Bats make up almost one quarter of all mammals species on earth. While many of the more than 1,300 species are thriving, others are endangered and facing extinction. In Britain, for example, several of the 18 bat species have declined significantly within the past 70 years. A British bat conservationist hopes to better understand the habits of those waning populations by using thermal imaging to track the nocturnal creatures. VOA's Deborah Block has more.