Baja California Treefrog

Pseudacris hypochondriaca hypochondriaca

Characteristics

Adults are .75 – 2 inches long from snout to vent. It is a small frog with a large head, large eyes, a slim waist, round pads on the toe tips, limited webbing between the toes, and a wide dark stripe through the middle of each eye that extends from the nostrils to the shoulders (good way to verify the Baja California treefrog). Legs are long and slender. Skin is smooth and moist. Often there is a Y-shaped marking between the eyes. The difference between a male/female is the male’s throat is darkened and wrinkled.

Dorsal body coloring is variable: green, tan, brown, gray, reddish, cream, but it is most often green or brown. The body color and the dark eye stripe do not change, but the body color can quickly change from dark to light, and dark markings on the back and legs can vary in intensity or disappear in response to environmental conditions. The underside is creamy with yellow underneath the back legs.

Tadpoles are up to 1 7/8” long (4.7 cm) blackish to dark brown and light below with a bronze sheen. The intestines are not visible. Viewed from above, the eyes extend to the outline of the head.

Comparison with California Treefrogs – Pseudacris cadaverina

Adults

Baja California Treefrogs have a dark stripe through each eye.

California Treefrogs do not have a dark stripe through each eye.

Baja California Treefrogs are found in a variety of colors including greens, greys and browns.

California Treefrogs are mostly pale with some dark markings.

Tadpoles

Baja California Treefrog tadpoles have eyes that when seen from above are on the edge of the outline of the head.

California Treefrog tadpoles have eyes that, when viewed from above, are set barely within the outline of the head.

California Treefrog tadpoles have a flatter body than those of Baja California Treefrogs, and a more acute snout.

Habitat

This species utilizes a wide variety of habitats, often far from water outside of the breeding season, including forest, woodland, chaparral, grassland, pastures, desert streams and oases, and urban areas. Although, in the breeding season, shallow bodies of water act as habitat due to its component in the laying of eggs. During active periods, adults are most commonly found in close proximity to and along stream channels. During the daytime, individuals seek refuge in cavities or small depressions on the surfaces of the boulders lining streams, often fully exposed to direct sunlight. These perches are usually within a few jumps from the nearest pool.

Range

Even though the Baja California treefrog exist on Santa Rosa, Santa Cruz and Catalina islands, the range of this frog is not clear, due to the small number of specimens sampled for the study that described the species. It is apparently found throughout southern California, south of Santa Barbara County and Bakersfield and on the offshore islands, excluding most of the southeast deserts. It ranges farther east into Nevada, and south into Baja California.

Diet

The Baja California treefrog eats a wide variety of invertebrates, primarily on the ground at night, including a high percentage of flying insects. During the breeding season, they also feed during the day. Typical of most frogs, prey is located by vision, and then the frog lunges with a large sticky tongue to catch the prey and bring it into the mouth to eat. Tadpoles are suspension feeders, eating a variety of prey including algaes, bacteria, protozoa and organic and inorganic debris.

Breeding

Reproduction is aquatic. Fertilization is external. The reproductive cycle is similar to that of most North American Frogs and Toads. Mature adults come into breeding condition and move to ponds or ditches where the males call to advertise their fitness to competing males and to females. Males and females pair up in amplexus in the water where the female lays her eggs as the male fertilizes them externally. The adults leave the water and the eggs hatch into tadpoles which feed in the water and eventually grow four legs, lose their tails and emerge onto land where they disperse into the surrounding territory.

Breeding and egg-laying occurs between November until July, depending on the location. Adults probably become reproductively mature in their first year. Males move to breeding waters and begin to make their advertisement call. These calls attract more males, then eventually females. Males call while in or next to water at night, and during daylight during the peak of breeding when calling can occur all day and night. Some males and females have been observed staying only a few weeks at a breeding site. Some males have been observed moving to another site. And others have been observed staying at a site the entire breeding season. Males are territorial during the breeding season, establishing territories that they will defend with an encounter call or by physically butting and wrestling with another male. Satellite male breeding behavior has been observed – a silent male will intercept and mate with females that are attracted to the calling of other territorial males.

Breeding locations include slow streams, permanent and seasonal ponds, reservoirs, ditches, lakes, marshes, shallow vegetated wetlands, wet meadows, forested swamps, potholes, artificial ponds, and roadside ditches. The Baja California Treefrog tends to avoid large lakes or streams with very cold water.

Females lay on average between 400 – 750 eggs in small, loose, irregular clusters of 10 – 80 eggs each. Egg clusters are attached to sticks, stems, or grass in quiet shallow water. The eggs hatch in two to three weeks. Eggs appear to be resistant to the negative effects of solar UV-B radiation and even to increased water acidification. Eggs can also survive freezing temperatures for a short time.

Tadpoles aggregate for thermoregulation and to avoid predation. Tadpoles metamorphose in about 2 to 2.5 months, generally from June to late August. In summer, there are often large congregations of new metamorphs along the banks of breeding pools. Metamorphosed juveniles leave their birth pond soon after transformation, dispersing into adult habitats.

Voice

Advertisement calls are heard during the evening and at night, and during the daytime at the peak of the breeding season. Males produce two different kinds of very loud 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. They also produce a slow trilled encounter call, a release call, and a land call, which is a prolonged one-note sound that is produced much of the year, especially during the beginning of the fall rains. The most commonly heard frog in its range.

(The 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 any of these species were used as movie sound effects.)

Quick and Cool Facts

• You can find the extended family of treefrogs in your back yard, along the beach, in the Mojave Desert, in woodlands, in grasslands or pastures, and even at 11,000 feet on Mount Whitney.
• Baja California treefrogs change color based on the air temperature and humidity.
• Baja California treefrog’s color change is to reduce the likelihood that it will become a meal for a bullfrog, raccoon, heron, snake, or other predator.
• Baja California treefrogs have special “sticky pads” on their feet that help them climb.
• Treefrog are the only frog in the West that makes the classic “ribbet” vocalization – the sound that Hollywood film producers have made familiar around the world.
• Frog music is heard most often in the spring, but treefrogs vocalize all year unless the temperature dips below freezing.
• Interestingly, the treefrogs coordinate their vocalizations, creating a frog chorus. One male acts as the “chorus master” and starts calling. Other males in the vicinity gradually join in as the chorus swells.

Reference:

https://www.nps.gov/chis/learn/nature/baja-california-treefrog.htm

www.californiaherps.com/frogs/pages/p.hypochondriaca.html