The study of bats is associated with a number of difficulties in planning, organizing, and conducting work. Hidden wintering in underground cavities makes winter counts of bats difficult. Many caves and mines are difficult to visit during the winter season due to their remoteness from cleared roads. In addition, inside underground cavities, animals can be located in narrow spaces or at a considerable height, which makes it difficult to determine the species and count the number of individuals. In addition, a systematic winter underestimation of animals is likely due to the insufficiently studied speleological sites and the existence of a certain number of unknown, undiscovered caves.

The study area is located in Kemerovo oblast near the border with Novosibirsk oblast (west of the Promyshlennovskii and Gurevskii districts of Kuzbass) and is a kind of “blank spot” on the map of faunal studies in the southern part of Western Siberia. The area is located within the Salair Ridge, data on the chiropterofauna of which by 2008 were characterized as fragmentary and extremely incomplete (Vasenkov et al., 2008).

In the past 10–15 years, the caves of the Salair Ridge have been well explored from Novosibirsk oblast (Vasenkov, 2009); however, the northeastern slope of the ridge remained unexplored. Finds of bats in the central part of Kemerovo oblast and in the Kuznetsk Highlands, near the border with the Republic of Khakassia, are also known (Orlova et al., 1963; Shubin, 1971; Stukanova, 1976). This is mainly due to the fact that work is being carried out in this region to study the fauna of mammals. In the area of our study, according to the Red Book of Kemerovo oblast, only a few records of bats are known in the vicinity of Tanai Lake (Ilyashenko and Luchnikova, 2012; Skalon and Ilyashenko, 2012). Despite the fact that there are caves and active protected areas, we do not have information about conducting winter counts or summer trappings in this area.

The purpose of this work is to study the population of bats in the caves on the northeastern slope of the Salair Ridge. This work is part of a project to study coronaviruses circulating in natural reservoirs in Siberia, their diversity, and the pathogenic potential. Such studies are difficult to carry out without data on the structure and dynamics of populations of the carriers of these viruses, routes of their seasonal movements, and, in the case of bats, places of mass wintering.

We conducted research in the Gurevskii and Promyshlenovskii districts of Kemerovo oblast at three points: Gavrilovskaya Cave (November 18, 2020, and May 2, 2021), Gavrilovskaya-2 Cave (single survey on May 2, 2021), and an adit of the Kopnenskoye deposit (November 18, 2020, January 5, 2021, and May 2, 2021, but registration was carried out only in January and May) and an unnamed cave in the canyon of the Istok River in the vicinity of the village of Vaganovo (single registration November 17, 2020).

The scheme of the area of work is shown in Fig. 1.

Fig. 1.
figure 1

Scheme of the area of study.

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Gavrilovskaya Cave is a small natural cavity about 15 m deep and about 280 m long, laid in limestone at a distance of 2 km from the village of Gavrilovka, Guryevsk district, Kemerovo oblast. Gavrilovskaya-2 Cave is located 600 m northeast of Gavrilovskaya Cave (the first) and is a narrow horizontal gap that turns into a grotto. The length of the cave is about 30 m, and the depth is about five. Here and below, the length of the cave means the total length of its passages and the depth is the difference between the height of the entrance to the cave and its deepest point.

The adit in Mount Kopna, also known as the adit of the Kopnenskii deposit, is a horizontal artificial cavity with a length of about 100 m, laid in obliquely falling shale, 4 km from the village of Ursk, Guryevskii district, Kemerovo oblast. This is an almost straight exploration adit with a section of approximately 2.5 × 2.5 m with a half-blocked oval entrance measuring 0.5 × 1 m.

The nameless cave in the canyon of the Istok River is referred to in some sources as Vaganovskaya and is located approximately 2.5 km from the village of Vaganovo, Promyshlennovskii district, Kemerovo oblast. The cave is a small (no more than 20 m long) with a horizontal slot, slightly rising up and narrowing at the end.

In the autumn–winter time in the caves near the Gavrilovskaya village, the adit of Mount Kopna, and the cave in the canyon of the Istok River, we carried out visual counts of the number of bats. Some of the animals were removed from the walls of the cave for ringing and measurement, and at the same time we determined the sex of the animal. In other cases, sex was not determined. In spring, visual counts of bats were carried out in the village of Gavrilovskaya, the village of Gavrilovskaya-2, and in the adit of Mount Kopna. Sex was not determined; only previously ringed animals were taken from the walls of the cave for repeated measurements. The air temperature was measured only during spring surveys with a WS-1500 digital thermometer with a separately located additional sensor. The measurements were carried out at a distance of at least 30 m from the entrance to the cave, while the body of the thermometer with the built-in sensor was placed at floor level, and the additional sensor was at the level of large concentrations of bats.

During the work in these three caves and one adit of Kemerovo oblast, we took into account at least 370 bats of five species: the eastern water bat (Myotis petax (Hollister 1912)), the Siberian bat (M. sibiricus (Kastschenko 1905)), the pond bat (M. dasycneme (Boie 1825)), Hilgendorf’s tube-nosed bat (Murina hilgendorfi (Peters 1880)), and Ognev’s long-eared bat (Plecotus ognevi (Kishida 1927)). As far as the authors know, this is the first time that bats have been counted in these natural and artificial cavities. We ringed 34 animals and determined the sex of 35 individuals. The results of winter and spring counts are presented in Table 1. In Gavrilovskaya Cave, we also found guano in a side branch near the entrance to the cave, but neither autumn nor spring bats were recorded in this part of the cave.

Table 1. Results of winter and spring counts of bats
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During repeated counts in these cavities, we found previously ringed animals: one eastern water bat and two Siberian bats in Gavrilovskaya Cave and three Hilgendorf’s tubenosed bats in the adit of Mount Kopna. In Gavrilovskaya Cave on May 2, 2021, one corpse of the pond bat was found at the entrance; in the rest of the counts, the corpses of bats were not found. The air temperature at floor level on May 2, 2021, in Gavrilovskaya Cave was 4.5°C, and in the adit of Mount Kopna, it was 5.5°C. Air temperature at the level of large concentrations of bats (0.7–2.0 m from the floor in Gavrilovskaya Cave and 1.5–2.1 m in the adit in Kopna) ranged from 4.4–4.6 to 5.3–5.6°C, respectively; i.e., it did not differ significantly from the temperature at floor level. It is likely that the temperature in these cavities remains positive throughout the winter and this can be further verified using autonomous temperature loggers. According to these data, wintering of bats in Gavrilovskaya and Gavrilovskaya-2 caves, as well as in the adit of Mt. Kopna, should be considered successful.

The role of these cavities in the summer reproduction and autumn swarming of bats, as well as the formation of wintering colonies, has yet to be studied. Thus, Gavrilovskaya Cave is comparable in size and structure to Barsukovskaya Cave. Barsukovskaya Cave hosts the largest wintering colony of bats beyond the Urals, numbering at least two thousand animals (Vasenkov, 2009). At the same time, slightly more than two hundred bats were counted in Gavrilovskaya Cave. A comprehensive comparison of these caves could become a good model for comparing the population of bats in the northwestern part (Novosibirsk oblast) and the northeastern slope (Kemerovo oblast) of Salair Range, the southern part of which reaches Altai krai. The nature of the location of guano also suggests the formation of a summer brood colony in this cave, although without special studies it is impossible to exclude the role of the summer–autumn swarming of the bat colony in the accumulation of the guano discovered. It should be noted that, during the repeated spring count in Gavrilovskaya Cave, we found more bats than in autumn. The number of recorded Hilgendorf’s tubenosed bats and pond bats increased by 70 and 49 animals, respectively. The number of recorded Siberian bats differs less markedly, while the number of eastern water bats is practically the same. Since we conducted an autumn count on November 18, 2020, after the snow cover had set in, the change in the number of counted animals should be explained by the movements of bats inside the cave during wintering. It should be noted that the data of the winter and spring counts in the adit in Mount Kopna practically coincide. This can be explained by the fact that this cavity is almost a direct mine working. There are not as many gaps and hidden cavities in the adit that are inaccessible to the eye of the surveyor, which are usually rich in natural caves.

On the contrary, Ognev’s long-eared bat in both cavities examined twice was found only in autumn or winter. This is probably due to the early awakening of the animals of this species; however, additional studies are needed to test this hypothesis.

The data obtained are also important for the development and implementation of environmental protection measures, since three of the five species of bats encountered are listed in the Red Book of Kemerovo oblast (pond bat, Ognev’s long-eared bat, and Hilgendorf’s tube-nosed bat). For Hilgendorf’s tube-nosed bat, this is the northernmost detection point on the territory of Kemerovo oblast. According to the Red Book of Kemerovo oblast, Hilgendorf’s tube-nosed bat can be found in the winter in the amount of several dozen individuals (Ovodov, 1972; Skalon and Ilyashenko, 2012). The wintering colony found by us in the adit of Mount Kopna has at least 150 individuals, so it can be considered the largest known wintering colony of this species in Kemerovo oblast. It is noteworthy that this colony is located in an artificial cavity. This indicates the importance of studying bats in abandoned and active mine workings.

Thus, in Kemerovo oblast for the first time, bats were counted in four underground cavities. The caves and the adit examined by us are of great interest and supplement our understanding of the distribution, seasonal movements, summer breeding, and wintering places of bats in Western Siberia, including rare species. This area is an unexplored part of the Salair Ridge. Here it is necessary to conduct additional research in order to monitor the known and discover new places of wintering and summer breeding of bats.