amphibians, the western spadefoot toad (Spea hammondii) is a good indicator of ecosystem health because it depends upon both aquatic and terrestrial environments; is susceptible to environmental contaminants, as it absorbs air and water through its skin; and is relatively long-lived, so can contribute to our understanding of environmental trends over time. The western spadefoot depends on seasonally wet habitats (e.g., vernal pools or temporary ponds) for breeding and larval development, which makes it an indicator for those habitats as well.

Although most of the remaining historical breeding sites in Orange County are now in protected lands, climate change continues to threaten the species by reducing the availability of suitable pools; prolonged climate-driven drought, invasive species, disease, and fire are among the challenges it faces.

To evaluate the health of western spadefoot populations in the Central and Coastal Study Areas, researchers assessed four key metrics. In both study areas, the condition of habitat availability scored in the range of significant concern, with strong evidence of declining trends and high confidence in the data across both. Breeding activity and hydroperiod length condition both scored in the caution range and also showed declining trends, with moderate confidence in the data. The condition for presence of invasive species was rated caution but showed no change in trends, with high confidence in the assessment.

More comprehensive surveys of potential breeding sites are needed to better estimate population health and guide management. Conservation actions could include protecting existing pools, enhancing hydroperiod conditions, and creating new breeding sites to help stabilize and expand populations.