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Grizzly Radio

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In 2019 our team conducted field research across the transboundary study area from mid-June through September. The vast majority of effort occurred in Glacier. Repeated survey effort in Waterton provided beneficial insights into army cutworm moth use of talus. This was achieved thanks to collaborating-assistance from WLNP staff. Access into Akamina-Kishinena Provincial Park in British Columbia is really challenging, and our effort there was limited in scope to a scouting trip to establish preferred access routes for future surveys.

Grizzly bear foraging at an army cutworm moth aggregation site, viewed from fixed-wing aircraft

Aerial Surveys

Inclement weather and turbulent conditions impacted aerial survey effort. Over the season, we attempted seven aerial surveys -five by fixed-wing airplane and two by helicopter. One fixed-wing survey was negated by cloud cover and one helicopter survey occurred after moths had migrated back to the Great Plains. Data from both these surveys are omitted from the following overall comparative results (fixed-wing = average of four surveys, helicopter = one-time count):

  • # of grizzly bear detections per minute survey time: Fixed-Wing: 0.05, Helicopter: 0.25
  • # of grizzly bear groups detected: Fixed-Wing: 5.3, Helicopter: 24
  • # of individuals observed: Fixed-Wing: 8, Helicopter: 30
  • Average group size: Fixed-Wing: 1.42, Helicopter: 1.25
  • Proportion of group detections containing one individual: Fixed-Wing: 0.63, Helicopter: 0.83
  • # of new (previously unknown) sites with grizzly bear detections: Fixed-Wing: 1, Helicopter: 4
Grizzly bear foraging at an army cutworm moth aggregation site, viewed from helicopter

Foraging grizzly bears were observed at moth aggregations found within 39% of project survey units (9 of 23). By this we mean, one or more grizzly bears were observed on one or more occasions, foraging somewhere within the boundaries of a pre-determined survey unit. These units vary in size, comprising a mountain or massif of peaks not separated by a mountain valley/drainage. Seven of the 30 total units were not surveyed due to the previously mentioned challenges.

Grizzly bear feeding at an army cutworm moth aggregation site, viewed in infrared-mode from helicopter

Ground Surveys

Two-person crews conducted ground surveys in 40% of all survey units (12 of 30). This represents efficient output from our 1.5-equivalent survey crews. Importantly, our crews operated in a safe-manner, achieving an accident and injury-free field season. The following summary outlines crew ground survey observations per determining grizzly bear use and describing army cutworm moth habitat.

Project technician conducting count-collection sampling method for army cutworm moths

Determining Grizzly Bear Use

  • Grizzly bear moth foraging sign was recorded in 75% of units surveyed (9 of 12)
  • A majority of bear sign was observed outside of survey plots; sign was located within only 12.5% of all survey plots investigated (15 of 120)
  • Average elevation of grizzly bear sign observed was 2775 meters
Tell-tale sign of grizzly bear use at an army cutworm moth aggregation site

Characterizing Army Cutworm Moth Habitat

  • Army cutworm moth were recorded inside 83% of units surveyed (10 of 12)
  • However, army cutworm moths were only found in 12% of all survey plots (14 of 120)
  • Average elevation of plots containing moths = 2800 meters; without moths = 2680 meters
  • 86% of plots containing moths were located in limestone talus
  • Average three-dimensional size of angular talus was larger at plots containing moths than plots not containing moths
  • Average distance to visible moisture (snow or water) at plots containing moths = 22 meters; without moths = 50 meters
  • Average ground temperature-at-depth of plots containing cutworms was 1.2 degrees Celsius lower than plots where the moths were not detected
Project technician measuring talus dimensions at a survey plot

Our research effort will continue this summer using the same field methods. However, we will reduce the number of survey units to somewhere close to 20 units this year and increase sampling effort within each unit. Project staff will be doubled in 2020 to conduct ground surveys in more units than what occurred in 2019. All aerial surveys this summer will be conducted using a helicopter.

This entry was posted in Results.
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