A Guide to California's
Reptiles and Amphibians

Sounds of Pseudacris hypochondriaca hypochondriaca - Baja California Treefrog

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Eggs and Tadpoles

Baja California Treefrog

Male frog floating on water at night producing the avertising call.

Advertisement Calls

An advertisement call is the most well-known call of a frog. It is produced by a male during the breeding season to attract females of his own species. It can also serve an agressive function to defend his calling site by warning rival males of his presence. Frogs usually make the calls around bodies of water that are suitable for breeding and egg laying. These calls can be heard during the evening and at night, and sometimes during daylight at the peak of the breeding season.

The Baja California Treefrog produces two different kinds of advertisement calls: a two-parted, 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 two-parted call of the Baja California Treefrog is known throughout the world through its wide use as a nighttime background sound in old 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 Northern Pacific Treefrog, and it is possible that the calls of all of these species were also used as movie sound effects.)

Diphasic (two-parted) Call

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

This is a very short recording of a single Baja California Treefrog calling two times at night in a riparian canyon in San Diego County (shown below.)

This is a 31 second recording of a small group of Baja California Treefrogs calling two times at night in a riparian canyon in San Diego County (shown below.) Insect noises are heard in the background.

Baja California Treefrog Habitat

This is :53 of a chorus of frogs starting up then winding down recorded at night in Kern County.

Baja California Treefrog Habitat

This is 37 seconds of a large group of frogs calling at night from a small pond in Nye County, Nevada, shown below.

This is short recording of one frog calling at night from a small pond in Nye County, Nevada, shown below.

Baja California Treefrog Habitat

Waveform and Sonogram

This is a recording of one repetition of the advertisement call of a Baja California Trefrog recorded at night in San Diego County. The image on the right 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 monophasic call made by male Sierran Treefrogs. It was recorded at about 9,000 ft. 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 sound is the same as the sound made by the Baja California Pacific Treefrog.)

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 7 second recording of trilled encounter calls made by male Baja California Treefrogs, recorded at a desert marsh in San Bernardino County (shown below) in mid March on a sunny afternoon. The recording starts with some typical advertisement calls, then ends with three trilled calls.

This is a 4 second recording of trilled encounter calls made by male Baja California Treefrogs, recorded at a desert marsh in San Bernardino County (shown below) in mid March on a sunny afternoon. The recording begins with one trill and ends with a second one. Normal advertisement calls can also be heard.

Baja California Treefrog Habitat

This is :09 of a chorus of frogs recorded at night in Kern County. Three encounter calls are heard slightly louder than the chorus.

This is :18 of a chorus of frogs recorded at night in Kern County with several encounter calls.

Baja California Treefrog Habitat

Land Call

The land call is a prolonged one-note kr-r-r-ek sound made much of the year, especially when it is raining. Land calls can be heard during the day, often in wooded areas away from water. I have seen frogs produce this call while they were sitting high on a tree branch as well as when they were on the ground.

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 distant treefrog land calls, and a few birds are heard in the background.

(This sound is the same as the sound made by the Baja California Treefrog.)

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.

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.

(This sound is the same as the sound made by the Baja California Treefrog.)

Short Videos

A male Baja California Treefrog calls at night as part of a chorus of frogs in Kern County. He starts with the two-parted call, then speeds up a bit slurring the two parts together into what is almost a one-part call which he then alternates with the two-parted call.	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 Baja California Treefrog.

In this short video we see three adult male Sierran Treefrogs make their encounter call. These calls were elicited by making a raspy noise near the frogs as they were sitting on the water in calling position. The call of each frog is slightly different. This species is identical in sound and appearance to the Baja California Treefrog.	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. This species is identical in sound and appearance to the Baja California Treefrog.

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

Carlos Davidson - Frog and Toad Calls of the Pacific Coast - Cornell Laboratory of Ornithology

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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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