Emballonura semicaudata is a small (five gram) cave-obligate bat that roosts in a range of cave types, including limestone caves, lava tubes, shelter-caves on overhanging cliffs, and rock crevices (Flannery 1995; Watling and Pernetta 1978; Grant et al. 1994; Hutson et al. 2001; Palmeirim et al. 2005, 2007; Wiles et al. 2011). Relatively large colonies appear common in the Palau subspecies while smaller colonies may be more representative of the other subspecies (Wiles et al. 1997, Wiles and Worthington 2002). Basic information on roost microclimate and habitat preferences are lacking for all subspecies (Hutson et al. 2001). It is important to note that subspecies that have undergone dramatic declines may be persisting in caves in sub-optimal conditions, after exclusion from their historical roosts. Pacific sheath-tailed bats are commonly found sharing caves with swiftlets (Aerodramus spp.) across their range (Watling and Pernetta 1978, Lemke 1986, Hutson et al. 2001, Tarburton 2002, Wiles and Worthington 2002, Palmeirim et al. 2005).

Although the species has occasionally been recorded flying in daylight under forest canopy it normally emerges at dusk to forage. While details of its diet are limited (Hutson et al. 2001), E. s. rotensis have been documented to primarily forage on Hymenopterans and Lepidopterans (Valdez et al. 2011).

The four subspecies are thought to prefer to forage in well-structured mature forest (native and non-native) with a high and dense canopy and relatively near to their roosting caves (Esselstyn et al. 2004, Palmeirim et al. 2005, Gorreson et al. 2009, Valdez et al. 2011, Welch et al. 2016). In Palau and Chuuk, the subspecies has occasionally been observed foraging over town streets (Bruner and Pratt 1979). Recent work has documented lower bat activity over introduced lantana shrub habitats (Welch et al. 2016).

Emballonura semicaudata is the only species of Emballonura found in the Pacific outside of the Solomon Island chain (Koopman 1993, 1997; Helgen and Flannery 2002). Currently, there are four recognized subspecies, including:

• E. s. semicaudata has a historical distribution that includes Samoa, American Samoa, Fiji, Tonga, and Vanuatu. In Samoa, it was historically found on Savai'i and Upolu islands, where it was relatively common and in American Samoa, it was found on Manua and Tutuila islands. This species is now recognized as Critically Endangered in American Samoa and Samoa (Hutson et al. 2001, Tarburton 2002), and has not been recorded in American Samoa since 2006 (Fraser et al. 2009). In Tonga, the subspecies was found on Eua and Niuafoou islands and was last collected in 1989. It has not been recorded in more recent surveys (Rinke 1991; M. Pennay, personal communications, 2007 in Scanlon et al. 2014). The species was collected from Espiritu Santo Island, Vanuatu in 1929 and appears to have been extirpated as more recent surveys have failed to detect the species (Helgen and Flannery 2002). In Fiji, E. s. semicaudata was historically found on Fiji’s three largest islands of Viti Levu, Vanua Levu, and Taveuni. It was also known from the Yasawa archipelago, the Lau Group, and Rotuma Island (Ingleby and Flannery 1991; Flannery 1995; Palmeirim et al. 2005, 2007; Scanlon et al. 2014). Unfortunately, the subspecies has declined dramatically across its range in Fiji and now appears to be restricted to Taveuni, the Natewa Peninsula of Vanua Levu, and a few small islands of the Lau Group (Ingleby and Flannery 1991, Flannery 1995, Palmeirim et al. 2005, 2007, Macedru 2010, Scanlon et al. 2014); recent surveys suggest it has been extirpated from Rotuma (Cibois et al. in press). A multinational team is collating leads of bats in caves and launching a systematic effort to confirm the status of cave bats in Fiji and launch proactive and sustainable conservation measures at important roosts (NatureFiji-MareqetiViti pers. comm.).
• E. s. rotensis, was historically found on Guam and the Marianna Islands. Unfortunately, it has been extirpated from Guam, Rota, Saipan, and Tinian (Lemke 1986; Wiles et al. 1995, 2011; Steadman 1999) and is now only known from three caves on Aguiguan Island (approximately 7 km² in size; Welch et al. 2016).
• E. s. palauensis, found on Palau, including Koror, Peleliu, Babelthuap, and Anguar, where it is common. It ranges from sea level up to 210 m asl (Wiles et al. 1997). Additional work in Palau in 2005 found the subspecies to still be fairly common and widespread (G. Wiles, pers comm. 2019). The current status of E. s. palauensis is unknown.
• E. s. sulcata occurs on the islands of Chuuk and Pohnpei in the Caroline Islands, and the subspecies appeared to be relatively common and widespread in good forest habitats on Pohnpei (G. Wiles, pers comm. 2019). The bat has also been observed by tourists visiting the Pahntakai cave on Pohnpei (A. Scanlon, pers comm. in 2018). It is not known if ecotourism ventures disrupt the bats at this site (as occurred to E. s. semicaudata in Yasawas, Fiji). The current status of E. s. sulcata is unknown.

The species was erroneously reported from the Marshall Islands (Helgen and Flannery 2002).

Although there have been no conservation actions to protect this species to date, it is fully protected by legislation in Samoa, Guam, and in the Northern Marianas Islands. Suitable conservation actions for this species include the protection of known roosting caves, and the identification of additional important roosting sites. Surveys are needed on population status and trends, as well as ecology, and threats (e.g., pesticide levels). A proposed survey of fossil remains on many of the southern islands of its historical range could yield potential translocation sites.