Biological Survey of Ironwood Forest National Monument
Lesser Long-Nosed Bat
by Karen Krebbs and Yar Petryszyn
On June 9, 2000, the President of the United States designated about 129,000 acres of land managed by the Bureau of Land Management (BLM) as the Ironwood Forest National Monument (IFNM) (Tersey et al. 2001). The IFNM has a large biological diversity as a result of the many geological and topographical variations within this area. The desert ironwood (Olneya tesota) provides habitat for and resources necessary to many plants and animals in IFNM. The ecological importance of the desert ironwood comes largely through the roles it plays for over 500 other species in the Sonoran Desert (Nabhan and Behan 2000). The desert ironwood along with species like the saguaro (Carnegiea gigantea), foothill palo verde (Parkinsonia microphylla), fishhook barrel cactus (Ferocactus wislizeni), and most of the hundreds of other plants growing in the IFNM, are almost exclusively Sonoran Desert species (Dimmitt et al. 2000). Cold drainage restricts the desert ironwood to the warmer slopes above valley floors in Arizona Upland (Lazaroff 2000). Ironwood populations occur from sea level to 1100 meters in elevation, where low winter temperatures and catastrophic freezes limit its distribution (Nabhan and Behan 2000). Desert ironwoods and other desert legumes are so important as nurse trees that many cacti, including saguaros, might not survive in our climate without them (Tersey et al. 2001). The rugged ranges within the IFNM also provide natural refuges for a variety of wildlife, including desert bighorn and migratory pollinators (Dimmitt et al. 2000). The IFNM is home to or believed to occur, species federally listed as threatened or endangered, including Nichol's Turk's head cactus (Echinocactus horizonthalonius var. nicholii) and the lesser long-nosed bat (Leptonycteris curasoae) , and contains historic and potential habitat for the cactus ferruginous pygmy-owl (Glaucidium brasilianum cactorum) (Tersey et al. 2001). The L. curasoae is the focus of this study.
The L. curasoae is a federally listed (endangered) species in both the United States and Mexico (Cockrum and Petryszyn 1991). It is one of three nectar-feeding bats that occur in the U.S., and it is one of two such species in Arizona. Relatively few species of bats undergo long distance migrations (Fleming and Eby 2001). More than one hundred thousand female L. curasoae migrate into northern Sonora, Mexico and southern Arizona each spring to establish maternity colonies and give birth to their young (Fleming and Eby 2001). Many of these bats migrate to these areas from as far as Jalisco, Mexico, a migration of over 1,609 kilometers. Due to the seasonal nature of their food supplies, they must time their migrations to coincide with the flowering or fruiting of their food plants. Therefore, these migrant nectarivores travel along "latitudinally broad paths of blooming plants" called nectar corridors (Fleming et al. 1993). Leptonycteris curasoae depend upon columnar cactus (northward migration) and agave (southward migration) nectar for much of the year, but switch to the nectar of certain tropical trees and shrubs in the fall and winter.
Four L. curasoae maternity colonies are known near the Arizona/Mexico border at the following locations: the Pinacate lava tubes, Copper Mountain, Bluebird Mine, and Old Mammon Mine. All of the maternity roosts are in the Sonoran desertscrub communities where the bats feed on nectar, pollen, and fruits of various columnar cacti. These areas are rich in saguaros and the bats take advantage of this nectar source during the time they are in their maternity colonies. In mid and late summer after young bats have learned to fly and additional nectar food sources are available in other areas, the mothers and young abandon their maternity roosts. When large numbers of L. curasoae appear in southeastern Arizona, the maternity colonies in southwestern Arizona show a complementary decrease in number of bats. During this time the L. curasoae are feeding upon the Palmer agave (Agave palmeri) in the mountain ranges of southeastern Arizona. It is not known with certainty whether the bats return to Mexico once the young are volant or they move from southwestern to southeastern Arizona, taking advantage of the nectar sources at higher elevations. The IFNM may be an important stopover for bats in mid and late summer while they are on the move to other nectar sources available in the mountain ranges.
QUESTIONIs there evidence of foraging or roost habitat for L. curasoae in the IFNM?
Information was obtained for L. curasoae on the use of saguaros as a food source in the IFNM . Night-vision devices were used to observe saguaros during evening hours in 3 different mountain ranges (Ragged Top, Watermans, and Sawtooths) in the IFNM. Nets were set up to catch bats in the Silver Bell and Sawtooth Mountains and roost surveys were conducted in the Silver Bell, Waterman, Ragged Top, and Sawtooth Mountains for L. curasoae.
During 2002 , Litton Night Vision Goggles (Model # M973) were used to observe activity at saguaros in the IFNM. The normal procedure for observation each evening was for the observer to sit in a lawn chair with the goggles on. The chair and observer was located from 3 to 6 meters from the saguaro. The night vision goggles are heavy and sitting in the chair helps prevent observer neck strain. The observers had small tape recorders to record comments during the observation time and hand counters to utilize if a bat approached the saguaro to forage. Each time the bat "hit" or fed at the flower or fruit, the number of "hits" were recorded on the hand counter. Motorola radios were used for communication between observers throughout the evening during the observation periods. Night vision goggles were used during 11 observation evenings for a total of 77 hours in 3 different mountain ranges (Ragged Top, Waterman, and Sawtooth Mountains). Two different saguaros were observed each evening by 2 observers. Saguaros were observed from a minimum of 2 hours to a maximum of 7 hours and 15 minutes each evening. Observation duration was dependent on weather conditions. When the moon was full and bright, observations were made without the night vision goggles. During these times the goggles were placed on the observers lap if needed but the moon's brightness was usually sufficient for these observations. Temperature, humidity, and wind speed were recorded with a weather instrument (Kestrel 3000) throughout the observation period. GPS coordinates were taken for each study location.
Mist nets for bats were used in two different mountain ranges (Silver Bell and Sawtooth Mountains). Bats use cattle tanks and wildlife guzzlers as water sources. Two- 6 meter nets were set up around a cattle tank off of the Silver Bell Road loop area in April 2002. In the Sawtooth Mountains, 2 different wildlife guzzlers were netted with 6 meter nets in May 2002.
Three different mountain ranges (Ragged Top, Sawtooth, and Waterman
Mountains) were surveyed for bat roosts. Natural caves and mine adits were checked for bat occupancy. We entered each cave or adit that was checked and if possible bats were hand netted for a positive identification. Electronic bat detectors and lights were used to locate bats. Some of the surveyed adits had areas that were inaccessible and we were not able to survey for bats.
Equipment utilized during the bat study included Litton Night Vision Goggles (Model # M973), Peterson Bat Detector (Model D-200), Kestrel 3000 Pocket Weather Station, and Garmin GPS 12.
We created GIS shapefiles for locations of all netting activities, roost surveys, and night-vision surveys. These files will be given to BLM.
RESULTS AND DISCUSSION
Fourteen trips were made to the IFNM between December 2001 and May 2003 in search of evidence of L. curasoae roosts or foraging. The Silver Bell, Waterman, Ragged Top, and Sawtooth Mountains were checked for roosts and netting sites, and saguaros were monitored for foraging bats (Figures 1 & 2). Physical checks of mine adits and natural caves were carried out in the Ragged Top, Waterman, and Sawtooth Mountains (Table #3). Nets were set up over a cattle tank and 2 wildlife guzzlers in the Silver Bell and Sawtooth Mountains (Table #1). Observations of saguaros in the Ragged Top, Sawtooth, and Waterman Mountains were carried out over 11 evenings for a total of 78 hours (Table #4). A night roost for nectar bats was located in the Waterman Mountains and a nectar bat was heard and observed for 2 evenings in the Ragged Top area (Figure 2).
Observations of saguaros with night-vision goggles were made in 3 different mountain ranges (Table 4). A total of 78 hours over 11 evenings were spent observing flowering saguaros. During the observation times, saguaros were chosen because they had open or partially open flowers or fruit that would be available to the nectar bats as food. Twenty-two saguaros were observed between the hours of 9:00 p.m. to 4:45 a.m. During observation periods, other nearby saguaros were also watched by the observer. If nectar bats were foraging in the immediate area, they would be seen and heard by the observer. A nectar bat was observed feeding at one of these saguaros during an observation period (Figure 1). Nectar bats have a distinctive wing sound that is unique and different from insectivorous bats (Krebbs personal observation).
On July 20, 2002 at 1:30 a.m. a nectar bat was heard flying through the nearby drainage. The bat did not feed at the saguaros being observed and appeared to be flying though this area (Krebbs personal observation). The bat was not heard again during this evening. On July 23, 2002 at 10:35 p.m. a nectar bat was heard in the drainage area and did approach one of the saguaros being observed. The bat circled around the chair of the observer (Karen Krebbs) several times and started feeding on the saguaro (Picture 1). The bat hit the saguaro fruit 4 times, each time circling around the observer's chair after it fed, and then flew to the drainage and returned to hit the saguaro one last time (Picture 1). A feeding period at the flower or fruit of the saguaro is referred to as a "hit". The bat left the area after this and did not return to the observation area for the remainder of the watch. The locations of these nectar bat detections are shown in Figure 1. At 12:35 a.m. on July 24, 2002 another bat flew around the observer and the saguaro 8-10 times, and even approached the fruit at the top of the plant (as if to feed on the fruit) but no wing sound was heard. It is assumed that this bat was not a nectar bat. Insectivorous bats will catch insects around saguaro flowers and fruit (personal observation). Other bats were seen and observed throughout the observation period on July 24, 2002 but only one of these bats had the typical wing sound of a nectar bat. All the other bats were assumed to be insectivorous bats.
While in the Ragged Top area during July 2002, flowering and fruiting saguaros were hard to locate. Most of the saguaros in this area had completed the flowering and fruiting process and locating plants to observe at night was difficult. One advantage of having fewer plants available to observe would be that the bats would be easier to observe. Since there were fewer plants for the bats to feed upon it was hoped that the bats would be easier to locate. We had hoped that fewer plants would work to our advantage and it appears that this was the case in the Ragged Top area. Any nectar bat moving through this area at night would probably take advantage of the few available saguaros. Since this drainage area (Picture 1 and Figure 1) was the only place a nectar bat was heard within the entire IFNM, it was hoped that another bat would be encountered. This appears to be what occurred on July 23, 2002.
The closest known maternity roost to the IFNM is the Old Mammon Mine. This mine is located approximately 16 km southwest of the southern end of the Sawtooth Mountains and approximately 39 km from Ragged Top at the northern end of the Silver Bell Mountains (Table #2). The L. curasoae is capable of flying distances of 48 km or more one way during a single night's foraging excursion. The females at the maternity roost in the Pinacate region of the Gran Desierto of Sonora are required to travel distances of 48 km or more (one way) to forage on food plants like the saguaro and organpipe cactus (Stenocereus thurberi) . For example, commuting distances of 25-35 km probably are not unique to bats living in the Bahía Kino region (Horner, et al. 1998). Petryszyn estimated that 6,000 L. curasoae were using the Old Mammon roost in 1989 and 5,000 bats in 1990. Historically, 10,000 bats were known to occupy this roost (Hoffmeister 1986). Estimated exit counts from 1991 to 2000 have varied from 3,600 to 6,000 bats (Hinman 2000). The Sawtooth, Silver Bell, Waterman, and Ragged Top Mountains are within the foraging range of the bats at the Old Mammon Mine. It is not known where the bats at the Old Mammon Mine move to once they leave the roost, or what distances they are traveling in a single night when they forage or during migration. The area surrounding the Old Mammon Mine has dense stands of saguaros and organpipe cactus, which L. curasoae feed upon (Petryszyn personal observation). We lack information as to whether the bats forage beyond this area when the females are utilizing the mine as a maternity roost or where the mothers and young move to once the young are volant. During migration, the bats either move east to utilize the available agaves in southeastern Arizona or south into Mexico. If the bats move east once they leave the maternity roosts, they could pass through the IFNM and the saguaros would be an important food source to these bats. Also during migration, the females may not be able to fly the longer distances with their youngsters. Stopover areas like the IFNM may be important to the underdeveloped and inexperienced juveniles.
In the desert, water sources are excellent sites to catch bats. Bats use water sites for drinking and to catch insects that are drawn to the water. Although the netting of bats was not the focus of this study, we believed that netting in some of the mountain ranges would give us an idea of some of the species of bats in these areas. We also hoped we would catch a L. curasoae during one of the netting sessions. Leptonycteris curasoae will drink at water sources and can be caught during this time (personal experience). Cattle tanks and wildlife guzzlers are sources of water that bats will use during times of drought or when water is scarce (personal experience). We set up nets in 2 different mountain ranges (Silver Bells and Sawtooths) in April and May of 2002. Nets were opened by 7:30 p.m. and closed at midnight. During all 3 netting sessions no bats were caught even though bats were heard and seen on 2 of the 3 nights. None of the bats observed in the Silver Bell and Sawtooth Mountains made any attempt to drink or feed near the water sources where the nets were placed. In the IFNM there are numerous cattle tanks and wildlife guzzlers for cattle and wildlife. The nearby agriculture fields also have canals and standing water that the bats can utilize as a water source. Bats may have been difficult to catch because of these water sources. We did not spend any additional time trying to catch bats with nets after our 3 attempts with nets failed.
We searched for bat roosts in 3 different mountain ranges (Watermans, Ragged Top, Sawtooths). All searches were carried out during daylight hours and each adit or natural cave was entered during these times. Powerful lights and Peterson Bat Detectors were used to locate bats inside the roosts. Hand nets were used to catch bats for positive identification. A total of 8 mine adits, natural caves, or faults were examined for the presence of bats. Several of these were checked more than one time. The Fortuna Mine at Ragged Top has 2 gated mine adits. In the past, Macrotus californicus have used both of these adits and the gates were installed several years ago to protect this species. There was no evidence of L. curasoae nectar or fruit fecal matter at the entrances of either of the adits. It is also doubtful that L. curasoae would utilize the gated adits. In May 2003, Karen and Ronnie Sidner returned to the Fortuna Mine to check for any evidence of L. curasoae. We were unable to complete our check of the mine adits because of a law enforcement investigation for a recent shooting in this area. Macrotus californicus was the most common species of bat found in many of the mine adits (Fortuna Mine, Silver Hills Mine, and Sawtooth Mountains). The vertical rock slab in the Sawtooth Mountains contained several insectivorous species of bats ( Pipistrellus hesperus, Myotis californicus, and Myotis ciliolabrum). The Silver Hills Mine adits are probably home to Tadarida brasiliensis although we were not able to confirm this because of the inaccessibility of some of the tunnels within the adits. We did find a lot of guano from insectivorous bats in certain sections of the adits in this mine.
In December 2001, in the area of the Silver Hills Mine, we located a night roost (Table #3 and Figure 2) for nectar bats that contained bat droppings with cactus fruit seed and yellow pollen stains. This night roost was located about 122 meters above the Silver Hills Mine adits and close to the top of Waterman Peak (1120 meters). The night roost is a small natural shelter along a fault in the rocks (approximately 1.8 m X 1.8 m X 3.6 m). At the bottom of the fault shelter was a large white-throated wood rat ( Neotoma albigula) den packed with numerous cacti spines. The rock fault is large enough to contain 15 to 20 nectar bats. Since both cactus fruit seed and yellow pollen stains were found throughout the rock fault roost, this might indicate that the bats are utilizing the roost at different times of the summer and taking advantage of both flowers and fruit of the saguaros within the IFNM. The cactus fruit seed and yellow pollen stains found in the roost appeared to be deposited within the last year (personal observation). The night roost is a significant discovery since it tells us that nectar bats are probably feeding and definitely roosting in the IFNM. This roost was checked in December 2001 and again in June 2002. The location of this roost is shown in Figure 2.
As a result of this study, we have identified one night roost for nectar bats and observed a nectar bat foraging at a saguaro. We suggest that the bats may be utilizing the areas within the IFNM as foraging grounds while they are in their maternity roosts or as a stopover during migration. The discovery of the night roost and foraging observation indicates the bats are roosting and foraging in the IFNM. Our opinion is that the presence of L. curasoae in the IFNM is probably low or incidental. Yearly monitoring of saguaros for the presence or absence of L. curasoae is recommended so that any changes in the use of the IFNM by nectar bats is recognized.
We suggest that IFNM personnel be aware of the problems that could develop for L. curasoae from public use of the monument . Will the L. curasoae population be impacted by off-highway vehicles, mountain bikes, or hikers? The night roost in the Waterman Mountains can be easily accessed by hikers, although the roost is not in any immediate danger. There are probably more nectar bat roosts that have not been discovered within the monument. The monument may be an important stopover area for migrating bats and the saguaro flowers and fruit would be an important food source to these bats. Although there were no bats caught in nets in the IFNM during this study, bats (including nectar bats) use water guzzlers and cattle tanks as a water source (personal observation). We recommend that the IFNM personnel recognize the presence of L. curasoae in IFNM management plans .
Although this species may not be abundant in the IFNM, several mountain ranges are within flying distance for this species from the Old Mammon Mine maternity roost. The female bats could utilize the IFNM area while they are in the maternity roost or when they are moving to other areas with the juveniles.
Cockrum, E.L., and Y. Petryszyn. 1991. The long-nosed bat, Leptonycteris: an Endangered Species in the Southwest? Occasional Papers. The Museum. Texas Tech University 142:1-32.
Dimmitt, M.A., G.P. Nabhan, Y.F. Gray, and K.A. Buck. 2000. Geological and Ecological Diversity in the Proposed Ironwood Preserve: Assessing Rock-Soil-Plant- Wildlife Relations in the Silver Bell, Ragged Top, Waterman and Roskruge Ranges of Pima County, Arizona. Report for the Pima County's Sonoran Desert Conservation Plan and for the United States Secretary of the Interior.
Fleming, T.H., and P. Eby. 2001. The ecology of bat migration. In T. Kunz and M.B. Fenton (eds.), Bat Ecology. University of Chicago Press, Chicago.
Fleming, T.H., R.A. Nunez, and L.S. Sternberg. 1993. Seasonal changes in the diets of migrant and non-migrant nectarivorous bats as revealed by carbon stable isotope analysis. Oecologia 94:72-75.
Hinman, K. 2000. Leptonycteris curasoae roost exit count numbers. Arizona Game & Fish Department. Phoenix, AZ.
Hoffmeister, D.F. 1986. Mammals of Arizona . The University of Arizona Press and The Arizona Game and Fish Department, Tucson.
Horner, M.A., T.H. Fleming, and C.T. Sahley. 1998. Foraging behavior and energetics of a nectar-feeding bat Leptonycteris curasoae (Chiroptera: Phyllostomidae). Journal of Zoology 244:575-586.
Lazaroff, D.W. 2000. Desert Air and Light. In S.J. Phillips and P.W. Comus (eds.), A Natural History of the Sonoran Desert. Arizona-Sonora Desert Museum Press, Tucson.
Nabhan, G.P., and M. Behan. 2000. Desert Ironwood Primer: Biodiversity and Uses Associated with Ancient Legume and Cactus Forest in the Sonoran Desert. Arizona- Sonora Desert Museum, Tucson.
Tersey, D., B. Drennen, and D. Moore. 2001. Pre-Plan Analysis For The Ironwood Forest National Monument. BLM Tucson Field Office.
We want to thank all of the Tucson BLM field office personnel (Darrell Tersey, Larry Shults, Maile Adler, and Francisco Mendoza) for their ideas, suggestions, and support for this project. Volunteers Tani Hubbard, Ronnie Sidner, Barbara Terkanian, and Bill Peachey helped with the roost searches and saguaro observations. Melanie Bucci helped Yar and me one evening with the bat netting. Tani Hubbard's GIS mapping skills were priceless and valuable. Erin Kimrey helped with the scanning of the drawing. Rancher Carl Davis took time out of his busy day to show Ronnie Sidner and me a bat roost in the Ragged Top area. Thanks to Tom Van Devender and Tani Hubbard for making helpful suggestions and editing the manuscript. Thanks also to Mark Dimmitt for putting the entire IFNM report together in one document for the BLM.
Table 1. [omitted for security concerns]
TABLE 2: Approximate distances from L. curasoae maternity roost at the Old Mammon Mine to 4 mountain ranges in the IFNM. Mtns. = Mountains;
km = kilometers.
Table 3 Table 1. [omitted for security concerns]
TABLE 4: Table 1. [omitted for security concerns]