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Bats in riparian-restoration sites along the lower Colorado River, Arizona.

The lower Colorado River, which spans from just upstream of Lake Mead to Mexico, has been altered intensely due to anthropogenic disturbances. Researchers estimate that > 160,000 ha of native riparian vegetation occurred historically on the lower Colorado River between Fort Mohave and Fort Yuma (Mearns, 1907). The natural flow and flood-pulse regime has been altered by construction of dams and channelization of the river. As a result, native riparian vegetation has been reduced by 94%, with >85% of woody riparian vegetation now dominated by invasive saltcedars (Tamarix). Prior to the Lower Colorado River Multi-Species Conservation Program ( pdf), 2,739 ha of native cottonwoods (Populus) and willows (Salix) occurred on the river in mostly small patches of [less than or equal to] 4 ha scattered throughout large stands of Tamarix. To date, >750 ha of native riparian vegetation have been planted along the river in large patches [greater than or equal to]40 ha. These restoration areas were planted with native species such as Fremont cottonwood (Populus fremontii), Goodding's willow (Salix gooddingii), coyote willow (Salix exigua), and honey mesquite (Prosopis glandulosa). Previously, most restored areas were cultivated.

Herein, we report on two species of bats that are noteworthy because they either have never been reported from the lower Colorado River (western red bat, Lasiurus blossevillii) or were presumed extirpated (Arizona myotis, Myotis occultus). in lowland desert regions of the southwestern united States, both species depend on riparian habitats for roosting, foraging, or both (Grinnell, 1914; Cockrum, 1960; Barbour and Davis, 1969; Hoffmeister, 1986). Documentation of these species within artificially created, native-riparian habitats may prove useful in measuring success of habitat-restoration projects (McCoy and Mushinsky, 2002; Palmer et al., 2005).

Western red bats have been recorded previously in Arizona in riparian systems such as the Big Sandy, San Pedro, and the Bill Williams rivers (Hoffmeister, 1986). Prior to our efforts, western red bats had not been reported along the lower Colorado River. We captured the first western red bat there in February 2009. In subsequent surveys, we captured 10 additional individuals. All captures were within three habitat-restoration areas: 'Ahakhav Tribal Preserve (34.1269[degrees]N, 114.3342[degrees]W), ca. 1.2 km SW Parker, La Paz County, Arizona; Palo Verde Ecological Reserve (33.6908[degrees]N, 114.5261[degrees]W), ca. 3.6 km NE Blythe, Riverside County, California; and Cibola Valley Conservation Area (33.4105[degrees]N, 114.6634[degrees]W), 1.2 km N Cibola, La Paz County, Arizona. Four males were captured during winter (January-February) and five males and two females were captured during late summer (August-September).

Arizona myotis occur commonly throughout high-elevation pine forests in Arizona and New Mexico (Findley and Jones, 1967; Barbour and Davis, 1969; Valdez et al., 1999). A few exceptions at lower elevations include populations along several large rivers (Colorado, Verde, and Rio Grande rivers),where they occupy cottonwood-dominated riparian habitats (Grinnell, 1914; Allen, 1922; Stager, 1943; Hayward, 1963). Arizona myotis was first described on the lower Colorado River (Hollister, 1909). The last known colony along the lower Colorado River was in Blythe Bridge, Riverside County, California, and La Paz County, Arizona (Stager, 1943), which was replaced in the 1950s. The species has been presumed extirpated from the Colorado River (P. Brown, pers. comm.).Since 2007, 15 individuals have been captured at the 'Ahakhav Tribal Preserve. All females captured during May 2007 were either pregnant or lactating, indicating a maternity colony. in 2010, two specimens were captured at the Cibola Valley Conservation Area. Voucher specimens from each site were deposited in the university of New Mexico Museum of Southwestern Biology (accessions 224058 and 224059).

These species of bats may prove useful for justifying restoration and monitoring success of restoration in southwestern riparian habitats. For example, preliminary data show higher rates of activity of western red bats in riparian areas > 20 ha. Small restoration areas monitored concurrently with large areas indicated no change in activity of western red bats over time. Presence of western red bats at large restoration areas was detected within 3-5 years of planting, which offers relatively quick feedback on use of habitats by this species. We anticipate that these trends will continue as more riparian habitats are created and suggest further research on the utility of these species as indicators of success of restoration programs.

We thank The Colorado River Indian Tribes for allowing access to the 'Ahakhav Tribal Preserve. We acknowledge personnel of the Arizona Game and Fish Department and California Department of Fish and Game for logistical assistance. T. Olson, S. Broderick, J. Kahl, C. Dodge, M. Given, J. Hill, S. Hines, L. Piest, and B. Vizcarra provided assistance in the field. We thank C. Dodge for translating the abstract and N. Muirhead for reviewing and editing the manuscript prior to submittal. P. Brown and B. Berry provided valuable knowledge and guidance that was the impetus for our research along the lower Colorado River. Funding was provided by the Lower Colorado River Multi-Species Conservation Program.

Literature Cited

ALLEN, G. M. 1922. Bats from New Mexico and Arizona. Journal of Mammalogy 3:156-162.

BARBOUR, R.W., and W. H. Davis. 1969. Bats of America. university Press of Kentucky, Lexington.

COCKRUM, E. L. 1960. The Recent mammals of Arizona: their taxonomy and distribution. university of Arizona Press, Tucson.

FINDLEY, J. S., AND C. JONES. 1967. Taxonomic relationships of bats of the species Myotis fortidens, M. lucifugus, and M. occultus. Journal of Mammalogy 48:429-444.

GRINNELL, J. 1914. An account of the mammals and birds of the lower Colorado Valley. University of California Publications in Zoology 12:51-294.

HAYWARD, B. J. 1963. A maternity colony of Myotis occultus. Journal of Mammalogy 44:279.

HOFFMEISTER, D. F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish Department, Tucson.

HOLLISTER, N. 1909. Two new bats from the southwestern United States. Proceedings of the Biological Society of Washington 22:43-44.

Mccoy, E. D., and H. R. Mushinsky. 2002. Measuring the success of wildlife community restoration. Ecological Applications 12:1861-1871.

MEARNS, E. A. 1907. Mammals of the Mexican boundary of the united States: a descriptive catalogue of the species of mammals occurring in that region; with a general summary of the natural history, and a list of trees. United States National Museum Bulletin 56:1-530.

PALMER, M. A., E. S. BERNHARDT, J. D. ALLAN, P. S. LAKE, G. ALEXANDER, S. BROOKS, J. CARR, S. CLAYTON, C. N. DAHM, J. FOLLSTAD SHAH, D. L. GALAT, S.G. LOSS, P. GOODWIN, D. D. HART, B. HASSETT, R. JENKINSON, G. M. KONDOLF, R. LAVE, J. L. MEYER, T. K. 0'DONNELL,L. PAGANO, AND E. SUDDUTH. 2005. Standards for ecologically successful river restoration. Journal of Applied Ecology 42:208-217.

STAGER. K. E. 1943. Remarks on Myotis occultus in California. Journal of Mammalogy 24:197-199.

VALDEZ, E. W., J. R. CHOATE, M. A. BOGAN, AND T. L. YATES. 1999. Status of Myotis occultus. Journal of Mammalogy 80:545-552.

Submitted 16 June 2011. Accepted 3 April 2012. Associate Editor was Stephen G. Mech.

Allen W. Calvert * and Sean A. Neiswenter

Bureau of Reclamation, Lower Colorado Region, Lower Colorado River Multi-Species Conservation Program Office, Boulder City, NV 89006 (AWC)

School of Life Sciences, University of Nevada, Las Vegas, 4505 Maryland Parkway, Box 454004, Las Vegas, NV 89154 (SAN)

* Correspondent:
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Title Annotation:Notes
Author:Calvert, Allen W.; Neiswenter, Sean A.
Publication:Southwestern Naturalist
Article Type:Report
Geographic Code:1USA
Date:Sep 1, 2012
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