New Zealand Journal of Zoology abstracts
Roost site selection by lesser short-tailed bats (Mystacina tuberculata) in mixed podocarp-hardwood forest, Whenua Hou/Codfish Island, New Zealand
Jane A. Sedgeley
Department of Zoology
University of Otago
P.O. Box 56
Dunedin, New Zealand
jsedgeley@doc.govt.nz; mohua@xtra.co.nz
Present address: Department of Conservation, Research, Development and Improvement
P.O. Box 13 049, Christchurch, New Zealand.
Abstract Roosting ecology of the lesser short-tailed bats (Mystacina tuberculata)
was studied in mixed podocarp-hardwood forest on Whenua Hou/Codfish
Island, New Zealand during winter 1996, and winter to summer
1998–99. The structural characteristics of roosts used by
communal groups and by solitary bats are described, and roost selection
is examined at three scales: forest stand, tree, and cavity.
Differences in structural characteristics and microclimate of roosts
used in winter and in summer are compared. Forty-three bats were
radio-tracked and 122 tree roosts located. Communal groups occupied
47.5% of roosts and solitary bats occupied 52.5%. Bats selected roosts
in Hall’s totara (Podocarpus hallii) trees more than
expected based on the availability of this tree species. Roost trees
had significantly larger stem diameters and greater numbers of cavities
than random trees. Communal bats demonstrated a higher degree of roost
selectivity than solitary bats. Communal roosts had significantly less
vegetation clutter surrounding roost entrances, larger stem diameters
at cavity height, larger internal cavity heights, and thicker cavity
walls than potentially available cavities. Communal roost cavities were
consistently larger than solitary roosts. Solitary roosts had less open
space around them than communal roosts and random cavities. Communal
roosts were well insulated and exhibited stable internal temperatures.
Structural and thermal characteristics did not differ between roosts
used in winter and in summer. Differences between characteristics of
communal and solitary roosts, and selection of well-insulated cavities
in some of the largest available trees, appears consistent among different
forest types used by lesser short-tailed bats in New Zealand, and with
behaviour of many other tree-dwelling bat species in temperate
climates. Descriptive statistics of trees provide guidance to forest
managers, especially those practicing silviculture, for identifying
potential bat roosting habitat. Regression analyses of cavity
characteristics provide insight into factors explaining the rarity of
favoured cavities. Intraspecific differences in roost selection by bats
should be considered when undertaking conservation management actions
such as identifying trees for retention through logging cycles, or
designating and designing reserves.
Keywords Chiroptera; short-tailed bats; roost
trees; roost selection; roost microclimate; temperate rainforest;
threatened species; conservation
Z05045; Received 1 August 2005; accepted 20 December 2005; Online publication date 18 April 2006
New Zealand Journal of Zoology, 2006, Vol. 33: 97–111
0301–4223/06/3302–0097 © The Royal Society of New Zealand 2006
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