Before 2016, Northwestern biological sciences professor Gary Galbreath worked with dead snakes only found in museums. But from 2016 to 2017, his research off the coast of Costa Rica, where he contributed to the description of a new subspecies of yellow sea snake, involved not just live but venomous reptiles.
Galbreath didn’t participate in much of the field work himself; he was more involved with measuring specimens in museums and analyzing the existing literature about the hydrophis platurus species. He describes the conditions under which his colleague went out to record data as treacherous, though.
“These snakes feed at night, so she was bobbing around in a little boat in the middle of the night in turbulent waters, hand-catching poisonous snakes and measuring them alive before releasing them,” he said. “It was quite a feat.”
His colleague was wildlife expert and author Brooke Bessesen, who has done extensive research in the Golfo Dulce, a tropical fjord off the coast of Costa Rica. Her research has focused on various species of animals native to the area. Galbreath and Bessesen met in 2016 at a museum, just a short time before they began discussing collaborating on the research that would successively describe a new taxon of sea snake native to the gulf and get published a mere year and a half later.
“We thought we might be dealing with a new definable variety of snake,” Galbreath said of his initial discussions with Bessesen. “As we acquired more data, it became striking how distinct these snakes are.”
The snakes Bessesen and Galbreath centered their research around, the hydrophis platurus xanthos subspecies, exist only in the Golfo Dulce. The waters in this area are warm and turbulent, a sharp contrast to the colder and calmer waters of the nearby Pacific Ocean. The snakes’ closest relatives, hydrophis platurus, inhabit the Pacific. Their yellow stomachs and a black scale pattern on their backs make them easily recognizable. They hunt in still waters and utilize a flat stretched position when catching their prey.
In contrast, the new subspecies of xanthic individuals described by Bessesen and Galbreath is entirely yellow, prefers choppier waters as their hunting grounds and catches their food in a curved S-shaped position.
So how did these changes come to occur? According to Galbreath, the unique aquatic conditions of the Golfo Dulce may have contributed to a much quicker natural selection process than might occur in other environments.
He and Bessesen hypothesized that the poorly oxygenated and relatively warm waters of the Golfo Dulce likely intensively selected snakes that could actually breathe and feed in a very localized and distinguished environment from the Pacific Ocean.
“If you have significant enough differences in survivability, which in turn affect reproduction, you can have populations becoming more and more different just within a century or two, and certainly within thousands of years,” he said.
While there remains a lot to learn about the new taxon, Bessesen and Galbreath also wrote about potential actions that could be taken to ensure the continued survival of this subspecies, which has a very narrow geographic range, in a time when climate change and human behavior is massively impacting wildlife around the globe.
“Our interest is in preserving the entire ecosystem as intact as possible,” Galbreath said. He indicated that the yellow sea snakes don’t currently face an imminent threat to their survival, but multiple factors such as hunting by collectors, overfishing and climate change could eventually have a detrimental effect on their numbers.
“We need to know a lot more about these snakes,” Galbreath said. He described their relative densities at different depths, their population distribution within the gulf and the extent to which genetic interchange with the subspecies’s closest relative might be possible as data still to be collected by scientists in the coming years.
“A couple years from now, we might have a much better idea of specific practical things that could be suggested for the conservation of these animals,” he said. “There’s a lot still to find out about them.”