Acoustic surveys reveal new record of the rare Smoky Bat Amorphochilus schnablii (Chiroptera, Furipteridae) in Chile after 71 years

The Smoky Bat, Amorphochilus schnablii , is a poorly known furipterid bat species endemic to the west coast of Ecuador, Peru, and the extreme north of Chile. The occurrence of this species in Chile has been limited to a single report from the year 1950, in the locality of Cuya in the Camarones valley, Arica

Amorphochilus is a monotypic genus of small bats (forearm 36-37 mm), with an exclusively neotropical distribution, where it is known only from a narrow strip on the west coast in central and southern Ecuador, Peru, and northwestern Chile.Its only species Amorphochilus schnablii (Peters, 1877), is an insectivorous bat with a preference for dipterans and lepidopterans (Mann 1978, Ibáñez 1985).It is found in arid regions and cultivated areas; it is a cave-dweller and known to roost in culverts, sugar mills, irrigation tunnels, and abandoned buildings in urban and rural areas (Cláudio 2019), where it forms monospecific colonies of up to 300 individuals of both sexes (Ibáñez 1985).
In Chile, A. schnablii is one of the least known bat species and one of the most difficult to find.This species is listed as Vulnerable by the IUCN (Velazco et al. c2015) and by the Chilean legislation (Decreto Supremo Nº 6/2017, MMA) because of a population decline, estimated to be more than 30 % over the past three generations, which is suspected from an observed shrinkage in distribution and information on habitat destruction and degradation.Although the known distribution of A. schnablii in Chile includes the coastal strip from the Arica and Parinacota region to the Loa River in the Tarapacá region (Galaz et al. 2020) its presence is based on a single report made by Mann (1950) 2018), which allowed us to reliably assign the recorded calls to this species.The parameters used in the acoustic identification were duration, initial and final frequencies, bandwidth, peak frequency, and the interpulse interval.
Search calls emitted by the A. schnablii in our study site were characterized by short (< 3ms) single broadband downward frequency-modulated pulses sweeping from 132 to 92 kHz (Table 1; Fig. 2).This frequency range and the pulse shape are consistent with those reported for specimens from Peru (Falcão et al. 2015, Ugarte-Núñez 2020) supporting the identity of our recordings.The new record presented here is of great interest considering the rarity of the reports of this species in Chile.This record fills a gap of 71 years with no data on the species and constitutes the most updated information for the species in the country.The lack of records in the literature can be explained by several factors, including the few bat surveys conducted in the extreme north of the country (Ossa et al. 2016, 2017, 2018, Rodríguez-San Pedro et al. 2021, 2022a, b).In addition, the known roost sites for this species are rock crevices in hard-to-reach cliff walls in coastal valleys

Figure 1 .
Figure 1.Geographical location of the Arica and Parinacota region, northern Chile, and records of the Smoky bat.a. Distribution map of records for Amorphochilus schnablii from Mann (1950) and the new record reported in the present study.b.Ambient where the echolocation calls were recorded in the Camarones valley.

Figure 2 .
Figure 2. Sonogram of echolocation calls of Amorphochilus schnablii a.A typical pulse sequence was recorded in the Camarones valley, Arica, and Parinacota region, Chile.b.A single pulse emitted by smoky bats in Peru (courtesy of Joaquin Ugarte) c.A single pulse emitted by smoky bats in Chile (right panel, this study).Spectrograms were generated on BatSound 2.1 software (Pettersson Elektronic AB, Upsala, Sweden), with a Hanning window type, frame overlap of 99%, and 512 FFT size.

(
Mann 1978), which makes the exploration and sighting of specimens difficult.However, A. schnablii seems to be a quite common bat species in southern Peru(Patron et   al. 2001, Aragón andAguirre 2014) where the bioclimatic conditions and landscape characteristics are similar to those found in the extreme north of Chile (Luebert and Pliscoff 2017).Thus, as sampling efforts began to increase in the region and complementary methods to inventory bats were used, this result was expectable.The recent findings of other bat species in the extreme north of Chile by acoustic detection such as Promops davisoni Thomas, 1921, Nyctinomops aurispinosus (Peale, 1848) (Ossa et al. 2018, Rodríguez-San Pedro et al. 2022a, b) along with this new record of A. schnablii reinforces the usefulness of the bioacoustics method in providing a more comprehensive assessment of bats in this little-explored zone, being a powerful tool for detecting uncommon species or difficult to capture with mist nets (MacSwiney et al. 2008).

Table 1 .
Descriptive analysis (mean ± SD) of the echolocation calls of Amorphochilus schnablii from Arica and Parinacota region, Chile.Echolocation calls of the species from Peru are also included.