Demography of Dall’s Sheep in Northwestern Alaska

Kleckner, Christopher; Udevitz, Mark; Adams, Layne

hforts to initiate research on sheep populationsy estimates of Dall’s sheep population size and composition in the western Brooks Rangeal variation in recent Baird Mountains aerial counts cannot be explained with reion observed each year or that a substantial number of sheep mo. Our understanding of Dall’s sheep population biology comes largely from studies in central or d live in a less hospitable environment characterized by short growing seasons and long, severe populations. To adequately manage sheep harvests in northwestern Alaska, we need a better underegion will allow population models to be developed that can provide focus for a useful dialog on management goals and strategiDall’s sheep in northwestern Alaska declined in the early 1990s following the severe 1989-90 and 1990-91 winters. In the Baird Mountains of Noatak National Preserve, estimates of adult sheep declined by 50% from 800 in 1989 to under 400 in 1991. Population counts remained low throughout 1991 to 1996, reaching a minimum of 244 adult sheep in 1996. Few lambs were observed during annual midsummer aerial surveys in 1991 to 1994. We suspect that these declines resulted from a combination of poorer nutritional condition and increased vulnerability of sheep to predation resulting from severe winter conditions. As a result of these declines, both subsistence and sport hunting seasons were closed by emergency order in 1991, resulting in substantial management controversy. The affected publics, although willing to accept te closures, questioned the validity of the sheep survey data and strongly emphasized their interest in restoring harvests as soon as populations increased sufficiently. In 1995 the Northwest Arctic Regional Advisory Council, the local advisory committee for the Federal Subsistence Board, passed a motion supporting ef in the region to better understand the factors limiting sheep populations and to evaluate sheep survey methodologies. Currentl are based on intensive fixed-wing aerial surveys conducted annually since 1986 in areas including the Baird Mountains. The annuasonable assumptions about reproduction and survival, suggesting that there is some variability in the proportion of the populatve during the survey. Prior to our research, no attempt had been made to estimate visibility bias or precision for these surveyssouthern Alaska and the southern Yukon. However, sheep in northwestern Alaska are at the northwestern extreme of their range anwinters. We expect patterns of productivity and survival for sheep in Noatak National Preserve to differ from the more southerlyrstanding of sheep demography. Along with unbiased population estimates, understanding the dynamics of sheep populations in the es and facilitate a cooperative strategy for managing sheep harvests in northwestern Alaska.

Demography of Dall’s Sheep in Northwestern Alaska

See also