The Yellow-Legged Frog
We have had several projects that are within the habitats of the Foothill Yellow-legged Frog. In honor of this threatened species, we wanted to create a post to educate a little bit about this hoppy friend.
This species is found primarily in lower elevation streams in the foothills and mountains of California and Oregon (California Herps & US Forrest Service). They can grow to be about 1.5 to 3 inches long. Its skin has a grainy texture and a gray to brownish hue with a yellow belly.
The Foothill Yellow-legged Frog lives in streams, rivers, and adjacent habitats. They lay eggs in the springtime, all based on their natural triggers caused by changing water flows. Their preferred egg-laying location is in well lit, stagnant water. The eggs are susceptible to predation and physical damage from the environment in this stage. Once the eggs survive incubation they should hatch at a time of the year that allows for the tadpoles to have ample access to algae and other food sources. Once fall rain comes in, it triggers juveniles to move upstream into more shaded locations.
Yellow-legged frog habitat near Lake Berryessa in California.
In 2019 this species was recognized by California as a threatened species, which is why we haven't heard much about them on our job sites until recently (Center for Biological Diversity). Their numbers have been declining so strongly in local areas that they are nearing extinction in about two-thirds of the locations that they are found in.
It's believed that the specific areas in which these populations live in have been impacted by local factors, specifically involving seemingly small changes in the stream that they reside in. Such changes that are believed to be responsible for their decline include altering the flow rate, depth, and temperature of their streams.
They are largely dependent on seasonal variations in the stream. These seasonal indicators trigger reproduction, movement, and overall life occurrences. The possible impacts for changing these factors such as the depth, flow rate, and temperature include:
Poorly timed breeding triggers based on unnatural environment cues
Inadequate tadpole health and growth rate
Physical damage to the egg masses
Habitat loss and destruction, hindering proper locations to reproduce and feed
Gene flow issues as reservoirs prevent healthy biodiversity in the population and could lead to populations being more susceptible to disease
Non-native predators in reservoirs that spread to rivers
Anthropogenic activities are likely responsible for these stream modifications and include:
Water Management Activities (e.g. Dams and Reservoirs)
Landscaping Changes (e.g. removing the habitat they live in)
Necessary bridge construction occurring in Yellow-Legged Frog habitat. Several wildlife biologists were out there making sure that all frogs were safely relocated downstream.
These activities are likely to cause unnatural changes in streamflow, depth, and temperature which impacts the frogs as it triggers reproduction and other life cues when they shouldn't be triggered. For example, it can really hurt the populations of these frogs when they are triggered to reproduce at a time when the tadpoles will not be able to survive.
If the frogs are triggered to breed by unnatural streamflow changes in the Wintertime, when it is too cold for their food source to grow, it can cause their offspring to not have enough food and succumb to the elements.
We want to avoid species from going extinct for several reasons. Some species have a medicinal or direct benefit to humans, such as bees that pollinate our foods, or plants that can grow medicines that we can concentrate. Other species may not have a direct benefit, but it's important to know that our ecosystems are delicately balanced. When we throw off nature's balances the impacts can be devastating and profound.
We hope that you consider being a part of the change to bring this species back to healthy populations. Keep your construction clean, hire professional biologists and stormwater inspectors to keep your site clean, and practice environmentally habits in your daily life.
Go Yellow-legged frog! We've got your back in the field.
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