Reduced Trapping Season
The delays we experienced due to the leptospirosis issue meant we missed the January-February 2022 window of opportunity to focus our removals on would-be breeders before breeding season began. However, we persisted in running one round of on-farm trials in March to gain insights as to whether we should continue our work. We conducted a single-round of trapping (24 hours from trap set to trap check) on five Willamette Valley farms (1 hazelnut grove, 2 dairy pastures, 2 vegetable farms), with each search team getting their own ¼ acre plot in the same fields.
Our primary comparison is between unassisted human searchers and canine-assisted searchers, with each trying to identify holes where a trap should be set. Unassisted human searchers rely on their eyes, looking for trails and holes with fresh scat and perhaps nibbled vegetation in the neighborhood. The dogs also use their powerful noses and ears.
Promising Results
Despite the many challenges and limitations, the results were encouraging. Canine-assisted teams and unassisted humans were virtually tied in trap success (0.41 voles/trap by canine teams, 0.40 voles/trap by unassisted human), but differences in efficiency were telling. We had the opportunity to compare efficiency among three different canine-handler teams, which revealed a range from 0.29 voles to 0.65 voles killed per minute of search time. When we compared the average efficiency and total search time spent by canine-assisted trappers (0.48 voles killed/minute of searching over a total of 97 search minutes) to that of an unassisted human (0.29 voles killed/minute of searching over a total of 232 search minutes), the value of canine-assistance became very clear. Our much-delayed 2022 season limited our data and the confidence we have in the results, but there were enough promising indications that we pressed on to trap again in winter of 2023.
Companion Study on Leptospirosis Infection Rates
Voles killed during our 2022 season are contributing to a parallel investigation being conducted by Drs. Sargent and Beechler of OSU’s Carlson College of Veterinary Medicine. This study seeks to better understand which Leptospira strains and serovars occur in voles in the Willamette Valley, in addition to estimating infection rates. This work is important in understanding whether current vaccinations for pets and livestock are a good “match” to the potential challenges on our region’s landscape.
