A Contribution to the Ecological Understanding of Bats in the Natural Metropolitan Park, Panama

A Contribution to the Ecological Understanding of Bats in the Natural Metropolitan Park, Panama Written by Heather Cray and Genevieve D Avignon McGill University In collaboration with: El Parque Natural
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A Contribution to the Ecological Understanding of Bats in the Natural Metropolitan Park, Panama Written by Heather Cray and Genevieve D Avignon McGill University In collaboration with: El Parque Natural Metropolitano Panama Field Study Semester Environmental Research in Panama ENVR 451 Project Authors: Heather Cray, BA Joint Honours Geography and International Development Studies, McGill University Genevieve D Avignon, BSc. Agriculture and Environment, McGill University Supervised by: Lcda. Amelia M. Muñoz-Harris, Parque Natural Metropolitano, Avenida Juan Pablo II, Panamá Prof. Rafael Samudio, Panama Field Study Semester ENVR 451 course, McGill University Number of Hours Total Spent on the Project: 303 Number of Field Hours: 61 2 Host Institution Parque Natural Metropolitano, Avenida Juan Pablo II, final. The Natural Metropolitan Park is located in Panamá City, Panamá, and is the only wildlife refuge in Panamá located within city boundaries. The park itself consists of 232 hectares of protected space, and is part of the Biological Corridor which exists along the east shore of the Panamá Canal, coupled with the Camino de Cruces and Soberania National Parks (Viquez & Denvers 2006). This protected area is one of the last refuges of the threatened Pacific Dry Tropical Forest in Central America, and provides a habitat for native flora and fauna species that require a large forested area (Viquez & Denvers 2006). The Park s objectives include providing opportunities for people to enjoy outdoor recreation, promoting environmental education and nature interpretation, facilitating ecological research and related scientific-cultural activities in addition to protecting the Curundu river s biological integrity and the buffer zone of the Panamá Canal Watershed (Viquez & Denvers 2006). The principal contact person for this project is: Lcda. Amelia M. Munoz Harris Tel: (507) / (507) Fax: Introduction The order Chiroptera comprises one quarter of all extant mammals (Jones et al. 2002) and its approximately 1,100 species (Shutt & Simmons 2006) are characterized by being the only mammals to have developed powered flight, making them completely unique in the animal kingdom. The earliest records of modern bats in North America, Europe, Africa, and Australia date from the early Eocene between 53 mya to 49 Mya (Speakman 2001; Gunnell & Simmons, 2005). Evolution of Chiroptera remains controversial in part because no transitional fossils have been found to explain their evolution (Simmons 1995; Sears et al., 2006). It is believed that a gliding, nocturnal, insectivorous mammal developed flight, and afterwards evolved echolocation using low-frequency signals (Arita & Fenton, 1997). The majority of scientists consider Chiroptera to be a monophyletic taxa including two recognized suborders, Megachiroptera and Microchiroptera. Megachiroptera are the old world fruit bats (Jones et al., 2002) relying on their visual acuity (Teeling et al., 2000) and olfactory system (Safi & Dechmann, 2005) to navigate and forage, while Microchiroptera taxa use complex laryngeal echolocation (Teeling et al., 2000). Bats are the most ecologically diverse and geographically widespread mammal (Ratcliffe, Fenton, & Shettleworth, 2006). They usually feed at night and rest in roost during the day. Some species create specialized roosts for themselves by cutting the leaves of palm trees to build a house-like structure, while most species rest in natural areas ranging from hollow trees, logs, caves, crevices, bridges, tunnels, culverts, and buildings (Reid 1997). Their feeding habits are quite diversified and their diet may include combinations of insects, fish, fruits, nectar, pollen, flowers, blood, birds, and other vertebrates (Samudio and Carrion de Samudio 1989) depending on the species. Their presence plays important roles in the ecosystems where they are found. 4 Ecologists consider Chiroptera to be the most important mammal order in neotropical rainforests because its contribution in pollination and seed dispersal is essential for the maintenance of plant biodiversity and regeneration (Santamaría and Méndez 2001). In spite of their ecological role and efficacy in insect control, people most commonly associate them with evil, darkness and a source of diseases (Fenton 1997). This association, along with their non-charismatic appearance, leads to a lower public support in many areas for their conservation. The Natural Metropolitan Park is located in the transition zone between the tropical dry and humid forests of the region, and is part of the Biological Corridor of the east shore of Panamá, and therefore it is an important refuge for a diversity of animals including 27 species of bats (Viquez & Denvers 2006). In Panamá, 114 species of bats have been identified and according to previous studies 26 were found in the park (Viquez & Denvers 2006; Samudio 2002). As part of its mandate, the park aims to protect the resident species while providing information and environmental education to the public. Since information regarding the importance of food and roosts in bat population ecology is not well understood for a majority of the 26 identified species in the park, it affects the ability to produce effective management plans for their conservation (Fenton 1997). The aims of this project are to increase knowledge of resident bat populations and help promote understanding and conservation of these species through public education. 5 Specific Objectives 1. Investigate natural and artificial habitats that exist for different species in the park 2. Identify and characterize species living around these sites 3. Perform an habitat survey to compare the conditions of each site and how it affects bat richness 4. Create document that analyzes the population of bats sampled in the park 5. Map the capture sites and areas where each species are found 6. Create an educational pamphlet of the resident bat species The general objectives are to establish a database of information about a sample of the population of bats living in the park, and make the appropriate correlations between the different habitats and their presence at these sites. An artificial site has also been selected to identify the diversity of species roosting in the building and thereby help the park create better management plans for the building and the bats living there. With these data, an informative guide will be designed to provide visitors of the park with detailed information describing the bat species present in the park for touristic and educational purposes. 6 Methods AREA OF STUDY The Parque Natural Metropolitano (PNM) was founded in 1988 to protect m 2 of highly endangered pacific dry forest in the heart of Panama City. It joins the Camino de Cruces and the Parque Nacional Soberanía in the Biological Corridor of the east shore of Panamá (Viquez & Denvers 2006). The park is located in the transition zone between the tropical dry and humid forests, and therefore consists of a mixture of these two biomes. This protected area is one of the last refuges of the threatened Pacific Dry Tropical Forest in Central America, and provides a habitat for native flora and fauna species that require a large forested area (Parque Metropolitano 2008). Figure 1: Map of the Natural Metropolitan Park, with specific study sites indicated 7 STUDY ORGANISMS Based on the Management Plan of the park (Viquez & Denvers 2006); and a later study by Samudio et al. (unpublished data) 26 bat species from five families were found in the park (see Appendix IV). SITE SELECTION This study was performed for four months in the Metropolitan National Park of Panamá City, Panamá. Sites were selected by a first inspection on foot of the forest surrounding the Sendero (trail) Momótides and accessible areas of the park. Six sites were chosen to have a representative sample of areas of humid and dry tropical forest and different percentages of canopy cover. The proximity to possible roost site was also taken into account during the selection process. Once located, these sites were re-visited for the capture of bats and habitat characterization. For each site, the GPS coordinate, the forest type (humid or dry), the average height of the canopy of trees, the percent canopy cover and the possible roost sites visible from the netting site were recorded. Dominant tree species were identified at each site by the help of an experienced park employee. Canopy cover was estimated in percentage, 0% representing no tree cover, 50% signifying that sunlight can penetrate to the ground for 50% of the area and 100% representing a habitat without sunlight penetration to the ground. The first site is an active artificial roost site, an abandoned building named El Castillo located in the junction of the path leading to the canopy crane and Camino Mono Titi and the road Juan Pablo II (Figure 2). Previous studies found a greater diversity of bats in the area of the Sendero Momótides (Castillo pers. communication) than other areas in the park, so three sites were chosen 200m apart in this area, at a quarter (site 2; Figure 3), half (site 5; Figure 6), and three-quarter (site 4; Figure 5) of the trail to maintain independence of treatment. An area near an 8 abandoned building in an open area at the limit of the park was chosen as third site (Figure 4). Lastly, the sixth site was chosen near a pond on the Sendero El Roble because it offered an entirely different habitat than the other sites due chiefly to the presence of stagnant water (Figure 7). Figure 2: Capture site 1: el Castillo 9 Figure 3: Capture site 2: Momótides ¼ trail Figure 4: Capture site 3: Open Area/Abandoned building 10 Figure 5: Capture site 4: Momótides ¾ trail Figure 6: Capture site 5: Momótides ½ trail 11 Figure 7: Capture site 6: Laguito site HABITAT CHARACTERIZATION Selection of a mapping method In order to characterize the selected sites according to available geographic data such as soil type, height above sea level, and spatial dispersion, the compilation of various sources of data was required using a Geographic Information System (GIS). Ultimately, it was decided that for a number of reasons, this GIS system would use the Google Earth interface as its backbone. One reason for selecting Google Earth as opposed to a more sophisticated program such as ESRI's ArcGIS was that the park itself and its employees did not have knowledge of, or access to, this type of expensive software. In contrast, Google Earth may be downloaded for free by any computer user and features a simpler interface in addition to many hundreds of online tutorials in multiple languages. Another factor in this selection was that the map files that the park supplied 12 were in a document format, with no spatial data attributed to them whatsoever. An attempt was made early on to solve this problem by digitizing photocopied GPS coordinates of sites in the park (the spreadsheet version of which can be found in Appendix II) to use as spatial control points, but this initiative failed because the datum in which this data had been collected had not been recorded and was evidently not any of the most common systems. The absence of georeferencing control points but the available spatially accurate and valuable maps therefore made the Google Earth's 'overlay' tool the most sensible way of garnering the required information. Overlaying maps using Google Earth In order to produce a coherent set of overlays using Google Earth, all four source layers had to be converted from their original format as Microsoft Publisher files into more useful.jpg and.tiff image files at a high resolution (300dpi), which was performed using Microsoft Publisher (these image files can be found in Appendix III). These images were then added to Google Earth's free software version 5.0 as image overlays, saved as.kmz files compatible with Google Earth, and by increasing their transparency and using the provided base satellite imagery at a straight overhead view, the boundaries of the park were lined up for the first map image. Each subsequent image was then added to the interface and lined-up with the first image, with further minor adjustments bringing each overlay to an identical spatial location. Creating spatial files and determining habitat characteristics The transformation of field-collected locational data (using a Garmin 'Blue Moon' hand held GPS unit) to a format compatible with the Google Earth interface was done in a two-step process. First, the coordinates in the Latitude/Longitiude system using the WGS 1984 datum were entered into an Excel spreadsheet with the site's name and the GPS accuracy (Appendix II). 13 The file was then modified to include a pre-existing Google Earth icon number for each site and an online resource called Excel to KML provided by Earth Point at was used to convert the Excel file to a.kml file. The transfer was then made permanent by saving the resulting file within the Google Earth itself. The resulting file, when combined with the spatially corrected map image overlays, allowed one to determine the elevation as well as the soil type of each site. CAPTURE AND SAMPLING This study was performed in the Metropolitan National Park of Panamá from January to April Bats were captured by mist-net according to the techniques described by Kunz & Kurta (1988). To maintain a uniform sampling effort across sites, a mist-net was put up for a total five hours (± 15 minutes) at each site between 18h00 and 22h00 which is recognized as the first activity peak for bats in this region (Thies, Kalko, & Schnitzler 2006; Castillo pers. comm.). For this study, thirty hours were dedicated to mist-netting in the field. Three nets were used alternatively between sites; two had a similar surface area of 14 m 2 while the last only covered 8.26m 2. Verification of the net was done every 30 minutes except for nights when two nets were set up and the time spent removing bats in one did not allow enough time to verify the other net with this frequency. In these cases, nets were verified as soon as removal was finished at the other site. All species caught were extracted and carefully manipulated for identification of the species, sex, level of maturity, reproductive stage, presence of parasite, and forearm length. Once all data were recorded, pictures of the animal were sometimes taken and then it was released to minimize stress associated with the capture and handling (Widemaier et al. 1994). The weather 14 conditions (temperature, humidity, time at sunset, moon phase) as well as time of capture and date were also recorded for comparison purposes. SPECIES IDENTIFICATION Figure 8: Bat capture and extraction using a mistnet. Supervised by bat expert Jorge Castillo. Each bat captured was identified using the Key to the bats of the Lowlands of Panamá by Handley and Samudio (see Appendix V) to which some modifications were made. When identification was uncertain, a brief description of important characteristics was recorded and multiple photos were taken of the individual. Other references were used and the additional information (description and pictures) was sent to bat specialists for accurate identification. AGE DETERMINATION As suggested by Anthony (1988), the bats caught for this ecological study were placed into broad relative age groups defined as juvenile, sub-adults and adults. Age category was determined visually by the observing the epiphyseal-diaphyseal fusion finger bones. Cartilaginous epiphyseal plates in finger bones (Fig 10: I) are present in juvenile bats (Andersen 15 1917; Anthony 1988) while adult bats have mineralized bones producing knobby and unevenly tapered finger joints (Figure 10: III). By flashing a light through the wing membrane, cartilaginous areas of young bat s fingers are lighter and barely visible while ossified areas for adults do not let as much light shine through and appear bulkier. All individuals without clearly mineralized bones and thick knobby joints were classified as sub-adults (Fig 10: II). Figure 10: Growth progression of the fourth metacarpal-phalangeal joint of Myotis lucifugus from the neonatal stage (I) to sub-adult stage (II) and adult stage (III). Image A shows the growth of the bone seen by transilluminating the wing while B shows the X-ray. (Illustration taken from Kunz and Anthony 1982) 16 SEXUAL DETERMINATION AND MATURITY The sex of the bats captured was identified according to the presence of sexual organs. The presence of a penis distinguished the males (Figure 11) while for females a combination of traits was used. Females were recognized by a vaginal opening (Figure 12) and the presence of nipples (Figure13). Many species such as Artibeus jamaicensis, males experience seasonal descent of the testes during the reproductive season (Racey 1988). Other males are classified as reproducing by the swelling of testes during spermatogenesis which make them more conspicuous (Racey 1988). During this study all males with obvious testes were noted to be in the reproducing season and mature. Female pregnancies were determined by palpation of the abdomen. Parity was also established by the appearance of the nipples. A mature female will retain enlarged nipple size and a keratinize appearance while immature or non-parous females have smaller nipples covered by hair (Racey 1988). Figure 12: Female Artibeus jamaicensis Figure 11: Male Artibeus jamaicensis showing pronounced genetalia 17 Figure 13: Mature female with nipple found underneath the arm close to the wing membrane. LIMITATIONS Roost-site identification An initial objective for this study was to identify the inhabited roost-sites of bats in the park. During the day, transects were performed to identify possible roost-sites such as hollow trees, palm leaves, caves, culverts, buildings, etc. However, several problems were experienced with this methodology. First, it was nearly impossible to access all the possible roosting sites due to lack of adequate equipment. Some bats use the under-branch of trees to roost (Kunz & Kurta, 1988), but with the canopy being so high, it was impossible make observations with the naked eye or binoculars, because the light source available did not provide sufficient contrast to see bats. Secondly, our focus was on the readily accessible roost sites, like culvert, buildings, hollow trees, palm leaves, but it also proved impossible to visually identify the presence of bats in these locations. When a camera was used to take pictures where access was difficult, no bats were found. In other areas, for example hollow trees, the angle of the photograph could not provide a 18 clear enough photo of the interior of the roosts to determine if they were occupied. Powell & Wehnelt (2003) also found daytime colony counts to be difficult and often underestimated population density, implying that population assessments are not as reliable when done during the day. Another methodology was explored where roost-site were re-visited at dusk in order to observe the bats leaving them. It was found by Warren & Witter (2002) that the time of first emergence of bats varied depending on the site, the date, and weather conditions for a same species; this implies observers must calculate an appropriate time-range to account for these variations. It was also noted that different species emerged at different times, therefore the assessment of the roost sites of many species requires a larger time frame than what was possible. Also, visibility was very limited at dusk. Bats were observed around the trees yet it was impossible to certify they originated from the roost-site or if they came from another location. Most roost-site studies require more than two researchers and often use volunteers (Warren & Witter, 2002; Jaberg & Blant, 2003) or a team of experts to locate them (Powell & Wehnelt, 2003). Other studies only looked at known ro
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