Characterizing the Width of Amphibian Movements During Postbreeding Migration

Abstract

Habitat linkages can help maintain connectivity of animal populations in developed landscapes. However, the lack of empirical data on the width of lateral movements (i.e., the zigzagging of individuals as they move from one point to point another) makes determining the width of such linkages challenging. We used radiotracking data from wood frogs (Lithobates sylvaticus) and spotted salamanders (Ambystoma maculatum) in a managed forest in Maine (U.S.A.) to characterize movement patterns of populations and thus inform planning for the width of wildlife corridors. For each individual, we calculated the polar coordinates of all locations, estimated the vector sum of the polar coordinates, and measured the distance from each location to the vector sum. By fitting a Gaussian distribution over a histogram of these distances, we created a population-level probability density function and estimated the 50th and 95th percentiles to determine the width of lateral movement as individuals progressed from the pond to upland habitat. For spotted salamanders 50% of lateral movements were ≤13 m wide and 95% of movements were ≤39 m wide. For wood frogs, 50% of lateral movements were ≤17 m wide and 95% of movements were ≤ 51 m wide. For both species, those individuals that traveled the farthest from the pond also displayed the greatest lateral movement. Our results serve as a foundation for spatially explicit conservation planning for pond-breeding amphibians in areas undergoing development. Our technique can also be applied to movement data from other taxa to aid in designing habitat linkages.

Limited influence of local and landscape factors on finescale gene flow in two pond‐breeding amphibians

“…We performed a sensitivity analysis using several link widths that represent a range from the mean to the maximum width of habitat utilized by migrating individuals (Coster et al . ). For spotted salamanders, we tested widths of 20, 40, 60 and 80 m. For wood frogs, we tested widths of 15, 30, 45 and 60 m. We evaluated 23 landscape variables along each link to test for connectivity (Table ).…”

“…Due to the abundant wetlands in this system, we made the assumption that successful dispersal between pairs of ponds along each link relies on relatively narrow linear pathways, because if there is too much zigzagging, individuals are likely to encounter and remain at other intervening ponds. To delineate link width, we used radio-tracking data on the lateral movement patterns of adults in our study area (Coster et al 2014). We performed a sensitivity analysis using several link widths that represent a range from the mean to the maximum width of habitat utilized by migrating individuals (Coster et al 2014).…”

“…To delineate link width, we used radio-tracking data on the lateral movement patterns of adults in our study area (Coster et al 2014). We performed a sensitivity analysis using several link widths that represent a range from the mean to the maximum width of habitat utilized by migrating individuals (Coster et al 2014). For spotted salamanders, we tested widths of 20, 40, 60 and 80 m.…”

Optimizing the Geometry of Wildlife Corridors in Conservation Reserve Design

“…The author highlights the critical research need to determine "the minimum width of effective corridors. " Coster et al (2014) proposed a method for calculating habitat width requirements and demonstrated the use of the method with migrating amphibians in Maine.…”

Behavior in a Changing Landscape: Using Movement Ecology to Inform the Conservation of Pond-Breeding Amphibians

“…Landscape structure and fragmentation have a direct influence on the costs of migration, and subsequently on individual fitness and the population growth rate. Migratory movements often follow a straight line (Ambystoma maculatum: Pittman and Semlitsch, 2013; Lithobates sylvaticus: Groff et al, 2017), but biased random walks or lateral movements have also been described in forests (Pittman and Semlitsch, 2013;Coster et al, 2014). The straightness of migratory movements is likely due to navigation mechanisms that rely on a combination of geomagnetic location and target-emanating olfactory cues, without any evidence of the use of a cognitive map (Rodda and Phillips, 1992;Joly and Miaud, 1993;Phillips, 1996;Sinsch, 2006;Diego-Rasilla et al, 2008;Landler and Gollmann, 2011).…”