Mountain Yellow-Legged Frog in San Jacinto area of San Bernardino National Forest.

Protected Status: The mountain yellow-legged frog was federally listed as Endangered (Southern California Distinct Vertebrate Population Segment) on July 2, 2002. Critical Habitat was proposed on September 13, 2005. This species is also a California Department of Fish and Game Species of Special Concern.

Ecology: 1) Where does it live?: The mountains of southern California at elevations of 1,200–7,500 feet (370–2,290 meters). They have been found at lower elevations (down to 1,500 feet (457 meters) where the right mountain stream characteristics occur (e.g., Eaton Canyon, San Gabriel River). In southern California, the mountain yellow-legged frog historically occurred in numerous drainages in the San Gabriel, San Bernardino, and San Jacinto Mountains and in at least one location on Palomar Mountain. Currently, the mountain yellow-legged frog is known to be in only seven places in portions of the San Gabriel, San Bernardino, and San Jacinto mountains, all at least partially on National Forest System lands. In southern California, mountain yellow-legged frogs inhabit perennial mountain streams (i.e. streams that contain plunge pools or backwaters year-round, although not necessarily flowing year-round) with steep gradients. They live in rocky shaded streams with cool waters originating from springs and snowmelt. They are diurnal (active during the day) and are seldom found more than two or three jumps from water. The coldest winter months are spent in hibernation, probably under water beneath the ice in lakes and under shelter in or at the edge of streams. Some individuals have been found over wintering in near-shore environments in deep crevices and under ledges. They emerge from over wintering sites and begin breeding in early spring, depending on local climate. At lower elevations in southern California, most activity occurs from mid-March to October; however, juveniles have been found in November and early January. At high elevations in southern California and the Sierra Nevada the period of activity is shorter, generally from May or June to mid-October. Normal home ranges of mountain yellow-legged frogs are probably not more than 33 feet (10 meters) along the stream. Males make weak vocalizations that may function in territorial defense and probably defend areas around themselves during the breeding season.

2) What does it eat?: Ladybugs, dragonfly nymphs, beetles, flies, ants, bees, wasps, true bugs and tree frog and Yosemite toad tadpoles.

3) What eats it?: a few examples: Garter snake, nonnative fishes and amphibians such as trout and bullfrogs, coyote, Brewer's blackbird, Clark's nutcracker.

4) Reproduction: In southern California, they breed March–June after high water in streams subsides. Eggs are typically deposited in shallow water and may be attached to undercut banks or vegetation. In streams in rocky canyons, the eggs may be attached to stones on the stream bottom. The time required to develop from fertilization to metamorphosis reportedly ranges up to 3.5 years, with reproductive maturity reached from 3 to 4 years after metamorphosis. Little is known about longevity, age distribution, or growth rate of mountain yellow-legged frogs.

5) Threats: Mountain yellow-legged frogs population seriously declined over the last three–four decades. This decline was not well documented, but they were abundant in the Sierra Nevada and many southern California streams prior to the late 1960s. It has been suggested that mountain yellow-legged frogs have been extirpated from 99 percent of their historic range in southern California. Remaining populations are now so small that population dynamics have been disrupted and dispersal links between local populations are extremely weak. The causes of the decline are not known, but experts believe the following factors play a significant role: (1) Past habitat destruction related to activities such as logging, mining, and habitat conversions for water development, agriculture, and commercial development; (2) nonnative predators and competitors such as introduced trout and bullfrogs. However, in the case of the southern populations, habitat destruction related to activities such as logging and commercial development doesn’t seem a significant factor in their decline because these activities are not prominent within the frog’s habitat in southern California. Other environmental factors that may adversely affect mountain yellow-legged frogs include pesticides, certain pathogens, ultraviolet-B radiation, or a combination of these factors. The lack of connectivity is a huge impact to frogs on the San Bernardino National Forest. The streams on this forest used to connect with suitable habitat at the foot of the mountains and now, once these drainages leave the Forest, they are almost all contained in concrete channels. When large wildland fires and floods occur, the frogs are washed out of the drainages, and are not able to repopulate from adjacent drainages even if those drainages were not affected by fires and flooding. Many of the drainages on this forest have been through this fire/flood scenario in the last 100 years and this may be why these frogs are absent from some of the historical locations. Large, high intensity wildland fires and subsequent flooding are probably the biggest threat to the remaining populations. The primary human caused threats to this species are (1) the increasing spread of nonnative predatory fish and amphibians (i.e., trout and bullfrog), (2) loss of breeding pools as a result of siltation or declining surface water, and (3) disturbance of individuals and egg masses by land use activities. Ongoing activities on National Forest System lands that are affecting mountain yellow-legged frogs include roads and trails, recreation facilities, and some small-scale mining and prospecting operations. There is uncertainty about the effects of introduced trout in southern California, because mountain yellow-legged frogs occupy stream habitats rather than lakes as in the Sierra Nevadas. Only rainbow trout were observed during surveys at two known mountain yellow-legged frog locations in southern California in 1997: Vincent Gulch (a fork of the upper San Gabriel River) and Fuller Mill Creek. The relationship between introduced trout and mountain yellow-legged frogs in southern California streams requires further study. Loss of breeding pools as a result of siltation or declining surface water is a significant threat to mountain yellow-legged frogs. Recreation use at Dark Canyon, Fuller Mill Creek, may be affecting mountain yellow-legged frogs at these locations. To avoid these impacts, it may be necessary to reroute trails and relocate campsites to encourage recreationists away from key-breeding areas. The potential risk to populations from large wildland fires and post-fire flooding is also a major concern. Siltation by any means, whether it is from intense grazing, mining, off-highway vehicles (OHV’s), or the aftermath of fires, can eliminate amphibian populations that breed in streams.

Protections and Recovery Plans: More survey work is needed to determine if more populations exist and to better determine the size of known populations. Reintroductions of mountain yellow-legged frogs to historically occupied sites may be an option, particularly in the areas of large suitable habitat. However, these specific habitat conditions necessary for reintroductions need to first be defined. Mountain yellow-legged frog populations on National Forest System lands are small, localized, and vulnerable to existing threats; therefore, they need site-specific management attention. Because of the extremely small population size, the species is at risk from local extinction that could result from environmental variation, natural catastrophes such as flood and fire, and chance variation in demographic population parameters. Genetic deterioration and disruption of meta-population dynamics are other concerns related to small population size.

Fuller Mill Creek contains both suitable and historical habitat for mountain yellow-legged frogs. Frogs are known to occupy portions of Fuller Mill Creek within and upstream of the private Pinewood in-holding. Although the habitat within the Fuller Mill Picnic Area is suitable for frogs, there are currently no known occurrences. However, it is possible for frogs to migrate or disperse into downstream suitable habitat. Passive monitoring occurred in 2001 and 2002 after directional signing was installed requesting voluntary avoidance of creeks in both Dark Canyon Campground and Fuller Mill Picnic Area. Employees in casual dress would monitor the creek adjacent to the campground and record all instances of activities in the water. Results of monitoring indicated that visitors chose to recreate in the creek despite interpretive signage and voluntary closure.

During 2003, the San Jacinto Ranger District experienced extreme drought conditions. During this year, portions of the North Fork San Jacinto River that were within Dark Canyon campground were dry. No monitoring of the creek was implemented. Active monitoring efforts in Dark Canyon Campground occurred in 2004. Employees and volunteers again monitored the creek adjacent the campground after greatly increasing the number of directional signage. Monitors were in official uniform and made contacts with the public to request avoidance of the creek. Monitors recorded several observations of forest visitors choosing to ignore requests to avoid the creek. Hikers were seen using the trail along the creek and several campers were discovered swimming in a deep pool upstream of the campground. Active monitoring as described did not occur at Fuller Mill Picnic Area in 2004 or 2005.