Natterer's bat is found in the same sort of buildings as the Long-eared bat but use different areas. If a bat is flying inside a building it is possible to hear the bats echolocation as the lowest calls are just inside our range of hearing. The sound is very quiet but has a slight 'pain' associated with it. This bat used to have the nickname of 'red armed bat' due to the pinky/red colour of the limbs. Another characteristic of the bat are its pink ears that jut out beyond the tip of the nose. The face is quite long and almost naked. The tail membrane has hairs along the edge. The fur, which is thick and woolly, is a dark sand colour on the back and contrasts with the almost white fur underneath.

Forearm 36 - 43mm / 1 - 1 ½ inches
Length 40 - 50mm / 1 ½ - 2 inches
Weight 7 - 12g / 1/3 oz

The favored roost site for these bats is in traditionally built barns that have a loft. Sometimes they are found in large wooden buildings and roost in gaps between timber joints.

• Emergence: late dusk approximately 1 hour after sunset. Compare emergence to other N. Irish bats.

• Flight: Low (1-6m) above ground level, wing beat slow, sometimes whirring, highly manoeuvrable in confined spaces - often 'flipping' - changing direction very quickly. Also able to hover for short periods.

• Habitat: relatively dense woodland, also above water. Over water, usually forages slightly higher than Daubenton's bat, often making sudden turns and taking insects in the air. Associated more with less calm water bodies. Also forages among tree branches, always with sharp turns. It is a foliage gleaner taking day-active insects from surfaces. Frequently this species gleans away from linear features in open fields and other grassland.

• Heterodyne: Echolocation calls of Natterer's bat are similar to Daubenton's bat. However, it sounds more like the gentle sound of stubble burning - this may be related to the habitat in which it is foraging. Echolocation is loudest at 50 kHz. It is often the case that this bat passes unnoticed. The pulse repetition rate is very high and is the most irregular of the three Myotis species.

• Time expansion: Calls are of very short duration and are extremely wideband. The FM sweep is often extremely linear. Often has strong harmonics. Occasionally during the mating season social calls can be heard although the function of these is unknown. See and hear time expanded call.