COMMISSION

Western Spadefoot Toad Monitoring and Management
The western spadefoot toad is a nocturnal amphibian that has been found at Carnegie
SVRA in previous years and about which very little is known. This species chooses to
breed in rain puddles in the floodplain and the ephemeral Corral Hollow Creek instead of
the various ponds in the SVRA. They can transform from eggs to juveniles in as little as
30 days. This strategy allows them to avoid competing with
other aquatic species for resources and to avoid predators
such as the California tiger salamander.
Although the western spadefoot toad is currently classified as
a species of special concern under the California Department
of Fish and Wildlife (CDFW), it is currently under review by
Western spadefoot toad metamorph
the United States Fish and Wildlife Service (USFWS) to be
listed as federally threatened. Prior to this listing proposal,
environmental scientists at Carnegie SVRA began targeted night surveys, starting in
December 2014, in an attempt to detect adult western spadefoot toads within the SVRA.
In February 2015, this species was found during an explosive breeding event that occurred
on a warm and rainy night. They were breeding
in various puddles that formed throughout the
floodplain, including the 4x4 play area and three
areas used for staging. Environmental scientists
mapped and fenced the breeding pools before
the SVRA opened the next day to protect the
egg masses from disturbance. Since little to no
rain was received after the initial February 2015
storms, many of these breeding pools dried out
before metamorphosis could complete, resulting
Western spadefoot toad monitor fencing
in desiccated tadpoles in some of the puddles. Despite the challenges that the drought
and abnormal rainfall patterns presented, some juveniles survived and hid in drying ponds.
Protective barriers were left standing until May 2015 when the last of the metamorphs
dispersed into their upland habitat.
During the winter of 2016, environmental scientists monitored and documented successful
breeding throughout the SVRA due to higher rainfalls. Other variables, such as water
temperature, ambient temperature, and vegetation were measured to allow for future
analysis of factors affecting breeding site selection and tadpole survivorship. Moving
forward, the monitoring program will expand to include dissolved oxygen measurements
and possibly telemetry research to discover where these toads are ultimately aestivating
(going dormant) during the dry summer months.
2017 Program Report 137