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A Status Review of Townsend’s Big-Eared Bat (Corynorhinus townsendii) in California Scott D. Osborn, Ph.D. Wildlife Branch/Nongame Wildlife Program August 25, 2016 Photos: S. Osborn, L.S. Harris, Katrina Smith Outline • • • • • • • Taxonomy & Species Description Geographic Range Ecology Threats Status and Trends Conclusions Recommendations Description • Medium-sized ”micro” bat (10-12 g) • Light brown dorsal fur; paler underparts • Forearm 39-48 mm • Ear 30-39 mm • Two-pronged nose lump • Broad, short wings FA = 44 mm Photos: Merlin Tuttle, Bat Conservation International Class Mammalia, Order Chiroptera, Family Vespertilionidae Genus Species Corynorhinus townsendii Subspecies Common Name townsendii pallescens ingens virginianus australis Townsend’s big-eared bat Ozark big-eared bat Virginia big-eared bat Corynorhinus rafinesquii Rafinesque’s big-eared bat Corynorhinus mexicanus Mexican big-eared bat Class Mammalia, Order Chiroptera, Family Vespertilionidae Genus Species Corynorhinus townsendii Subspecies Common Name townsendii pallescens ingens virginianus australis Townsend’s big-eared bat Ozark big-eared bat Virginia big-eared bat Corynorhinus rafinesquii Rafinesque’s big-eared bat Corynorhinus mexicanus Mexican big-eared batt Class Mammalia, Order Chiroptera, Family Vespertilionidae Genus Species Corynorhinus townsendii Subspecies townsendii pallescens ingens virginianus australis Common Name Ozark big-eared bat Virginia big-eared bat Corynorhinus rafinesquii Rafinesque’s big-eared bat Corynorhinus mexicanus Mexican big-eared bat Range Calif. Range Foraging Habitat Photos: S. Osborn, NPS, W. Schlegel Roosting Habitat Photos: J. Chenger, S. Osborn, Sierra County Historical Society, BLM COTO Annual Cycle WINTER FALL Build Energy Reserves Mating Pup-Rearing Foraging Hibernation Torpor (Mating) Emergence Pregnancy Foraging SPRING SUMMER Photos: Aaron Corcoran, Katrina Smith, S. Osborn Diet Photos: Aaron Corcoran Threats • • • • • • • • Habitat Loss/Degradation (Roost) Habitat Loss/Degradation (Foraging) Disease Mining Environmental Contaminants Climate Change (incl. Drought) Overexploitation Competition Status & Trends Summary of Pierson & Rainey (1998) Photos: WBWG, TWS-WS, NPS Status & Trends Summary of Pierson & Rainey (1998) Metric Number of adult females (18 colonies) Number of maternity colonies Average colony size Current Historical (ca. 1990) 3,004 1,365 46 22 (43) 164 112 Status & Trends Maternity Sites • Randall House • Kentucky Mine • Lava Beds N.P. • Pinnacles N.P. • Hearst Castle • Santa Cruz Island Hibernation Sites • Lava Beds N.M. • White-Inyo Mtns • Pinnacles N.P. Recent Case Studies Randall House, Pt. Reyes Nat’l Seashore Maternity Roost Exit Counts: Fellers and Halstead 2015 Photo: Sonja Williams Santa Cruz Island, Channel Islands N.P. Maternity Colony Counts: Prisoner’s Harbor Scorpion Ranch roost discovered; monitored No Data (roost lost ~1970) Scattered Obs. Brown et al. 1994; Drost 2003, Brown and Berry 2007, NPS unpubl. data Lava Beds N.M. Weller et al. 2014 Photos: S. Osborn, J. Chenger, Katrina Smith Case Study Summary Hibernation Lava Beds N.M. White-Inyo Mountains Pinnacles N.P. Maternity Randall House Kentucky Mine Lava Beds N.M. Pinnacles N.P. Hearst Castle Santa Cruz Island Statistically significant population increase over 22 years No statistical inference possible; many repeat visits had lower counts than initial visits 10-plus years earlier No inference possible Statistically significant population increase over 25 years Statistical tests not conducted; colony appears stable No inference possible Statistical tests not conducted, but colony appears to be stable or increasing Statistical tests not conducted, but colony appears to be stable or increasing No statistical tests conducted, but colony has decreased from historical size Key Findings (Title 14 CCR 670.1) 1. Present or threatened modification or destruction of habitat 2. Overexploitation 3. Predation 4. Competition 5. Disease 6. Other natural occurrences or human-related activities Recommendations • The best available scientific information indicates to CDFW the petitioned action is not warranted. • CDFW recommends to the Commission that Townsend’s big-eared bat not be added to the list of Threatened and Endangered species under CESA. • The Department presents several management recommendations in the Status Review report. Questions?
