Is there a best time/season to hear frogs and amphibians calling? I’ve heard new moons are best because the frogs are less afraid of predators. – Beth, Berkeley
Thank you for the question, Beth! Frogs and toads (which are, technically, also frogs), are amphibians in the order Anura, and inhabit a variety of different habitat types around the world, such as tropical rainforests, temperate grassland, and even deserts. Sensitive to environmental changes, these ectothermic animals are important indicator species and are facing one of the largest and fastest extinctions in today’s world. Unlike their fellow “class” mates, the salamanders and caecilians, anurans are known for their amphibious lifestyle, jumping skills, and their ability to call. Ranging from the tiniest squeak to a cacophonous symphony, a frog and toad’s vocalization is often the most recognizable feature of these brilliant creatures.
Most frogs are able to create a call or noise that is distinctive to their species. Generally, this is accomplished by taking air through the larynx and vocal sac — an inflatable bulbous protrusion (multiple in some species) at the throat. Depending on the type of frog, calls can be barely audible to almost deafening. The size of the frog does not dictate the magnitude of the calls, as evident with Puerto Rico’s coqui, a tiny tree frog with one of the loudest known vocalizations — upwards of 100 decibels. Typically, calls are used to attract other frogs, particularly potential mates, and are usually done by males during the breeding season. Frogs may also vocalize to establish territorial claims or when disturbed.
A number of frog species range in the greater San Francisco Bay Area. Natives include the ubiquitous Sierran/Pacific tree frog (Pseudacris sierra), the burly California toad (Anaxyrus boreas), the comical-looking western spadefoot toad (Spea hammondii), the elusive foothill yellow-legged frog (Rana boylii), and Mark Twain’s “celebrated jumping frog,” the California red-legged frog (Rana draytonii). The large and destructive American bullfrog (Lithobates catesbeianus) and Golden Gate Park’s isolated population of African clawed frog (Xenopus laevus) are our invasive Anura species. All of these frogs vocalize and are most often heard during the breeding season.
Frogs typically begin their mating rituals with the coming of steady rainfall in late winter to late spring. (Some species, such as the foothill yellow-legged frog, may continue breeding into the summer.) They take to their preferred breeding sites and habitat, and the sound of excited males fills the air as they attempt to attract receptive females with their song. Water bodies, such as ponds, creeks, vernal pools — and in the case of explosive breeders such as spadefoot toads, puddles — become venues for a show of croaking, wrestling amongst rival males, and reproductive hugging, which is known as amplexus. Generally, frogs tend to be most active at night, and calls are best heard during their nocturnal romps.
Nocturnal activity amongst reptiles and amphibians is very dependent on the type of animal and its ecological niche. Moon phase may potentially play a role in activity, but amphibians, particularly frogs and toads, are usually in areas that offer many places to hide, such as reed-filled ponds or waterways in which they can submerge if need be. So moon phase should not directly affect their activity, especially vocalization during breeding season. As for reptiles, the lizards and turtles of the Bay Area are diurnal and are not active at night. Snakes, however, can often be encountered while crossing roads on warm nights in search of prey or mates. They can be quite conspicuous and may refrain from activity based on moon phase. When the moon is brighter, it is more likely that these animals are to be exposed and seen by potential nocturnal predators, such as owls and coyotes.
However, as evident with new discoveries within the world of herpetology, such as the influence of territorial status on male poison frog parental care, or that the bite of Komodo dragons are actually venomous, there are always exceptions to the rules! Certain environmental factors may limit or expand animal activity. Getting outdoors, exploring different habitats, and naturalizing are the best ways to encounter frog calls, amongst the plethora of other interesting natural occurrences.
Zach Lim is a naturalist and director at Tree Frog Treks, a science education organization. A San Francisco native, he is interested in citizen science and nature photography, particularly that of Northern California flora and fauna. His photos can be seen on Instagram and Flickr.
Ask the Naturalist is a reader-funded bimonthly column with the California Center for Natural History that answers your questions about the natural world of the San Francisco Bay Area. Have a question for the naturalist? Fill out our question form or email us at atn at baynature.org!
