Dall’s sheep in Gates of the Arctic National Park and Preserve, Alaska: 2010 survey report
Rattenbury KL and Schmidt JH. 2011. Dall’s sheep in Gates of the Arctic National Park and Preserve, Alaska: 2010 survey report. Natural Resource Data Series. NPS/GAAR/NRDS—2011/198. National Park Service, Natural Resource Stewardship and Science. Fort Collins, Colorado
In 2009 and 2010, the National Park Service (NPS) Arctic and Central Alaska Networks tested aerial distance sampling and hierarchical modeling to estimate Dall's sheep (Ovis dalli dalli) abundance in Gates of the Arctic National Park and Preserve (GAAR). This report details the field methods and summarizes results for the 2010 survey. Further information regarding data analysis and interpretation for both surveys can be found in Schmidt et al. (2011). In 2010, we flew 318 20-km long contour transects generated on a 9-km grid across available sheep habitat in GAAR (26,921 km2 survey area). We detected 220 groups totaling 557 individuals on 86 transects. Data were analyzed using spatially-explicit Bayesian modeling, and the estimates were adjusted for group size effects on detection. We estimated that there were 10,072 sheep (95% Bayesian credible interval of 8,081-12,520 sheep) in GAAR in 2010. The total and adult abundance estimates for GAAR, as well as an abundance estimate for the Itkillik Preserve subsection of GAAR, did not differ significantly between 2009 and 2010 and are comparable to the census conducted in GAAR from 1982-1984 (Singer 1984). Estimated lamb abundance was double in 2010 versus 2009 (19.3% versus 10% of total abundance). These surveys showed distance sampling and hierarchical modeling to be an efficient and precise means to estimate park-wide abundance of sheep in GAAR, and these methods will be adopted for monitoring long-term trends in Dall’s sheep abundance in GAAR and other NPS units in Alaska.
- Type
- Published Report
- Authors
- Rattenbury, Kumi; Schmidt, Joshua
- Date of Issue
- 2011-10
- Publisher
- National Park Service, Natural Resource Stewardship and Science
- Units
- GAAR , NRSS
- Keywords
- Aerial Survey, Arctic Network, Central Alaska Network, dall's sheep, Distance Sampling, Gates Of The Arctic National Park And Preserve