Basic Information
Common Name: Townsend's Big-eared Bat
Scientific Name: Plecotus townsendii pallescens
Species Code: PLETOW
Management Category: SO (significant occurrence at risk of loss)
Occurrence Map
Table of Occurrences
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Species Information

MSP Species Background

Goals and Objectives

Goal: Protect Townsend's big-eared bat diurnal, nocturnal, and maternity roosts from destruction and human disturbance and enhance foraging habitat within commuting distance of nocturnal and maternity roosts to increase resilience to environmental and demographic stochasticity, maintain genetic diversity, and improve chances of persistence over the long-term (>100 years).

local NFO 2017, 2018 SO
MON-RES-SPEC PLETOW-1

Management units: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11

In 2017-2018, finalize the results of research begun in 2015 on Townsend's big-eared bat to identify nocturnal, diurnal, and maternity roosts, foraging areas, and water sources associated with roosts in order to identify seasonal and annual changes in use and important foraging areas and monitor reproductive status. Collect habitat covariates associated with roosting and foraging habitat and assess threats to bats at all preserves where they occur and develop management recommendations.

Action Statement Action status Projects
RES-1 Submit project metadata, survey data, and report with management recommendations to the MSP web portal. In progress
Criteria Deadline year
Townsend's Big-Eared Bat Surveys and Reports Completed in 2018. 2018
Threat Name Threat Code
Altered hydrologyALTHYD
Human uses of the PreservesHUMUSE
Urban developmentURBDEV
local NFO 2017, 2018, 2019, 2020, 2021 SO
MON-IMP-IMG PLETOW-2

Management units: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11

Beginning in 2017, annually inspect the vicinity of Townsend's big-eared bat roosts on an annual basis (see Table of Occurrences), taking care not to disturb bats, and use a regional monitoring protocol to collect covariate data on human activities and other threats to determine management needs.

Action Statement Action status Projects
IMP-1 Conduct regional IMG monitoring protocol surveys to quantify signs of human activity near occupied or potential roosts and to identify other potential threats. Care should be taken to avoid disturbing roosting bats. In progress
IMP-2 Based upon threat evaluation, determine if routine management or more intensive management is warranted. Unknown
IMP-3 Submit monitoring data and management recommendations to the MSP web portal. Unknown
Criteria Deadline year
Annual monitoring of Townsend's big-eared bat completed 2021
Threat Name Threat Code
Human uses of the PreservesHUMUSE
Urban developmentURBDEV
Code Obj. code Statement
PLETOW-1 MON-RES-SPEC In 2017-2018, finalize the results of research begun in 2015 on Townsend's big-eared bat to identify nocturnal, diurnal, and maternity roosts, foraging areas, and water sources associated with roosts in order to identify seasonal and annual changes in use and important foraging areas and monitor reproductive status. Collect habitat covariates associated with roosting and foraging habitat and assess threats to bats at all preserves where they occur and develop management recommendations.
local NFO 2017, 2018, 2019, 2020, 2021 SO
MGT-IMP-IMG PLETOW-3

Management units: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11

Beginning in 2017, perform routine management activities such as protecting occurrences from disturbance through fencing, signage, and enforcement.

Action Statement Action status Projects
IMP-1 Perform routine management activities such as protecting occurrences from disturbance through fencing, signage, and enforcement. Available for implementation
IMP-2 Submit project metadata and management data to MSP web portal Unknown
Criteria Deadline year
Routine Management Completed as Needed Based Upon Monitoring Recommendations 2021
Threat Name Threat Code
Human uses of the PreservesHUMUSE
Urban developmentURBDEV
Code Obj. code Statement
PLETOW-2 MON-IMP-IMG Beginning in 2017, annually inspect the vicinity of Townsend's big-eared bat roosts on an annual basis (see Table of Occurrences), taking care not to disturb bats, and use a regional monitoring protocol to collect covariate data on human activities and other threats to determine management needs.
regional NFO 2018, 2019 SO
MGT-PRP-MGTPL PLETOW-4

Management units: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11

In 2018-2019, prepare a management plan for Townsend's big-eared bat that prioritizes management actions to protect roosts from disturbance, ensures sufficient roosts for seasonal temperature requirements and for reproduction, and enhances foraging habitat using data from annual roost monitoring and recommendations from the Townsend's big-eared bat research study.

Action Statement Action status Projects
PRP-1 Prioritize management actions, focusing on reducing threats and expanding occurrences in areas most likely to remain viable over the long-term in the context of future land development. available for implementation
PRP-2 Identify areas where Townsends big-eared bat and pallid bat management can be complimentary. available for implementation
PRP-3 Develop a plan for Townsends big-eared bat that prioritizes management actions for the next five years and details tasks, lead entities, responsibilities, and timelines, budgets. available for implementation
PRP-4 Submit management plan to MSP web portal available for implementation
Criteria Deadline year
Management Plan for Townsend's big-eared bat prepared by 2018 2021
Threat Name Threat Code
Altered hydrologyALTHYD
Human uses of the PreservesHUMUSE
Urban developmentURBDEV
Code Obj. code Statement
PLETOW-1 MON-RES-SPEC In 2017-2018, finalize the results of research begun in 2015 on Townsend's big-eared bat to identify nocturnal, diurnal, and maternity roosts, foraging areas, and water sources associated with roosts in order to identify seasonal and annual changes in use and important foraging areas and monitor reproductive status. Collect habitat covariates associated with roosting and foraging habitat and assess threats to bats at all preserves where they occur and develop management recommendations.
PLETOW-2 MON-IMP-IMG Beginning in 2017, annually inspect the vicinity of Townsend's big-eared bat roosts on an annual basis (see Table of Occurrences), taking care not to disturb bats, and use a regional monitoring protocol to collect covariate data on human activities and other threats to determine management needs.
PLETOW-3 MGT-IMP-IMG Beginning in 2017, perform routine management activities such as protecting occurrences from disturbance through fencing, signage, and enforcement.
regional NFO 2020, 2021 SO
MGT-IMP-MGTPL PLETOW-5

Management units: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11

Beginning in 2020, implement highest priority management actions for Townsend

Action Statement Action status Projects
IMP-1 Management actions to be determined by the implementation plan. waiting for precedent action
IMP-2 Submit project metadata and management data to MSP web portal. waiting for precedent action
Criteria Deadline year
Management actions implemented for Townsend's big-eared bat 2021
Threat Name Threat Code
Altered hydrologyALTHYD
Human uses of the PreservesHUMUSE
Urban developmentURBDEV
Code Obj. code Statement
PLETOW-4 MGT-PRP-MGTPL In 2018-2019, prepare a management plan for Townsend's big-eared bat that prioritizes management actions to protect roosts from disturbance, ensures sufficient roosts for seasonal temperature requirements and for reproduction, and enhances foraging habitat using data from annual roost monitoring and recommendations from the Townsend's big-eared bat research study.
regional NFO 2020, 2021 SO
MON-IMP-MGTPL PLETOW-6

Management units: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11

Beginning in 2020, monitor the effectiveness of management actions implemented for Townsend's big-eared bats on Conserved Lands

Action Statement Action status Projects
IMP-1 Submit metadata, monitoring data and reports to MSP web portal. waiting for precedent action
Criteria Deadline year
Monitoring data submitted to MSP web portal within one year of management actions being completed. 2021
Threat Name Threat Code
Altered hydrologyALTHYD
Human uses of the PreservesHUMUSE
Urban developmentURBDEV
Code Obj. code Statement
PLETOW-5 MGT-IMP-MGTPL Beginning in 2020, implement highest priority management actions for Townsend
Bat Community Management and Monitoring
Both the pallid bat (Antrozous pallidus) and Townsend’s big-eared bat (Corynorhinus townsendii), have been proposed as covered species in the North County MSCP plan and are included in the MSP. These two species are believed to be at high to moderate risk of loss in the MSP area because of their low numbers and sensitivity to human disturbance. However, their population status, locations of roosts (diurnal, nocturnal, and maternity), primary foraging areas, water sources used, threats, and connectivity between populations in the MSP area are largely unknown. For this reason, San Diego County-wide surveys for these species were needed to document where they were found and what their current population status was. Information gleaned from these surveys will allow land managers to implement appropriate management actions to conserve their habitats. The MSP identified this work as a priority for implementation starting in 2015. In 2015, the SDNHM under contract to USGS surveyed areas with known pallid and Townsend's big-eared bat occurrences as identified in the MSP and in other high potential sites based on previous survey work by USGS and the SDNHM. A variety of methods were used (roost surveys, mist-netting, acoustic surveys, etc.) to identify and map the primary roosts and foraging areas used by pallid bat and Townsend's big-eared bat.
Bat Management in San Diego County
This is a planned 2-year Study. In 2015 and 2016, the SDNHM, under contract to USGS, will survey areas with known pallid and Townsend's big-eared bat occurrences in MUs 3, 4, 5, 6 and 8 as identified in the MSP and in other high potential sites based on previous survey work by USGS and the SDNHM, including areas in North County and potentially areas adjacent to the MSP.
El Monte Preserve Bat Hotel
The goal of this project is to aid the recovery of locally declining bat species, by: 1) Creating a thermally stable, long-term (i.e., 50-75 years) roost site, or “bat hotel” on the El Monte Preserve; 2) Creating replicable building plans for the “bat hotel,” so it can be used as a prototype on other conserved lands; and 3) Engaging and educating the public about the ecological importance and conservation value of bats, both online and through in-person educational events. Both the Townsend’s big-eared bat (Corynorhinus townsendii) and pallid bat (Antrozous pallidus), California Species of Special Concern, were observed within 3.5 miles of the El Monte Preserve during 2017 bat surveys conducted at El Monte County Park. de Boer Engineering will build the roosting structure in close coordination with Drew Stokes, Wildlife Biologist and local bat expert for the San Diego Natural History Museum. Together, de Boer Engineering and Mr. Stokes designed the structure to be long lasting, low maintenance, and cost efficient. We envision the “bat hotel” as a prototype for additional structures to be constructed on suitable preserves throughout the MSCP Plan Area, thereby contributing to a long-term recovery strategy for this taxon on a landscape scale.
SR 94 Wildlife Infrastructure Plan
Proposed road improvements to SR 94 provide an opportunity to mitigate the potential barrier effects of the highway. This project identifies where improvements to existing infrastructure on SR-94 could improve connectivity across the South County preserves, using Best Management Practices from the scientific literature; recommends wildlife movement monitoring to identify where new crossings are needed; and identifies where additional conservation would enhance the integrity of South County linkages. The review prioritizes infrastructure improvements of 35 existing undercrossings inspected by wildlife experts in the field along 14.6 miles of SR-94 where the highway bisects conserved lands. The majority of the recommendations for infrastructure improvement focus on increasing the diameter, and thus the openness ratio (cross-sectional area divided by length), of the undercrossing itself, removing vegetation and debris blocking the undercrossing, restoring habitat in the approach to the undercrossing, and installing fencing to both (1) keep animals off the highway and (2) funnel wildlife to the undercrossings.
File name Lead Author Year Type
Bat communities of Rancho Jamul Ecological Reserve and Santa Ysabel Open Space Preserve before and after 2003 wildfires Rochester, Carlton; Backlin, Adam R.; Stokes, Drew; Mitrovich, Milan; Brehme, Cheryl; Fisher, Robert N. 2010 report
Bat Management in San Diego County Myers, Brian; Stokes, Drew; Preston, Kris; Fisher, Robert N.; Vandergast, Amy 2022 powerpoint presentation
DRAFT Final report for focused pallid bat (Antrozous pallidus) and Townsend’s big-eared bat (Corynorhinus townsendii) surveys in San Diego County, California 2018 report
Recording - May 2022 SDMMP Management and Monitoring Coordination Meeting Fisher, Robert N.; Vandergast, Amy; Myers, Brian 2022 recording
State of the Regional Preserve System in Western San Diego County Preston, Kris; Perkins, Emily; Brown, Chris; McCutcheon, Sarah; Bernabe, Annabelle; Luciani, Emilie; Kus, Barbara; Wynn, Susan 2022 report
The San Diego River Park Foundation’s Boulder Creek – Townsends Big-Eared Bat Project Last Quarterly Progress Report and Final Report 2020 report

Current Distribution Rangewide

Occurs primarily in the western-most portion of the species' range in California, Oregon, Washington, Nevada, Idaho with more occurrences in Arizona, Colorado, New Mexico, Texas, and Wyoming [1;2; both from 3]. There are extensive zones of intergradation with the other subspecies, C. t. townsendii, throughout much of its range in California, Nevada, Idaho, Oregon and Washington [3;1 cited from 4;5] with C. t. townsendii also occurring in possibly southwestern Montana and northwestern Utah [3]. Patchy distribution strongly correlated with the availability of caves and cave‐like roosting habitat, degree of human disturbance at roosts, and population centers occur in areas dominated by exposed, cavity forming rock and/or historic mining districts [3;4;5;7].

Known Populations in San Diego County

Occurrences found in El Monte County Park, Hellhole Canyon Preserve, Spring Canyon, Marron Valley Mitigation Bank, Otay Mountain Wilderness Area, Dulzura Conduit, Barret Reservoir Open Space, Bureau of Land Management, Hollenbeck Canyon Wildlife Area, Rancho Jamul Ecological Reserve, San Diego National Wildlife Refuge, Cleveland National Forest, Anza Borrego Desert State Park, Santa Ysabel West Open Space Preserve, Cuyamaca Rancho State Park, Santa Ysabel nEast Open Space, East Otay Mesa, Mason Wildlife Refuge, Portrero Park, Ramona Grasslands Preserve, Del Dios Highlands Open Space Preserve, and San Felip Valley Wildlife Area

List Status

SSC; Currently in evaluation process for State listing of Threatened and/or Endangered

Habitat Affinities

Species is found from inland deserts to the cool, moist coastal redwood forests, in oak woodlands of the inner Coast Ranges and Sierra Nevada foothills, and lower to mid‐elevation mixed coniferous‐deciduous forests [3;4;6;7]. Has been reported in a wide variety of habitat types ranging from sea level to 3,300 meters. For roosts and hibernicula, prefers open surfaces of caves or cave‐like structures, such as subsurface hard rock mines, and large undisturbed spaces in buildings, bridges, and water diversion tunnels [6]. Though roost availability may be low in California Coastal regions, roost fidelity may be quite high [8]. Most commonly found in abandoned mines in San Diego County and appears to be located wherever there are historic mining districts, including within the MSCP area [7].

Taxonomy and Genetics

In the Microchiropteran bat family Vespertillionidae [3;6]. California has two subspecies of Corynorhinus townsendii (C. t. townsendii and C. t. pallescens), as defined in the last taxonomic revision of the species [1 cited from 4].

Seasonal Activity

A late flyer, emerging an average of 46 minutes after sunset [9]. A study suggested 2 peaks of activity during the night. Another study showed that during lactation, females returned to the nursery roost up to 3 times per night, but after lactation remained away from the roost all night [5].

Life History/Reproduction

Colonial species. Maternity colonies form between March and June (based on local climate and latitude). Colonies typically range from a few dozen to several hundred individuals, with colonies of over 1,000 documented [3;6]. Most mating generally takes place in migratory sites and hibernacula between September/October and February, but many females are inseminated before hibernation begins [6;10]. Sperm is stored until ovulation occurs in spring. Gestation lasts 56-100 days, depending on temperature, size of the hibernating cluster, and time in hibernation. A single litter of 1 is produced annually, occurring between May and July [3;6]. Young are weaned in 6 weeks and fly 2.5-3 weeks after birth. Growth rate depends on temperature. Maternity group begins to break up in August. Females mate in their first autumn, males in their first or second autumn. About half of young females return to their birth site after their first hibernation. Subsequent return rates are 70-80%. A longevity record of more than 21 years has been reported and annual survival has been estimated at about 50% for young, and about 80% for adults [6].

Diet and Foraging

Foraging associations include edge habitats along streams and adjacent to and within a variety of wooded habitats. Tend to follow densely vegetated gullies when dispersing from the main roost, and spend the majority of their foraging time within a forested habitat [6;11]. Likely a Lepidopteran specialist, feeding primarily on both small and medium‐sized moths [6;7;10]. Beetles and a variety of soft-bodied insects also are taken. Captures prey in flight using echolocation or by gleaning from foliage. Flight is slow and maneuverable. Capable of hovering. Forages with many other species [10].

Dispersal

Relatively sedentary species makes short movements to hibernation sites [10]. Has been documented making one-way commute distances of 5-13 km on foraging ventures [7;11;12].

Threats

Threatened by disturbance of roosts that results in displacement of the colony, reduced reproductive success, or death; deliberate vandalism that kills or injures bats; and introduction of pathogens, particularly the fungus that causes White Nose Syndrome. Also impacted by pesticides, chemicals for mineral processing, wind energy developments, artificial lighting, pest control activities, small population size, climate change [3;4;6], new and renewed mining operations, urban and suburban development, and predation by non‐native species (domestic cats and black rats) [3]. Primary cause for decline in western San Diego County is likely rapid urbanization [4].

Literature Sources

[1] Handley, C.O. 1959. A revision of American bats of the genera Euderma and Plecotus. Smithsonian Institution.

[2] Piaggio, A.J., and S.L. Perkins. 2005. Molecular phylogeny of North American long-eared bats (Vespertilionidae: Corynorhinus); inter- and intraspecific relationships inferred from mitochondrial and nuclear DNA sequences. Molecular Phylogenetics and Evolution, 37:162-775.

[3] California Department of Fish and Wildlife. 2016. A Status Review of Townsend's Big-Eared Bat (Corynorhinus townsendii) in California. Report to the Fish and Game Commission.

[4] Pierson, E.D. and W.E. Rainey. 1998. Distribution, status, and management of Townsend's big-eared bat (Corynorhinus townsendii) in California. State of California, Resources Agency, Department of Fish and Game.

[5] Pierson, E.D. 1999. Species conservation assessment and conservation strategy for the Townsend's big-eared bat.

[6] California Department of Fish and Wildlife. 2013. Evaluation of the Petition from the Center of Biological Diversity to List Townsend's Big-Eared Bat(Corynorhinus townsendii) as Threatened or Endangered Under the California Endangered Species Act.

[7] Miner, K. L. and D. C. Stokes. 2005. Bats in the south coast ecoregion: status, conservation issues, and research needs. U.S. Forest Service.

[8] Sherwin, Rick. Townsend's Big-Eared Bat. 2005. Western Bat Working Group. Available from http://wbwg.org/western-bat-species/. Accessed September 20 2016.

[9] Clark, B.S., D.M. Leslie, and T.S. Carter. 1993. Foraging activity of adult female Ozark big-eared bats (Plecotus townsendii ingens) in summer. Journal of Mammalogy 74, no. 2: 422-427.

[10] Harris J. 2000. Townsend's Big-Eared Bat. Zeiner, D.C., W.F.Laudenslayer, Jr., K.E. Mayer, and M. White, eds. 1988-1990. California's Wildlife. Vol. I-III. California Department of Fish and Game, Sacramento, California.California Wildlife Habitat Relationships System. California Department of Fish and Game.

[11] Fellers, G.M. and E.D. Pierson. 2002. Habitat use and foraging behavior of Townsend's big-eared bat (Corynorhinus townsendii) in coastal California. Journal of mammalogy 83, no. 1: 167-177.

[12] Brown, P.E., R. Berry, and C. Brown. 1994. Foraging behavior of Townsend’s big-eared bats (Plecotus townsendii) on Santa Cruz Island. Pp. 367-369 in Fourth California islands symposium: update on the status of resources (W. L. Halvorson and G. J. Maender, eds.). Santa Barbara Museum of Natural History, Santa Barbara, California.