The objective of this study is to estimate size of the brown bear population on Sitkalidak Island and to determine basic movement and resource use patterns. The study has benefited from excellent cooperation among partners: Kodiak Brown Bear Trust, Safari Club International Foundation, Alaska Department of Fish and Game, Old Harbor Native Corporation, and Koniag Regional Corporation.
The study was initiated during May 26-28, 2012. Nine adult females and 1 adult male were captured by helicopter darting techniques and affixed with radio collars. We had planned to mark 10-12 females but inclement weather forced us to end the capture operation on the afternoon of May 28. Nevertheless, we attained a good distribution of marked animals. The sample included one male, 4 single females, and 6 females attended by new to 2 year-old-cubs. An added bonus of the capture effort is that three of the females had previously been captured and radio collared in a pilot study. Even though the radio collars were no longer functioning, the data previously acquired from these animals will enhance our data set.
During June 5-10, 2012, the intensive aerial survey of the study area was completed. Three replicate surveys of the study area were accomplished before bad weather again prevented a planned fourth survey. A correction factor of 0.41 was determined from sightings of radio collared bears. In other words, marked bears were sighted on 40% of those occasions in which they could have potentially been seen. Applying this correction factor to all bear sightings resulted in a population estimate of 68 independent bears (excludes cubs) and 84 total bears.
The 2012 study results, by comparison with data reported in 1998, confirm the thoughts of local residents and biologists that the bear population on Sitkalidak Island has been increasing since cattle ranching, and associated illegal bear control, were terminated in the early 1980s. The 1998 study (Barnes and Smith 1998) used extrapolation from populations studies conducted on Kodiak Island to estimate the population on Sitkalidak Island at 21 independent and 30 total bears. The 2012 estimates are about three times greater than those obtained in 1998. The 2012 results most likely will result in a revised harvest strategy for Sitkalidak Island.
A recent radio-tracking flight (August 7) revealed that the adult females are all alive and in relatively high elevation areas. Only one of the 14 cubs has been lost since the capture operation. The one radio collared male managed to shed his collar. Continued tracking of these study animals will produce data on movements, resource use, survival and productivity.
The study has been very successful despite the weather problems that are typical on Kodiak. Funding provided by SCI Foundation ($50,000), lodging and logistical support by Old Harbor Native Corporation, and photo/video work contributed by Koniag Regional Corporation were critical to project success. Excellent cooperation among all partners resulted in efficient field operations and a strong data set.
By Marcus Gray, Coordinator of Science-Based Conservation Programs & Research, SCI Foundation