They began by anaesthesizing the cobras and inserting tiny electrodes in the necks of cobras to measure the electrical activity of different muscles after the snakes came to and flared their necks.
The researchers write about the process in the current “Journal of Experimental Biology.”
During the study, eight muscles were identified as key in opening the hood; the levator costae and the intercostal muscles.
“A second set of muscles connecting ribs to skin primarily keep the skin taut, rather than to displace the ribs relative to the vertebrae,” the authors say in their paper’s abstract. “A third set of muscles coursing between ribs function primarily to transmit forces between adjacent ribs rather than to move ribs.”
Kardong, who for decades has worked out of a lab filled with snake cartoons and the trademark sound of wary rattlesnakes, says the research is aimed at answering larger questions of how animals redesign themselves over time.
“We are an example of a co-opted, remodeled system,” he says, referring to humans. “So is the cobra, but simpler.”
He says the cobra’s ancestors would have already had venom 30 or 40 million years ago. Over time, the cobra developed a threatening display because some predators have methods for getting around a snake’s strike a seemingly low-tech tool with a lot of high-tech biology behind it. The snake also developed an eye-spot in the center of its hood, enhancing its intimidation.