Figure 7.

The clutter–masking trade-off. Scheme showing the effect of masking on bat echolocation calls along the duration–intensity axis. The grey oval represents the natural repertoire of the bats. In our flight room, with no clutter and no masking, bats used calls from the middle of this repertoire (1). Clutter drives the calls to be shorter and less intense (2), but when masking is added to clutter, the bats are ‘pushed’ back towards the centre (3). Masking without clutter causes bats to use longer and more intense calls (4), which are also typical for more open environments.