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Introduction
Myotis atacamensis is a widely distributed bat species from southern Peru to northern Chile (Aragón & Aguirre, 2014; Rodriguez-San Pedro et al., 2014; Simmons, 2005). Its type locality is San Pedro de Atacama, Antofagasta Region, Northern Chile, at an altitude of 2.400 m(Lataste, 1892; LaVal, 1973). The habitat of this species includes only semiarid and arid environments, which produces a fragmented population scheme (Iriarte, 2008; Mann, 1978; Ossa et al., 2015). Because of the dependence on its habitat and increasing fragmentation during the last years, the Atacama Myotis was recently declared an endangered species by the IUCN (Vargas-Rodriguez et al., 2016).
The Atacama Myotis is an insectivorous bat, with short periods of activity from dusk to midnight (Galaz et al., 2009). It is one of the smallest bats in Chile and South America, along with Myotis chiloensis (Canals et al., 2005; Mann, 1978). The distribution ranges of these species overlap in the Coquimbo and Valparaiso regions (Iriarte, 2008; Rodriguez-San Pedro et al., 2015, 2014), however they are easily recognizable in hand because of the lighter fur color and shorter forearm of M. atacamensis (Ossa et al., 2010b, 2015).
Recent studies of the echolocation calls of the Myotis species in Chile differentiate the species easily because of the higher frequency range of M. atacamensis with respect to M. chiloensis (Ossa et al., 2010a; b, 2015; Rodríguez-San Pedro & Simonetti, 2013; Rodriguez-San Pedro et al., 2015). We present here the highest records of M. atacamensis, exceeding by 1075 and 1056 meters the previous records of the species.
We used a Song Meter SM3Bat (Wildlife Acoustics Inc. USA) to record bat echolocation calls in 2 villages in the Parinacota Province, Arica and Parinacota Region, northern Chile (Figure 1). The recorder was installed during 1 night at each village (Table 1), and was set to record bats from dusk to sunrise at a sampling rate of 256 kHz, recording bats that echolocate up to 120 kHz (Obrist et al., 2010). Files obtained in the field were analysed using the software Avisoft SAS Lab Pro (Avisoft Bioacoustics, Germany); we measured the frequency at the start, end and maximum amplitude of each pulse (kHz) and the duration of the pulses (ms) in searching phase.(Figure 2)
Figure 1 Distribution map of extant localities of Myotis atacamensis in southern Peru and northern Chile (Vargas-Rodriguez et al. 2016). Black circles represent the new records.
Figure 2 Sonogram of a characteristic pulse of Myotis atacamensis. Y-axis represents frequencies (kHz) and X-axis represents time (ms) Spectrogram was created using Avisoft SAS Lab Pro V5.2.07 (Avisoft Bioacoustics, Germany). Parameters were: Fast Fourier Transform length: 512; frame size 100%; Overlap 75%.
Table 1 Study sites, date, altitude, coordinates and number of files of Myotis atacamensis obtained in one night of sampling.
Table 2 Echolocation parameter measurements for files obtained in the field (this study) and comparison with other datasets obtained in the field.
We obtained 35 calls of M. atacamensis (Table 1), from which we measured 1171 pulses in the search phase (Table 2). Measurements were as follows: start frequency: 67.0 ± 10.2 kHz; end frequency: 47.7 ± 2.9 kHz; peak frequency: 52.0 ± 3.2 kHz; duration of the pulses: 3.3 ± 3.3 ms and interval between pulses: 134.9 ± 65.8 ms. Those values are coincident with values obtained in other recent studies in the Tarapacá Region (Ossa et al., 2015) and Valparaíso Region (Rodriguez-San Pedro et al., 2015). Very few bat surveys have been done in the Arica and Parinacota Region, which results in a lack of information about this group of mammals in the area (Sierra-Cisternas & Rodriguez-Serrano, 2015). The presence of M. atacamensis at higher altitudes could be a result of seasonal migration, searching for food and avoiding the high temperatures at lower altitude as other Myotis species in the Northern Hemisphere (Norquay et al., 2013; Ruedi & Castella, 2002).
The localities reported here for Myotis atacamensis increase its altitudinal distribution by more than 1000 meters of altitude, proving that this species is not restricted to coastal habitats and lowlands as previously thought (Galaz & Yáñez, 2006; Wilson, 1997). Myotis atacamensis use high altitude valleys to obtain refuge and to feed; the presence of old mines and villages allow this species to hibernate during the cold season (Mann, 1945). The Atacama Myotis have been recently classified as Endangered (Vargas-Rodriguez et al., 2016) because of its highly fragmented populations in the coastal desert of northern Chile and southern Peru, but valleys are closer to each other in the highlands and are not separated by desert pampas, so the populations probably are less fragmented.
During the same field work we searched for bat echolocation calls at the Caquena village (18°03'S -69°12'O; 4402 m) with no results, certainly because of the cold temperature and strong winds in the area. This kind of field work is crucial to determine the distribution ranges of endangered bat species in Chile, in environments where probably no bat studies have been done in the past.
