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Roosting Behavior and Roost Selection by Migrating Silver-Haired Bats (Lasionycteris noctivagans)

R. Barclay,P. Faure,D. Farr

Published 1988 in Journal of Mammalogy

ABSTRACT

Because roosts play a vital role in the lives of bats, the function and selection of roosts have received much attention (Kunz, 1982a). Roosts may provide bats with a thermally stable environment or space in which groups can cluster thereby reducing the energetic costs of thermoregulation (Kurta, 1985; Trune and Slobodchikoff, 1976). Also, roosts may provide protection from predators (Fenton, 1983) and from rain, wind, and sunshine (Vaughan, 1987; Vaughan and Vaughan, 1986), and may serve as sites where social groups can congregate or be defended (Morrison, 1979). Although individuals of many species use traditional roosts within and between seasons (Barbour and Davis, 1969), others show less fidelity and are less likely to rely on spatial memory to locate roosts. Some species locate roosting conspecifics by vocal communication (Barclay, 1982a; O'Shea and Vaughan, 1977), and the odor of feces and urine also could act as a cue to the location of roosts. Presumably, visual and echolocation information also is used by bats searching for roosts. Although considerable is known regarding the roosting ecology and behavior of some bats, relatively little is known about crevice-dwelling species, partly because they are difficult to locate (Kunz, 1982a). Solitary, migratory species also are poorly studied compared with colonial, hibernating ones. The purpose of this study was to investigate the characteristics of day roosts used by a solitary, migratory, crevice-dwelling species, the silver-haired bat (Lasionycteris noctivagans) during its northward migration to summer breeding areas. In particular, we wished to determine the functions of roosts and how the bats locate and select roosts. Lasionycteris noctivagans is a small (adult mass 11 g) vespertilionid, widespread over much of North America (Kunz, 1982b). Despite this, information regarding its ecology and behavior is sparse and its summer roosting habits are virtually unknown (Kunz, 1982b). There are indications that females form small nursery colonies in hollow trees (Parsons et al., 1986), and L. noctivagans generally is regarded as a tree-roosting bat although there are few reports of this species roosting in trees. The roosting behavior during migration is unknown and should be interesting because the bats must locate new roosts in unfamiliar areas each night. The study was conducted in the vicinity of the University of Manitoba Field Station, Delta Marsh, Manitoba (50011'N, 98023'W). Along the southern shore of Lake Manitoba, a narrow (X width = 80 m) 30-km-long forested ridge separates the lake from the marsh (MacKenzie, 1982). Four species of trees (Manitoba maple, Acer negundo; green ash, Fraiinus pennsylvanica; peach-leaved willow, Salix amygdaloides; and cottonwood, Populus deltoides) dominate the forest community. L. noctivagans migrates through the study area in "waves" in May and early June (Barclay, 1984) and individuals likely travel around the lakeshore rather than across the lake. During this part of the year, L. noctivagans commonly is found roosting in trees on the ridge. During May and June 1984-1986, two to four people made almost daily visual searches of trees in a 2-km portion of the ridge to locate roosting L. noctivagans. Trees generally were searched to a height of 2.5-3.0 m although in 1985 ladders were used to search to a height of 6 m. Searches using ladders were discontinued in 1986 because only one bat and few suitable roost sites were present above 3 m. Roosts were flagged and inspected daily for the duration of the study. Roosts were described by noting the species, height (measured with an inclinometer), and breast height circumference of roost-trees, and the height of the roost itself and its general type (e.g., fold of bark, split in trunk). Selection of certain species of trees by bats was assessed by comparing the frequency of use of the various species relative to their abundance on the ridge (MacKenzie, 1982). For each species, mean height and circumference of roost trees were compared to means of a random sample. We found 177 L. noctivagans roosting in 36 different roosts in 32 trees during the study. We removed some individuals from their roosts during the day and caught others in Tuttle traps (Tuttle, 1974) at night. Sex of each bat was recorded and each was weighed, banded on the forearm with a colored-plastic split ring,

PUBLICATION RECORD

  • Publication year

    1988

  • Venue

    Journal of Mammalogy

  • Publication date

    1988-11-29

  • Fields of study

    Biology, Geography, Environmental Science

  • Identifiers
    DOI 10.2307/1381639
  • External record

    Open on Semantic Scholar

  • Source metadata

    Semantic Scholar

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