March 2013 update on the SNAMP Fisher Team
Field Activities: The field team is currently monitoring 36 radiocollared fishers by fixed wing aerial radiotelemetry, including 18 females and 18 males. Telemetry flights are continuing five days per week, weather permitting. There was a single mortality of a radiocollared fisher during the last two months; the intact carcass of a young adult male fisher was recovered from a small cavity beneath a tree on a remote mountain ridgeline near Jerseydale on February 16. The field crew is also continuing camera surveys within the main study area to identify the presence or absence of fisher. Pacific Southwest Research station staff has been trapping fisher in the area since January, capturing 19 total fishers. Older radiocollars were replaced on 11 recaptured fishers. In addition, eight fishers new to the project were captured. Trapping was completed this week, and the crew is now preparing for start of the denning season in late March.
Analysis: Project Scientist Dr. Rick Sweitzer is working on an analysis of survival and population of fishers combining the SNAMP Fisher and Kings River Fisher Projects. Other authors include Craig Thompson, Kathryn Purcell, Reginald Barrett, Mourad Gabriel, and Greta Wengert. The draft manuscript is titled “Survival, causes of mortality, and an evaluation of the current status of the fisher population in the Sierra National Forest, California”. Some preliminary findings include:
- Survival trends are lower for all age and sex classes of fishers in the SNAMP study than the Kings River. Nearly half (n = 51) or 47% of the 109 fishers captured and radio-collared on the SNAMP Fisher project are known to have perished, compared to 42% of around 101 fishers in the Kings River.
- Survival trends are lower for male compared to female fishers of all ages in the SNAMP area, which is the same for juvenile and adult fishers in the Kings River area.
- In the SNAMP Fisher project area, adult female fishers experienced very low survival (57%) during population year 3 (2010-11; Apr 1, 2010 to Mar 31, 2011). In all other years, however, adult female survival exceeded 80%, and was over 90% in both 2009-10 (Year 2) and 2011-12 (Year 4). Adult female survival in the SNAMP Fisher study area is 82% for 2012-13 (Year 6) so far. Adult male survival has rebounded to 87% this year (Year 6), from a low of 43% in Year 3.
Please review the full version of the update for more information on the field and analytical activities currently underway on SNAMP Fisher.