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Patterns of island occupancy in bats: influences of area and isolation on insular incidence of volant mammals

Authors

  • Winifred F. Frick,

    Corresponding author
    1. Department of Forest Science, 321 Richardson Hall, Oregon State University, Corvallis, OR 97331 USA,
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    • Present address: Department of Ecology and Evolutionary Biology, Earth and Marine Science A308, UC Santa Cruz, Santa Cruz, CA 95064 USA.

  • John P. Hayes,

    1. Department of Forest Science, 321 Richardson Hall, Oregon State University, Corvallis, OR 97331 USA,
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    • Present address: Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, 110 Newins-Ziegler Hall, PO Box 110430, Gainesville, FL 32611 USA.

  • Paul A. Heady III

    1. Central Coast Bat Research Group, PO Box 1352, Aptos, CA 95001-1352 USA
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*Correspondence: Winifred F. Frick, Department of Forest Science, 321 Richardson Hall, Oregon State University, Corvallis, OR 97331 USA. E-mail: wfrick@batresearch.org

ABSTRACT

Aim  The influence of landscape structure on the distribution patterns of bats remains poorly understood for many species. This study investigates the relationship between area and isolation of islands and the probability of occurrence of six bat species to determine whether persistence and immigration abilities vary among bat species and foraging guilds.

Location  Thirty-two islands in the Gulf of California near the Baja California peninsula in north-west Mexico.

Methods  Using logistic regression and Akaike information criterion (AIC) model selection, we compared five a priori models for each of six bat species to explain patterns of island occupancy, including random patterns, minimum area effects, maximum isolation effects, additive area and isolation effects and compensatory area and isolation effects.

Results  Five species of insectivorous bats (Pipistrellus hesperus, Myotis californicus, Macrotus californicus, Antrozous pallidus and Mormoops megalophylla) displayed minimum area thresholds on incidence. The probability of occurrence tended to decrease at moderate distances of isolation (c. 10–15 km) for these species (excepting A. pallidus). The distributions of two non-insectivorous species (Leptonycteris curasoae and Myotis vivesi) were not influenced by island size and isolation.

Main conclusions  Minimum area thresholds on incidence suggest that island occupancy by insectivorous bats may be limited by resource requirements. Islands smaller than 100 ha typically did not support occupancy or use by insectivorous bats, except at minimal isolation distances. Insectivorous bat species may also be more sensitive to moderate levels of habitat isolation in some landscape contexts than previously expected. Our results suggest that differences in foraging habits may have important implications for understanding the distribution patterns of bats.

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