A Guide to California's
Reptiles and Amphibians

Sounds of
Sierran Treefrog - Pseudacris sierra

(Jameson, Mackey, and Richmond, 1966)

(= Pacific Chorus Frog, = Pacific Treefrog. SeeAlternate Names)

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Click the speaker icon to listen to an mp3 sound file.

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Tadpoles

Male calling at night

Male being picked up across its back extending its throat pouch and producing the release call

Calling male with throat sack partially extended.

Sierran Treefrog
Pictures and Information.

Male frogs and toads sometimes make a variety of sounds. These calls can have different functions.

Advertisement Calls

The advertisement call is the most well-known call of a frog or toad. It is made by a male during the breeding season to establish his territory and repel rival males and to attract females as potential mates. Males usually make the call in or near bodies of water near areas that are attractive to a female as a good place to lay her eggs. Advertisement calls can be heard during the evening and at night, and often during daylight at the peak of the breeding season. Sometimes an advertisement call will be heard outside of the breeding season and away from water. The reason for this is not understood.

Each species has its own unique advertisement call. This is necessary to differentiate them when there is more than one species calling. The evolution of this specific male advertisement call and its recognition by females is considered to be an important isolating mechanism in the evolution of a species.

The Sierran Treefrog produces two different kinds of very loud advertisement calls: a two-part, or diphasic call, typically described as rib-it, or krek-ek, with the last syllable rising in inflection, and a one-part, or monophasic call, also called the enhanced mate attraction call.

The call of the Baja California Treefrog is known throughout the world through its wide use as a nighttime background sound in many Hollywood movies, even those which are set in areas well outside the range of this frog. The call of the Baja California Treefrog is identical to that of the Sierran Treefrog and the Pacific Treefrog, and it is possible that the calls of all of these species were also used as movie sound effects.

Diphasic (two-part) Call

This call is produced during the day and at night, often in large choruses.

These are solo calls made by two consecutive frogs during daylight in Alpine County.

This is a 30 second continuous recording of a group of frogs calling at night from a flooded field in Stanislaus County.

This is a 60 second continuous recording of a large group of distant frogs calling on a cold night in early February in Marin County.
A large nocturnal chorus like this sounds like a loud high-pitched buzz making it difficult to hear the individual calls.

This is a 30 second continuous recording of a distant group of frogs calling at night from a vernal pool in an urban area of Butte County
with a heavy wind sound in the background.

Waveform and Sonogram

This is a recording of one repetition of the advertisement call of a Sierran Trefrog recorded at night in San Joaquin County.
The image above is a visual representation of this call. Click on it to see a larger image.
Click here for information about how to read the waveform and sonogram images.

Monophasic (one-part) (enhanced) Call

This call is produced during the day and at night. It is produced at a high rate when a male is approached by a female, and he continues to produce it until he has amplexed the female.

This is a 12 second recording of the fast enhanced mate attraction call made by a male Sierran Treefrog. It was recorded at about 9,000 feet of elevation in Alpine County in late June at the beginning of the breeding season when the snow was melting around the breeding pond. Another deeper single-note call is heard along with birds and flowing water.

This is a recording of two males making the enhanced call in Alpine County. It begins with one male calling, then a second joins in, and they slowly sync up their calls until they are evenly spaced.

Trilled Encounter Call

The trilled encounter call is a raspy trilled sound. It is an aggressive signal aimed at other males and is used to establish spacing between them at the calling site during a breeding chorus. The encounter call is typically heard during the beginning of the chorus when territories are being established and then later when a male intrudes on the territory of another male either physically or with very loud calling.

This is a 13 second recording of the encounter calls made by three male frogs in Alpine County during daylight.

This is a 6 second recording of several trilled encounter calls made by a male Sierran Treefrog at a high-altitude pond in Alpine County during daylight. Advertisement calls are also heard.

Land Call

The land call is a prolonged one-note kr-r-r-ek sound. Land calls can be heard during the day, often in wooded areas away from water. I have heard frogs produce this call while they were sitting high on a tree branch as well as when they were on the ground, usually hidden in dense vegetation.
The call is sometimes referred to as the "Fall awakening call" and it does appear to be made mostly during Fall when the rains are beginning and the frogs are coming out of their summer slumber.

This is a 36 second recording of the land calls of a single Sierran Treefrog during daylight in November near a pond beside the ocean in Marin County. Ocean waves, other treefrog land calls, and a few birds are heard in the background.

Daytime Calls

During daylight, frogs often make a variety of calls which probably help them to warm up and establish a territory before they begin the full chorus. A group of frogs calling during daylight, can sound much different than a full night chorus (or day chorus during the peak of the breeding season.) Typically there are fewer frogs making weaker calls and they will start and stop, leaving long stretches of silence. Sometimes they make what sounds like a series of land calls, other times they make the faster one-part enhanced call. Sometimes they make the encounter call. When a lot of frogs start calling, they will then start making the two-parted call. And sometimes one or two frogs will simply make the two-part call repeated at longer intervals than in a full chorus.

This is a 60 second continuous recording of a group of frogs calling from a small pond on a sunny day in late February in Contra Costa County. A variety of calls can be heard in this chorus. Red-winged Blackbirds can also be heard singing.

This is a 23 second continuous recording of one frog calling from a small pond on a sunny day in late February in Contra Costa County. He makes a weak elongated two-parted call, then another frog starts calling towards the end. Red-winged Blackbirds can also be heard singing.

This is a 13 second continuous recording of a frogs calling from a small pond on a sunny day in late February in Contra Costa County. This call is similar to the rapid one-part enhanced call. Another frog makes an encounter call towards the end. Red-winged Blackbirds can also be heard singing.

Release Call

The release call is made by a frog when another male frog attempts to clasp its back in amplexus. A frog will also produce this call when it is grabbed across the back by a human, and probably also when it is grabbed by other types of predators. (See picture above left.)

This is a 5 second recording of 3 release calls produced by a male Sierran Treefrog in breeding phase as it was grabbed across the back. (The frog was not harmed.) Recorded in Alpine County.

Short Videos


Three adult male Sierran Treefrogs make their advertisement call one afternoon in early March in Contra Costa County.	Three adult male Sierran Treefrogs make their trilled encounter call. The call of each frog is slightly different. I got the frogs to make these calls near the camera by imitating the encounter call when I was close to the frogs which were sitting on the water in calling position.	A male Sierran Treefrog makes a few advertisement calls, until a second frog between him and the camera makes a raspy trilled encounter call. The first frog responds with his encounter call, but when the second frog continues, he then turns to face his aggressor and charges toward him, continuing to make his encounter call. The second frog changes his call to a faster one part call. Finally they both stop, and the first frog sucks in his throat sac and dives underwater.

An adult male Sierran Treefrog makes a one-part call while floating on the water on a sunny afternoon in Contra Costa County.	A male Sierran Treefrog makes the one-part or enhanced call from the edge of a small temporary snow-melt pond at 8,600 feet elevation in Alpine County. This species is identical in sound and appearance to the Pacific Treefrog.

You can listen to more recordings of Sierran (Pacific) Treefrogs on this cd:

Carlos Davidson - Frog and Toad Calls of the Pacific Coast

and on the cd that comes with this book:

Lang Elliott, Carl Gerhardt, and Carlos Davidson - The Frogs and Toads of North America - Houghton Mifflin Harcourt.

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Sounds of Sierran Treefrog - Pseudacris sierra

Sounds of
Sierran Treefrog - Pseudacris sierra