An acoustic technique for monitoring off-highway vehicle (OHV) use with sound level meter data: Camparison with Trailmaster records

Abstract

Off-highway vehicle (OHV) use is of growing interest to land managers. Trail counters are typically used to monitor OHV activity, but accuracy of this technique remains relatively untested. As part of an ongoing study comparing the distribution of American martens (Martes americana) with OHV use in the Lake Tahoe Basin, verifiable OHV detections were collected using two techniques, (1) photographs from Trailmaster 1500 camera systems (TMs) placed across roads/trails and (2) continuous 2-s, A-weighted equivalent-continuous sound levels (LAeq2s) collected using Larson-Davis 720 Sound Level Meters (SLMs) placed either near roads/trails or paired with TM animal detection stations. Events were identified in the SLM data by comparing time-history profiles collected in the field with profiles of known snowmobile passes. Errors in SLM event counts were assessed using independent observer logs and compared with the TM records. SLMs were consistently more reliable detectors of snowmobile use. During the Winter 2004 season, TM records were reliably matched to SLM logs only 48% of the time. TMs consistently missed passes and overestimated events compared to SLMs. In conclusion, SLMs proved to be more sensitive and reliable detectors of OHV activity. These results have implications in both wildlife research and land management applications.