Sunday, March 23, 2014
Homing & navigation in the invasive Python bivittatus
By Mickie Andersson, University of Florida News Center
GAINESVILLE — If you pick them up and drop them in a new location, most snakes will move rapidly but erratically, often traversing the same terrain before giving up and settling into their new digs.
A team of researchers including scientists from the University of Florida has discovered that the giant snakes — which have invaded and affected the food chain in Everglades National Park and Big Cypress National Preserve — can find their way home even when moved more than 20 miles.
The findings, published last week by the Royal Society’s Biology Letters, change how researchers understand pythons’ behaviors and intellect.
“This is way more sophisticated behavior than we’ve been attributing to them,” said Frank Mazzotti, a UF wildlife ecology and conservation professor based at the Fort Lauderdale Research and Education Center. “It’s one of those things where nature makes us go ‘wow.’ That is truly the significance of this.”
In 2006 and 2007, researchers captured 12 pythons and surgically implanted radio transmitters that allowed them to track the snakes’ movements. As a control group, they returned six of the snakes to the spot of their capture and turned them loose.
The remaining six snakes were taken to spots ranging from 13 to 22 miles away from where they had been captured and turned loose. To the researchers’ surprise, the snakes oriented themselves toward “home” and maintained their bearings as they traveled.
And although it took between 94 and 296 days for five of the six snakes to get within three miles of home, partly due to it being the snakes’ dormant season, the reptiles kept that orientation — a clear signal to scientists that the snakes have both “map” and “compass” senses.
The relocated snakes appeared to use local cues at the release site to understand their position relative to home (the map sense), and appeared to use cues along the way (their compass sense) to ensure that they remained on track, although the researchers don’t yet know what those cues are: smell, perhaps the stars, light or some kind of magnetic force.
Mazzotti said it’s helpful for researchers to know that the snakes move purposefully through their environment, but in reality, it’s not that much help.
“It amps up a little bit our concern about the snakes, but given all the other things we know about pythons, the amount of increasing concern is minor,” he said.
The Burmese python has been an invasive species in South Florida since about 2000, likely stemming from accidental or purposeful releases by former pet owners. The largest python found in the Everglades area had grown to more than 18 feet.
The snakes suffocate and eat even large animals, such as deer and alligators, and in 2012, a research team that included Mazzotti found severe declines in sightings in python-heavy areas of native animals including raccoons, opossum, bobcats and rabbits.
In 2012, the federal government banned the import and interstate trade of four exotic snake species: the Burmese python, the yellow anaconda, and North and South African python.
Pittman SE, Hart KM, Cherkiss MS, Snow RW, Fujisaki I, Smith BJ, Mazzotti FJ, and Dorcas ME. 2014. Homing of invasive Burmese pythons in South Florida: evidence for map and compass senses in snakes Biol. Lett. March, 2014 10 3 20140040; doi:10.1098/rsbl.2014.0040 1744-957X.
Stickel, WH. Cope JB. 1947. The home ranges and wanderings of snakes. Copeia, 127-136.