Elk Movement in Response to Early-Season Hunting in Northwest Colorado

We conducted a 2-year field experiment to determine whether archery and muzzleloading hunting seasons caused elk to move prematurely onto private land during late summer. The study site was divided into north and south areas, and each area received both an early- and late-opening treatment. Early-opening treatment was an archery season that opened 1 week earlier (23 Aug) than the historical opening, and late-opening treatment was an archery season that opened weeks later (13 Sep), yielding a 21-day difference in opening dates. We relocated 80 radiocollared female elk, captured at random locations on summer ranges, approximately 2 times per week for a 3-month period surrounding early- and late-opening dates each year and classified each elk location as being on public or private land. Elk receiving the late-opening treatment moved 10 days later than elk receiving the early treatment (P = 0.013, 1-sided ANOVA). Because elk on the north area appeared to respond differently to treatment than elk on the south area, we performed a post hoc analysis separately by area. In the north area, elk receiving the late-opening treatment moved 14 days later than elk receiving the early treatment (P = 0.006, 1-sided t-test), compared to a 6-day difference for elk in the south area (P = 0.218). During the study period, approximately twice as many radiocollared elk moved to private land on the north area (44%) compared to the south area (23%). We concluded that the opening of archery season caused a shift in the timing of elk movements on the north treatment area but had little effect on the south area. The greater response of elk to hunter activity on the north area may be due to topographical and migration differences between areas. Changing opening date to delay or shift the timing of elk movement onto private land may depend on availability of habitat refuges on public land and historical migration patterns.