Flexible use of visual and acoustic cues during roost finding in Spix’s disc-winged bat Thyroptera tricolor

The ability of an animal to detect environmental cues is crucial for its
survival and fitness. In bats, sound certainly plays a significant role in
the search for food, spatial navigation, and social communication. Yet,
the efficiency of a bat’s echolocation could be limited by atmospheric
attenuation and background clutter. In this context, sound can be
complemented by other sensory modalities, like smell or vision. Spix’s
disc-winged bat (Thyroptera tricolor) uses acoustic cues from other group
members to locate the roost (tubular unfurled leaves of plants in the
order Zingiberales). Our research focused on how individuals find a roost
that has not been yet occupied, considering the urge to find a suitable
leaf approximately every day, during nighttime or in daylight. We observed
the process of roost finding in T. tricolor in a flight cage,
manipulating the audio/visual sensory input available for each trial. A
broadband noise was broadcast in order to mask echolocation, while
experiments conducted at night significantly reduced the amount of light.
We measured the time needed to locate the roost under these different
conditions. Results show that with limited visual and acoustic cues,
search time increases significantly. In contrast, bats seemed capable of
using acoustic and visual cues in a similarly efficient manner, since
roost search showed no strong differences in duration when bats could use
only sound, only vision, or both senses at the same time. Our results show
that non-acoustic inputs can still be an important source of information
for finding critical resources in bats.