Taylor’s checkerspot (Euphydryas editha taylori) Captive Rearing and Reintroduction: South Puget Sound, Washington, 2017-2018.

This report summarizes work on Taylor’s checkerspot captive rearing and translocation conducted in July 2017-December 2018. The captive rearing section borrows heavily from annual reports produced by the Oregon Zoo (Lewis et al. 2018) and Mission Creek (Curry et al. 2018) programs. A total of 5,514 eggs were produced at the two facilities with 32.1 percent (1,772) of eggs produced by captive-mated females and 67.9 percent (3,742) by wild females. In all, 4,730 prediapause larvae (4,573 wild and 156 captive) were produced, with 3,765 of those (3,615 wild, 150 captive) surviving to diapause.

All available postdiapause larval Taylor’s checkerspots were released at one new translocation site (TA15) in 2018, with excess adults split between TA15 and TA7S when their role in the captive rearing program was complete. A total of 3,336 postdiapause larvae from Mission Creek were released at TA15 on 9 and 15 March. One hundred fifty-eight adults (89 females, 69 males) were released at TA15 on 11 and 22 May, and 152 adults (90 females, 62 males) were released at TA7S on 12 and 24 May. In addition, 3,262 prediapause larvae were released at TA15 on 11 June and 1,913 were released at TA7S on 14 June.

To confirm site occupancy, quantify minimum survival, and identify issues that may be cause for concern, we conducted surveys for postdiapause larvae in thirteen 4×4-m survival plots at TA15 (10 with Mission Creek larvae and 3 with Oregon Zoo larvae) on three occasions in the weeks following release. Daily post-release survival (Mission Creek = 0.932; Oregon Zoo = 0.976) was not different between rearing facilities (z = 0.5464; p = 0.5823), confirming lab results that suggest the increased mortality at the Zoo is the result of larvae failing to transition from diapause to wake-up. Survival for larvae from both facilities was similar to that reported in the literature (Moore 1989) for E. editha in California.

We used distance sampling to quantify daily population density, daily population size, and to illustrate the distribution of adults at five translocation sites (R50, SCS1, GHP, TA7S and TA 15), one potential colonization site (SCS2) and at R76 (source site). A total of 19,773 checkerspot observations were recorded during distance surveys in 2018, setting a new annual record, with the greatest number (7,305) observed at R50. Peak day encounter rates were high, with about 30 percent more butterflies observed at R50 (0.29 checkerspots/m) compared to SCS1 (0.20/m), but both sites harbored about twice as many butterflies as in 2017. Rates at R76 (0.19/m for transects 1-16; 0.22/m for transects 1-12) were about four times higher than in 2017. The peak day encounter rate at TA15 (0.03 checkerspots/m), was also respectably high for a first-year site.

Long-term monitoring and population goals were used to assess progress at R50 and SCS1. Based solely on natural reproduction, adult checkerspots were distributed across the entire 25-ha monitoring area at R50 for the first time. In addition, the peak single day abundance estimate for 2018 (8,832; 95% CI: 6,857-11,377) was the highest recorded for that site, but did not surpass R76 (14,263; 95% CI: 9,801-20,755), which covers 55 percent more area and also had a strong year. This population is officially established based on the project definition and continues to expand. Checkerspots at SCS1 occupied 76.9 percent of the 20-ha monitoring unit in 2018, and extensive restoration continues to improve habitat across the site. The peak single day abundance estimate of adults in 2018 (4,188, 95% CI: 3,527-4,973) indicates this site far exceeded its Year 2 goal and is on track to meet all establishment criteria by 2021.