Estimating bobcat and Canada lynx distributions in British Columbia

Abstract

Understanding the distribution of a species is useful before undertaking management and conservation actions. Distribution estimates provide ecological insights about a species, and help frame the scope and scale of research questions. However, compiling reliable distribution information is a challenge for elusive mesocarnivores such as bobcats (Lynx rufus) and Canada lynx (L. canadensis). In British Columbia, Canada, bobcats and lynx are key mesocarnivores ecologically and are important furbearers, but their distributions are poorly understood. We compiled and compared 5 independent sources of bobcat and lynx records in British Columbia to gain a better understanding of their provincial distributions: trapping records, hunting records, vehicle-kill records, trapper surveys, and images solicited from the public. Our objectives were to compare bobcat and lynx distributions derived from each of these data sources, and provide reliable estimates for the distribution of each species in British Columbia between 2008 and 2017. Although each method has unique advantages and limitations, all data sources indicated similar distributions, and each data source provided unique locations for the final distribution maps that we derived. Bobcats were restricted to the southern half of British Columbia, whereas lynx occurred across most of the interior of the province. Bobcat and lynx distributions broadly overlapped in southern British Columbia, but image detections generally occurred at higher elevations for lynx than bobcats. We demonstrate the utility of combining multiple data sources when estimating species distributions, and highlight the usefulness of citizen science in such studies. Ó

Measuring agreement among experts in classifying camera images of similar species

“…It would be valuable to conduct a study based on sequences of images for each animal to compare agreement among experts in their classifications when multiple rather than single images are available. However, we note that in our public solicitation for images (Gooliaff et al, ), approximately half of detections from remote cameras (44%) and conventional cameras (52%) still had only single images.…”

“…The true misclassification rate is probably somewhere between these two bounds. Although we could not conclusively determine whether expert classifications were correct, 102 images were from locations where only one of the two species is known to be present: 29 bobcat images were from the southern coast of BC where lynx are likely absent, and 73 lynx images were from north of Highway 16 in northern BC where bobcats are likely absent (Figure ; Gooliaff et al, ). If our classifications of these images are correct, then the majority classification of all experts was correct for all images in this subset excluding three images that had a majority classification of “unknown.” The misclassification rate for this subset of images would be 4%, excluding classifications of “unknown” (i.e., 91 out of 2,481 individual expert classifications of either “bobcat” or “lynx” did not match our classification).…”

“…However, while we expected experts to have greater agreement for images that we provided locations for, we were surprised to find that experts had greater agreement for southern images than northern images when the location was provided. We expected the opposite because bobcats are likely absent in northern BC; thus, there was essentially only one choice for northern images, whereas knowing the location of southern images should have provided little help since both species are common there (Figure ; Gooliaff et al, ). Instead, some experts classified images from northern parts of the province as “bobcat,” counter to our expectation.…”

“…We measured agreement among experts in their classifications of bobcat and lynx images that we collected through citizen science. In a separate study, we solicited 4,399 images of bobcats and lynx from the public across British Columbia, Canada to examine the provincial distribution of each species (Figure ; Gooliaff et al, ). We received 2,648 images (837 separate detections) of bobcats and lynx from remote cameras ( x̅ images per sequence = 3.2, median = 2, range = 1–38, 44% of detections had only a single image), and 1,736 images (748 separate detections) from conventional cameras and camera phones ( x̅ images per sequence = 2.3, median = 1, range = 1–26, 52% of detections had only a single image).…”

“…We selected 27 experts from across western North America to classify the images; we chose experts from (a) northern BC and the Yukon ( n = 9), where lynx are common but bobcats are likely absent (Figure ; Gooliaff et al, ), (b) southern BC ( n = 8), where both species are common (Figure ; Gooliaff et al, ), and (c) the northwestern contiguous US ( n = 10), where lynx are rare but bobcats are common (Hansen, ; McKelvey et al, ). We considered people as bobcat or lynx experts if they were biologists who had field or image‐classification experience on either species.…”