Bat Usage of a Major Karst Area on Northern Vancouver Island

Island Karst Research

General Project Information

FRBC reference: HQ96172-RE
SCBC reference: FR-96/97-300

Awardee's Name: Martin Davis
Organization: Island Karst Research

Title of Project: Bat Usage of a Major Karst System on Northern Vancouver Island.

Report of the 6 Month Period from May 24, 1996 to November 24, 1996

Author: Martin Davis
Contributing Authors: Trudy Chatwin, David Nagorsen

Contents

General Project Information

Contents

Abstract

Introduction

Objectives

Study area description

Figure 1 - Location map

Methodology

Electronic temperature and humidity monitoring

Table 1: Experimental design

Ultrasonic bat detection

Bat captures by mist netting

Cave inspection

Bone collection

Figure 2: Cave, data logger and mist net location map

Objectives: Quarterly Task Activity Chart

Plate 1: Bat photographs from study area

Results

Electronic and visual bat detection

Table 2: Bat detection summary

Data logger placements

Table 3: Preliminary temperature data

Bat mist net captures

Figure 3: Sex ratios of Labyrinth bat captures

Table 4: Study Area bat captures

Table 5: Bone identifications

Plate 2: Myotis lucifugus skeleton

Cave Exploration

Plate 3: Bear skeleton, Wormhole Cave

Discussion of Results

Electronic bat detection

Visual observation of bat use

Bat mist netting

Climate data

Bone identifications

Recommendations for 1997 Field Season

Extension

Acknowledgments

Literature Cited

Statement of expenditures

Appendices

A. Bat Detector Log

B Guano Collection Sheet Log

C. Report on Labyrinth Cave Field Trip, 1995 (David Nagorsen)

D. Climate Data, 1996

Abstract

In order to determine environmental variables that affect bat hibernacula choice and other cave usage in coastal temperate forests in British Columbia, we initiated the study. The Study Area are the only known hibernation site for Keen's Long-eared Myotis (Myotis keenii) and have extensive cave systems at a range of elevations in both natural and harvested forest. Temperature and humidity loggers were deployed on the surface, within entrances and deep within caves near sea-level, at 600 metres and 900 metres elevation in both natural forests and 20 to 25 year old clearcuts.

Temperature of high elevation caves ranged from 3.1o to 5oC between July and October. Cave use by bats was monitored by placing remote ultrasonic detectors near cave entrances and within caves. Also, cave inspection, placement of guano catchment sheets, bone collection and netting provided information on which cave systems were used by bats and when. Most significant caves with entrances above 800 metres elevation exhibit use by bats, including one cave system within a logged environment. Thus far, five species of Myotis have been recorded using the caves and forest; Myotis keenii, Myotis lucifugus, Myotis yumanensis, Myotis volans and Myotis californicus.

During a mid-August netting session near the entrance to Labryinth Cave we observed and captured 22 bats during a swarming or night roost event. Our findings thus far point to the importance of the caves for bats at all times of the year. Further temperature and humidity data, future systematic ultrasonic detection work, bat capture and possibly radio telemetry work will provide very important information on bats and their relationship to forested karst environments.

Introduction

Very little is known regarding bat habitat requirements in coastal forests, particularly in karst environments where at least four species of Myotis bats utilize cave systems for hibernation and roosting purposes. Carbonate, or karst-forming rock, underlies 3.5% of Vancouver Island but little is known about its significance to forest biology. In general bats have two essential and separate habitat requirements. They require habitat for roosting and feeding purposes. Roosting habitat has specific requirements in terms of thermal, and security properties.

Maternity roosts are generally in warm locations such as cavities in wildlife trees sitting well above the forest floor (Vonhof, 1996). In contrast hibernation roosts are often located in cool, stable areas such as caves (Fenton, 1992). Foraging habitat varies with different species of bats. In order to formulate both provincial and landscape level forest management plans for conservation of bats, roosting and feeding requirements must be considered. The goal of our project is to determine physical habitat characteristics of bat cave hibernacula and summer roost sites and how forest practices in the overlying terrain may affect the characteristics.

Very little is known about wintering bats in British Columbia, particularly the endangered Keen's Long-eared Myotis (Myotis keenii) (Nagorsen and Brigham, 1993). In May, 1994, the first known limestone cave bat hibernaculum in B.C. was discovered by the author and other members of the BC Speleological Federation in the Study Area. The author, under contract to Pacific Forest Products, conducted a cave/karst inventory in mid to late 1994 and identified 153 cave entrances in this drainage. Of these, about 30% show signs of bat use.

A field trip with David Nagorsen, Mammal Curator at the Royal British Columbia Museum and representatives from the BC Ministry of Environment, Ministry of Forests, BC Speleological Federation and Pacific Forest Products, was organized to identify bats in the hibernacula. The bats were identified as Myotis lucifugus; Myotis volans, and tentatively, Myotis keenii. As the latter bat is red-listed, no collection was made. However, two skeletons collected within the same cave were positively identified as such (Nagorsen and Van Zyll de Jong, 1995, Nagorsen, 1996). This is the first record of cave use by this species. This hibernacula supports the highest species diversity yet found in the province. It is only the second recorded hibernation site for the Little Brown Myotis in B.C.

Winter survival is a critical aspect of a bat's life history. We need to determine the physical habitat characteristics of winter hibernacula and how forest practices in the overlying terrain might affect them. As stable, low temperatures and high humidity are critical for bat hibernation (Kunz, 1982), we predict that cave elevation may be an important determinant for hibernation sites. Our objective is to determine if and how forest practices affect temperature, air flow and humidity regimes in caves. The Study Area drainage provides an excellent opportunity for this type of investigation as it has multiple caves at various elevations (some used by bats and some not), as well as caves which underlie both harvested and unharvested areas.

This study is designed to provide information that will clarify potential bat habitat characteristics in other coastal forested karst environments, determine in which seasons the bat caves are most vulnerable and determine how forest harvesting affects the karst habitat for bats, particularly the endangered Keen's Myotis.

Objectives

1. To locate and determine caves used by bats through electronic sensing and discreet visitation.
2. To determine physical characteristics of bat hibernacula through recording temperature, humidity and airflow patterns within caves of different elevational gradients that may or may not be used by bats.
3. To determine summer distribution and habitat use patterns of bats.
4. To determine the impact of clearcut logging on cave environmental conditions.
5. To determine past bat usage patterns in the caves through study of bat skeletons and guano deposits.
6. To make recommendations for conserving bats and bat habitat in the coastal karst environment, both locally (site specific to this area) and provincially, including conservation of the rare Keen's Myotis.

Study Area Description

The study area comprises an approximately 600 hectare area. It ranges in elevation from sea level to 1126 metres. It is underlain by limestone and characterized as karst topography, with several well developed and extensive cave systems, with a total of 18 kilometres surveyed here to date. The systems have multiple entrances, many of which are used by bats, and are developed largely within 100 vertical metres from the surface. The Study Area is primarily in the Coastal Western Hemlock biogeoclimatic zone, with the higher elevations in the Mountain Hemlock zone. They are in the Windward Islands Ecosection.

Methodology

Study of bat habitat use falls under three broad categories: electronic sensing, cave inspection and bat capture or inspection. The first objective in studying bats, due to their extreme sensitivity, is to minimize disturbance and to not affect their natural patterns of movement in the long term. Electronic monitoring is the most discreet and has the least impact of the three.

Electronic temperature and humidity monitoring

There are several types of electronic monitoring in use. Between July and November, 1996, temperature and relative humidity data loggers have been placed in caves and surface sites at sea level, mid elevation (about 500 metres) and high elevation (800-950 metres)(see figure 2). Loggers were placed in comparable caves with similar elevations within cutblocks of 20-25 years post-harvesting age and adjacent surface sites. Pairs of temperature and humidity loggers have been placed 10 metres within selected cave entrances and also deep within caves (preferably >100 metres from an entrance where possible) where more stable deep flow conditions suitable to bat hibernation may exist.

A total of 29 temperature loggers and 23 relative humidity loggers were placed between July and October, 1996 at elevations ranging from 950 metres to sea level. All sites are replicated to the greatest extent possible. For low elevation caves, finding caves of sufficient length to replicate deep cave sites (>100 metres from entrance) was not always possible, so shorter caves were utilized.

Cave entrance variables	Treatment type=logged	Treatment type=unlogged
Low eleveation-near entrance	2	2
Mid-elevation-near entrance	2	2
High elevation-near entrance	2	2
Low elevation-deep in cave	2	2
Mid elevation-deep in cave	2	2
High elevation-deep in cave	2	2
Total sample sites	12	12

For study purposes, "near entrance" is within the cave, about ten metres from the entrance. "Deep in cave" is greater than one hundred metres from the nearest entrance. Known bat hibernacula are included as sample sites.

Temperature and humidity data will be analyzed using a balanced ANOVA design to determine significant differences in physical cave environments. These data will then be correlated with bat presence (determined through remote detection and actual observation of the hibernation and summer day roost sites) at the various locations.

Ultrasonic Bat Detection

Detectors are being used to sense movement into and out of caves and through the forest. These can give information regarding timing of entry and emergence from hibernacula, summer use of caves as roosting sites, feeding activity and concentrations in the forest, and may lead to identification of species by call frequency and type. Detectors used include heterodyne Minibats, (tunable to single frequencies) and digital Anabats, (which record a wide frequency range). They are triggered by either ultrasonic sounds (bat echolocation calls) or motion sensing, depending on the site requirement.

Ultrasonic bat detectors were initially placed at cave entrances with the highest probability of recording calls, until the equipment and methods were found to be reliable enough to expand the search. They were later deployed at over twenty different entrances and ten surface sites, including near bodies of water and along forest margins.

Bat captures by mist-netting

Bat mist-netting sessions were conducted on five nights in July and August to confirm identification and reproductive status of bats in the study area. Bat mist-netting methodology conformed to standards set by the Resources Inventory Committee; Standardized Inventory Methodologies for Components of British Columbia's Biodiversity: Bats (1995). No harp traps were utilized in 1996. Mist nets were set up before dusk in different locations each night within the netting session. As bat density in the overall study area appeared to be low, bat detectors were used to determine areas that might have higher bat use.

Nets were set in these areas which included: over ponds, at the intersection of clearcut and amabilis fir forest and a flyway outside Labyrinth Cave entrance (Figure 2 ). Mist nets were opened for at least three hours post-sunset. Captured bats were held for at least 30 minutes and then species, sex, reproductive condition, mass and forearm length were recorded. There is difficulty distinguishing Myotis lucifugus from Myotis yumanensis (Nagorsen and Brigham 1993) so in cases of uncertainty, the species complex (MYLU/MYYU) was recorded (Table 4).

Cave Inspection

Signs of bat use in caves are noted during cave inspections; these include: bones, presence of guano and sightings of live bats. Hibernacula location involves traversing the caves and cave systems to locate unknown hibernacula. This is deemed necessary because electronic sensing can only be done at a limited number of sites and there are known to be more than 150 cave entrances in the study area and over 18 kilometres of known cave passage.

Many of the entrances are known to be interconnected and to date, most bats seen within the caves use larger passages deep within the systems for hibernation. Visitation for these purposes takes place in the fall, as prevailing wisdom among bat specialists is that potential disturbance impacts are minimized when the bats have good fat stores in preparation for hibernation. Experienced cavers conduct this survey with minimal disturbance.

White plastic sheets have been placed at various sites thought to be likely to be used by bats, including guano deposits found, in order to monitor guano deposition. The sheets are about one square metre in size.

Bone Collection

Bone remains found in the Study Area provide positive identification of the bat species that have been using caves and are continuing to provide information on other Vancouver Island fauna. Bone remains are collected by cavers, following appropriate protocols and are passed on to Dave Nagorsen, Mammal Curator at the RBCM for measurement and identification. Some bone specimens will also be radiocarbon dated to provide ages. Sites are marked within the cave and photographed.

Objectives

Quarterly Task Activity Chart from original proposal.

QUARTER 1

TASK / ACTIVITY

1. Purchase and manufacture equipment
   Purchased 30 temperature loggers, 25 humidity loggers, plus software and optical data shuttle. Manufactured electronic triggers for bat detectors, based on either ultrasonic or motion sensing triggers.
2. Write work plan - Yes
3. Liase with timber license holder - Yes
4. Hire workers
   Two skilled field assistants were hired: one for one month, one for six months. One project supervisor (the applicant) was employed for six months All three were previously unemployed forestry workers.
5. Establish base camp - Yes
6. Install temperature and humidity data loggers at cave entrances and in forest
   Between July and October 1996, 29 temperature and 23 humidity loggers were deployed, including six temperature loggers on surface sites.
   For more information, see Data logger placements.
7. Search for cave entrances in areas not covered by 1994 inventory (old cutblocks, inoperable timber areas, subalpine and alpine areas)
   Three new caves were found in a cutblock above 800 metres elevation, fulfilling a requirement for a data logging site in this category. At least one has significant bat use. Bones of bats and other animals including a large unidentified bear have been found within these caves.
   For more information, see Bones under Discussion of Results.

TASK / ACTIVITY

1. Continue environmental monitoring of cave entrances - Yes
2. Place environmental sensors and data loggers at hibernacula site(s) - Yes
3. Setup and monitor bat detectors and recorders in cave entrances and forest
   Between late May and late October, about 62 hours of tapes were recorded, about half of which registers bat calls, most of which are confirmed as Myotis (40-60 kilohertz). In October, some unidentified calls between 60-80 khz. were documented. Most calls were recorded from high altitude caves (> 700 metres elevation). Summer use of caves by Myotis (primarily males) as night roosts has been documented.
   For more information, see Electronic bat detection.
4. Capture bats to verify identification and monitor habitat use patterns
   In the course of five netting sessions, 24 bats were caught. Bat species identified through this method were Myotis lucifugus, Myotis volans, Myotis yumanensis and Myotis californicus.
   For more information, see Bat Mist Net Captures.
5. Search caves for summer roosting sites, bat skeletons and guano deposits
   Roosting sites were generally identified remotely through electronic bat detection and netting at entrances. Seven bat remains have been identified, including three recently deceased (<2 years) individuals. Species identified through this method were Myotis keenii, Myotis yumanensis, Myotis volans and Myotis lucifugus. Guano deposits are being recorded on an ongoing basis, including placement of plastic sheets over old guano piles to monitor current use.
   For more information, see Bone Identifications.

TASK / ACTIVITY

Note: Project received 6 months funding. Time line for task activity was based on receiving funding at beginning of 1996 calendar year. However, many of the stated goals in the last two quarters have also been met.
1. Continue environmental monitoring and data logging - Yes
2. Continue monitoring bat detectors for entry by bats into caves for hibernation - Yes
3. Search caves for additional hibernacula and place environmental sensors and data loggers at sites. - Yes
4. Analyze data - Yes
5. Presentation
   A presentation has been scheduled at the 1997 Karst and Cave Management Symposium, Highlighting Forest Karst Ecosystems. This will be held in Bellingham, Washington from October 6-11 and is being jointly co-hosted by the National Speleological Society (USA), the BC Speleological Federation, the U.S. Forest Service, the B.C Ministry of Forests and other governmental and non-governmental organizations on both sides of the border. Invitations to attend are also being sent to experts in the fields of bat research and karst ecology from several other countries.

TASK / ACTIVITY

1. Maintain data loggers - Yes
2. Present annual report - Yes (This report)

Plate 1.

Results

Electronic and visual bat detection

All calls, both surface and subsurface have been attributed to Myotis species thus far. Ten entrances have registered calls, although bats have been visually observed at one other and are suspected (due to presence of guano deposits) at many more. Although almost all calls occur during twilight or darkness, there is no particular time of night with greatest activity that can be inferred without further monitoring of specific sites.

In general, the number of calls tapers off somewhat throughout the night, although there are exceptions to this. By far the greatest incidence of calls occurred at three sites: Labyrinth Cave entrance (a major summer roost or swarming site), Bogdown (a bog on the limestone/volcanic contact with heavy summer insect concentrations) and along a leeward forest edge of an old clearcut. In some cases, the bat calls at the latter location were so frequent that fifty-minute long tapes in the audio recorders were used up several hours before dawn. (see Bat Detection Log, Appendix A).

It appears that bats use caves above 800 metres elevation far more frequently than those at lower elevations. This is also demonstrated by guano deposition monitoring sites (See Guano Collection Sheet Log, Appendix B).

Table2, shown below quantifies recorded calls from cave entrances and selected surface sites. To date, the search has been conducted over sites varying in elevation from 486 to 950 metres elevation. All calls were within the 40-60 kilohertz range typical of Myotis, except for calls recorded along a forest edge during September 24-25, which were in the 60-80 khz. range. All sightings are recorded from caves; 'flying' bats refers only to bats seen within caves or emerging from entrances.

Table 2 - Bat Detection Summary - May 30 to October 28, 1996.

Data logger placements

Temperature and humidity data loggers were placed at all planned locations between July 23, 1996 and November 3, 1996. Although it is too early to report any findings of significance regarding climate data, some preliminary observations deserve mention.

Deep cave temperatures (>100 metres from an entrance) were stable between July and October at all stations, regardless of elevation, with variations within 1oC. At sea level, the average is about 8oC. At mid elevation caves (500-600m), they range from 5-6oC, with the higher temperature represented by a cave underlying a regenerating clearcut (logged 25 years ago). At high elevations (800-950m), very stable temperatures of 3.2oC have been recorded in caves with forest cover; logged over caves (23 years ago) are at about 3.5oC, with a daily variation of .5oC. In all cases, relative humidity is at or near 100% in these sites. For further information, see the Table 3 below and preliminary climate data in Appendix D.

Table 3 - Preliminary Temperature Data - Bimonthly Averages

Bat mist-net captures

In a total of 15 net- nights of mist-netting we caught 24 bats of 4 species for a total capture index of 1.6 bats per net-night (Table 2). Mist-netting confirmed that Myotis lucifugus, Myotis californicus, Myotis volans, and probably Myotis yumanensis use the study area during summer. Forest capture rate was low (.1 bat per net-night) but 1 net-night (August 14, 1996) in a flyway to Labryinth Cave resulted in 22 captures. The captures at Labyrinth Cave have confirmed the cave as either an important night roost or a bat swarming- location for Myotis volans, Myotis lucifugus and possibly Myotis yumanensis. Of the 22 bats caught on this night, 20 were male adults. Only 2 non-reproductive females were captured, both at the Labyrinth Cave entrance (Table 4).

Table 4 - Study Area Bat Captures

Figure 3

Plate 2

Myotis lucifugus, RCBM #19501

Table 5

Cave Inspection

Prior to this study, 153 cave entrances had been identified within the Study Area. In the course of this study, three new cave entrances, apparently part of a larger system, have been discovered at high elevation in terrain that has been previously logged. This area was not covered in the previous karst inventory (Davis, 1995) , which exclusively searched areas considered 'operable timber'.

This cave system, which has evidence of significant bat use both past and present, has provided another portion of the required model for comparative study between caves in logged and unlogged environments. To date, 1,273 metres of cave have been surveyed here. Of particular interest are the extensive bone deposits that have been discovered. This cave system, named Wormhole, has revealed a complete, articulated skeleton of a large bear (Ursa sp?) that may be quite old. Specimens collected are awaiting radiocarbon dates.

Also of interest, an as-yet unidentified species of moth has been found to enter many of the caves to roost or hibernate on the walls in September/October.

Inspection of guano sheets has generally confirmed that most summer bat use of caves is above 800 metres elevation. For further information about results of guano collection, see Appendix B.

Much ongoing exploration has been occurring, which adds to our knowledge of the cave systems and their use by various fauna, including bats. All caves are mapped as they are explored and this is being added to the proponent's database of caves at the Study Area. Also, newly discovered passages found to be used by bats are being documented.

Plate 3

Discussion of Results

Electronic Bat Detection

To date, preliminary taped evidence confirms preferential use of high elevation caves (above 800 metres) by bats, although mid elevation caves are receiving occasional use. This is understandable in terms of the low, stable temperatures known to be favored for hibernation by Myotis (McManus, 1970). However, some activity has been recorded throughout summer and fall in most caves monitored. More work is needed to determine whether this represents roosting or swarming behaviour. Their summer preference for high elevation caves may indicate site fidelity to the hibernacula.

Initially, detectors were placed just inside cave entrances, but results were poor. This was eventually attributed by visual/aural observation to the probability that bats use ultrasonic calls in caves infrequently and depend on memory and/or passive ultrasonic detection to avoid obstacles (also see Rollins, 1992). Detection improved markedly when detectors were redeployed just outside, pointing toward entrances.

Also, use of removable cones on Minibats was found to limit sensitivity overall and they were eventually removed from all units. Overall, it has been observed that bat detectors do have drawbacks in that they often miss calls, as witnessed by direct observation. Adjusting sensitivity on either digital or heterodyne devices to compensate inevitably leads to false triggering by ceiling drips or wind. Until the technology of bat detectors improves, they are useful mainly as a general guide to direct other forms of search. Unfortunately there is scant literature regarding cave use of detectors as it is a developing field technique.

Visual observation of bat use

Visitation of caves has provided evidence of use by bats of all significant caves (in this case, >100 metres in length) above 500 metres elevation. This has been inferred by observation of bats in flight or roosting, recording and collection of bat remains ranging from ancient to recent, and tracking deposition of guano by placement of plastic sheets at sites considered suitable for summer roosting. Some guano deposition has been recorded in lower elevation caves; however, this evidence is considered questionable until the guano is analyzed to confirm bat origin as opposed to rodent.

Bat mist-netting

The low overall capture rates for the study area are similar to rates in other western temperate rainforests in Clayoquot Sound (van den Driessche et. al 1997), western Washington (West and Thomas 1991), and western Vancouver Island (Bradshaw personal communication 1996). Low capture rates in these forests may be due to not being able to place our nets where bats are flying (i.e.: higher in forest canopy), the abundance of water in these forests not limiting bat drinking or foraging locations so that bats are more dispersed over the landscape as compared to bats in drier interior forest locations and/or low overall density of bats in these forests.

Bat species diversity at the Study Area appears to be limited to 5 species of the genus Myotis. Netting confirmed the use of forests by California Myotis which has not been observed using the caves. The Myotis genus bats are smaller bats ranging in mass from 4.5 grams to just over 7 grams with short broad wings (Bradshaw, 1996). It is interesting that no larger long winged, faster flying species such as Silver-haired Bats (Lasionycteris noctivagans), Hoary Bat (Lasiurus cinereus) or Big-brown Bat (Eptesicus fuscus) were ever detected by netting, ultra-sonic detection, cave remains or visual inspection. The cluttered forest structure and/or the narrow confines of the caves may somehow limit the larger, less maneuverable bats in the Study Area.

The skewed sex ratio of captured bats (22 males to 2 females) actually conforms to sex ratio patterns observed in other studies of bats in montane areas with high rainfall. Thomas and West (1991) found only males and non-reproductive females in the western Washington Cascades. They postulated that low clouds and frequent rain may make timing of insect availability too patchy for pregnant or lactating females to successfully complete a reproductive season. Males and non-reproductive females can use torpor with very minor energetic cost and therefore can make use of cooler, wetter sites such as the Study Area.

The capture of 22 bats outside Labyrinth Cave on August 14, 1996 is particularly interesting. We estimated that less than 25% of the bats using the cave were captured, as many more bats were flying around than were captured. No Myotis keenii were captured at this night roost, despite the fact that the cave is used by this species for winter hibernation. Further work is required to determine if this is because M. keenii are just extremely rare or if they use the caves exclusively for hibernation. In some regards this capture event conforms to typical bat night roost patterns in that all bats were captured between 22:15 hours and 03:30 hours, and no bats used the cave as a day roost.

Night roosts provide shelter and are perhaps used for some social function while bats rest and digest between bouts of foraging. However, Perlmeter (1996) found that M. lucifugus and M. volans were selecting night roosts (bridges) with significantly higher temperatures than ambient temperatures. In these bridge night roosts there was a predominance of reproductive females, so that the high temperature roosts may be required for reproduction whereas the cooler caves in the Study Area may be suitable night roosts for males and non-reproducing females. However the possibility exists that the captures represented a bat swarming event.

Our capture of mostly males, timing of the event, and the degree of flying about witnessed conforms to swarming behaviour described in Fenton (1969) and Schowalter (1980). Swarming most likely is within range of the August 1 to August 17 swarming reported by Fenton and Scholwalter. At this point in our study it is difficult to determine what is the function of the behaviour we observed on the August 14th night, but we now know that the caves are extremely important to forest-using bats at all seasons of the year. Further studies will elucidate temperature regimes in the cave and ambient environment, whether the caves are used as night roosts or for swarming and the relationship between forest day roosts and night roosts.

Climate Data

In the 1996 field season, all temperature and humidity loggers were placed between July and October. The last data downloads were in mid October, so little climate data is available at present. They will have to be in place for a minimum of one year before there will be sufficient data for a comprehensive analysis. Preliminary information does indicate that the caves above 800 metres elevation have the lowest stable temperatures, which have been shown to be most conducive to efficient energy conservation during hibernation (McManus, 1970).

All temperature loggers are functioning well. However, it has been found that humidity loggers in caves generally fail after one month and need to be replaced on a regular basis which is not always possible due to funding restrictions and the labour involved in constantly accessing deep cave sites. However, most humidity loggers remain at a constant 100% unless they are adjacent to entrances. It is thought at this point that due to the relative constancy of cave humidity, temperature logging will reveal more data.

Bone Identifications

Bone collection sites and elevational concentrations closely mirror discovery of the distribution of living populations and species of bats in the caves; that is, most specimens have been found at higher elevations and are consistent with current species using the caves.

Further collections will be occurring in future. Of particular interest is a cave, 'Wormhole', discovered this year under terrain that was logged in 1974 where cavers have found several recently deceased individuals. A collection will be made and hopefully, climatological analysis will reveal whether the cave is subject to temperature fluctuations that may have caused a die-off of hibernating bats.

Recommendations for 1997 Field Work

1. Continue maintenance and downloading of data loggers to develop cave and surface climate profiles over a year in logged and forested environments.
2. Conduct systematic bat detection and mist netting at significant cave entrances and other surface sites in order to build a profile of seasonal bat use of surface and subsurface habitat at different elevations, in logged and forested environments.
3. Capture bats, affix radio transmitters and determine summer roost characteristics, including possible location of maternity colonies in the forest.
4. Continue exploration, guano monitoring and bone collection in the caves in order to better understand subsurface bat habitat use, both past and present.

Devices that we are developing for the 1997 field season include:

• an electronic counter which uses motion sensors to count the passage of bats past points within cave entrances.
• a time decompression device to analyse the individual 'clicks' within bat calls, with the intent of developing 'voiceprints' that may lead to identification of individual species by call.
• a bat detector that uses motion sensing to trigger the recorder, as opposed to using the call as a trigger. This may improve response time and eliminate problems with false triggering.

Extension

To date, extension activities have included field trips within the area with representatives from Ministry of Environment, Lands and Parks (Parks, Strathcona District: Ron Quilter, Brent Blackmun, and Kate Alexander); representatives from the BC Speleological Federation, the University of Victoria Caving Club and other caving groups, including some from the U.S.A and Alberta. Also visiting the area was at least one international visitor (Germany) and a group of Venturers. In some cases, much new information was brought to light by the activities of cave explorers in the area, such as the discovery of many bat remains, including the dead Keen's Myotis that was found still hanging from a wall. Cavers have been very careful to minimize disturbance of living bats at the Study Area; generally it is not a problem as most cave visits take place during daytime in summer, when bats use the caves only after 11 PM.

In the course of the study, we have kept of log of people visiting the area. We have counted over 80 user-visits between May 29 and November 2. These were all cavers, or affiliated with cavers, apart from the visits by government representatives mentioned previously.

Another activity has been the establishment of a website by Island Karst Research on the Internet. This site provides a copy of this report, with locations and other non-essential information deleted, as well as photographs of bats at the Study Area. It is also used for field updates.

It can be accessed at:

http://www.camosun.bc.ca/~colesr/batproj.html

A presentation has been scheduled at the 1997 Karst and Cave Management Symposium, Highlighting Forest Karst Ecosystems. This will be held in Bellingham, Washington from October 6-11 and is being jointly co-hosted by the National Speleological Society (USA), the BC Speleological Federation, the U.S. Forest Service, the B.C Ministry of Forests and other governmental and non-governmental organizations on both sides of the border. Invitations to attend are also being sent to experts in the fields of bat research and karst ecology from several other countries.

Acknowledgments

The author wishes to thank Laura Friis, Small Mammals and Herpetology Specialist at Ministry of Environment for her advice and contribution of bat detection equipment; Ken Wright and Sean Pendergast for assistance with bat netting; Paul Griffiths, for advice; Kirk Safford and Mitch Meredith for manning the bat detectors and cave exploration; all the cavers, too numerous to mention that have contributed through cave exploration and mapping.

Literature Cited

Bradshaw, Paul. (1991). The Physical Nature of Vertical Forest Habitat and its Importance in Shaping Bat Species Assemblages. In Barclay, Robert M.R. and R. Mark Brigham (editors). Bats and Forests Symposium: October 19-21, 1995, Victoria, British Columbia, Canada. Research Branch, B.C. Ministry of Forests, Working Paper 23/1996.

Davis, M.J. (1995) Study Area Inventory, report prepared for Pacific Forest Products, Ltd. Produced by Island Karst Research.

Fenton, MB. (1969). Summer activity of Myotis lucifugus (Chiroptera: Vespertilionidae) at hibernacula in Ontario and Quebec. Can J Zoology 47: 597-602.

Fenton, M. Brock (1992) BATS, Facts on File, Inc., NYC, NY.

Firman, M.; Getty, M.; and Barclay, R.M.R. (1993) Status of Keen's Long-eared Myotis in British Columbia, Ministry of Environment, Lands and Parks, Wildlife Working Report No. WR-59, Victoria. pp. 6-15.

Ministry of Environment, Lands and Parks (1995) Standardized Inventory Methodologies for Components of British Columbia's Biodiversity: Bats, (Draft). Resources Inventory Committee, Elements Working Group. Based on original document entitled Preliminary Inventory Manual for Sampling British Columbia's Bats, written by Patrick F.J. Garcia and Robert M.R. Barclay, 1993.

McManus, J.J. (1974) Activity and Thermal Preference of the Little brown bat, (Myotis velifer), PhD dissertation, University of Arizona.

Nagorsen, David W. and Brigham, R. Mark (1993) Bats of British Columbia, Royal British Columbia Museum, Victoria. UBC Press, Vancouver.

Nagorsen, David W. and van Zyll de Jong, Stanley (1995) "Report on Labyrinth Cave Field Trip, 18 May 1995" Appendix 'C', Study Area Inventory, Report prepared for Pacific Forest Products, Ltd. by Island Karst Research, 1995. Reprinted as Appendix 'C', this report.

Perlmeter, Stuart I. (1991). Bats and Bridges: Patterns of Night Roost Activity in the Willamette National Forest. In Barclay, Robert M.R. and R. Mark Brigham (editors). Bats and Forests Symposium: October 19-21, 1995, Victoria, British Columbia, Canada. Research Branch, B.C. Ministry of Forests, Working Paper 23/1996.

Rollins, Jonathan L. (1992) Management Considerations for Caves and Related Karst Features in the Southern Canadian Rockies, Masters Thesis, Environmental Science, University of Calgary. p. 64.

Schowalter, DB. (1980). Swarming, reproduction, and early hibernation of Myotis lucifugus and M. volans in Alberta, Canada. J. Mammalogy 61: 350-354.

Thomas, D.W. and S.D. West. (1991). Forest Age Associations of Bats in the Southern Washington Cascade and Oregon Coast Ranges. In Ruggiero, L.F., K.B. Aubry, A.B. Carey and M.H. Huff (Technical Coordinators). Wildlife and Vegetation of Unmanaged Douglas-Fir Forests. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Portland, Oregon, General Technical Report PNW-GTR-285.

van den Driessche, R., M. Mather, L. Crampton, and T. Chatwin. (1996) An Inventory of Bats in Clayoquot Sound, Vancouver Island, British Columbia. unpublished report to the Ministry of Environment, Lands and Parks, Nanaimo, B.C.

Vonhof, M.J. 1996. Roost-site Preferences of Big Brown Bats (Eptesicus fuscus) and Silver-haired Bats (Lasionycteris noctivagans) in the Pend d' Oreille Valley in Southern British Columbia. In Barclay, Robert M.R. and R. Mark Brigham (editors). Bats and Forests Symposium: October 19-21, 1995, Victoria, British Columbia, Canada. Research Branch, B.C. Ministry of Forests, Working Paper 23/1996.

Appendices

Appendix A

Appendix B

Appendix C

Description: Cave is situated at about 900m in an extensive karst landform. The area is forested and lies in the mountain hemlock biogeoclimatic zone. Snow was still on the ground 18 May; ambient temperature readings ranged from 12-19 degrees C.

Observations: Three species of bats were found hibernating in the cave: little brown myotis (Myotis lucifugus), long-legged myotis (Myotis volans), and a long-eared myotis (presumably Keen's long-eared myotis, Myotis keenii).

The Keen's long-eared myotis was hibernating about 250m from the entrance [more like 150m - MD]; air temperature in this area was 4.5 degrees C. To prevent disturbance, the bat was not handled. However, the long ears were clearly evident. Identification as Keen's long-eared myotis is based on a skull from a bat skeleton (deposited in the collection of the RBCM, LA-1) collected by Martin Davis near the entrance. Discriminant analysis using twelve measurements (van Zyll de Jong and Nagorsen 1994) diagnosed the skull as Myotis keenii with a probability of 96%.

The little brown myotis were in three separate clusters: a tightly packed cluster of 19 individuals, 2 individuals roosting side by side, and 3 individuals side by side. A solitary long-legged myotis was also hibernating nearby. The long-legged myotis was collected as a voucher specimen (RBCM 19460) and identification was verified from the skull. The 3 aggregations of little brown myotis and the long-legged myotis were all within a radius of about 15m. A temperature reading from this area of the cave was 5 degrees C. The area was about 350m (actually 200m. - MD) from the cave entrance but vertical shafts nearby may provide access.

Bat droppings were found throughout most of the cave system including areas where no hibernating bats were observed. In addition to bats, skeletons of two black-tailed deer (Odocoileus hemionus) and a deer mouse (Permyscus sp.) were found in the cave. Presumably they are animals that wandered into the cave and perished. Two deer bones were collected as potential material for radiocarbon dating if funding becomes available.

Signifigance: Labyrinth Cave is the only known signifigant bat hibernacula on Vancouver Island (Nagorsen et al. 1993). With three species, it supports the highest species diversity of any hibernacula in the province. This is the only known hibernaculum in the province with a small population of the little brown myotis. The only other hibernation record for BC is a solitary individual found in a mine tunnel near Williams Lake (Nagorsen et al. 1993); however, this species probably hibernates throughout its range in the province.

Nothing is known about the winter biology of Keen's long-eared myotis, a species on the provincial red list (Nagorsen and Brigham 1994). The skull and observation of a live individual in Labyrinth are the first evidence for use of caves by this species.

Although the population is small (about 25 bats), the presence of droppings throughout the cave suggests that Labyrinth is an important roost for bats. A little brown myotis skull found in nearby Plume Cave and bat droppings observed by cavers in other caves of the Study Area suggest that the entire cave system in this area is important for bats.

In addition to roosting bats, the Study Area karst caves are also of considerable scientific value beacause they contain deposits of vertebrate bones, some of which are probably ancient. The most signifigant finds were made in Plume Cave by Martin Davis [and Scott Macnab, Alisa Vanderberg, Ron Steer and Art Peters - MD]. Bones of Townend's vole (Microtus townsendii), deer mouse (Peromyscus sp.), shrew (Sorex monticolus or S. vagrans), blue grouse (Dendragapus obscurus) and incisor teeth of the Vancouver Island marmot (Marmota vancouverensis) were recovered in the cave. The occurrence of Vancouver Island marmot and Townsend's vole is inconsistent with the forested habitat that surrounds Plume Cave today; these animals presumably inhabited the area at an earlier time when the vegetation was an open meadow.

Recommendations/Conservation: Hibernating bats are highly vulnerable to human disturbance. Because the cave and the hibernation sites are inaccessible, disturbance or vandalism is unlikely. However, the caving community should be encouraged to avoid caving in Labyrinth during the hibernation period (October-May).

The cave system also is sensitive to forestry operations. Logging could alter the hydrology or modify the microclimate inside the cave. The forest ouside the cave also provides summer roosts for bats (i.e., wildlife trees).

More winter bat inventories should be conducted in other caves associated with the Study Area karst. However, any research activity in Labyrinth should be avoided during the critical hibernation period. Two useful projects with minimal impact on hibernating bats are: monitoring the cave's winter microclimate (temperature, humidity) with continuous recorders and assessing night roost and fall swarming activity with bat traps and bat detectors set at the cave entrances.

Acknowledgments: The helicopter flights were funded by the Ministry of Forests. Martin Davis and Alisa Vanderberg are acknowledged for their expertise in guiding us through Labyrinth and collecting the Keen's long-eared myotis bat skull.

(literature cited, letter from Stan van Zyll de Jong not included.)

Appendix D

The following pages show six examples of temperature data being gathered from caves and surface sites at about the 500 metre elevation. There is one example each from surface data loggers situated in a 20 year old clearcut site and in an old growth forest, adjacent to the caves for which data is shown. Each cave has a logsite about ten metres from their entrances, and another which is greater than 100 metres from the entrance. Slot Canyon Cave is in the old growth; Whistling Cave is in the clearcut. The data from Whistling Cave entrance indicates that this particular entrance draws in surface air in summer, whereas Slot Canyon Cave is 'exhaling'.

Island Karst Research's Main Web Site