This report summarizes work on Taylor’s checkerspot captive rearing and translocation conducted July 2019-December 2020. The captive rearing section borrows heavily from annual reports produced by the Oregon Zoo and Mission Creek programs. At least 8,039 eggs from wild females and 8,923 eggs from captive-bred females were harvested at rearing facilities at the Oregon Zoo and Mission Creek Corrections Center for Women in 2019. In all, 12,924 prediapause larvae (7,212 wild and 5,712 captive) were produced, with 3,317 larvae released prior to diapause in 2019 and 9,506 larvae (7,034 wild, 2,472 captive) entering diapause in captivity in June 2019.
In a substantial departure from our strategy to date, all offspring of both captive-mated and wild females from both rearing facilities were released into the field in March 2020. This decision was the result of several factors including 1) ongoing high mortality following wake up at the Oregon Zoo, 2) declining funding projections and lost revenue sources, 3) the cost of the captive mating process relative to production, and 4) concerns over our ability to operate during the impending COVID-19 pandemic in early March 2020. In addition, a key objective of the captive mating program was to retain a captive colony to protect against loss of the wild source population. As there are now three strong populations in the South Puget Lowlands, maintaining this objective is less urgent than it was in 2008 when work began.
Another casualty of the COVID-19 pandemic was the loss of the captive rearing program at the Oregon Zoo. This is highly unfortunate as the Zoo has been fundamental to the inception and development of captive rearing for Taylor’s checkerspot, and has been a valuable partner to Mission Creek, TESC and WDFW.
A total of 4,935 postdiapause larvae were released at TA15 on 28 February, 4 and 17 March 2020. In addition, 2,183 larvae were released at TNQ on 9 March 2020. No adults were released in 2020. Neither were prediapause larvae available for release due in part to the safety restrictions employed in response to the coronavirus pandemic.
COVID-19 restrictions prohibited WDFW staff from conducting most field work until after 1 May, when the flight season was about half over. On all sites we used distance sampling to quantify daily population density, daily population size, and to illustrate the distribution of adults. A total of 11,305 checkerspot observations were recorded during distance surveys, with the greatest number again recorded at R50. Peak day encounter rates at TA15 (0.129 /m) and SCS2 (0.064/m) were notable for being significantly higher than in 2019, whereas at most sites they were lower. In contrast to year’s past, counts at SCS2 followed the same timing and pattern of decrease as at SCS1, suggesting that site is now functioning as a population segment rather than just a pool of dispersing adults from SCS1.
Long-term monitoring and population goals were used to assess progress at R50 and SCS1. Based solely on natural reproduction, adult checkerspots effectively occupy the entire 24.8-ha monitoring area at R50 for a third straight year. The R50 population was deemed to have met the project definition for establishment in 2016. Checkerspots at SCS1 occupied 83.0 percent of the 20-ha monitoring unit in 2020 and are increasing in number at SCS2. This site remains on track to meet all establishment criteria by 2021.