A predictive habitat occupancy model for North American river otter (Lontra canadensis) along low order streams in inland New Jersey
Date
2014
Authors
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Publisher
University of Delaware
Abstract
The North American river otter (Lontra canadensis ) is a semi-aquatic furbearer species that historically ranged throughout North America. Starting in the mid-1800s and continuing through the early 1900s, the negative effects associated with anthropogenic disturbances (i.e. overharvest, development and ultimately habitat alternation) led to local extinctions. Researchers debate whether current land use patterns are affecting river otter occupancy. New Jersey is the most densely populated state in the United States, thus it provides a perfect study area to test potential anthropogenic effects on river otters. Using occupancy modeling to examine river otter habitat preferences, I measured presence/absence at 244 low order stream sites from January-April 2011-2012 along with 19 corresponding site/landscape covariates in both Northern and Southern New Jersey. In Southern New Jersey, I detected otters at 83/141 sites (58.9%) with a detection probability of 97.7% across repeat visits and a predicted occupancy of 59.4 ± 0.04%. In Northern New Jersey I detected otters at 31/103 sites (30.1%) with a detection probability of 44.5% across repeat visits and a predicted occupancy of 58.8 ± 0.04%. I used program PRESENCE to construct 50 occupancy models per region. The top model for both regions shared 3 covariates including water depth, water quality, and % Low Intensity Development. The Southern model also included % Commercial/Industrial/Transportation/Recreational (CITR), distance to lake and bank slope while the Northern model included stream width and mink presence. I determined the influence of each covariate on otter occupancy for both models and found that water depth, water quality, stream width and mink presence were positively correlated with otter occupancy. While %CITR, %Low Intensity Development, bank slope, and distance to lake were negatively correlated with otter occupancy. Thus, I would suggest constructing lakes and ponds and protecting wider and deeper streams in order to maintain river otter populations.