FINAL REPORT. Stephen P. Cross Department of Biology Southern Oregon University Ashland, Oregon 97520

Transcription

1 FINAL REPORT ESTIMATION OF BAT COMMUNITY SIZE AT OREGON CAVES IN LATE-SUMMER AND EARLY-FALL 2002, OREGON CAVES NATIONAL MONUMENT Stephen P. Cross Department of Biology Southern Oregon University Ashland, Oregon David L. Waldien Department of Fisheries and Wildlife Oregon State University Corvallis, Oregon Supported by the National Park Service Contract Order No. P9340B0010,' I\8 - -, I'\ X '.:,- I~ K'' \t.

2 FINAL REPORT ESTIMATION OF BAT COMMUNITY SIZE AT OREGON CAVES IN LATE-SUMMER AND EARLY-FALL 2002, OREGON CAVES NATIONAL MONUMENT Stephen P. Cross Department of Biology Southern Oregon University Ashland, Oregon Ph. (541) scrossalsou.edu David L. Waldien Department of Fisheries and Wildlife Oregon State University Corvallis, Oregon Ph. (541) December, 2002 Supported by the National Park Service Contract Order No. P9340B0010

3 2 INTRODUCTION Oregon Caves National Monument has several cave systems within its boundary of which the main cave system is commonly referred to as Oregon Caves. There are three major gated openings to Oregon Caves. The Main Entrance, the 110 Opening hereafter referred to as the 110 Exit. and the Main Exit. At least three additional openings were known to us or were identified during the course of this research, Carbide, the grated opening adjacent to the Main Entrance, Ice Box, the grated opening behind the Resource Cabin, and the small opening above the 110 Exit. During our work, these three openings were not considered major access points for bats to the cave system but concurrent research using echolocation detectors examine the use of all three openings by bats (Cross and Waldien 2003). This report addresses the use of Oregon Caves, specifically the Main Exit and the 110 Exit, by bats. The Main Entrance was not sampled as part of this study. Oregon Caves is a unique and important habitat feature for the bat community in the forested landscape of southwest Oregon. Oregon Caves is a focal point for much of the bat community in the area because it functions as a nighttime congregation site (night-roost) for a large number of bats (Cross 1977, Cross and Schoen 1989, Cross 1997). Yuma myotis (Myotis yumanensis) captured at Oregon Caves have been documented day-roosting five miles away (Cross 1977). Further, the research at Oregon Caves has shown that some bats exhibit strong fidelity to Oregon Caves and return to use the cave for several years (Cross 1977); one longeared myotis (M. evotis) was recaptured at Oregon Caves 24 years after it was banded (Cross 1982). The extensive use of Oregon Caves as a night-roost and the fidelity to the site provides an opportunity to sample the forest-dwelling bat community at the openings to the cave system and allows opportunities for consistent long-term research and monitoring. To our knowledge, Oregon Caves is one of the sites most extensively sampled for bats in the Pacific Northwest and survey results have documented use by eight species of bats at Oregon Caves. The long-eared myotis and males of all species dominate captures (Cross 1977, Cross and Schoen 1989, Cross 1997). The use of Oregon Caves as a night-roost in the fall has been documented numerous times through extensive sampling in 1958 (Albright 1959), 1976 and 1977 (Cross 1977), 1987 (Cross and Schoen 1989), and 1996 (Cross 1997). Limited sampling

4 was also conducted from 1978 to 1983 in an attempt to track longevity of individual bats tagged by Albright (1959) in 1958 (Cross ). Continued sampling at Oregon Caves will provide baseline information on the size and composition of the bat community for long-term monitoring efforts. Further, survey efforts will meet directives from the National Park Service to inventory and monitor the biological resources within Oregon Caves National Monument. Prior to 1990, estimates of the size of the bat community using the cave have ranged from approximately 650 bats to over 950 bats (Cross 1997). However, the community estimate from 1996 suggested a dramatic decrease in the number of bats using the cave in the fall from over 800 bats at the Main Exit in 1988 to less than 500 bats at the Main Exit in 1996 (Cross 1997). Although it is possible that there has been a major decrease in the number of bats using the Main Exit (Cross 1997), alternative scenarios may also be plausible. Unfortunately, the variability associated with past estimates as a result of low numbers of recaptures makes it difficult to ascertain a very clear picture of the trend in the numbers of bats using Oregon Caves. Although the apparent decrease in the number of bats using Oregon Caves in 1996 may be attributed to a real decrease in the number of bats using the cave, the decrease may also be related to changes in how the bat community uses the cave (Cross 1997). Prior to 1996, survey efforts for bats provided evidence that the majority of the bats used the Main Exit with relatively few bats using the 110 Exit (Cross 1977, Cross and Schoen 1989, Cross 1997). However sampling has not been done at the Main Entrance and only occasional surveys occurred at the 110 Exit (Cross 1977, Cross and Schoen 1989, Cross 1997). Although the number of bats using the Main Exit appears to have dropped significantly since 1988, understanding of the status of the bat community using the entire cave-system is incomplete without surveys for bats at the 110 Exit or other openings that the bats may use. Objectives 1. Determine community composition and relative abundance of different species at Oregon Caves in August and September. 2. Estimate the size of the bat community using Oregon Caves in August and September. 3. Compare the use of the Main Exit and the 110 Exit by the bat community. 4. Provide baseline data for long-term monitoring efforts of the bats at Oregon Caves.

5 4 METHODS We used bat traps (Tuttle 1974) at both the Main and 110 Exits on six nights between 17 August and 24 September 2002 to capture bats (Table 1). Surveys for bats took place every 10 to 14 days. The first survey consisted of a single night at each exit on two consecutive nights, followed by two simultaneous 2-night sessions, and ended with a single night at both exits simultaneously (Table 1). A bat trap was placed outside the gate at the 110 Exit near the bottom of the steps and the trap at the Main Exit was also placed outside the gate just inside the edge of the cliff face. Both traps required the use of blocking material to prevent bats accessing the cave around the trap; trap locations were consistent with historic surveys at each entrance. Bat traps were installed prior to sunset or immediately following the exit of the final tour from the cave at the Main Exit. Trapping generally started at or slightly before civil sunset and ended 5 hr later at which time the traps were removed from the openings. This protocol is consistent with the survey protocol that was established in 1988 (Cross and Schoen 1989). Capture data were grouped in 30 minute periods after civil sunset (e.g., 0-29, 30-59, etc.) to examine patterns in captures at the Main Exit, 110 Exit, and both Exits combined. All surveys occurred on nights when the ambient temperature was >19 0 C at the Main Exit at civil sunset. All captured bats were identified to species and sex and age determined. Individuals were punch-marked with a small-animal tattoo (Bonaccorso and Smythe 1972) and released within 10 minutes of capture. Marks were given to all bats captured, unique for each opening and for each night of survey; recaptured bats received additional unique punch-marks each night they were captured. Upon capture, individual bats were examined for punch-marks to determine capture history. Capture histories of individuals from the entire data set were developed by grouping capture records based on species, sex, and dates of capture at a given Exit. In some cases, this method provided unique capture histories for specific individuals. However, in most cases this method provided capture histories for one of several potential bats of the same sex and species that may have had an identical capture history. We used capture-recapture data to estimate species-specific and community level abundances of bats at the 110 Exit, Main Exit, and both Exits combined. We used the Lincoln- Peterson estimator (Brower and Zar 1984) and the Schnabel estimator (Mosby 1963) to allow direct comparison with previous community estimates. Calculations were performed with a

6 5 commercial computer program called Ecostat (Towner 1992). We also used the Modified Lincoln-Peterson estimator to reduce the tendency of the Lincoln-Peterson estimator to overestimate the numbers of bats using the cave system or the individual exits (Bailey 1951, 1952). The formula is: P = (M (N+1)) / (R + 1), where P is the estimate of the number of bats, M is the number of bats marked and released in the Mark Period, N is the total number of bats captured in the Census Period, and R is the number of bats recaptured in the Census Period. For both Lincoln-Peterson estimators, we used the first three survey dates as the Mark Period and the latter three survey days as the Census Period. Recaptures within the Mark Period and multiple recaptures within the Census Period were excluded to ensure individuals were only counted once during each period. For estimates at individual openings, bats moving between the two exits were also excluded. We provide community estimates from past sampling for direct comparisons. We also used program Capture (White et al. 1982) to estimate abundance of the entire bat community, long-eared myotis, and long-legged myotis (M. volans) at both the Main and 110 Exits individually and combined. We did not use program Capture to estimate the number of individuals of other species at Oregon Caves because of the low levels of captures or recaptures. The use of an additional estimator for the 2002 data was undertaken because the relatively high levels of recaptures in 2002 allowed us to establish recapture histories for individuals and to use more robust estimators than were used in the past. We used the model selection option in Program Capture to identify the appropriate estimator (White et al. 1982). We used Model M(th) with the Chao estimator because it allows time and heterogeneity to affect daily capture probabilities, it is a robust estimator (performs well with minor violations of assumptions), and was either the best model or a competing model for most of the estimates we desired to calculate. RESULTS We captured 350 individual bats of eight species 472 times (excluding 24 within night recaptures) (Table 1). The long-eared myotis was the most abundant species and represented 54.9% of the individuals captured (Table 2). The Yuma myotis (16.6%) and long-legged myotis (12.3%) were the next most abundant species and all other species comprised < 7.5% of the captures (Table 2). Species proportions are similar to those observed from past research (Table

7 6 Table 1. Summary of captures by site, date, species, and sex during surveys of bats at Oregon Caves, August and September, Recaptures can be determined by subtracting the number of "individuals" from number of "captures." Sex and species acronyms are: F = female; M = male; COTO = Corynorhinus townsendii, Townsend's big-eared bat; EPFU = Eptesicusfuscus, big brown bat; MYCA = Myotis californicus, California myotis; MYEV = M evotis, long-eared myotis; MYLU = M lucifugus, little brown myotis; MYTH = M thysanodes, fringed myotis; MYVO = M. volans, long-legged myotis; MYYU = M yumanensis, Yuma myotis. Site Main Exit Date 17-Aug 28-Aug 29-Aug 11-Sep 12-Sep 24-Sep COTO F M o o o o 1 2 o o EPFU F M o o 0 MYCA F M o o 0 o 0 MYEV F M MYLU F M 0 1 MYTH F M MYVO F M MYYU Total F M Captures Subtotal Individuals Subtotal Exit 18-Aug 28-Aug 29-Aug 1 1-Sep 12-Sep 24-Sep

8 7 Table 1. Continued 110 Exit Captures Subtotal Individuals Subtotal Main Exit & 110 Exit Captures Grand Total Individuals Grand Total

9 8 Table 2. Relative abundance (% of total individuals) of species during surveys of bats at Oregon Caves, August and September, 2002, and from 1976, 1988, and Species acronyms are identified in Table 1. Main Exit Main Exit MainExit' & 110 Exit' Main'Exit 110 Exit MainExit & 110 Exit' Species COTO EPFU MYCA MYEV MYLU MYTH MYVO MYYU 'Data from 1976, 1988, and 1996 were obtained from Table 4 (Cross 1997). Table 3. Summary of recaptures by species, sex, and site at the Main Exit and the 110 Exit during surveys of bats at Oregon Caves, August and September, Sex and species acronyms are identified in Table 1. Main Exit 110 Exit Main Exit & 110 Exit Main Exit & 110 Exit Species F M F M F M Total COTO EPFU 0 MYCA 0 MYEV MYLU MYTH MYVO MYYU Total

10 9 2). Overall, males represented 76% of the individuals captured. Fifteen individuals at the Main Exit were subsequently recaptured at the 110 Exit whereas only nine individuals captured at the 110 Exit were recaptured at the Main Exit. Excluding within night recaptures, we recaptured bats a total of 122 times (Table 3). Most recaptures were from two of the more abundant species (e.g., long-eared myotis [67%] and long-legged myotis [22%]) and 95.6% of the recaptures were of male bats (Table 3). Although most of the individuals recaptured were recaptured only one time, 10 individuals of two species (long-eared and long-legged myotis) were recaptured four times (Table 4). Only six female bats were recaptured, one time each (Table 4). The estimate of the number of bats using Oregon Caves (both exits) during the fall of 2002 ranged from 621 bats with the Schnabel estimator to 735 (95% CI = 596 to 875) bats with the Lincoln-Peterson estimator to 934 (95% C1 = 762 to 1178) with Model M(th) and the Chao estimator (Table 5). However, given the imprecision of the estimates at the Main Exit due to low recapture success, it is prudent to take a more conservative approach to define possible community level estimates. Given the relatively precise estimates at the 110 Exit, a conservative estimate of around 700 bats (approximate 95% CI = 600 to 1000) can be derived by adding the Table 4. Summary of the number of recaptures of individual bats by species and sex at Oregon Caves, August and September, Sex and species acronyms are identified in Table 1. Captured 1 time 2 times 3 times 4 times Species Individuals F M F M F M F M COTO EPFU MYCA MYEV MYLU MYTH MYVO MYYU Total

11 10 number of individuals captured at the Main Exit (125 bats) to an estimate from the 110 Exit; in this case we used the estimate from Program Capture. The number of bats using the Main Exit appears to have increased since the 1996 sample but estimates at the Main Exit continue to have a large standard error and wide confidence intervals (Table 5) making it difficult to identify precise trends. Captures of long-eared myotis remained relatively constant throughout the 5-hr sample period (Figure 1) after gradually increasing during the first 1.5 hours. Captures of the longlegged myotis peaked 2 hr after civil sunset at the 11O Exit but displayed a bimodal pattern with peaks in capture around 2 and 4 hr after civil sunset at the Main Exit (Figure 1). The Yuma myotis appear to use both exits later in the evening with peaks 3.5 hr at the Main Exit and 4.5 hr after civil sunset at the 110 Exit (Figure 1). We identified several major differences in the use of the two exits by the bat community. There were differences in the numbers of individual bats captured, in numbers of bats recaptured, and in species composition between the two exits. Captures at the 110 Exit accounted for 64.3% of the individual bats but represented only six of the eight species captured (Table 1). Although the Main Exit represented <50% of the individuals captured, all eight species were encountered at the Main Exit (Table 1). Townsend's big-eared bats (Corynorhinus townsendii; 76% of this species) and long-eared myotis (68% of this species) were proportionally more abundant at the 110 Exit. Further, differences in the captures of males were observed between the two opening sampled. Males accounted for 74% of the bats captured at the 110 Exit but represented 80% at the Main Exit. Males were relatively more abundant at the Main Exit (82%) for long-eared myotis than at the 110 Exit (77%). Finally, 82.8% of the recaptures were at the 1 0 Exit (Table 3). Counter to the pattern in the number of individual bats captured at each exit (Tables 1 and 5), the estimate of the number of bats using the Main Exit was greater than the estimate at the 1 0 Exit but also had a larger confidence interval (Table 5). Although 58% of the bats captured at the 110 Exit consisted of long-eared myotis, estimates suggest that long-eared myotis may constitute <50% of the bat community at the 110 Exit (Table 5). Estimates at the Main Exit have relatively imprecise estimates (large confidence intervals) due to limited recaptures whereas estimates at the 110 Exit tend to be more precise (smaller confidence intervals; Table 5).

12 I1 Table 5. Community and species size estimates derived from capture/recapture data at Oregon Caves, August and September, Species acronyms are identified in Table 1; nc = not calculated. Lincoln- Modified Model Year Species MNA Peterson 95% CI Lincoln-Peterson Schnabel M(th) 95% CI Main Exit' 1958 Allsp to 1081 nc 831 nc Main Exit' 1976 All sp to 1108 nc 712 nc Main Exit & 110 Exit' 1977 All sp to 1533 nc 787 nc Main Exit] 1988 All sp to 1206 nc 827 nc Main Exit & I IOExit' All sp to 1278 nc 1037 nc Main Exit] 1996 All sp to 667 nc 437 nc I10 Exit 2002 All sp to to 787 MYEV to to 351 MYVO to to 84 MainExit Allsp to to 1193 MYEV to to718 MYVO to to 117 Main Exit & I IOExit All sp to to 1178 MYEV to to 590 MYVO to to 113 '1958 estimates from Albright 1959; 1976 and 1977 estimates from Cross 1977; 1988 estimates from Cross and Schoen 1989; 1996 estimates from Cross 1997.

13 Exit 0 I- 0 C 0 0I Time Period -* MYEV - &_ MYVO - -. MYYU Main Exit.4-a 0 I- 0 C 0 C. L_ o IL Time Period -*- MYEV - U_MYVO - - MYYU Figure 1. Patterns of captures, in relation to civil sunset, of Myotis evotis (MYEV, long-eared myotis), M volans (MYVO, long-legged myotis), and M yumanensis (MYYU, Yuma myotis). Definition of time period and method of calculations are provided in the methods.

14 13 Differences were also observed among the different species using Oregon Caves. Although males comprised 76% of all individuals captured, there were species specific patterns in their captures (Table 1). Males represented 78.6% of the most abundant species (long-eared myotis) and comprised as much as 88.4% of long-legged myotis, the third most abundant species. However, males comprised only 56% of Townsend's big-eared bats, which was the fourth most abundant species (Table 1). Further, the long-eared and long-legged myotis were the species most often recaptured (Tables 3 and 4). DISCUSSION Survey results from 2002 are consistent with past surveys in that the long-eared myotis was the most abundant-species captured; the relative abundance of other species was also similar to historic surveys (Cross 1977, Cross and Schoen 1989, Cross 1997). Further, the prevalence of males in the captures of most species is also generally consistent with previous surveys. One exception is with Townsend's big-eared bat where females comprised 44% of the 2002 captures. This deviates somewhat from historic patterns but could be related to the relatively small sample size of this species at Oregon Caves in historic surveys as well as the 2002 survey. Alternatively, it could also be related to the lack of consistent surveys at the 110 Exit where Townsend's big-eared bats appear to be relatively more abundant in the 2002 captures. The overwhelming prevalence of males in the captures and recaptures is consistent with the use of Oregon Caves in late summer and early fall as a nighttime congregation site. Males of most species likely come into the cave and remain in the area waiting for the arrival of females and opportunities for breeding. Males remaining in the area for longer periods of time would increase their chance of breeding and subsequently being recaptured. Conversely, females were rarely recaptured and likely come to the cave, breed, and leave in a relatively short period of time thus being exposed to limited opportunities for recapture. The abundance of bats using Oregon Caves in 2002 appears to be greater than estimates from 1996 and is similar to past estimates. Although the size of the bat community in 2002 may rival historic estimates (Table 5), limited and inconsistent sampling of bats at the 110 Exit in the past makes it difficult to interpret the current status of the bat community at Oregon Caves as a whole relative to past estimates. Given the imprecision of past estimates at the Main Exit and

15 14 patterns of captures at the Main Exit, it is plausible that the number of bats using the Main Exit exceeds that of However, without data based on consistent sampling at the 110 Exit, inferences from past estimates should be limited to the Main Exit. In the past, the majority of the bats appeared to use the Main Exit (Cross 1977, Cross and Schoen 1989) or the relative use of the 110 Exit by bats was unknown because sampling did not occur at the 110 Exit (Cross 1978, 1979, 1980, 1981, 1982, 1983, 1997). Our surveys in 2002 provide strong evidence that a relatively large portion of the bat community at Oregon Caves now use the 110 Exit and that the number of bats at the 110 Exit likely exceeds the number of bats at the Main Exit. This shift in how the bat community uses Oregon Caves is critical to understand and incorporate into long term monitoring efforts. The relative precision of the community estimate at the 110 Exit this year is attributable to a large number of bats that were recaptured there. The structural opening at the 110 Exit may contribute to recapture success there because the narrow and steep access likely funnels the bats into the trap. The trap placement at the Main Exit is located at the outer edge of the opening and bats likely have greater opportunities to avoid the trap. Placing the trap inside the tunnel at the Main Exit may increase recapture success by limiting opportunities for bats to avoid the trap and ultimately increase the relative precision of estimates at the exit. Management Recommendations We recommend mild pruning of vegetation and tree limbs at the 110 Exit to ensure an open but constricted flight path for the bats to help funnel bats into the cave entrance where the trap would be placed. Based on observations during our surveys, most bats appear to access the 110 Exit via the developed trail or through the thin screen of trees overlooking the Cliff Nature Trail and the Resource cabin. A third flight path was over the rocky area to the north of the stairwell into the 110 Exit. The main access path maintained for human passage would not require additional modification to increase bat access. Limited pruning of limbs on the screen of trees overlooking the Cliff Nature Trail and of the shrubs on the north side of the access stairwell might maintain or enhance access of the 110 Exit by bats. However, care should be taken to avoid excessive pruning that removes vegetation that restricts the flight of bats and funnels them into the Exit.

16 15 Based on the apparent shift in the use of Oregon Caves by bats from the Main Exit (Cross 1977, Cross and Schoen 1989, Cross 1997) to the 110 Exit in 2002, we see no major reason to maintain a management policy to open the louver above the airlock door in the Main Exit Tunnel for the bats in the late summer or fall. Patterns in the echolocation data also suggest that bats use the 1 0 Exit to a much greater extent than they use the Main Exit (Cross and Waldien 2003). Therefore, the benefits to the bats to opening the louver is likely limited and should be evaluated in the context of potentially negative effects to other resources in the cave. Although this is a plausible argument, research should be conducted to specifically examine the potential positive and negative impacts of opening the louver above the airlock door. Future Research and Monitoring We recommend that estimates of the bat community at Oregon Caves be completed in 2003 to complement the work completed in 2002 and attempt to obtain more precise estimates at all major openings to the cave. Openings to sample should include the Main Entrance, 110 Exit, and the Main Exit. The Carbide Opening near the Main Entrance, the Icebox Opening behind the Resource Cabin, and the small opening above the 110 Exit should also be considered for inclusion in a sample design. Data from echolocation monitoring (Cross and Waldien 2003) can be used to evaluate the likely importance of each opening by bats and inclusion in future sample designs. The estimate from the 110 Exit provides the best quality baseline data, due to the relatively small confidence interval, useful for future comparisons in a long-term monitoring program. The greater number of bats that use the 110 Exit, in conjunction with the higher levels of recapture at that location make it the logical choice for long-term monitoring. However, a significant number of bats were also documented using the Main Exit and two species (big brown bat and California myotis) were only captured at that location. Therefore, a better understanding of the status of the bat community using Oregon Caves would be better monitored through consistent and equal sampling of all major openings (Main Entrance, 110 Exit, and Main Exit) and perhaps any of the other openings that are deemed to be important to bats (Cross and Waldien 2003). To maximize the potential benefit of data to a long-term monitoring program, effort should be made to increase opportunity of recaptures. Given the recapture pattern observed at

17 16 the 110 Exit, future sampling at the Main Exit should attempt to increase the recapture success at the exit by moving the trap farther inside the opening. The restricted flight path in the tunnel may result in increased recapture success and ultimately yield more precise estimates of the number of bats using that exit. Similarly, surveys at the Main Entrance or any other opening should be approached in a manner to maximize opportunities for recaptures by placing a trap inside the opening to take advantage of the restricted flight path. Careful consideration of the number of nights sampled, the intervals between the nights, the beginning and ending dates of the surveys, and the length of surveys within a night should be considered with future work. Given the later peak in captures of Yuma myotis at both the 110 and Main Exits, consideration should be given to extending the length of the surveys to at least six hours from civil sunset. Increasing the length of the survey may help refine the view of how different species use the cave later in the night. However, it may also increase the possibility of alienation of some of the bats. Capture of bats may also be influenced by the interval between sample nights. In general, capture success was reduced on the second night of consecutive-night sampling at both the Main and 110 Exits (Table 1) which suggests the possibility of short-term alienation to the site. Reduced captures were more apparent during subsequent samples at the Main Exit than at the 110 Exit suggesting that the potential for alienation may be less at the 110 Exit or that the bats are more susceptible to capture at the 110 Exit. A balance in future sample designs needs to be obtained where the length of the sampling within a night, the number of nights sampled, and the interval between nights sampled maximizes the efficiency of the sampling, avoids unduly alienating bats to an opening, meets the objectives of the research, and is logistically feasible. We suggest that future mark/recapture studies of bats Oregon Caves consider the use of bands for marking the bats. Benefits of bands include being able to track individual bats over long time periods and reduction of possible trauma from multiple punch-marking. However, bands should only be considered if recent improvements to reduce the incidence of injury or mortality associated with banding have been well documented.

18 17 ACKNOWLEDGMENTS Funding for this research was provided through the National Park Service Order No. P9340B0010. This work was conducted under the auspices of the Oregon Department of Fish and Wildlife Permit We thank the staff of Oregon Caves National Monument for their interest and help in facilitating this work. Field assistance was provided by: K. Aiello, A. Baker, B. Cherner, M. Cooley, L. Grant, C. Johnson, A. Lavalle, D. Littell, H. Ober, F. Nogash, S. Rhodes, T. Rodhouse, D. Sarr, M. Schnoes, S. Stockert, M. Stoddard, and E. Pfaff. R. Sidner made many helpful suggestions on the final draft of the report. LITERATURE CITED Albright, R Bat banding at Oregon Caves. Murrelet 40: Bailey, N.T.J On estimating the size of mobile populations from recapture data. Biometrika 38: ,1952. Improvements in the interpretations of recapture data. Journal of Animal Ecology 21: Bonaccorso, F.J., and N. Smythe Punch-marking: an alternative to banding. Journal of Mammalogy 53: Brower, J.E., and J.H. Zar Field and laboratory methods for general ecology. Wm. C. Brown Co., Dubuque, Iowa. 266 pp. Cross, S.P A survey of the bats of Oregon Caves National Monument. Contract report to the National Park Service, CX pp.,1978 to Annual letter reports to Superintendent, Oregon Caves National Monument, concerning annual bat capture studies., Bats. Pp in A.Y. Coopereider, R.J. Boyd, and H.R. Stuart, (eds.), Inventory and monitoring of wildlife habitat. U. S. Dept. Inter., Bur. Land Manage. Service Center, Denver, Co. xviii, 858 pp. Cross, S.P Estimation of bat community size at Oregon Caves in late summer and early fall, Final Report. i33pp.

19 18 Cross, S.P., and C. Schoen Bats at Oregon Caves: 1988 Status Report. Contract Report; NPS CX pp. Cross, S.P., and D.L. Waldien Bat usage patterns at Oregon Caves during June through September, 2002, as determined by echolocation detection. Report in progress. Mosby, H.S Wildlife investigational techniques. The Wildlife Society, Washington, D.C. 419 pp. Towner, H Ecostat: an ecological analysis program. Trinity Software, P.O. Box 960, Campton, New Hampshire 03223, USA. 38 pp. Tuttle, M.D An improved trap for bats. Journal of Mammalogy 55: White, G.C., D.R. Anderson, K.P. Burnham, and D.L. Otis Capture-recapture and removal methods for sampling closed populations. LA-8787-NERP. Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA. 235 pp.