Gap crossing by chipmunks: an experimental test of landscape connectivity

Abstract

Eastern chipmunks (Tamias striatus) are forest specialists common to eastern North America. Numerous studies suggest that chipmunks require fencerow corridors between woodlots to maintain functional connectivity in agricultural landscapes. We tested this hypothesis by conducting a homing experiment to assess whether chipmunks would cross nonforested gaps of different sizes. Chipmunks in 11 landscapes were translocated a constant distance of 220-250 m across gaps ranging in size from 0 (continuous forest) to 240 m (mostly gap). Logistic regression analysis demonstrated that the probability of an adult chipmunk returning to its home range was not related to the size of the gap that had to be crossed (χ 2 = 0.781, n = 60, P = 0.377, ρ 2 = 0.011). Chipmunks crossed the entire range of gap sizes and there was no evidence of a threshold in connectivity. These results suggest that forest woodlots may be functionally connected for chipmunks even without fencerow corridors, and that landscape configuration in the study area may not have isolating effects on chipmunk populations. More empirical studies are required to identify whether functional connectivity thresholds are present in mammal populations as theoretical studies suggest.Résumé : Les tamias rayés (Tamias striatus) sont des animaux abondants, spécialistes des forêts dans l'est de l'Amérique du Nord. De nombreuses études indiquent que les tamias nécessitent la présence de corridors de haies entre les boisés pour que la connectivité entre les boisés reste fonctionnelle dans les paysages agricoles. Nous avons testé cette hypothèse au moyen d'une expérience de homing au cours de laquelle nous avons vérifié si les tamias traversaient des brèches non boisées de différentes tailles. Des tamias de 11 paysages ont été déplacés sur une distance constante de 220 à 250 m au-delà de brèches mesurant de 0 (forêt continue) à 240 m (surtout des brèches). Une analyse de régression logistique à démontré que la probabilité qu'un tamia regagne son domaine n'est pas reliée à la taille des brèches à traverser (P 2 = 0,781, n = 60, P = 0,377, D 2 = 0,011). Les tamias ont traversé des brèches de toutes les tailles et nous n'avons vu aucun signe de l'existence d'un seuil de connectivité. Nos résultats indiquent que les boisés sont connectés fonctionnellement, même en l'absence de corridors de haies, et que la configuration du paysage dans la région étudiée n'est pas nécessairement un facteur d'isolation pour les populations de tamias. Il faudra procéder à d'autres études empiriques pour déterminer s'il existe des seuils de connectivité fonctionnelle chez les populations de mammifères comme l'indiquent les études théoriques.[Traduit par la Rédaction] Bowman and Fahrig 1561

Tana River Mangabey Use of Nonforest Areas: Functional Connectivity in a Fragmented Landscape in Kenya

“…Uezu et al (2005) similarly found that a forest patch that was structurally isolated was functionally connected for three (of seven) Atlantic Forest bird species. Bowman and Fahrig (2002) likewise found woodlots without corridors in Ontario, Canada, functionally connected for chipmunks; biologists previously thought chipmunks were forest specialists who require corridors. THE MATRIX AS SELECTIVE FILTER.-The matrix has been referred to as a selective filter (Gascon et al 1999) in that some species are able to move through the matrix while others are not (Estrada & Coates-Estrada 1996).…”

Possibilities for On-line Detector Connectivity Checks in Beam Loss Monitoring Systems

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Patch occupancy by squirrels in fragmented deciduous forest: effects of behavior

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