Snake Compass

Python skeleton Source: Worrapol Koranuntachai /123rf

Python skeleton
Source: Worrapol Koranuntachai /123rf

Burmese pythons (Python bivittatus) are a successful invasive species in Florida that have been profiting from local wildlife and few natural predators. Native to Southeast Asia and listed by the IUCN as vulnerable or endangered in their original habitats, abandoned or escaped pythons have been thriving in the Florida Everglades, to the dismay of conservationists trying to protect indigenous species there. Not much is known about how the snakes move or take up a new residence.

As it turns out, pythons have a distinct sense of  direction and territory when it comes to their habitat. A recent study published by the Royal Society journal Biology Letters suggests that pythons use a homing instinct to venture out from their usual territory and then find their way back.

A research team tracked several pythons – some of them trapped and removed miles away from their territories, some left in their adopted areas – to see whether the snakes that had been removed would be able to find their way home.

Source: Deimos in Flames / Deviantart

Source: Deimos in Flames / Deviantart

And indeed, all the relocated snakes demonstrated great determination to return to where they’d been captured in the first place. Most of them succeeded in finding their way back. The snakes which had been tagged and released without relocation moved around within a much more limited area, usually returning to their own territory.

The snakes clearly have both a ‘map sense’, which tells them where they are in relation to ‘home’, and a ‘compass sense’, which tells them in which direction to guide their movement. And it’s likely that this ability isn’t limited to the Burmese python – snake navigational abilities just haven’t yet been widely studied across many species.

According to this article, researchers say the internal python map “could be magnetic, like sea turtles, while the compass could be guided by the stars, olfactory (smell) cues, or by polarised sunlight – all of which have been shown to be used by reptiles.” Gaining knowledge of how snakes travel and navigate should prove useful in controlling their spread.

What I find interesting is how well the Burmese python has adjusted its internal compass to an entirely new corner of the planet from where it evolved. Having said that, another study published late last year suggests that Burmese pythons are among the most rapidly evolving vertebrates in the world.

How did the Burmese python learn to redefine home so quickly?

Source: gortan123/123rf

Source: gortan123/123rf

Twilight and Sunstones

 

Arctic sunset Photo: Patrick Kelley/USGS

Arctic sunset
Photo: Patrick Kelley/USGS

I freely admit that I can follow a map well enough, and also know the most rudimentary basics of navigating by the sky. Still, I managed to get lost yesterday, even with a Google map and the chipper assistance of voice GPS. I can only offer as an excuse that I was headed up a remote Swiss valley and there were a few too many roundabouts. In the end I followed my nose, the Luddite’s rudder, and found my way (more on this trip along the Absinthe Trail another time).

In the case of the Vikings, some of their navigational technology has remained a mystery for centuries. Researchers have been working to decipher what is assumed to be an 11th-century navigational device. The Uunartoq artifact, a broken half-disc of engraved wood, was found beneath a Benedictine monastery in Greenland in 1948. It was long thought to be a compass of some kind.

A recently published paper goes one step further, and suggests that the Uunartoq piece is something a bit more exotic – it could be a twilight compass, capable of guiding mariners by the sun, even when the sun is below the horizon.

A calcite stone, also known as a 'sunstone'. These stones are birefringent, which means that they have 2 refractive indexes. A light beam that enters such material is refracted at two different angles. Caption/Photo: Ricardo Esplugas

A calcite stone, also known as a ‘sunstone’. These stones are birefringent, which means that they have 2 refractive indexes. A light beam that enters such material is refracted at two different angles.
Caption/Photo: Ricardo Esplugas

Aligning compass points using two ‘sunstones’, crystals which have two refractive points rather than one, the plate might have caught light sources no longer visible to the human eye. Not necessarily an instrument of extreme precision, but something that could keep a ship more or less on course until the sun came up again and new measurements could be taken.

This medieval sea navigation makes a deep impression on me. Once painstakingly learned, how was this precious information passed along within cultures and across generations?

And, just as intriguing, how was something this valuable ever lost and forgotten?

Sun compass vs. twilight compass Via: CAnMove

Sun compass vs. twilight compass
Via: Proceedings of the British Royal Society via CAnMove