Table 1 Sampling effort and number of individual grizzly bears detected at natural bear rub sites monitored in the Northern Continental Divide Ecosystem in northwestern Montana, USA during 2004, 2009–2012.

From: Using bear rub data and spatial capture-recapture models to estimate trend in a brown bear population

Year

Rub sites

Sampling occasions

Cumulative rub sampling daysa

Individual grizzly bears detected

2004

4,802

4

312,882

274

2009

3,579

2

289,822

249

2010

4,608

2

344,942

334

2011

4,711

2

342,157

321

2012

4,635

2

342,972

355

  1. The number of rub sites monitored only includes those visited ≥ 1 time after the initial visit to remove hair that could have been deposited the previous year.
  2. aCumulative number of days between the first visit and last collection of the year for each rub sampled per year. For example, if we surveyed 1,000 rubs 1 time after surveying them 60 days earlier, and sampled 2,000 rubs 2 times at 45-day intervals and 100 rubs 3 times at 40-day intervals, rub sampling effort for that year would be (1,000 × 60) + (2,000 × 45 × 2) + (100 × 40 × 3) = 60,000 + 180,000 + 120,000 = 360,000 rub sampling days. Sampling days began to accrue after the initial “clean-off” visit to each rub each year.
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