Macaregua : the cave with the highest bat richness in Colombia

Bats provide crucial ecosystem services like pest control and pollination and depend heavily on roost quality for their survival. Bats favor caves for the establishment of large populations thanks to favorable microclimatic conditions. Colombia has an important cave system in the Santander region that has not been fully explored, thus its importance for bat conservation remains largely unknown. Here we report the most updated list of the species present in the Macaregua Cave (Santander, Colombia) and comment on its use by different species. We found eight species that use the cave permanently or sporadically in addition to two previously known species. We also found a high population that ranges between 7,000–10,000 individuals. Macaregua Cave can now be recognized as the most bat-diverse (S = 10) cave in Colombia, harboring an important bat population of pest controllers and seed dispersers.


INTRODUCTION
Bats are known to provide crucial ecosystem services, such as pest control and pollination (Kunz et al. 2011), but rely on the availability of suitable roosts for maintaining their populations (Kunz and Lumsden 2003).One of the main roosts used by bats are caves, which are dynamic and complex ecosystems.Within a cave, climatic conditions (i.e., temperature) can be stable for long periods of time and nutrient cycling and energy flow can take thousands of years (Culver and Pipan 2009).Nevertheless, water currents that traverse a cave system leach soil nutrients constantly, and fluctuating water currents that filters in from the exterior of the cave determines the chemical composition and structural shape of the cave's roof (Romero 2009).Caves are used by many species of bats as roosting sites, and some species depend heavily on caves throughout their life history (Murray and Kunz 2005).For example, many species use them as roosting sites for establishment and persistence, hibernation, or as a place to avoid predators and provide parental care (Glover and Altringham 2008;Berková and Zukal 2010).The constant microclimatic conditions in caves allow for the establishment of colonies of millions of individuals (Betke et al. 2008), which are known to save millions of dollars each year on pesticides to protect food crops (Kunz et al. 2011).
Aside from the ecosystem services bats provide outside of the caves, bats play an important role in the nutrient cycling of the caves themselves (Niu et al. 2007); they are one of the only organisms that enter and exit caves permanently, and by doing so they transport to these caves organisms such as seeds, fungal spores, fern spores, and microarthropods.Moreover, the guano bats produce accumulates and provides organic matter for soil organisms (Lopes et al. 2000).Bats themselves can be food for other organisms that inhabit the caves such as giant centipedes (Scolopendra), and occasional visitors such as snakes and medium sized mammals (Romero 2009).
The most intensively studied cave systems in Colombia are located in the departments of Antioquia, Boyacá, Huila, Tolima, and Santander (Muñoz-Saba et al. 1998).In the latter, 15 bat species from the families Phyllostomidae, Vespertilionidae, Mormoopidae, and Natalidae have been reported to inhabit cave systems (Muñoz-Saba et al. 2007).The most diverse family in the caves of Santander is Phyllostomidae, with 11 species (Muñoz-Saba et al. 2007).Aside from these sporadic studies, little is known about caves in Colombia, and despite their importance as a threatened ecosystem worldwide, caves in Colombia are facing strong anthropic pressure due to growing and uncontrolled tourism and unchecked speleological practices.
This research focuses on Macaregua Cave in Santander, Colombia.The last anecdotal information about this cave dates from the 1970s, with the work by Cadena captured and identified bats throughout.Captures were done ad libitum using small mist nets and insect nets, and some bats were manually captured at their roosts.We also used a modification of the harp trap proposed by McCracken and Bradbury (1981), with a customized pocket made out of fabric with a lateral zipper and a string to close its uppermost part.In order to make a preliminary assessment of the number of individuals in the cave, we took photographs of the cave's roof and then counted the bats directly from the pictures.We corrected this estimate by directly counting bats while the roof was being photographed.Although we acknowledge this technique might produce over or underestimations, our direct counts did not differ from the number of bats we were able to count from the photographs.
Each captured individual was measured using standard procedures (Tirira 2007).We measured their total length and weight, length of tail, foot, ear, forearm, wingspan, tragus, leaf nose, calcar, and pollex.Reproductive status was recorded following Racey (2009).Bats were identified using the keys by Timm and LaVal (1998) and Linares (1998) and were released afterwards.Some individuals were collected as vouchers and deposited in the Museo Javeriano de Historia Natural (MUJ) (collection numbers MUJ 1720-1808, permit DLG No. 00001153 issued by Corporación Autónoma Regional de Santander C.A.S.).We followed the guidelines proposed by Sikes and Gannon (2011) to euthanize specimens, thus complying with the voucher policy of Check List.We used the nomenclature suggested by Simmons (2005) and adopted the current classification for the bats of Colombia (Solari et al. 2013).For analysis, bats were and Villarraga on Natalus tumidirostris Miller, 1900 and the first report for Colombia of the fungus Histoplasma carried out by Grose and Marinkelle (1970).Aiming to contribute to the research efforts in this cave system in Colombia, we describe here the composition of the bat assemblage in Macaregua Cave.

Study area
Macaregua Cave (06°39′36.2″N, 073°06′32.3″W) is located in the county of San Francisco, municipality of Curití, department of Santander, Colombia (Figure 1).The altitude of its entrance is 1,565 m and it is situated in the Cordillera Boyacense-Santandereana biospeleological zone (Muñoz-Saba et al. 2007).The mean annual precipitation is 1,550 mm, with a unimodal rainfall pattern; a dry season from November to March, with precipitation that oscillates between 22 to 93 mm, and a rainy season from April until October, which ranges from 199 to 220 mm.The vegetation around the entrance of the cave is a tropical dry forest dominated by species from the families Boraginaceae, Fabaceae, Myrsinaceae, Rubiaceae and Caesalpiniaceae.Agriculture is the most important economic activity in the area; tobacco, coffee, beans, and maize are the most common crops.Agave is also planted for the production of "fique" (genus Furcraea), and cattle farming is also used as a mean of subsistence.
The cave has two main galleries; one is dry and approximately 80 m long, and the other has a running stream (henceforth moist gallery) and is approximately 610 m long (Figure 1).Another set of galleries (henceforth second set), which are approximately 180 m long, branch off from the moist gallery at 420 m.The moist galleries show a mean temperature of 25°C and 90% of relative humidity.The average height of the cave is 3.2 m, with some sections reaching 6 m.The cave's width ranges from 3 to 11 m, with two narrow (< 40 cm) and short (< 50 cm) ramifications of 55 and 65 m of length each (Figure 1).Pawlak and Szafranski (1977) determined that Macaregua was 770 m, but they did not specify if this measurement pertained to the moist gallery or to the combination of the dry and moist galleries.Given that they did not provide any other descriptor of the cave, it's not possible to assess any changes in its dimensions over time.

Methodology
We have visited the cave eight times (March and July/ August 2010; January/February and November 2011; April, June, and November 2012; and February/March 2013) to study the social structure and activity patterns of the bats that inhabit the cave, especially those of Carollia perspicillata (Linnaeus, 1758).During these visits, we measured physical aspects of the different galleries and grouped into trophic guilds according to Schnitzler and Kalko (2001).Aside from direct captures, we performed a literature and a data base survey of available collections in Colombia and elsewhere to complete the catalogue of the species that have been registered in the cave.To do so, we consulted the curators of the collections deposited in the Universidad de Antioquia (Medellín), La Salle Museum (Bogotá), and Universidad del Valle (Cali), and searched the online catalog of the mammal collection in the Instituto de Ciencias Naturales (ICN) (http://www.biovirtual.unal.edu.co/ICN/).We performed a final query in the VertNet database using the word "Macaregua" as search key (http://portal.vertnet.org/).We acknowledge that there are other specimens captured in Macaregua deposited in other collections.Nevertheless, we based our account on data we have collected and used references from other collections only when we did not have vouchers from those species (e.g., Micronycteris megalotis (Gray, 1842); see Table 1).

RESULTS
With our captures and direct observations we found eight species inhabiting the Macaregua Cave, comprising four families: Phyllostomidae, Vespertilionidae, Natalidae, and Mormoopidae (Table 1).Carollia perspicillata was the most abundant species, followed by Mormoops megalophylla (Peters, 1864) and Natalus tumidirostris.According to our photograph counts, we estimate that the total number of bats in the cave ranges between 7,000 and 10,000 individuals.Species were not randomly distributed across the cave.For example, Desmodus rotundus (É.Geoffroy, 1810) generally used deep crevices in the roof, where it formed compact groups, and was only found between 170 m and 290 m from the entrance.In comparison, C. perspicillata formed harems in shallow crevices and rocks protruding from the roof after the first few meters from the entrance but only up to 500 m.Mormoops megalophylla was found mainly in the deepest section of the second set of moist galleries of the cave, at 550-600 m from the entrance, and with few individuals along the curse of the water stream.Occasionally, we found some individuals in the dry gallery between 20 and 80 m.Myotis nigricans (Schinz, 1821) was also found occasionally in the dry gallery at 20 m.Natalus tumidirostris and M. megalophylla shared the second set of moist galleries, but the former mainly uses the last 200 m of the cave.Its population fluctuates around 500 individuals.After giving birth, N. tumidirostris creates cohesive maternity nurseries in this area of the cave.Micronycteris schmidtorum Sanborn, 1935 was found twice (April and November 2012) at 70 m from the entrance in the moist gallery.One individual of Dermanura bogotensis (K.Andersen, 1906) was captured in the first meters of the cave and one individual of Glossophaga soricina (Pallas, 1766) between 100 and 150 m from the entrance.
Pérez-Torres et al. | Bats of the Macaregua Cave, Colombia (S = 5).According to our data, the literature review, and the database query, Macaregua Cave harbors at least ten bat species (Table 1).

DISCUSSION
The available information indicates that Macaregua Cave holds the richest bat community of any cave in Colombia (Muñoz-Saba et al. 1998;Muñoz-Saba et al. 2007;Sampedro-Marín et al. 2007;Sampedro-Marín and Mendoza 2009).The next most speciose cave is the Caja de Agua Cave (department of Huila) with six species (Muñoz-Saba et al. 2007).At a continental scale, the Olhos d' Água Cave and Las Vegas Cave, in Brazil and México respectively, are the most speciose caves in America, with 13 species (Medellín and López-Forment 1985;Trajano and Gimenez 1998), followed by the Actun Lol-Tun Cave, Mexico, with 12 species (Arita 1996).According to criteria proposed by Arita (1993), the abundance of individuals found in Macaregua Cave is high (> 1,000 individuals).At a regional scale, the ten species we report constitute 30% of the species found in the department of Santander (Solari et al. 2013) and 44% of the species registered for the cave system in this department (Muñoz-Saba et al. 2013).The query in the online catalogue of the mammal collection of the Instituto de Ciencias Naturales of the Universidad Nacional de Colombia showed that 24 species have been registered for the cave system in the department of Santander.Hence, Macaregua Cave has 41.6% of the total species richness found in the area.This highlights that Macaregua harbors a representative assemblage of species at the regional scale and constitutes a key element for the conservation of Colombian bats.
Mormoops megalophylla was first collected in Macaregua by P. Hershkovitz in 1951 (Field Museum of Natural History: FMNH 72130-72140, 72297-72335), and then later, in 1966, by C. Marinkelle, who collected a series of 19 specimens .According to Muñoz-Saba et al. (2013), M. megalophylla has also been reported in the El Yeso, La Antigua, and El Nitro caves.Our report also confirms the presence of M. nigricans using caves in Colombia, and it is a new record for the bats that inhabit Macaregua.As a comparison, Myotis keaysi J.A. Allen, 1914 has been reported for the El Tigre and La Virgen caves (ICN 17507-17509;17635-17639) and Myotis oxyotus (Peters, 1867) for El Nitro and La Alsacia caves (MUJ 1586-1587), both in the department of Santander.
Carollia perspicillata is a frugivorous bat that disperses large amounts of seeds of pioneer species and is fundamental in forest regeneration (Altringham 2011).In addition to Macaregua, this species has also been reported for Resumidero and La Antigua caves (ICN 19559-19560;17644-17647), El Nitro and La Alsacia caves (MUJ 1582(MUJ , 1584)), and 17 other caves in Santander (Muñoz-Saba et al. 2013).Desmodus rotundus was first collected in Macaregua in 1948 (MLS 1119) by A. Rouhaire (Hno.Nicéforo María).This species has been recorded from 19 other caves in Santander, including the Muerto, La Iglesia, and La Antigua caves (ICN 19508;17504-17506;17649-17651).Glossophaga soricina and M. schmidtorum probably use the cave sporadically.Only three individuals have been captured during the years we have visited the cave, and they were roosting alone.Glossophaga soricina has been reported in other caves in Santander (El Saun, La Antigua, El Muerto, and El Nitro), Huila (Caja de Agua), and Tolima (La Carbonera and El Tigre) (Muñoz-Saba et al. 2007, 2013), but this is the first record for M. schmidtorum.Our data also represent the first report of D. bogotensis using caves in Colombia.However, because we captured only one individual (MUJ 2187), and it was located in the first few meters of the cave, its presence could be accidental and needs further investigation.
Aside  Marinkelle and Grose (1968) reported the presence of Leptonycteris nivalis (Saussure, 1860) in Macaregua, but their record may represent L. curasoae according to the current distribution of these species.These authors also did not provide a voucher specimen.Finally, our study adds three new species for the list provided by Muñoz-Saba et al. (2013) for the bats of the cave system of Santander: M. nigricans, M. schmidtorum, and D. bogotensis.
The caves in the department of Santander contribute to the persistence of bat species at a regional scale because they are intensively used for resting and reproduction.With this study, we confirm that this is the case for the bats that inhabit Macaregua Cave.There is a need, however, for more research addressing detailed aspects of the ecology and functional importance of the bats present in Macaregua and other caves in the region.These studies will potentially highlight the importance of bats as providers of key ecosystem services (e.g., biological control of pests, seed dispersal and pollination) and reinforce the need to protect the cave systems in Santander and in other departments in Colombia.

ACKNOWLEDGEMENTS
To the Laboratorio de Ecología Funcional (Pontificia Universidad Javeriana, Bogotá) for financial and logistical support; to Enrique Villarraga for his pioneering work in Macaregua and showing us the cave; to Elías Gómez and Flor Daza for allowing access to the cave and lodging in their premises; to Sergio Solari and Miguel Rodríguez for taxonomic confirmations on collected specimens; to Fundación Chimbilako; and to Andrés Zipa, Andrés Chamat, Ana Lucía Rueda, Estefanía Delgado, Pavel Arciniegas, Maria Teresa Herrera, Camilo López, and other members of the Laboratorio de Ecología Funcional of the Pontificia Universidad Javeriana for help during field trips.We also thank the Corporación Autónoma Regional de Santander C.A.S. for the permits issued to conduct this study; this study made part of the project "Ecology of bats in cave systems in the department of Santander" supported by the Pontificia Universidad Javeriana (ID 5696).

LITERATURE CITED
et al. | Bats of the Macaregua Cave, Colombia

Figure 1 .
Figure 1.Location of the Macaregua cave in Santander, Colombia.Arrow at the right hand corner of the rightmost panel indicates the entrance of the cave.