What do echolocating animals eat? Is there any evidence that echolocating animals terminate attacks on some prey which means rejecting some items without making physical contact? Evidence of this kind would provide a clear indication of the discrimination powers of the echolocating animal. How much variability is there in the diets of echolocating animals and how does this mirror prey availability. These matters bear on the discrimination ability animals can achieve through echolocation.
We need evidence obtained from moving animals responding to moving targets, the normal situation for hunting bats or dolphins under many circumstances. For the same reason, we need to know how echolocating animals perform in clutter and how (if?) they adjust their sounds according to the situation. Central to this matter is the question of variability in call design.
The question of call design and variation must be considered in the context of the role of echolocation calls in communication. How much of the variation in call design can be attributed to communicative effects?
What is the role of echolocation in the lives of facultative echolocators?
Do fish and other marine organisms show parallels to the hearing—based defense common in many nocturnal insects?
There are excellent opportunities for collaborative field work involving researchers studying echolocators and their prey. Such collaboration often can produce more effective results than studies approaching the question from one point or another.