In a paper published by The Journal of Neuroscience, biologists Lutz Kettler of the Technische Universität München and the University of Maryland's Catherine Carr explain how they gave alligators Ketamine and headphones to gain insight on the auditory systems of dinosaurs. According to the scientists, this study was designed to help navigate the "neural maps" of alligators to learn how these animals (whose ears are located behind their eyes) identify different sounds.
The emphasis of the experiment was on the interaural time difference (ITD), which measures the time between the origin of a noise and when that sound gets to each ear. By using Ketamine, the team led by Kettler and Carr were able to put 40 alligators in a euphoric state long enough give each gator a pair of earbuds that record the ITD. From this they not only learned more about the animals' prehistoric predecessors, but they also found another connection between reptiles and birds.
Crocodilia—which includes alligators and crocodiles—is one of the oldest animal orders that exist today. They have roamed the earth for roughly 250 million years and are the closest living relatives of dinosaurs. The second oldest is birds. As a result of their difference in appearance and habitat, scientists have been searching for the missing link between reptiles and the avian animals. Although the result of this experiment doesn't pinpoint an exact relative, it does further confirm that the two species are family.
"We conclude that the available acoustic cues and the architecture of the acoustic system in early archosaurs led to a stable and similar organization in today's birds and crocodiles," the paper's abstract reads. "Although physical features, like internally coupled ears, head size or shape, and audible frequency range, vary among the two groups."