Importance of Mangroves for Bat Research and Conservation: A Case Study from Vietnam with Notes on Echolocation of Myotis hasselti

Abstract

Mangrove ecosystems play important ecological roles, including the mitigation of global climate change and biodiversity conservation. However, they have received little attention from scientists for the research and conservation of bats and general biodiversity. In Vietnam, bat species inhabiting mangroves have been relatively unstudied, while this ecosystem is located along the country’s coastal zones and has declined dramatically due to the development of agriculture, wind energy and other threats. To initially fill this gap, five bat surveys were conducted between September 2019 and November 2021 within Ha Long Bay and Ben Tre province, which contain representative mangrove areas of northern and southern regions of Vietnam, respectively. Bats were captured using mist nets, mobile nets and hand nets. Their echolocation calls were recorded and analyzed using the PCTape system and Selena software, respectively. Five species were captured and recorded: Cynopterus brachyotis, Macroglossus minimus, Myotis hasselti, Myotis pilosus and Taphozous melanopogon. They are all new to both Ha Long Bay and Ben Tre province. Four species (C. brachyotis, M. minimus, M. hasselti and M. pilosus) have been rarely documented from other ecosystems in Vietnam but have commonly been recorded and captured in mangrove areas. Of these species, M. pilosus is a globally “Vulnerable” species. While searching for prey, Myotis hasselti emitted high energy echolocation calls sweeping from about 96 to about 24 kHz with a signal duration of about 5 ms. This species sometimes uses social calls of a horseshoe-shaped structure, which last about 15 ms and are emitted about 26 ms in front of a search call. Results from our surveys indicated the importance and potential of mangroves for bat research and conservation.

First Records of Bats (Mammalia: Chiroptera) from the World’s Largest Cave in Vietnam

“…The hindfoot with long claws and other morphological features of the three Myotis individuals captured at Son Dong Cave fit the identification of M. pilosus. Echolocation call structure and frequency of M. pilosus in Son Dong Cave are also similar to those of the species from other areas of Vietnam [13,15,16]. The external characteristics and measurements of two other Myotis individuals are almost identical to those of Myotis muricola (Figure 3; Table 1).…”

“…Vietnam has 19 Myotis species including M. pilosus and M. muricola [13]. Myotis pilosus is distinguishable from other Myotis species in Vietnam by its body size with a forearm length of over 50 mm and a hindfoot including claws that is approximately three-quarters of the tibia length [9,13,15,16,22]. The hindfoot with long claws and other morphological features of the three Myotis individuals captured at Son Dong Cave fit the identification of M. pilosus.…”

“…Externally, the posterior nose leaf of A. dongbacanus is more fleshy than that of A. stoliczkanus [13] and the upper canine of A. dongbacanus is longer than that of A. stoliczkanus [13]. To date, A. dongbacanus is only known in karst areas in northern Vietnam, whereas A. stoliczkanus is a widespread species with records from various areas and a wide range of ecosystems in northern and central Vietnam [9,13] as well as Phong Nha-Ke Bang National Park over the past decades [9,[14][15][16]23]. Therefore, the characteristics of the posterior noseleaf and echolocation calls of the captured and observed individuals in Son Doong Cave can be assigned to A. stoliczkanus.…”

“…Echolocation calls recorded in natural habitats were carefully compared with the calls of the captured bats when they were released for identification. All recorded calls were also compared with an unpublished database of the first author and data in selected publications [12][13][14][15][16][17][18][19][20][21].…”