Academic journal article The American Midland Naturalist

Description of Spring Roost Trees Used by Female Indiana Bats (Myotis Sodalis) in the Lake Champlain Valley of Vermont and New York

Academic journal article The American Midland Naturalist

Description of Spring Roost Trees Used by Female Indiana Bats (Myotis Sodalis) in the Lake Champlain Valley of Vermont and New York

Article excerpt

ABSTRACT.-

Extensive effort has been directed at the roosting ecology of the federally endangered Indiana bat (Myotis sodalis) during the maternity season; however, spring roosting ecology has received much less attention. In April 2002, radio transmitters were attached to the back of 19 female Indiana bats as they emerged from a hibernaculum in northeastern New York. Thirty-nine roost trees were found in the vicinity of the Lake Champlain Valley of New York and Vermont over the span of 224 bat days (i.e., 1 bat located for 1 d equals 1 bat day). Distances from hibernaculum to roost trees ranged from 14.6 to 40.0 km (mean = 26.9 km). Shagbark hickory (Carya ovata) was the most common (33.3% of all trees, 39.7% of all bat days) of 11 tree species used. Roost trees had a mean diameter of 45.6 cm, were 18.9 m tall and were similar in structure to those used during summer by Indiana bats elsewhere in their range. This study provides the first large-scale examination of trees used by female Indiana bats after spring emergence, supplying critical life history information useful for the conservation of this species.

INTRODUCTION

The federally endangered Indiana bat (Myotis sodalis) has experienced a continued decline in population levels since the 1960s (Clawson, 2002). This continued decline has prompted extensive research into the ecology of this species. In recent years, the roosting ecology of female Indiana bats during the maternity season has been intensively studied (Kurta et al, 1996; Callahan et al, 1997; Menzel et al, 2001; Britzke et al, 2003). This emphasis has resulted in increased knowledge of the ecology of this species, but has failed to identify the reason for the continued population decline.

Unlike the roosting ecology of bats during the maternity season, roosting ecology during spring and fall has received relatively little attention. Rommé et al (2002) tracked female Indiana bats during the spring to determine home range, but failed to characterize roosts used. Gumbert (2001) tracked a small number of female Indiana bats during spring in Kentucky, but likewise failed to locate a large number of roosts. Other studies on the roosting ecology of Indiana bats in spring have focused on adult males (Gumbert et al, 2002; Hobson and Holland, 1995).

Bats in the northeastern United States typically enter hibernation in mid-September and emerge in mid-April. During this 7-mo period, bats of the genus Myotis lose 25-30 % of their body mass (Thomas et al, 1990; Fenton, 1970). Upon emergence from hibernation, female Indiana bats may migrate 532 km to their summer range (Kurta and Murray, 2002). Migration may incur a high energetic cost, thereby increasing the energetic demands females experience during spring. Because of reduced fat reserves after emergence from hibernation, unpredictable prey densities, and cold temperatures typical of spring in the northern portion of the species range, selection of appropriate roost sites that maximize energy conservation may be especially necessary (US Fish and Wildlife Service, 1999). This study was the first large-scale investigation of the spring roosting ecology of female Indiana bats in the northeastern United States.

METHODS

Bats were captured at Barton Hill Mine, Moriah, Essex County, New York on the eastern edge of the Adirondack Mountains. Nine female Indiana bats were captured on 15 April 2002, while another 10 bats were captured on 16 April 2002. Bats that were held overnight were fed mealworms and given water to drink; all bats were fed and given water after processing on the second night. Bats were weighed, sexed and banded with an individually numbered aluminum band (Porzana, Ltd., Leominster, United Kingdom). A 0.5-gram transmitter (Holohil Systems, Ltd., Carp, Ontario, Canada) was attached to the dorsal surface of bats using surgical glue (Skin-Bond Cement, Smith and Nephew, Inc., Largo, Florida).

Six frequencies were used by the 19 transmitters (1-5 bats/frequency). …

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