Burmese pythons living in south Florida have a homing instinct that allows them to navigate distances of 20 or so miles back home. And of course “home” is used loosely, since Burmese pythons are invasive in Florida, as we well know.
A team led by Shannon Pittman of Davidson College in North Carolina captured 12 adult Burmese pythons (Python molurus bivittatus) in Everglades National Park and surgically implanted radio transmitters. As a control, they returned half of the giant snakes back to where they were captured and turned them loose. The other six were taken 13 to 22 miles from their capture locations.
The translocated snakes oriented their movement homeward and maintained their bearings as they traveled, making progress on most days. They seldom strayed any more than 22 degrees from the correct path.
It took between 94 and 296 days, but five of six snakes returned to within 3 miles of the original capture location. (The sixth one at least moved in the right direction.) Compared with the more random movements of the control snakes, the displaced snakes moved straighter and faster, and displayed structure that indicated oriented movement. They were on a mission, traveling nearly 1,000 feet a day, while the control snakes averaged about 300 feet.
“Navigating back to a home location after displacement requires a map sense, to determine position relative to home, and a compass sense, to maintain oriented movement towards home," Pittman tells New Scientist. Local cues at the release site help them understand where they are in connection to home (map sense), and cues along the way guide them along the right track (compass sense).
The researchers don’t know what those cues are just yet. The map may be some magnetic force, and the compass could be guided by smell, light, or even the stars.
"We know that snakes tend to come back to some of the same sites throughout their lives – such as overwintering locations or refuges," Pittman tells BBC. Staying in familiar territory may help them find prey and mates, and their “map and compass sense” allows them to return home after exploratory forays.
While the journeys of homing pythons might seem modest compared to the incredible journey of Shadow, Chance, and Sassy in Homeward Bound, this is the first demonstration that big snakes can navigate at all, and these distances are way longer than any other snake has been known to travel. “This is way more sophisticated behavior than we’ve been attributing to them,” study coauthor Frank Mazzotti of the University of Florida says in a press release.
The work was published Biology Letters this week.
Image: Everglades National Park / NPS