Fish and Wildlife Service:

Designation of Critical Habitat for the Southern California Distinct Population

Segment of the Mountain Yellow-Legged Frog (Rana muscosa)

Critical Habitat

Critical habitat is defined in section 3 of the Act as--(i) The specific areas within the geographical area occupied by a species, at the time it is listed in accordance with the Act, on which are found those physical or biological features (I) Essential to the conservation of the species and (II) that may require special management considerations or protection; and (ii) specific areas outside the geographical area occupied by a species at the time it is listed, upon a determination that such areas are essential for the conservation of the species…..

Methods

As required by section 4(b)(1)(A) of the Act, we use the best scientific data available to determine areas that contain the features essential to the conservation of the mountain yellow-legged frog….

Primary Constituent Elements

In accordance with section 3(5)(A)(i) of the Act and regulations at 50 CFR 424.12, in determining which areas to designate as critical habitat, we consider those physical and biological features (PCEs) that are essential to the conservation of the species, and within areas occupied by the species at the time of listing, that may require special management considerations or protection. These include, but are not limited to space for individual and population growth and for normal behavior; food, water, air, light, minerals, or other nutritional or physiological requirements; cover or shelter; sites for breeding, reproduction, and rearing (or development) of offspring; and habitats that are protected from disturbance or are representative of the historical geographical and ecological distributions of a species.

Space for Individual and Population Growth and Normal Behavior

Mountain yellow-legged frogs are a highly aquatic, cryptic, diurnal species that occupy mountain streams which have cool waters and originate from springs and snowmelt (Jennings and Hayes 1994a, b). Mountain yellow-legged frogs are most often found in creeks with permanent water in at least some portion of the reach.

Food, Water, Air, Light, or Other Nutritional or Physiological Requirements

Mountain yellow-legged frogs appear to be principally insectivorous, feeding on a wide variety of invertebrates, including beetles (Coleoptera), ants (Formididae), bees (Apoidea), wasps (Hymenoptera), flies (Diptera), true bugs (Hemiptera), and dragonflies (Odonata) (Long 1970). Terrestrial insects and adult stages of aquatic insects may be the preferred food for adult mountain yellow-legged frogs (Bradford 1983); larger frogs consume more aquatic true bugs likely because of their more aquatic behavior (Jennings and Hays 1994a). Some predation of tadpoles by adult mountain yellow-legged frogs appears possible as evidenced in Sierra Nevada populations (Mathews and Pope 1999). The riparian zone, with the associated vegetation canopy (PCE 2), is necessary to maintain the prey base needed for the nutritional requirements of the mountain yellow-legged frog.

Cover or Shelter

Mountain yellow-legged frogs are preyed upon by the western terrestrial garter snake (Thamnophis elegans), two-striped garter snake, Brewer's blackbird (Euphagus cyanocephalus), Clark's nutcrackers (Nucifraga columbiana), raccoons, and coyotes (Canis latrans) (Jennings et al. 1992; Jennings in litt. 2005; Mathews et al. 2002; Mullally and Cunningham 1956; USFS 2002). Pools with bank overhangs, downfall logs or branches, and/or rocks (PCEs 1 and 2) provide cover from predators for mountain yellow-legged frogs….

Primary Constituent Elements for the Mountain Yellow-Legged Frog

Pursuant to our regulations, we are required to identify the known physical and biological features (PCEs) essential to the conservation of the mountain yellow-legged frog. Areas designated as critical habitat for the mountain yellow-legged frog contain both occupied and unoccupied streams and riparian areas within the species' historical geographic range, and contain sufficient PCEs to support at least one life history function….

Criteria Used To Identify Critical Habitat

We are designating critical habitat in areas within the geographical area occupied by the species at the time of listing in 2002, as well as some specific unoccupied areas outside the geographical area occupied by the species at the time of listing, but were historically occupied, because we have determined that such areas are essential for the conservation of the species.

Stream Reaches Occupied at the Time of Listing

We have defined occupied critical habitat as: (a) Those streams known to be occupied by the mountain yellow-legged frog at the time of listing in 2002; (b) the riparian, upland, and aquatic habitats 262 ft (80 m) from the centerline of the stream including tributaries; and (c) aquatic habitats within 4,905 ft (1,495 m) upstream from the upstream-most occurrence and 4,905 ft (1,495 m) downstream from the downstream-most occurrence on the main stem of the river or creek known to be occupied, including any tributary that flows into it (see the following sections for explanation of these values)….

Stream Reaches Unoccupied at the Time of Listing

The streams not known to be currently occupied that are being designated as critical habitat were all historically occupied, and the designation of these areas as critical habitat will decrease the degree of fragmentation within the current geographic distribution of the mountain yellow-legged frog. We believe that the designation of these additional areas not known to be currently occupied by the mountain yellow-legged frog is essential for the conservation of the species because:

(1) The current, overall population size of the mountain yellow-legged frog is extremely small, and it must increase in order to insure long-term survival of this species in southern California (cf. Backlin et al. 2004). While the occupied units provide habitat for current populations, additional units will provide habitat for population augmentation either through natural means, or by re-introduction….

(2) Population augmentation either through natural means or by re-introduction into the additional subunits may increase the viability of the occupied subunits as well as the existence of the mountain yellow-legged frog in southern California as a whole (i.e., increase the likelihood of persistence at the local population level and of this DPS range-wide);

(3) Additional subunits will serve to decrease the degree of fragmentation of the current geographic distribution of the mountain yellow-legged frog within each of the three mountain ranges (i.e., increase connectivity between streams that are known to be currently occupied);….

Special Management Considerations or Protection

When designating critical habitat, we assess whether the primary constituent elements, within the areas determined to be occupied at the time of listing, may require special management considerations or protection. Threats to those features that define the primary constituent elements for the mountain yellow-legged frog include the direct and indirect impacts of some human recreation activities, watershed management practices, water diversions from streams, fire management practices, and hazardous materials spills along roadways adjacent to streams.

Subunits 1A, 1B, 1C, 1D, 2A, and 3A may require special management due to threats posed by recreational activities, including camping, hiking, fishing, and recreational mining (USFS 2002). In areas occupied by mountain yellow-legged frogs, human use in and along streams can disrupt eggs, larvae, and adult frogs (Jennings 1995), change the character of the stream (e.g., sediment), and its bank and associated vegetation in ways that make sections of the stream less suitable as habitat for the species (Stephenson and Calcarone 1999). For example, logging activity, recreational mining, or heavy trampling may alter and/or decrease the availability of habitat features such as bank overhangs, downed logs or branches, and rocks, or may alter pool substrate, thereby reducing or eliminating available foraging, resting, breeding or egg-laying sites, and increasing suspended sediments and turbidity (Service 2005) (PCE 1). Human activities associated with heavy recreational use could also erode or denude stream banks or shores, reduce the extent of riparian vegetation, potentially reduce the available prey base for frogs, alter the amount of stream shade, and increase sedimentation within stream channels due to erosion from exposed soils (Service 2005) (PCEs 1 and 2). Heavy recreational use is specifically cited as a potential threat in Subunit 1A (Bear Gulch and Vincent Gulch, the San Gabriel River--East Fork), Subunit 1C (Little Rock Creek), and Subunit 3A (Fuller Mill Creek and Dark Canyon); recreational mining is cited as a potential threat in Subunit 1A (San Gabriel, East Fork) (Jennings 1994, 1995, 1998, 1999; USFS 2002). However, due to the proximity of the San Bernardino, San Gabriel and San Jacinto Mountains to large urban centers, resulting in high recreational use of these areas, there is potential for recreational impacts to all of the areas being designated as critical habitat…..

Critical Habitat Designation

We are designating three units, divided into 14 subunits, as Critical habitat for the mountain yellow-legged frog. The critical habitat subunits described below constitute our best assessment at this time of (1) Areas determined to be occupied at the time of listing that contain the primary constituent elements essential for the conservation of the species and that may require special management considerations or protection, and (2) those additional areas found to be essential to the conservation of the mountain yellow-legged frog. The three units designated as critical habitat are: (1) The San Gabriel Mountains Unit, (2) the San Bernardino Mountains Unit, and (3) The San Jacinto Mountains Unit….

Critical Habitat Unit 1: San Gabriel Mountains Unit

Unit 1 is comprised solely of USFS lands and lies entirely within the San Gabriel Mountains of the Angeles and San Bernardino National Forests in Los Angeles and San Bernardino counties, California. This unit is comprised of seven subunits (1A, 1B, 1C, 1D, 1E, 1F, and 1G), including four subunits (1A, 1B, 1C, and 1D) that were known to be occupied at the time of listing and are currently occupied and three subunits (1E, 1F, 1G) that are not known to be currently occupied but were historically occupied. The populations in Unit 1 represent the northern- and western-most known occurrences of the mountain yellow-legged frog.

Subunit 1A: San Gabriel River, East Fork
Subunit 1A is comprised of 2,474 ac (1,001 ha) of Federal land along approximately 26.5 mi (42.7 km) of several stream reaches in the upper section of the East Fork of the San Gabriel River, including the Bear Gulch, Vincent Gulch, Fish Fork, Iron Fork, and Alder Gulch streams….

Subunit 1B: Big Rock Creek
Subunit 1B is comprised of 625 ac (253 ha) of Federal lands along approximately 6.1 mi (9.9 km) of Big Rock Creek….

Subunit 1C: Little Rock Creek
Subunit 1C is comprised of 615 ac (249 ha) of Federal lands along approximately 6.1 mi (9.8 km) of Little Rock Creek….

Subunit 1D: Devil’s Canyon
Subunit 1D is comprised of 279 ac (113 ha) of Federal lands along approximately 3.1 mi (4.9 km) of Devil's Canyon. This currently occupied subunit is located within the San Gabriel Wilderness in the Angeles National Forest….

Subunit 1E: Day Canyon
Subunit 1E is comprised of 635 ac (257 ha) of Federal lands designated as critical habitat along approximately 6.5 mi (10.4 km) of Day Canyon and two of its tributaries. This historically occupied, but not known to be currently occupied, subunit is located in the San Bernardino National Forest….

Subunit 1G: Bear Creek
Subunit 1G is comprised of 116 ac (47 ha) of Federal lands along approximately 1.2 mi (2 km) of the upper reaches of Bear Creek, a tributary of the West Fork of the San Gabriel River….

Critical Habitat Unit 2: San Bernardino Mountains Unit...

Critical Habitat Unit 3: San Jacinto Mountains Unit...