Warner_RM_1982.pdf

MAMMALIAN SPECIES No. 191, pp. 1-3, 4 figs. Myotis auriculus. By Richard M. Warner Published 23 November 1982 by The American Society of Mammalogists Myotis auriculus Baker and Stains, 1955 Southwestern Myotis Myotis evotis auriculus Baker and Stains, 1955:83. Type locality 10 mi W and 2 mi S Piedra, 1,200 ft, Sierra de Tamaulipas, Tamaulipas, Mexico. Myotis auriculus, Genoways and Jones, 1969:8. First use of current name combination. CONTEXT AND CONTENT. Order Chiroptera, Suborder Microchiroptera, Family Vespertilionidae, Subfamily Vespertilioninae, Genus Myotis, and Subgenus Myotis. Findley (1972) placed M. auriculus in the evotis species group which also includes M. evotis, M. keenii, and M. septentrionalis (see Van Zyll de Jong, 1979). Two subspecies are currently recognized. M. a. auriculus Baker and Stains, 1955:83, see above. M. a. apache Hoffmeister and Krutzsch, 1955:1. Type locality Snow Flat, 8,750 ft, Graham Mountains, Graham County, Arizona. DIAGNOSIS. Myotis auriculus is a medium-sized member of the genus with long, brownish ears (Fig. 1). The length of the ears (> 17 mm) separates this species from all other North American species of Myotis except M. thysanodes, M. milleri, and other members of the evotis species group (see CONTEXT AND CONTENT). M. septentrionalis and M. keenii are both smaller than M. auriculus. The former two species usually have a forearm length less than 36 mm, ears less than 19 mm, and greatest length of skull less than 15.6 mm. These same three measurements for M. auriculus are generally greater than 37, 19, and 15. 7 mm, respectively. Additionally, neither M. keenii nor M. septentrionalis occur within the range of M. auriculus (compare Fig. 2 to Fig. 2 in Fitch and Shump, 1979). From M. milleri this species also differs in size, M. auriculus being larger for all skull and external measurements other than ear height. For example, in M. milleri forearm length is usually less than 37 mm and greatest length of skull is less than 15.5 mm, which can be compared with the values for M. auriculus given above. Qualitatively, M. auriculus differs from M. milleri in having a more inflated skull, in possessing a distinct sagittal crest (absent in M. milleri), and in lacking a distinct microscopic fringe of hairs on the posterior margin of the uropatagium (present in M. milleri). M. auriculus can be distinguished from M. thysanodes by the lack of a distinct macroscopic fringe of hairs on the posterior margin of the uropatagium. The following can be used to distinguish M. auriculus from M. evotis: lack of a distinct microscopic fringe of hairs on the free border of the uropatagium; brownish rather than blackish ears; ears shorter, usually less than 21 mm from the notch as opposed to normally greater than 21 mm in M. evotis; flight membranes lighter colored; dorsal hairs brown basally rather than black; more inflated frontal region of the skull; median postpalatal process long, broad, and rounded (see Fig. 3) not short and pointed; relatively longer dentary, usually more than 82.5% of the condylobasal length. The above is mainly after Findley (1960) and Genoways and Jones (1969). GENERAL CHARACTERS. Averages and extremes of measurements (in mm) for five female M. a. auriculus are: total length, 93.2 (86 to 97); tail length, 42.0 (39 to 45); length of hindfoot, 9.3 (8 to 10); length of ear from notch, 19.6 (18 to 20); forearm length, 38.5 (37 .3 to 40.2); greatest length of skull, 16.1 (15.8 to 16.4); condylobasal length, 15.4 (15.0 to 15.6); length of maxillary toothrow, 6.6 (6.5 to 6. 7) (Baker and Stains, 1955). Averages of the same measurements for four M. a. apache (sex not specified) are: 94; 46; 10.5; 19.4; 38.5; 15.8; 15.1; 6.4 (Hoffmeister and Krutzsch, 1955). Means, plus or minus the standard errors of the means, of four mensural characters from samples of 30 adult female and 30 adult male, respectively, M. a. apache are: head and body length, 53.4 ± 0.58, 52. 7 ± 0.47; forearm length, 37 .20 ± 0.191, 36. 77 ± 0.206; condylocanine length, 14.30 ± 0.045, 14.19 ± 0.040; and length of the maxillary toothrow, 6.42 ± 0.021, 6.36 ± 0.022 (Williams and Findley, 1979). Williams and Findley found no evidence of sexual dimorphism in size in this species. Additional measurements can be found in Baker and Stains (1955) and Genoways and Jones (1969). Dorsal coloration is a dull brown with the hairs possessing a darker basal band. The ventral pelage is huffy. The flight membranes are brown and there is no obvious or microscopic fringe of hairs on tht posterior margin of the interfemoral membrane. The long, brownish ears (Fig. 1) are particularly distinctive. The nominate subspecies is darker overall than M. a. apache. The skull is characterized by its relatively large size, the inflated frontal region, and the long, rounded median postpalatal process (Fig. 3). Photographs of the skull, as well as photographs of living specimens, were published in Barbour and Davis (1969). Illustrations of the skull, upper molariform teeth, and a baculum were presented in Genoways and Jones (1969). DISTRIBUTION. Myotis auriculus is a bat of the southwestern United States and northern Mexico (Fig. 2). The nominate subspecies has been reported from the Mexican states of Nuevo Leon, Tamaulipas, and Veracruz. M. a. apache is more widely distributed, occurring from north-central Arizona and northcentral New Mexico south to the Mexican state of Jalisco. Distributions of the subspecies are shown in Fig. 2. Records of occurrence are available in Easterla and Baccus (1973), Findley et al. (1975), Gardner (1965), Jones et al. (1970), Matson and Patten (1975), and Warner and Czaplewski (1981). Altitudinal range is from 366 m to at least 2,226 m. Ecological range is from desert scrub to pine-fir forest and may vary seasonally (Hoffmeister, 1970). FORM AND FUNCTION. The baculum of M. auriculus is saddle-shaped with a large distal knob (Fig. 4). Genoways and Jones (1969) found the baculum of M. auriculus to be smaller and less complex than those of M. evotis and M. keenii septentrionalis ( =M. septentrionalis ). Individual variation in bacular size and fine structural detail are to be expected (Genoways and Jones, 1969; Krutzsch and Vaughan, 1955). Allen (1895) pointed out the occurrence of aberrant tragi in an individual collected in Arizona. He suggested that the abnormally small and blunt tragi were the result of an injury. Koopman (1963) suggested that injury was an unlikely cause as both tragi were similarly deformed. The urine-concentrating ability of M. auriculus is average relative to other insectivorous bats (Geluso, 1978, 1980). The urine osmolality of eight M. auriculus tested under water-denied conditions ranged from 2,300 to 3,700 mosmol/kg with a mean of 2,950 ± 66 mosmol/kg. The urine concentrating ability of this species relative to other insectivorous bats is reflected in the FIGURE 1. Adult male Myotis auriculus from Arizona. 2 FIGURE 2. Distribution of M. a. auriculus (stippling) and M. a. apache (oblique hatching). Scale represents 1,000 km. comparative development of the renal medulla as measured by a number of indices (Geluso, 1978, 1980). Geluso suggested that the relative urine concentrating abilities and correlated renal morphology of M. auriculus were reflections of the mesic environments it inhabits. ONTOGENY AND REPRODUCTION. A single young is usually born in June or early July. Barbour and Davis (1969) stated, with little supportive evidence, that parturition apparently occurs later in areas south of Arizona. This is undoubtedly an oversimplification. The timing of parturition is probably affected by climatic factors and can be expected to show considerable spatial and temporal variability. Myotis auriculus is known to live a minimum of 3 years, 2 months based on the recapture of banded individuals (Cockrum, 1973). ECOLOGY AND BEHAVIOR. In Arizona and New Mexico M. auriculus is primarily found in ponderosa pine (Pinus ponderosa) forests (Findley et al., 1975; Jones, 1965; Warner and Czaplewski, 1981). Barbour and Davis (1969) considered this species to be an inhabitant of "arid woodlands and desert scrub." Seasonal migrations may result in this species selecting different habitats during different seasons (see Hoffmeister, 1970). JonPs (1965) found this species to be active primarily from 1.5 to 2.0 h afte1· sunset and at temptratures of 11° to l9°C. A trimodal activity pattern was presented in Cockrum and Cross (1964) with a major period of activity between 30 and 89 min after sunset and minor periods from 120 to 149 and 180 to 209 min after sunset. Seasonally, Jones (1965) captured this species from April to early September in New Mexico. Black (1974) and Husar (1976) found that M. auriculus ate mostly moths. Males ate significantly more moths than females (Husar, 1976). Fenton and Bell (1979) observed southwestern myotis gleaning insects, primarily moths with 30 to 40 mm wingspans, from buildings and tree trunks. They observed that the bat would land briefly on the substrate while picking the insect off of the surface. A gleaner foraging strategy was previously predicted for this species on the basis of morphological evidence (Findley, 1972) and brain volume relative to body weight (Eisenberg and Wilson, 1978). Sonagrams and descriptions of echolocation calls were published in Fenton and Bell (1979). The FM signal, with a peculiar initial upsweep, has most of the energy at 60 kHz. The call is short and of low intensity in comparison with those of congeners studied. While engaged in gleaning behavior no distinct feeding buzz is produced, the repetition rate remaining essentially constant during approach and capture phases. The mean estimated flight speed of four M. auriculus traversing a 30.8 m course was 12.9 km/h (Hayward and Davis, 1964). GENETICS. Both standard (Baker and Jordan, 1970; Baker and Patton, 1967) and G-banded (Bickham, 1979) karyotypes of M. auriculus have been described. The following description folMAMMALIAN SPECIES 191 FIGURE 3. Dorsal, ventral, and lateral views of cranium and lateral view of mandible of an adult male M. a. apache (NAU 3941). Scale represents 5 mm. lows Bickham's terminology. The diploid number is 44, in common with all members of the genus studied thus far, but the number of autosomal arms (FN) is 52, not 50 as found in most species of Myotis. The higher fundamental number is due to chromosome 25 being biarmed rather than acrocentric, as is usually found in members of this genus. The Y chromosome is larger than that found in most Myotis species; it is nearly the size of chromosome 23 rather than approximately the size of the smallest chromosome (number 25), as is commonly found in this genus. FIGURE 4. Lateral (left) and dorsal (right) views of baculum of M. a. apache (NAU 3941). Scale represents 0.5 mm. MAMMALIAN SPECIES 191 Bickham (1979) considered the additional arm and the larger Y chromosome in M. auriculus to be derived characters. REMARKS. Myotis auriculus and M. evotis are apparently parapatrically distributed with a narrow zone of overlap in Arizona and New Mexico. Allen (1897) may have been the first to discern that the southern form of long-eared Myotis (auriculus) differed from the northern form (evotis ). In his monograph he included, in Plate II, diagrams of the uropatagium of both forms. The northern example (from Wyoming) had a distinct microscopic fringe of hairs on the posterior margin; this fringe was lacking on the illustration of the southern form (from Veracruz). M. auriculus has had a rather complex taxonomic history, which was reviewed by Genoways and Jones (1969). The generic name, Myotis, means mouse-eared. The specific epithet refers to the long external ear pinnae of this species. The subspecific name apache refers to the Apachian biotic province in which this subspecies occurs. LITERATURE CITED Allen, G. S. 1897. Revision of the North American bats of the family Vespertilionidae. N. Amer. Fauna, 13:1-135. Allen, J. A. 1895. On a collection of mammals from Arizona and New Mexico, made by Mr. W.W. Price, with field notes by the collector. Bull. Amer. Mus. Nat. Hist., 7:193-258. Baker, R.H., and H.J. Stains. 1955. A new long-eared Myotis (Myotis evotis) from northeastern Mexico. Univ. Kansas Puhl., Mus. Nat. Hist., 9:81--&i. Baker, R. J., and R. G. Jordan. 1970. Chromosomal studies of some Neotropical bats of the families Emballonuridae, Noctilionidae, Natalidae, and Vespertilionidae. Caryologia, 23:595--604. Baker, R. J., and J. L. Patton. 1967. Karyotypes and karyotypic variation of North American vespertilionid bats. J. Mamm., 48:270-286. Barbour, R. W., and W. H. Davis. 1969. Bats of America. Univ. Press of Kentucky, Lexington, 286 pp. Bickham, J. W. 1979. Banded karyotypes of 11 species of American bats (genus Myotis). Cytologia, 44:789-797. Black, H. L. 1974. A north temperate bat community: structure and prey populations. J. Mamm., 55:138-157. Cockrum, E. L. 1973. Additional longevity records for American bats. J. Arizona Acad. Sci., 8:108-110. Cockrum, E. L., and S. P. Cross. 1964. Time of bat activity over water holes. J. Mamm., 45:635--636 and 46:356. Easterla, D. A., and J. Baccus. 1973. A collection of bats from the Fronteriza Mountains, Coahuila, Mexico. Southwestern Nat., 17:424-427. Eisenberg, J. F., and D. E. Wilson. 1978. Relative brain size and feeding strategies in the Chiroptera. Evolution, 32:740751. Fenton, M. B., and G. P. Bell. 1979. Echolocation and feeding in four species of Myotis (Chiroptera). Canadian J. Zoo!., 57: 1271-1277. Findley, J. S. 1960. Identity of the long-eared Myotis of the southwest and Mexico. J. Mamm., 41:16-20. 1972. Phenetic relationships among bats of the genus Myotis. Syst. Zoo!., 21:31-52. Findley, J. S., A. H. Harris, D. E. Wilson, and C. Jones. 1975. Mammals of New Mexico. Univ. New Mexico Press, Albuquerque, 360 pp. 3 Fitch, J. H., and K. A. Shump, Jr. 1979. Myotis keenii. Mamm. Species, 121:1-3. Gardner, A. L. 1965. New bat records from the Mexican state of Durango. Proc. Western Found. Vert. Zoo!., 1:101-106. Genoways, H. H., and J. K. Jones, Jr. 1969. Taxonomic status of certain long-eared bats (genus Myotis) from the southwestern United States and Mexico. Southwestern Nat., 14: 1-13. Geluso, K. N. 1978. Urine concentrating ability and renal structure of insectivorous bats. J. Mamm., 59:312-323. 1980. Renal form and function in bats: an ecophysiological appraisal. Pp. 403-414, in Proceedings Fifth International Bat Research Conference (D. E. Wilson, and A. L. Gardner, eds.). Texas Tech Press, Lubbock, 434 pp. Hayward, B., and R. Davis. 1964. Flight speeds in western bats. J. Mamm., 45:236-242. Hoffmeister, D. F. 1970. The seasonal distribution of bats in Arizona: a case for improving mammalian range maps. Southwestern Nat., 15:11-22. Hoffmeister, D. F., and P.H. Krutzsch. 1955. A new subspecies of Myotis evotis (H. Allen) from southeastern Arizona and Mexico. Chicago Acad. Sci., Nat. Hist. Misc., 151:1-4. Husar, S. L. 1976. Behavioral character displacement: evidence of food partitioning in insectivorous bats. J. Mamm., 57:331-338. Jones, C. 1965. Ecological distribution and activity periods of bats of the Mogollon Mountains area of New Mexico and adjacent Arizona. Tulane Studies Zoo!., 12:93-100. Jones, J. K., Jr., H. H. Genoways, and L. C. Watkins. 1970. Bats of the genus Myotis from western Mexico, with a key to species. Trans. Kansas Acad. Sci., 73:409418. Koopman, K. F. 1963. The identity of bats (genus Myotis) collected in Arizona by Miller, Price, and Condit in 1894. Amer. Mus. Novitates, 2140:1-3. Krutzsch, P. H., and T. A. Vaughan. 1955. Additional data on the bacula of North American bats. J. Mamm., 36:90100. Matson, J. 0., and D. R. Patten. 1975. Notes on some bats from the state of Zacatecas, Mexico. Contrib. Sci., Los Angeles Co. Mus., 263:1-11. Van Zyll de Jong, C. G. 1979. Distribution and systematic relationships of long-eared Myotis in western Canada. Canadian J. Zoo!., 57:987-994. Warner, R. M., and N. J. Czaplewski. 1981. Presence of Myotis auriculus (Vespertilionidae) in northern Arizona. Southwestern Nat., 26:439-440. Williams, D. F., and J. S. Findley. 1979. Sexual size dimorphism in vespertilionid bats. Amer. Midland Nat., 102:113126. Editors for this account were DANIEL F. WILLIAMS and SYDNEY ANDERSON. Managing editor was TIMOTHY E. LAWLOR. R. M. WARNER, DEPARTMENT OF BIOLOGICAL SCIENCES, C.U. 5640, NORTHERN ARIZONA UNIVERSITY, FLAGSTAFF, 86011. PRESENT ADDRESS: MUSEUM OF VERTEBRATE ZOOLOGY, 2593 LIFE SCIENCES, UNIVERSITY OF CALIFORNIA, BERKELEY 94720.