Because we can’t bring back extinct prehistoric life-forms (yet), gators are one of the closest possible creatures to study — which is why a few got high on ketamine and plugged into earbuds.
Dinosaurs are closely related to birds and diapsids (certain reptiles like lizards, snakes, crocodiles and of course, alligators). Gators and birds are also direct relatives of archosaurs, which were crawling all over during the Triassic period. This is why scientists used them to study their neural maps, the passages that information about soundwaves gets zapped through.
What the team of researchers, led by biologist Catherine Carr and neuroscientist Lutz Kettler, were looking at was the the gators’ interaural time difference (ITD), the lag in a sound’s arrival time to each ear. Those few microseconds are critical in telling animals where sounds are coming from. Knowing where a rustle or splash originated can tell a gator where its next meal is lurking.
“Birds are dinosaurs and alligators are their closest living relatives,” Carr, who recently published a study in the Journal of Neuroscience along with Kettler, explained to Motherboard. “Features shared by both groups might reasonably be inferred to have been found in extinct dinosaurs so we assume dinosaurs could localize sound.”
Birds evolved differently from mammals when it came to localizing sounds, so Carr and Kettler wanted to see if their much scarier cousins had a similar ITD. This is why they anesthetized 40 American alligators with ketamine and demedetomidine to keep them from chewing anyone’s arm off. When the gators were knocked out, they were fitted with earbuds in their ear flaps and had electrodes stuck on their heads.
Would anyone have dared do this to a T. Rex if those were still roaming the earth?
Those electrodes must have made the gators look like reptilian hospital patients, but they were actually recording the scaly carnivores’ auditory neural responses to a series of tones and clicks they subconsciously heard through their earbuds. To keep them from freaking out, nature sounds were played in the background.
“One important thing we learn from alligators is that head size does not matter in how their brain encodes sound direction,” Kettler told Motherboard.
Another thing they found out was that out alligators hear much like birds. Though their brain anatomies are hardly alike, they still use similar neural mapping systems to locate sounds. This means the inner ears and brains of archosaurs probably functioned the same way.