49752 Federal Register / Vol. 59, No. 188 I Thursday, September29, 1994 / Rules and Regulations DEPARTMENT OF THE INTERIOR one of 19 recognized subspecies of the pocket mouse as a distinct species, he little pocket mouse (Perognathus subsequently concluded that P. Fish and Wildlife Service longimembris) (Hall 1981). This species pacificus represented two subspecies of is one of the smallestmembers of the the little pocket mouse, P. Iongirnembris 5OCFRPart17 ~ iLk; family Heteromyidae, which consists of pacificus and P. 1. cantwelli, after RIN 1018—AC39 spiny pocketmice (Heteroniys and examining additional specimens (von Liomys), pocket mice (Perognathus and Bloeker 1932). Subsequent toa Endangered and Threatened Wildlife Chaetodipus), kangaroo rats biometric analysis of 331 specimens of and Plants; Determination of (Dipodomys), and kangaroo mice the little pocketmouse, Huey (1939) Endangered Status for the Pacific (Microdipodops). Virtually all (if not all) recognized P. 1. pacificus tobe inclusive Pocket Mouse members of this family are nocturnal, of the two subspecies described by von granivorous and have external, deep, Bloeker (1932). Subsequent taxonomic AGENCY: Fish and Wildlife Service, fur-lined cheek pouches (Ingles 1965; treatments (e.g., Hall 1981; Williams et Interior. Dr. P. Brylski, consulting mammalogist, al. 1993) haveretained the Pacific ACTION: Final rule. pers. comm., 1993). pocket mouse as a distinct subspecies. Perognathus longiniembris ranges in Although a taxonomic review of P. SUMMARY: The Fish and Wildlife Service size from about 110 to 151 millimeters longiniembris may be appropriate, the (Service) determines the Pacific pocket (mm) (4.3 to 5.9 inches) from nose to tip Pacific pocket mouse has been mouse (Perognath us Iongimembris of tail (Hall 1981) and weighs 7 to 9 pacificus) to be an endangered species described as distinct from related forms grams (1/4 to ½oz.) (Burt and (Dr. D. Williams, mammalogist, in iitt, throughout its range in coastal southern Grossenheider 1976). The body pelage is 1993). California, pursuant to the Endangered spineless,bristle-free, and Under section 3(15) of the Act (16 Species Act of 1973, as amended (Act). predominately brown, pinkish buff or U.S.C. 1531 et seq.), the term “species” Critical habitat is not being designated. ochraceousbuff aboveand light brown, is defined to include recognized Thissmall rodent is an obligate resident pale tawny, buff, or whitish below. subspecies. Therefore, throughout the of river and marinealluvium and There are typically two small patchesof remainder of this rule, Perognathus coastal sage scrub plant communities in lighter hairs at the base of the ear. The longimembris pacificus (hereafter the immediate vicinity of the coast. tail canbe either distinctly or referred to as the Pacific pocket mouse), Although the Pacific pocket mouse indistinctly bicolored. The little pocket is treated as a “species”. formerlyoccurred at a minimum of 8 mouse exhibits a high degree of The Pacific pocket mouse is endemic general locales encompassing some 29 geographic variation in pelage color to the immediate coast of southern sites from Los Angeles County southto (Hall 1981; see also Ingles 1965). California from Marina del Rey and El San Diego County,the onlyknown, Vocalizations of this species include a Segundo in Los Angeles County, south confirmed population extant occurs on high-pitched squeal. to the vicinity of the Mexicanborder in the Dana Point Headlands in Orange The Pacific pocket mouse is the San Diego County (Hall 1981, Williams County, California. A maximum of 36 smallestsubspecies of the little pocket 1986, Erickson 1993). The species has confirmed, individual Pacific pocket mouse, ranging up to 131 mm (5.2 not been recorded outside of California mice has beendetected on 3.75 acres of inches) in length from nose totip of the (Williams et al. 1993; Erickson 1993). identified occupied ha’bitat during the long tail. The tail, hind foot, and skull Erickson (1993) noted further that the last 20 years. The Pacific pocket mouse structures of Pacific pocket mice are Pacific pocketmouse has not been is threatened with extinction due to also the smallest of all little pocket reliably recorded more than - documented depredation by domestic mouse subspecies (Huey 1939). approximately 2 miles (3 kilometers) cats and habitat loss and fragmentation Stephens (1906) labeled the species an inland from the coast or above 600 feet as a result of past and continuingland * * exceedingly small [p]ocket (180 meters) in elevation. development projects. Thisrule Emlouse * * * “The Pacific pocket The habitat requirements of the implements and guarantees continued mouse is one of the smallest rodents in Pacific pocket mouse are not well Federal protection provided by the Act the world. understood, but they are known to occur for the Pacific pocket mouse, which was The Los Angeles pocket mouse on fine-grain, sandy substrates inthe emergency listed as endangered on (Perognathus Iongiinembris brevinczsus), immediate vicinity of the PacificOcean January 31, 1994 for a period of 240 which occurs mostly northeast of, and (Mearns 1898, von Bloeker 1931; days. well inland from, the Pacific pocket Grinnell 1933; Bailey 1939). The Pacific EFFECTIVE DATE: September 26, 1994. mouse, is the onlyother subspecies of pocket mouse is or was known to little pocket mouse that occurs in inhabit coastal strand, coastal dunes, ADDRESSES: The complete file for this rule is available for inspection, by southern California west of the deserts. river alluvium, and coastal sage scrub appointment, during normal business Individual Los Angelespocket mice growing on marine terraces (Grinnell hours at the U.S. Fish and Wildlife range in size from 125 to 145 mm (4.9 1933;Meserve 1972; Erickson 1993). Service, Carlsbad Field Office, 2730 to 5.7 inches) long. Overall, Los Angeles Stephens (1906) trapped a female Loker Avenue \Vest, Carlsbad, California pocket mice have longer tails, hind feet, “~ * * on a dry mesa a short distance skulls, and nasal bones than Pacific back from the seashore.” von Bloeker 92008. pocket mice (Huey 1939). (1931a) reported that Pacificpocket FOR FURThER INFORMATION CONTACT: Mr. The Pacific pocket mouse was mice detected near San Diego were Gail C. Kobetich, Field Supervisor, at originally described by Meamns (1898) as found only in open patches of ground the address listed above (telephone 619/ a distinct species, Perognathus that were otherwise surrounded by 431—9440). pacificus,based on the type specimen weedy growth. M’Closkey (1972) and SUPPLEMENTARY INFORMATION: that was collected on the shore of the Meserve (1972, 1976b) detected the Pacific Ocean at Mexican Boundary Pacific pocket mouse on sandy Background Monument 258 in San Diego County, substrates in coastal sage scrub habitats The Pacific pocket mouse California. Although von Bloeker in the San Joaquin Hills in Orange (Perognathus longimembris pacificus) is (1931a,b) initially recognized the Pacific County, California. Brylski (1993) Federal Register I Vol. 59, No. 188 / Thursday, September 29, 1994 / Rules and Regulations 49753 detected the onlyknown, confirmed Pacificpocket mice primarily eat the “Spyglass Hill” inthe San Joaquin Hills population extant on the Dana Point seeds of grasses and forbs (von Bloeker from 1968 to 1971 (M’Closkey 1972; Headlands on loose sand substrates ina 1931; Meserve 1972, 1976a). Meserve Meserve 1972;R. MacMillan. pers. coastal sage scrub community (1976a) observed further that other plant comm., 1994). Forty-four specimens or dominated by California buckwheat materials were consumed, albeit in live captures from “Spyglass Hill” were (Enogonum fasicukztum) and California comparatively smaller quantities. P. recorded from 1968—1971 (see Erickson sage (Artemisia californica). Brylski Brylski (pers. comm., 1993) observed 1993). The only known, confirmed (1993) commented that the Pacific that “Pacific pocketmice foraged population extant of the Pacificpocket pocket mouse’s preferred habitat mainly on the seeds of grasses and,to mouse was rediscovered inJuly of 1993 “~ * * appears to be open coastal sage a lesser degree, on leafyvegetation.” on the Dana Point Headlands in Orange scrub on fine, sandy soil.” Jameson and Peeters (1988) reported County, California (Brylski 1993). C. Little quantitative information is that little pocket mice, like other pocket Cantwell had previously collected 10 available on the ecology and life history mice species, also eat soil-dwelling specimens of this species at this locale of the Pacific pocket mouse. However, insects. in May of 1932 (voucher specimens on the attributes of the little pocket mouse Relatively little is known of the deposit at the Natural History Museum and the available data that pertain tothe breedingbiology of Pacific pocket mice. of Los Angeles County). Pacific pocket mouse subspecies suggest Erickson (1993), relying largely on data Possible, recent records from Crystal that this small rodent is facultativelyor provided by Meserve (1972), noted that Cove State Park (approx. 16 kin (10 mi) partially fossorial, relatively sedentary, “[plregnant and lactating females have NW Dana Point) resulting from pitfall primarily granivorous, and able to been found from April through June trapping (see R. MacMillan, pers. become torpid, estivate, or hibernate in withimmatures noted from June comm., 1994) await confirmation given response to adverse environmental through September.” P. Brylski (pers. the uncertainty expressed by the