IRC staff and volunteers monitoring a spadefoot toad pond
The Western spadefoot toad is a species that has been commonly found throughout California’s Central Valley and in coastal ranges from just south of Monterey County all the way to Baja California, Mexico. Though the spadefoot toad spends the majority of the year burrowing up to three feet underground, following the wet and rainy season they emerge to produce the next generation of toads. In order for the breeding season to be successful, spadefoot toads require temporary pools or shallow streams that retain water for at least 35 days. However, due to California’s historic drought, the population of spadefoot toads on the Landmarks and surrounding areas has significantly decreased in recent years, so much so that they’ve been listed as a species of special concern under the National Community Conservation Planning program.
The main cause of this population decline is likely southern California’s dry conditions, which make it challenging for spadefoot toads to locate the shallow bodies of water necessary for breeding. As a result, Irvine Ranch Conservancy alongside OC Parks, The Nature Conservancy and the USGS have joined forces to help spadefoot toad breeding and overall survival with the implementation of a major habitat restoration and enhancement project in OC Parks’ Limestone Canyon.
The main cause of this population decline is likely southern California’s dry conditions, which make it challenging for spadefoot toads to locate the shallow bodies of water necessary for breeding. As a result, Irvine Ranch Conservancy alongside OC Parks, The Nature Conservancy and the USGS have joined forces to help spadefoot toad breeding and overall survival with the implementation of a major habitat restoration and enhancement project in OC Parks’ Limestone Canyon.
Spadefoot toad tadpole and eggs IRC and its partners developed a plan to create several ponds, and enhance existing ponds, within a 2.5-acre area located in OC Parks’ Limestone Canyon where a previous USGS survey found an existing spadefoot toad population. The pools were placed strategically and constructed in a way to maximize water capture following a rain event. The team installed synthetic liners in some ponds to help retain moisture while incorporating bentonite clay into the soil, which expands in the soil to help fill cracks and hold water. Both these treatments will help combat the effects of drought and hold water long enough for a full breeding cycle for the toads. Though these ponds are designed to capture naturally occurring water from rain, IRC plans to monitor them and keep at least one pond filled with water to ensure a healthy and functional habitat.
In addition to the pond enhancements, restorative work will also be done to the surrounding vegetation to provide habitat for the spadefoot toads and help them travel through the landscape to the breeding ponds. The current phase of site preparation for the habitat enhancement project is focused on removing non-native plants and depleting the non-native seed back and could take up to several years. Once this phase is complete, the team will plant native seeds and container plants that will give the toads the cover and habitat they need to safely access the breeding ponds.
After a few years of site prep, seeding native plants and maintaining and weeding the land, the last year of maintenance for this project is forecasted to be around 2028-2029. IRC plans to continue working with USGS for future monitoring, as well as recruiting volunteers to monitor the pools and check for eggs, tadpoles, water levels and more.
For more information about the restoration efforts on the Landmarks, visit IRConservancy.org, LetsGoOutside.org or follow the Landmarks on Facebook, Instagram and Twitter.
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