Technical Summary and Supporting Information for an Emergency Assessment of the Northern Myotis Myotis septentrionalis – 2012

Graham Forbes, Co-Chair, Terrestrial Mammal Subcommittee, COSEWIC

February 2012

Table of Contents

Figures

Tables


COSEWIC – Committee on the Status of Endangered Wildlife in Canada

Assessment Summary – February 2012

Common name
Northern Myotis

Scientific name
Myotis septentrionalis

Status
Endangered

Reason for designation
Catastrophic declines and predicted functional extirpation (<1% of existing population) in the northeastern United States will very likely apply to the Canadian population of this species within 2 to 3 generations. There have been massive mortality events recorded in New Brunswick in 2011, significant declines in Quebec and Ontario hibernacula, and evidence of flying bats in winter at numerous sites where White-nose Syndrome (WNS) is known. WNS is recorded in 4 Canadian provinces and expanding at 200-400 km/yr. If the spread of WNS continues at the current rate, the entire Canadian population would likely be impacted within 11-22 years.

Occurrence
Alberta, British Columbia, Manitoba, New Brunswick , Newfoundland and Labrador, Northwest Territories, Nova Scotia, Prince Edward Island, Ontario, Quebec, Saskatchewan, Yukon

Status history
Designated Endangered in an emergency assessment on February 3, 2012.

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Executive Summary

Between 5.7 and 6.7 million bats, of several species, mainly Little Brown Myotis but including Northern Myotis, are estimated to have died in the last 6 years in the northeastern United States and eastern Canada. Mortality associated with White-nose Syndrome (WNS), caused by a fungus likely from Europe, has reduced populations by >75% in infected hibernacula, and the closely related Little Brown Myotis has been modelled to be functionally extirpated (<1% population) in 16 years in the northeastern U.S. (Frick et al. 2010). The same pattern would be expected for the Northern Myotis. There is strong evidence that the same result will occur in the Canadian population of Northern Myotis; significant declines and mortality events were recorded in Canada in 2011 and susceptibility to WNS is expected to be similar across Canada.

Population size and trends for the Northern Myotis before the arrival of WNS are not known, but they were considered abundant and stable. The mortality rate of Northern Myotis in infected caves for 2 years or more is 98% in 5 states of the northeastern United States and >90% in Ontario, and 99% in the first Quebec site. Twenty-three of the 32 sites in the northeastern U.S. were reduced to 0 bats. It is assumed that the rate of spread of the disease and the mortality levels recorded to date will continue westward and impact most of the Canadian population within 20 years.

Imminent decline and threat to the survival of this species is based on results from the northeastern U.S. and eastern Canada and the predicted spread of WNS across the Canadian population in the near future. It is likely that significant declines from WNS could occur across the Canadian range of this once-abundant species within two to three generations.

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Technical Summary

Myotis septentrionalis
Northern Myotis (Northern Long-eared Bat) – Chauve-souris nordique

Range of occurrence in Canada:
Alberta, British Columbia, Manitoba, New Brunswick , Newfoundland and Labrador, Northwest Territories, Nova Scotia, Prince Edward Island, Ontario, Quebec, Saskatchewan, Yukon

Demographic Information
Generation time.
Range of 3-10 years accounts for mean age of longevity – 1 year for subadult period = 14; mean age of adult females = 10, and data from banding data on Little Brown Myotis in Manitoba, which suggests 3 years.
3-10 years (est.)
Is there an observed continuing decline in number of mature individuals?
Populations considered stable until present, although they receive minimal survey attention.
Yes, significant declines noted in some sites in last 2 years
Estimated percent of continuing decline in total number of mature individuals within 2 generations (6-20 yrs).
Populations considered stable until present, although they receive minimal survey attention.
Unknown for past but  considered high in future
Inferred percent reduction in total number of mature individuals over the last 3 generations (9-30 yrs).
Populations were considered stable until WNS, although they receive minimal survey attention.
Unknown, but likely stable prior to WNS
Projected percent reduction in total number of mature individuals over the next 3 generations (9-30 yrs). 
Catastrophic decline is predicted in eastern range within 5 years and remainder of range within 11-22 years, based on mortality data and rate of spread to date.
At least 90% (assuming continued spread westward and north)
Estimated percent reduction in total number of mature individuals over 3 generations, over a time period including both the past and the future. At least 90% (assuming continued spread westward and north)
Are the causes of the decline clearly reversible and understood and ceased?
WNS is cause of mortality but without any remedy it is expected to continue; spores persist in cave environments.
Understood, but not ceased, nor currently reversible
Are there extreme fluctuations in number of mature individuals?
Variation in individual hibernacula recorded but extreme fluctuations not evident for any known populations.
Unknown, but not likely

 

Extent and Occupancy Information
Estimated extent of occurrence.
Newfoundland to British Columbia, north to Yukon and NWT, edge of range in Nunavut
Well over 20,000km²
Index of area of occupancy (IAO)
(Always report 2x2 grid value).
Hibernacula and maternity roosts historically reused specific locations but summer foraging is over entire range.
Well over 2,000km²
Is the total population severely fragmented?
Range is contiguous (with possible exception of the Island of Newfoundland)
No
Number of locations*
1 location, based on WNS as an all-encompassing threatening event.
1
Is there an observed continuing decline in extent of occurrence? 
Predictions are based largely on mortality data from northeastern U.S.
Not yet, but predicted over next 3 generations
Is there an observed continuing decline in index of area of occupancy?
Predictions are based largely on mortality data from northeastern U.S.
Not yet, but predicted over next 3 generations
Is there an observed continuing decline in number of populations? 
Predictions are based largely on mortality data from northeastern U.S.
Not yet but predicted over next 3 generations
Is there an observed continuing decline in number of locations*?
Canadian population exists as 1 location
No

Is there an observed continuing decline in area of habitat?
Hibernacula are habitats critical for population sustainability; WNS appears to turn sites into mortality sinks. Declines recorded in some hibernacula, and may have occurred in others based on WNS history

Are there extreme fluctuations in number of populations?

Yes
No
Are there extreme fluctuations in number of locations*?
Canadian population exists as 1 location
No
Are there extreme fluctuations in extent of occurrence?No
Are there extreme fluctuations in index of area of occupancy?No

 

Number of Mature Individuals (in each population)

Population
N Mature Individuals
(estimated minimum)
Unknown, considered common in central-eastern Canada, less abundant westward. Numbers of Northern Myotis in hibernacula much less than Little Brown Myotis, although species identification difficult in some caves. 
TotalUnknown, < million (?)

 

Quantitative Analysis
Probability of extinction in the wild is at least [20% within 20 years or 5 generations, or 10% within 100 years].
Model predictions (Frick et al. 2010) for similar species in northeastern U.S. (based on 30 years pre-WNS data and 4 years documented declines since WNS) predict 99% probability of ‘regional extinction’ within 16 years. If WNS spreads at current rate (range 200-400 km/yr), spread across Canada will occur within 11-22 years, within the 5 generations (15-50 years).
Assuming results from Little Brown Myotis apply to Northern Myotis, probability of extinction is 99% in northeastern U.S. Similar results expected for central and eastern Canada. If rate of spread continues westward, probability of extinction would be similar.

 

Threats (actual or imminent, to populations or habitats)
White-nose Syndrome is caused by a fungal pathogen (Geomyces destructans) that likely originated in Europe and was first recorded in North America in 2006, and 2010 in Canada. All Myotid species that hibernate in cold, damp conditions are vulnerable. Mortality of Northern Myotis in 30 infected hibernacula averages 98% in northeastern United States after several years of exposure. Autumn mixing of bats results in likely spread to all hibernacula.

 

Rescue Effect (immigration from outside Canada)
Status of outside population(s)?
Is immigration known or possible? 
Northern Myotis are mobile and some undertake movements of 200-300km between seasons and hibernacula.
Likely
Would immigrants be adapted to survive in Canada? 
Climate and food sources are similar to American conditions but any immigrants would not be adapted to Geomyces destructans.
Yes/No
Is there sufficient habitat for immigrants in Canada?
Roosts and food are not thought to be limiting but hibernacula infected with Geomyces destructans would become population sinks.
No
Is rescue from outside populations likely?
Populations only exist south of Canada and they have been near extirpated in the American northeast; populations in western United States predicted to be significantly reduced within 3 generations and unlikely able to recolonize Canadian population.
No

 

Current Status
COSEWIC:  Not assessed. Considered abundant throughout most of range. Assessment for endangered status is underway in the United States; public comment and review in progress.

 

Status Summary:
Status and Reasons for Designation
Status:  
Endangered
Alpha-numeric code:  
A3bce+4bce; E
Reasons for designation:
Catastrophic declines and predicted functional extirpation (<1% of existing population) in the northeastern United States will very likely apply to the Canadian population of this species within 2 to 3 generations. There have been massive mortality events recorded in New Brunswick in 2011, significant declines in Quebec and Ontario hibernacula, and evidence of flying bats in winter at numerous sites where White-nose Syndrome (WNS) is known. WNS is recorded in 4 Canadian provinces and expanding at 200-400 km/yr. If the spread of WNS continues at the current rate, the entire Canadian population would likely be impacted within 11-22 years.

 

Applicability of Criteria
Criterion A (Decline in Total Number of Mature Individuals):
Meets A3b,c,e: COSEWIC criterion of ‘projected reduction in total number of mature individuals is >50% over 3 generations’ is projected or suspected to be met because we expect nearly 100% of hibernacula will be affected in <22 years (3 generations is 9-30 years), and likely at near 100% mortality. This projection is based on evidence of WNS in Canada and documented declines averaging 98% in 32 infected hibernacula in 5 nearby U.S. states after 2 years of exposure. Significant declines (i.e. >90%) reported in Ontario and Quebec hibernacula.
Meets A3b because the number of mature individuals is projected to decline by over 90% over the next 3 generations based on the current rates of mortality recorded in 32 infected hibernacula in the U.S. after 2 years of exposure. Similar patterns are being documented in eastern Canada, and hibernacula across Canada are expected to be affected in 3 generations, given a continued rate of spread of 200-400 km/year.
Meets A3c because the EO and IAO are projected to decline by more than 50% over the next 3 generations as populations are extirpated following the spread of the disease. Bats were extirpated from 23 of 32 hibernacula in the northeastern U.S. by 2010, 5 years after the discovery of WNS.
Meets A3e because Geomyces destructans, the cause of WNS, is believed to be an introduced pathogen from Europe and is responsible for population declines of over 90% in hibernacula within two years of infection.
Meets A4b,c,e because impact of WNS at present, combined with future predictions, exceeds 50%, and reduction or cause may not cease and may not be reversible, given lack of remedy (see rationale for b,c,e above).
Criterion B (Small Distribution Range and Decline or Fluctuation): not applicable
Criterion C (Small and Declining Number of Mature Individuals): not applicable
Criterion D (Very Small or Restricted Total Population): not applicable
Criterion E (Quantitative Analysis):
Using results from Little Brown Myotis as a surrogate for this species, the COSEWIC criterion of minimum 20% probability of extinction within 20 years or 5 generations is met because results from nearby and similar regions have modelled regional extinction of Little Brown Myotis within 16 years at 99% probability. This species has the same life-history strategy and are impacted by WNS. This species is predicted to be impacted across the Canadian range before the 5-generation (15-50 yrs) threshold.

* See Definitions and Abbreviations on COSEWIC website, IUCN 2010 (PDF; 493 KB) for more information on this term.

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Emergency Assessment – Northern Myotis

Graham Forbes, Co-Chair, Terrestrial Mammal Subcommittee, COSEWIC

Context for the report

The Species at Risk Act and Section 5.5 of the Operations and Procedures Manual for COSEWIC contains the context of an emergency assessment. The following report outlines evidence of the serious decline in the population of the Northern Myotis that results in an imminent threat to their survival.

Overview of the species and evidence of threat to survival  

The Northern Myotis (Myotis septentrionalis) (also called Northern Long-eared Bat) is a common, insect-eating bat found throughout much of southern Canada and the northern United States (Fig. 1). Approximately 40% of its global range is in Canada. Due to its being relatively common and widespread, limited effort has been made to determine overall population size. Information on overwintering sites (hibernacula) are generally well known in central and eastern Canada, but less so in western Canada where the species appears to be less common. There are no records of the species overwintering in Yukon and Northwest Territories.

In this assessment, the impact of White-nose Syndrome (WNS) is treated as equal between the Little Brown Myotis and Northern Myotis, and results from the better studied Little Brown Myotis are applied to the Northern Myotis if data on Northern Myotis are absent. The Northern Myotis is very similar in size, life-history characteristics (i.e. age to breeding, number of offspring, life expectancy) and food habits (Caceres and Barclay 2000). The main difference is that Little Brown Myotis typically forage over water while Northern Myotis typically forage within the forest (Broders et al. 2005). Both species are highly susceptible to White-nose Syndrome. Both species hibernate in the same hibernacula and it is difficult to identify to species if bats are at a distance, or in crevices. Little Brown Myotis are considered more common but, because most data on abundance in hibernacula combine Little Brown and Northern Myotis, the two species are not always considered separately within cave monitoring data.

Small-bodied bat species that winter in caves or mines are dying from White-nose Syndrome (WNS), caused by a fungus, Geomyces destructans (Gd), that is hypothesized to have originated in Europe (Pikula et al. 2012, Turner et al. 2011), and was first detected in North America in 2006 (Lorch et al. 2011). The fungus grows in humid, cold environments, typical of caves where bats hibernate (Blehert et al. 2009). Mortality during winter is hypothesized to be caused by starvation through excessive activity; insect-eating bats that would normally hibernate become active, dehydrated and hungry because of infection from the fungus that grows on them while their body temperature (Turner et al. 2011) and immunity (Carey et al. 2003) is low. The bats leave the caves in search of food and water but die outside, or at the hibernacula entrance. Physiological processes associated with hydration, and damage to wings, may also be related to mortality (Cryan et al. 2010).

The Little Brown Myotis is predicted to be functionally extirpated (i.e. <1% of existing population) in the northeastern United States within 16 years (Frick et al. 2010). This prediction would also apply to Northern Myotis. An estimated 1 million bats (multiple species) died in the northeastern U.S. within 3 years of WNS arrival (Kunz and Tuttle 2009). A recent mortality estimate of 5.7-6.7 million bats within 6 years of WNS arrival was made by the WNS management team in the United States (U.S. Fish and Wildlife Service news release; January 17, 2012). Mortality results to date support the predictions in the Frick et al. (2010) model (Turner et al. 2011).

The populations of affected species are not expected to recover quickly because bats, typically, have slow population growth rates. Mortality is high in yearlings while adults are long-lived and only produce 1 young every year or two. Such a life-history strategy heightens the vulnerability of these bat species to high adult mortality rates. Experience from the U.S. indicates significant declines often occur in the second year after first detection (Turner et al. 2011) and thus we emphasize data with > 1yr post-exposure in this report. Population declines in infected areas (much of the northeastern United States) have been catastrophic. Population declines in 32 hibernacula infected for 2 years or more in the northeastern United States have been >98% for Northern Myotis (Table 1; Turner et al. 2011). Twenty-three of 32 hibernacula (72%) declined to 0 bats. As of 2011, WNS has been recorded in 190 hibernacula in 16 states and 4 provinces. The same results are occurring in Canada where WNS has been reported for > 2 years (see details below).

Recent Canadian data  

In eastern Ontario, 8 hibernacula are being monitored for changes in abundance; all had significant declines after 1 year of exposure to WNS, with an average decline of 30%. After 2 years of exposure, the average decline was 92% (Table 2). All of these caves contained Northern Myotis but the exact numbers are not known because of difficulty in identifying species at a distance.

In Quebec, 5 hibernacula are being monitored relative to WNS using laser counters at the hibernacula entrance. In autumn 2011, one hibernaculum (Mine-aux-Pipistrelles, in southern Quebec near the U.S. border and the closest site to the origin of WNS) had a decrease from >5000 to 8 bats (min. 99% decline) of all species, concurrent with hundreds of dead bats on the ground (Mainguy and Desrosiers 2011). Ten percent of the bats in the hibernaculum were Northern Myotis; abundance was 526-769 during the two preceding pre-WNS years then declined to 1 bat in November 2011, a 99% decline. Ten other sites are monitored by observation but access and quality of survey results varies; 1 site (Emerald Mine) with 10% Northern Myotis recorded signs of WNS and “many” dead bats in February 2010.

In New Brunswick, 11 sites have been monitored for WNS in 2010-12. The first record of WNS was in March 2011 when over 80% of 6000 bats in Berryton Cave died in 1 month (McAlpine et al. in press). A total of 350 bats were counted in December 2011. Of a sample of 357 dead bats from the 2011 event, 8.4% (30) were Northern Myotis (D. McAlpine, pers. comm.). WNS was recorded in an additional 3 sites in December 2011.
In Nova Scotia, permission to enter caves is restricted and surveys have been limited to winter-time visits to the entrance of caves, collecting dead bats, and reports from the public of bats flying during winter. Carcasses are submitted to veterinary pathologists, who have confirmed Gd.

As of autumn 2011, WNS has not been recorded in Prince Edward Island or Newfoundland, or west of Ontario.

Recent summer data  

Data from summer are sporadic and systematic acoustic monitoring has only recently begun in many jurisdictions. Where available, summer data indicate similar declines as reported during winter. Therefore, it is unlikely that empty hibernacula during winter indicate bats have simply moved to new and unsurveyed sites. Preliminary results from 200 transects conducted in 24 states indicate significant declines in summer abundance in WNS range (i.e. near extirpation of Northern Myotis in New York State with most transects no longer detecting this species; Britzke et al. 2011 unpub. data). In Virginia, captures at 5-6 autumn swarm sites declined from early-WNS levels of 21 Northern Myotis captures per site to approximately 2 bats per site in 2011 (Fig. 4) (Rick Reynolds, pers. comm., unpublished data; Virginia State Biologist).

Summer data on population size or trends from maternity colonies of Northern Myotis are not known for Ontario, Quebec or the Maritimes.

Imminent threat to survival  

An imminent threat to the survival of this species is based on three assumptions: a) the expectation that mortality results from the northeastern United States will apply to the Canadian population; b) that there is a high probability that WNS will rapidly spread to all hibernacula in the Canadian range; and c) there is no likelihood of rescue effect.

a) Application of U.S. results to Canada  

The outbreak of WNS occurred first in the northeastern U.S. and more data are available for this population on the effects of WNS after multiple years. Also, hibernacula were generally better monitored and population trends more known in the U.S., which facilitated population modelling of WNS impacts. Mortality rates recorded in the U.S. are expected for Canadian populations because hibernacula conditions, such as temperature and humidity, are similar and fall within the range of Gd growing conditions. There likely is movement of some bats between the two countries and no genetic differences are expected between bats in the northeastern U.S. and Canada. As such, there is no reason to expect increased resistance within Canadian bats and results from the northeastern U.S., including the population model, mortality rates, and rate of spread should be similar.

b) Rate of spread  

White-nose Syndrome was first recorded 6 years ago (February 2006) in a cave near Albany, New York (Frick et al. 2010, Fig. 2). It has spread at a rate of approx. 200-400 km per year, reaching Ontario and Quebec in 2010, and New Brunswick and Nova Scotia in 2011 (Fig. 1, 2). Straight-line distance of WNS spread from the epicentre at Albany, NY to the farthest site (Missouri) from 2006-2011 was approximately 1000km, a rate of 200km/yr. A recent case from Oklahoma is 2200km from the epicentre (440 km/yr) (Turner et al. 2011, Fig. 1, 2). In Canada, the rate to New Brunswick was 200km/yr, and from the epicentre to the farthest western site to date (Wawa, Ontario) was 250 km/yr. The average rate of spread appears to range between 200-400 km/yr. The distance from the epicentre to the first site in Ontario (Cochrane) was 1000km, which may indicate WNS can spread in large leaps, either by bat or human movement, or that WNS was already present in Ontario sites closer to Albany.

The vector for transmission is believed to be bats that have been in contact with conidia of infected bats or walls of hibernacula, and people visiting caves. An unknown proportion of Northern Myotis move hundreds of kilometres between their summer and winter ranges. Swarming behaviour in August and September is likely a main mechanism for Gd transfer between subpopulations. Swarming behaviour shows young where to go to hibernate and also heralds the start of the mating season. Extensive bat-to-bat contact during swarming is believed to be instrumental in the spread of WNS (B. Fenton, pers. comm.). Bats have been recorded swarming at one site but hibernating in another (Humphrey and Cope 1976), potentially transmitting spores between sites (Turner et al. 2011).

WNS is expected to continue spreading throughout Canada and the western United States because most caves and mines used by bats have similar conditions. Based on Gd growing conditions (minimum and maximum temperatures in hibernacula, and the relationship of temperature and lipid reserves in Little Brown Myotis) (Hallam and Federico 2011), it is predicted that much of the United States has the conditions for WNS, and assuming spread between colonies will occur as it has in eastern North America, much of the area will be impacted by WNS by 2018 (Fig. 3). The predictive map was not made for Canada but similar hibernacula conditions in Canada would suggest similar potential for WNS as shown in the U.S. map (Fig. 3).

It has been suggested that the rate of spread may not be as fast in western Canada because colonies are more dispersed than in the east (C. Willis, pers. comm. 2012). There are no data to accept, or refute, this statement because so little is known on hibernacula in western regions of Canada, and the dynamics of transmission of WNS across different densities of bats is unknown. From what we know to date, WNS impacts colonies of different density: it appears to be first detected in a large hibernaculum, and then is found in adjacent hibernacula containing fewer bats. If we use the recorded average rate of spread (200-400 km/yr), and assume it will continue at this rate, WNS will occur on the west coast of North America within 11-22 years. Additionally, the WNS site in Oklahoma is 500km from the Rocky Mountains, and it is possible that WNS will move northward into Canada via the Rocky Mountains, instead of crossing the Canadian prairies.

There also is the strong possibility that WNS will reach western populations faster than predicted based on the movement of bats. The discovery of Gd in North America was at a cave that has high human visitation. It is suspected that Gd was accidently brought to North America by tourists who had visited caves in Europe (Turner et al. 2011). There is concern that Gd will be transmitted to western hibernacula by tourists or spelunkers who visit multiple sites.

In conclusion, the dynamics of movement in bats is not well understood and there may be differences in spread of WNS among the Rocky Mountain region, but there is strong evidence that WNS will continue to spread and be as catastrophic in the western region as it has to date in eastern North America. The precautionary principle would suggest that the observed rate of spread could be assumed to apply from eastern to western Canada.

c) Potential for refugia and rescue effect

There is no expectation of a rescue effect. The Northern Myotis in Canada is at the northern edge of its geographic range (Fig. 1) and therefore any rescue would need to come from southern populations in the United States. High mortality rates associated with WNS have occurred in the regions south of Canada and populations are so reduced that immigration north into Canada is very unlikely.

Southern regions in the United States, and possibly coastal areas, where it is warmer and bats need fewer lipid reserves, may not be susceptible to WNS (Fig. 3). However, Gd spores have been recorded in soil in hibernacula (Lindner et al. 2011) and it is likely that any populations expanding northward would be impacted by WNS when they use hibernacula in Canada.

There is no expectation that western populations of Northern Myotis will be immune to WNS, further precluding the possibility of rescue effect for eastern bats. Bats in northern hibernacula hibernate in relatively colder conditions (1-2˚C) (S. Carrierre, pers. comm. Jan. 2012) and may be less susceptible to WNS because Gd does not grow as well at that temperature (Gargas et al. 2009). However, numbers of bats in these conditions would be a small percentage of the Canadian population, and thus would not offset massive declines. Also, any northern populations expanding into the south would be susceptible to persistent spores within southern hibernacula.

Hope for any recovery of the species is based on the likelihood that some small percentage of the population will be resistant to the effects of Gd. These survivors would pass on this resistance to their offspring and populations would increase. It is believed that such a situation occurred in Europe because several species of bats get WNS but mortality levels are low (Turner et al. 2011).

There is evidence that some individuals exposed to WNS can survive, based on laboratory (Meteyer et al. 2011) and banding studies (Dobony et al. 2011). In the Dobony study, in Fort Drum, New York, a small number (i.e. <20) of Little Brown Myotis were captured in summer showing evidence of WNS-related wing damage and then recaptured the following year. Five females were recaptured after two years, and with lactation noted in some females, there is evidence of possible reproduction in some animals. One cave in New York has had a population of 1000 bats for 4 continuous years, suggesting stabilization (Turner et al. 2011). These results suggest hope for recovery. It is noted, however, that declines at these sites were 88% (Ft. Drum) and 93% (New York) and apparent stability at some hibernacula may be due to movements of uninfected bats from other areas, and that lactation does not mean that pups survived if adults are physiologically stressed (Dobony et al. 2011).

Factors related to specific COSEWIC criteria  

Generation time  

Generation time in the COSEWIC guidelines is based on the mean age of the breeding population. The average breeding age of Northern Myotis is not known. In the wild they start breeding after one year, continue breeding annually and have been recorded to live over 19 years (Hall et al. 1957), but likely live to the same age (30 years) as the very similar Little Brown Myotis (Fenton and Barclay 1980). The mean age of breeding animals, therefore, is likely near 10 years for Northern Myotis. 

However, data from 22 years of banding of Little Brown Myotis in Manitoba were analyzed for this report by Craig Willis and he recommends a shorter generation period. Dr. Willis writes: “based on our data 5 years would be a very generous average. Over the 22 year period, folks have been collecting banding data in Manitoba and NW Ontario, the mean ± SD from capture (before 2000) to last recapture is 3.04 ± 2.85 years (n = 1,386 recaptures between 1989 and 2011). In other words, after about 3 years on average, they disappear. We occasionally get a bat or two close to 20 but they are exceedingly rare.” (Craig Willis, pers. comm. January 2012). Similar conclusions on generation time could not be found in the literature and the results from Manitoba constitute a single study; however, the sample size is robust and suggests that the generation time is likely less than 10 years for this species. As a compromise, generation time in this report is given as a range of 3-10 years.

COSEWIC criteria use 3 generations, thus the time period over which declines must be calculated is 9-30 years for Northern Myotis.

Limits of census data  

Several COSEWIC criteria rely on population trend information. Estimates on the number or percent of bat mortality in Canada are severely limited because of little survey effort. Northern Myotis are relatively common in part of their range; as such, they have not been a priority for surveys. In addition, bats are inherently difficult to survey.
Overwintering sites are critical to their survival but we do not know all the caves that contain bats, or the number of bats within these caves, especially in larger provinces of Ontario and Quebec.

Systematic acoustic surveys of summer bat activity levels have begun in some jurisdictions, but it is unclear if some areas have already been impacted by WNS before the survey. In the end, however, the lack of summer acoustic data should not preclude an emergency assessment because WNS is already present in the jurisdictions, and population declines that occurred in the U.S. will likely occur in Canada, if they have not already.

Threat and number of locations  

The Northern Myotis population in Canada would comprise a single location because the fungus is most likely an invasive, exotic pathogen impacting a naive population. Hibernacula conditions are similar across the range of Northern Myotis and mortality rates are predicted to be the same for the entire population. WNS impacts many Myotid species (Turner et al. 2011) and since the genetic variation between species of Myotis is greater than that within the species itself, it is unlikely that any genetic-based differences in the Canadian population would provide resistance.

Designatable units

Northern Myotis in Canada comprise a single designatable unit. The distribution of Northern Myotis in Canada is continuous and there is no known significant genetic or other differentiation within the species’ range to warrant separate designatable unit status.

Acknowledgements

This overview was written with input from numerous people involved with bats and White-nose Syndrome in North America, and was, in part facilitated by discussion during the recent North American Bat Research Conference in Toronto (October 2011). The author wishes to thank everyone and, in particular, to Al Hicks, Lesley Hale, Simon Dodsworth, Jeremy Coleman, Krishna Gifford, Brock Fenton, Mark Brigham, Hugh Broders, Jeff Bowman, Mark Elderkin, Justina Ray, Don McAlpine, Karen Vanderwolf, Carl Herzog, Rick Reynolds, Craig Stihler, Calvin Butchkowski, Eric Britzke, Emily Brunkhurst, Erin Fraser, Julien Mainguy, Tom Hallam.

The report was reviewed by bat and WNS specialists Jeremy Coleman, Brock Fenton, Mark Brigham, Ian Barker, Hugh Broders, and Craig Willis, as well as members of the COSEWIC Terrestrial Mammals Subcommittee and the Emergency Assessment on Bats Subcommittee.

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Figure 1. Approximate distribution of Northern Myotis and White-nose Syndrome, as of October 2011. Distribution based on Van Zyll de Jong (1985) and National Wildlife Health Centre. Note: New information indicates that the distribution in Newfoundland should extend over the entire Island, except the Avalon Peninsula, and the distribution in western Canada should extend westward into Yukon Territory to near the Alaskan panhandle. (Map created by J. Wu, COSEWIC Secretariat).

Map of the approximate distribution of the Northern Myotis and White-nose Syndrome, as of October 2011. New information indicates that the distribution in Newfoundland should extend over the entire Island, except the Avalon Peninsula, and the distribution in western Canada should extend westward into Yukon Territory to near the Alaskan panhandle.

Text Version for Figure 1:

Map of the approximate distribution of the Northern Myotis (zone indicated by grey shading) and White-nose Syndrome (zone indicated by striped shading) across North America, as of October 2011.

The distribution of the Northern Myotis is shown extending west from the southern portion of the Island of Newfoundland to British Columbia, north into the Northwest Territories, and south across much of the northeast and central United States, extending west beyond the Missouri River.

New information indicates that the map should show the Newfoundland distribution extending over the entire Island, except the Avalon Peninsula, and the distribution in western Canada extending west into Yukon to near the Alaskan panhandle.

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Figure 2. Location of confirmed and suspected cases of White-nose Syndrome in North America as of October 2011. First record was in Albany, New York (shown as a circle) in 2006. The suspected case in Oklahoma is >2000km from epicentre. Source: National Wildlife Health Centre.

Map of the location of confirmed and suspected cases of White-nose Syndrome in North America as of October 2011.

Text Version for Figure 2: 

Map of the location of confirmed and suspected cases of White-nose Syndrome in North America over four years. The location of the first detection near Albany, New York, is also indicated.

For 2010 to 2011, confirmed cases are indicated by dark red shading and suspected cases in dark pink textured shading. For 2009 to 2010, confirmed cases are indicated by blue shading and suspected cases by light blue textured shading. For 2008 to 2009, confirmed cases are indicated by purple shading and suspected cases by purple textured shading. For 2007 to 2008, confirmed cases are indicated by dark grey shading; no suspected cases are indicated.

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Figure 3. Baseline simulation of the epizootic dispersal based on minimum and maximum temperatures in hibernacula and lipid reserves in Little Brown Myotis. The projected epizootic wave throughout the U.S. study area as determined by 1000 simulations. The dynamic evolution of the epizootic wave of Gd-affected hibernacula for the stochastic resolution of the suite of 1000 simulations is indicated. The projected years of the Gd-affection occur according to the colour scheme: red shades, 2007-08; dark orange shades,  2008-09; light orange shades, 2009-10; yellow shades, 2010-11; light green shades, 2011-12; medium green shades, 2012-13; darker green shades starting in Oklahoma, 2013-14; additional dark green shades, 2014-15; light blue shades, 2015-2016; dark blue, 2016-17; purple, 2017-2018. White represents caves that are unaffected during the 15-year simulation. The size of the circle is indicative of the size of the colony in the cave. Image was created from Google Earth. Map supplied by Tom Hallam (University of Tennessee, Knoxville) in association with publication: Hallam and Federico (2011).

Map showing the results of a baseline simulation of the epizootic dispersal of Geomyces destructans based on minimum and maximum temperatures in hibernacula and lipid reserves in Little Brown Myotis.

Text Version for Figure 3:

Map showing the results of a 15-year baseline simulation of the epizootic dispersal of Geomyces destructans  (Gd) across North America based on minimum and maximum temperatures in hibernacula and lipid reserves in Little Brown Myotis. State and provincial boundaries are indicated.

The projected years of Gd-affection for hibernacula are depicted according to the following colour scheme: red dots, 2007 to 2008; dark orange dots, 2008 to 2009; light orange dots, 2009 to 2010; yellow dots, 2010 to 2011; light green dots, 2011 to 2012; medium green dots, 2012 to 2013; darker green dots starting in Oklahoma, 2013 to 2014; additional dark green dots, 2014 to 2015; light blue dots, 2015 to 2016; dark blue dots, 2016 to 2017; purple dots, 2017 to 2018. White dots represent caves that are unaffected during the simulation. Dot sizes indicate the size of the colony in the cave.

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Table 1. Change in Northern Myotis (Myotis septentrionalis) population counts at winter hibernacula with a minimum of 2 years’ exposure to White-nose Syndrome in 5 states of the northeastern United States. Adapted from Turner et al. (2011).
State (# sites)Pre-WNS ## >2 yrs Post-WNS
New York (18)61917
Pennsylvania (5)9402
Vermont (5)1363
Virginia (1)79
West Virginia (3)40
Totals (32)170631

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Table 2. Changes in abundance estimates for bats using hibernacula (caves or mines) in Ontario. The majority of bats are Little Brown Myotis, but sites also include Northern Myotis and Tri-colored Bat. Average decline is 90% in sites with >2 years of post-WNS exposure. Information courtesy of Ontario Ministry of Natural Resources.

Site Name
Individuals Counted and Date Count CompletedPercent Change
2009 to 2010
Percent Change
2010 to 2011
Total Percent Change
200920102011
Craigmont30,461
November 2, 2009
24,837
November 1, 2010
1,457
October 24, 2011
-18%-94%-95%
Hunt (Renfrew)14,378
October 20, 2009
7,005
November 7, 2010
2,638
November 5, 2011
-51%-62%-82%
Crystal Lake725
Fall? 2009
539
November 29, 2010
10
November 4, 2011
-26%-98%-99%
Croft*N/A3000+
October 2, 2010
1,537
November 4, 2011
N/A-49%+-49%+
Silver CraterN/A251
November 29, 2010
29
November 4, 2011
N/A-89%-89%
MacDonaldN/A21
November 23, 2010
0
November 4, 2011
N/A-100%-100%
WatsonN/A96
November 23, 2010
0
November 4, 2011
N/A-100%-100%
Clyde ForksN/A117
November 30, 2010
7
November 2, 2011
N/A-94%-94%

*Croft population estimate in 2010 was only completed in a portion of the mine (approximately 50% chamber length counted)

Notes:

  1. All sites are known to be infected with Geomyces destructans either through lab testing or visual observation. Abundant mortality has not been documented at any of the sites although small numbers have been recorded. None of these sites are monitored frequently enough in the winter to observe abundant mortality episodes; however, a notable decline in population is evident at all sites. 

  2. WNS was first visually observed in Craigmont Mine during the 2008-2009 season.  It was documented during a site visit on May 6, 2011. The 2009 population estimate is indicative of the pre-population estimates periodically recorded at Craigmont and Hunt Mines. WNS was confirmed by CCWHC through lab results in Craigmont and Hunt Mine in 2009-2010 season.

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Figure 4. Fall swarm captures in Virginia. Work was predominantly conducted in September and early October. MYLU = Myotis lucifugus, MYSE = Myotis septentrionalis, PESU = Perimyotis subflavus. The values within brackets (i.e. ‘n-6’) refers to number of sites sampled. (Figure courtesy of Rick Reynolds, Virginia State Biologist.)

Chart showing fall swarm captures of bats in Virginia between 2009 and 2011. The work was conducted mainly in September and early October.

 

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References

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