The use of sound echoes to detect objects in the environment. By comparing the outgoing pulse with the returning echoes the brain can produce images of the surroundings. (Gareth Jones, 2005)
The following Vertebrates use echolocation to some degree: bats, dolphins, shrews, some birds, and whales.
Figure 1. The dorsal view of a fossilized skeleton of the late Eocene bat: Onychonycteris finneyi. It was found at the Green River Formation in Wyoming (Simmons et al 2007).
Bats are flying mammals in the order Chiroptera (meaning ‘hand-wing’ in Greek). This is further broken down into two suborders: Mega- and Microchiroptera. The former are known as the old world fruit bats, and are unable to echolocate except for very few species of the genus Rousettus. Instead, Megachiroptera rely on vision and smell to find fruits and nectars. With a few species using a click echolocation. Most species of bats in the suborder Microchiroptera, also known as Echolocating bats, however, rely heavily upon echolocation because they are insectivores. Only very few species eat fruits and nectars.
Because of the similarities in flight mechanisms between both suborders, and one’s almost complete lack of echolocation, there is a huge debate about how both suborders evolved. One hypothesis is that both suborders had a common ancestor. However if this were the case, why have the old world fruit bats lost both the ability for echolocation and all traces of the anatomical adaptations that would have made it possible? Another hypothesis is that they evolved separately, suggesting convergent evolution. But given a mammal forelimb, how many ways could it develop into a wing? Is it plausible that flight evolved twice in mammals? Though this is a very intriguing debate, we will not be focusing on it in this website. Instead, we will provide an in-depth view into Microbat echolocation through the lens of Tinbergen’s four questions.
A visual representation of Tinbergen's 4 questions. Image from Dr. Suzy Renn