Upland Movement Patterns and Habitat Selection of Adult Eastern Spadefoots (Scaphiopus holbrookii) at Cape Cod National Seashore
There is a paucity of empirical results regarding many aspects of the movement ecology and upland habitat use and preferences of the Eastern Spadefoot Toad (Scaphiopus holbrookii), an ephemeral, wetland-breeding anuran that is rare throughout a number of states in the northern portion of its range. We radio-tracked 45 adult Eastern Spadefoots in a coastal dune ecosystem at Cape Cod National Seashore, Massachusetts, United States and assessed a number of attributes related to the upland movement ecology and habitat preferences of this species. The mean maximum distance that we found for each of the 19 successfully tracked individuals, immediately post-breeding from the breeding wetlands, was 130.4 ± 28.0 m with a range of 3 – 449 m. Paired logistic regression results indicated that individuals selected areas closer to deciduous shrub edges and areas with greater percent cover of 1) ground-running pitch pine (Pinus rigida) branches at a 1-m scale, 2) deciduous shrubs at a 1-m scale, and 3) reindeer lichen (Cladonia sp.) at a 5-m scale compared to randomly selected locations. We recorded surface activity during 22/24 (∼91.7%) nocturnal survey nights and during 77/127 (∼60.6%) toad-nights; the presence of rainfall was the only significant predictor (positive) of surface activity. Our results provide an assessment of upland movement patterns and habitat preferences that will help guide the development and implementation of effective conservation and management strategies for this regionally rare species.Abstract
Map of the study area identifying the location of the four breeding wetlands where initial captures of individuals occurred in 2006 (denoted as black triangles on the inset map) and the locations of capture for all individuals captured in 2008 in the uplands (denoted as white circles on the inset map).
Distribution of distances from the closest edge of the breeding wetland for each individual tracked, postbreeding, during 2006. Bars are the distribution of distances for all telemetry locations for all individuals (N = 19) pooled and are associated with the left-hand y-axis; circles (filled circles = males [N = 12]; open circles = females [N = 7]) indicate the farthest distance from the closest edge of the breeding wetland each individual was located during telemetry surveys and are associated with the right-hand y-axis.
Distances from the closest edge of the breeding wetland, over time, for each (A) male and (B) female S. holbrookii tracked for at least the first 100 days postsurgery in 2006.
Distribution of minimum estimated burrow residency times for individuals tracked for ≥90 days through the end of September during either 2006 (N = 12 individuals) or 2008 (N = 4 individuals); only data through the end of September in each year was used for this analysis as it is likely that surface activity typically declines shortly after September in most years due to colder air temperatures. Precise burrow residency times (i.e., to within 1-day precision) were not possible as each individual was only located 1–2 times per week.
Euclidean distances between successive burrow locations when individuals shifted burrow locations between consecutive telemetry fixes. Only data from 2006 are presented as there was an insufficient amount of burrow shifts during 2008 to allow for reliable estimates of the interburrow movement distance distribution.
Cover map showing predictive relative probability of occurrence for a subset of the study area. The subset was constructed using predictions from the top-ranked, paired logistic regression model using only variables derived from the remotely sensed raster cover map multiplied by the relative probability of occurrence from the best-fit exponential function of Euclidean distance from the closest edge of the breeding wetland.
Cross-validation for the top-ranked paired logistic regression model compared to the null distribution of relative probability of occurrence values. Vertical tick marks on the x-axis denote the predicted relative probability of occurrence values for each of the 107 unique relocations.
Representative photos of (A) a sparse deciduous shrub and (B) ground-running pitch pine edge, two of the upland habitats used most commonly used by S. holbrookii.
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