Because we can not bring back extinct prehistoric forms of life yet, alligators are one of the closest possible creatures to study – that's why some people went after ketamine and were hooked on atria.
Dinosaurs are closely related to birds and diapsids (some reptiles such as lizards, snakes, crocodiles and of course alligators). Gators and birds are also direct relatives of the archosaurs, which crawled everywhere during the Triassic Period. This is why scientists have used them to study their neural maps, the passages through which information on sound waves is zapped.
The team of researchers, led by biologist Catherine Carr and neuroscientist Lutz Kettler, was interested in the inter-temporal time lag (ITD) of gators, the one-hour delay of sound arrival at each ear. These few microseconds are essential for telling animals where the sounds come from. Knowing where a rustling or splashing comes from can tell an alligator where his next meal is hiding.
"Birds are dinosaurs and alligators are their closest living relatives," said Carr, who recently published a study in the Journal of Neuroscience with Kettler, explained to the motherboard. "One could reasonably assume that features common to both groups were found in extinct dinosaurs, so we assume that dinosaurs could locate the sound."
As birds evolved differently from mammals when it came to locating sounds, Carr and Kettler wanted to know if their much more frightening cousins had a similar ITD. That's why they anesthetized 40 American alligators with ketamine and demedetomidine to keep them from chewing anyone's arms. When the gators were knocked out, they put earphones in the ear cups and electrodes remained stuck to the head.
Would any one have dared to do that to a T. Rex if they were still wandering on the earth?
These electrodes had to make the gators look like reptilian hospital patients, but they were recording the auditory neural responses of the scaly carnivores to a series of sounds and clicks they had unconsciously heard through their earpieces. To prevent them from panicking, sounds of nature were played in the background.
"One important thing that alligators tell us is that the size of their head does not matter in the way their brains code the direction of sound," Kettler told Motherboard.
They also discovered that alligators hear much better than birds. Although their cerebral anatomies are not very similar, they still use similar neural mapping systems to locate sounds. This means that the ears and brains of the archosaurs probably worked the same way.
For the moment at least, it's the closest we can discover to know how T. Rex could hear without a time machine or the other reality of Jurassic Park.
(via the motherboard)