Eight bat species were known and documented from the California Channel Islands when J.C. Von Bloeker (1967) presented at the First California Islands Symposium in 1965. Additional bat surveys by P.E. Brown (1980) in the 1970s resulted in “Distribution of bats of the California Channel Islands,” which was presented at the second symposium in 1978. Methods of detecting and identifying bats have changed over the past century. Museum collection methods using shotguns have been replaced by mist-netting and recording of echolocation calls. Currently, capture or acoustic records have identified 14 bat species (56% of the 25 species known to occur in California) on 6 of the 8 California Channel Islands, with occasional sightings of flying bats on Anacapa and San Miguel Islands. Bats now compose 78% of the native mammals on the islands (Collins 2012). Acoustic recording equipment has become smaller and easier to use in the field, and recorded echolocation signals are now recognized as valid “vouchers” if the species emits calls that are separable from others. For example, echolocation signals have identified western red bat (Lasiurus blossevillii), hoary bat (Lasiurus cinereus), western yellow bat (Lasiurus xanthinus), and Mexican free-tailed bat (Tadarida brasiliensis) from San Nicolas Island, and western mastiff bat (Eumops perotis) and canyon bat (Parastrellus hesperus) from Santa Cruz Island. Acoustic data have identified 3 new species for the California Channel Islands, as well as several new records on individual islands. As acoustic monitoring and other techniques are used more extensively, the number of species documented will increase and the proportions that are resident, vagrant, or transient on each island can be better resolved.