GOROBEYKO U.V., SMIRNOVA A.A.
Amurian zoological journal 2026; 18(1): 254-272
Bat swarming is the concentration of actively flying bats at the entrances to caves and grottoes in late summer or early autumn, and is one of the least studied aspects of the Far Eastern bats' life. Although this phenomenon is well documented in North America, Europe, and Siberia, only one observation has been reported for the Russian Far East (Khabarovsk Krai). This article presents the results of annual field bat observations conducted during the first half of October (2022-2025) on Lozovy (Chandalaz) Ridge, a limestone massif with an abundance of diverse karst forms, including caves. Four small caves unsuitable for wintering were surveyed: Bliznets, Malen'kaya, Mechta Speleologa, and Skvoznaya. Skvoznaya Cave is a tunnel that pierces the ridge near its summit. Bat captures were carried out using mist nets at the cave entrances. In 2025, a camera trap was installed at the upper entrance to Skvoznaya Cave. At least three dozen visits to all surveyed cavities, except for Mechta Speleologa Cave, were recorded for two of the four bat species inhabiting the area: Hilgendorf’s Tube-nosed Bat and Ognev’s Long-eared Bat. Among the individuals examined, adult sexually mature males with enlarged testes predominated. Activity began immediately after sunset, reaching its peak 2-3 hours after sunset (by 8-9 p.m.), and was observed almost exclusively at the entrances to underground cavities. The greatest number of bats was recorded at the upper entrance to Skvoznaya Cave. Considering current hypotheses on the nature of swarming, the observed autumnal bat activity is consistent with at least two main hypotheses (mating and social), making Lozovy Ridge the first known site of bat swarming in Primorsky Krai. However, swarming in October is considered relatively late, which may be attributable to the warmer climate of Chandalaz: in all years of observation, nighttime temperatures did not fall below +7 to +9 ℃.
