Jackson, H. B., K. A. Baum, T. Roberts* and J. T. Cronin. 2009. Habitat-specific movement and edge-mediated behaviour of a saproxylic insect, Odontotaenius disjunctus Illiger (Coleoptera: Passalidae). Environmental Entomology 38: 1411-1422.


The ability to disperse among patches is central to population dynamics in fragmented landscapes. Although saproxylic (= dead wood dependent) insects live in extremely fragmented forest ecosystems and comprise a significant proportion of the biodiversity therein, few studies have focused on dispersal of members in this group. We quantified the terrestrial movements of Odontotaenius disjunctus Illiger, a common saproxylic beetle in eastern North American forests. Individual movement behavior was measured in deciduous forest and two common matrix habitats (urban lawn and cattle pasture).  Probability of emigrating from a forest fragment was assessed at the high-contrast boundary between forest and pasture. Seasonal, diurnal, and sex-biased patterns of O. disjunctus dispersal were determined from captures at drift fences encircling inhabited logs. Contrary to theory and observed patterns in other animals, movement was 1.6 and 2.7 times faster and 1.1 and 1.5 times more linear in suitable habitat (forest) than in unsuitable matrix (lawn and pasture, respectively). Net displacement in the forest exceeded predictions of a correlated random walk, but net displacement in matrix habitats was less than expected. When confronted with a high-contrast boundary, O. disjunctus was 14 times more likely to move toward the forest than the pasture.  The importance of temperature was indicated by its positive relationship with movement rate and the abundance of dispersers during the day and warm seasons (spring and fall). Reluctance to cross boundaries into open fields and slow movement within open fields suggest a low likelihood of O. disjunctus movement among forest fragments.

Keywords: bess beetle, horned passalus, coarse woody debris, landscape matrix

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