by Anthony P. Clevenger, PhD, Western Transportation Institute, Montana State University
Viable wolverine populations require the survival of reproductive females. Managing potentially disruptive human activity where breeding females live is of paramount importance for successful reproduction and ultimately viable populations.
Historically, it has proved challenging to identify where successful denning occurs without using invasive techniques, including live capture and equipping or implanting individuals at den sites with telemetry collars or radio tags. Denning habitat models and aerial surveys have been used in the United States; however, these techniques have proved unsuccessful and costly.
Noninvasive survey methods are growing in popularity among biologists, largely because they do not require the capture, handling or immobilization of animals. They can be applied at landscape scales, and thus are ideal for studying wide-ranging species like wolverines.
A new system was recently developed that integrates cameras with a “run-pole” to identify individual wolverines from chest markings. In our study we used the same system to determine if reproductive females could be identified through photographs, thereby providing critical information on the location of maternal areas.
We secured the approximately 4-foot-long pole horizontally to a large tree about 3 to 4 feet above the ground, with bait attached. A camera is positioned in front of the pole, so that when wolverines stand on their hind legs to access the bait, it provides a view of their chest markings and genitals.
With the help of a Christine Stevens Wildlife Award, we tested the feasibility of the pole, camera, and bait system for identifying gender and reproductive condition of wolverines in Banff and Yoho National Parks in the Canadian Rockies. Between 2010 and 2013, we surveyed wolverines using noninvasive hair traps to assess population genetics and used the genetic data to install our camera system in areas where females were detected.
During spring 2014, we set up 10 systems in areas known to be occupied by female wolverines. The camera systems were left for at least 30 days before we returned to collect the camera and disassemble the site.
Of the 10 sites, wolverines visited half. At 4 of the 5 sites, wolverines used the run-pole and stood on their hind legs, providing full view of their chest and genitals. More than 1,200 frontal-view photographs of wolverines were obtained at the sites, allowing us to identify wolverine gender and reproductive condition at 3 of the 5 sites from four different animals. We also found that photographs from white-flash cameras were superior to infrared cameras, although reproductive condition could be determined with infrared in most cases as well.
Motorized recreation and access have dramatically increased in the last decade, all impacting wolverine habitat. Conservation of this enigmatic species requires management that is informed by surveys that identify where reproductive females live. Current methods to identify maternal areas have been intrusive and marginally effective. The methodology we tested is low-cost and has the potential to allow us to create a “reproductive map” for wolverine populations and identify critical areas that require heightened management for wolverine protection.