Tangled Web

Snakes & Ladders - Painted quilt Artist: Denise Furnish

Snakes & Ladders – Painted quilt
Artist: Denise Furnish

Like weeds, when we talk about invasive species, we usually know which ones we mean. They’re the ones we don’t like.

So, when we talk about non-native species of plants and animals, we don’t usually mean horses or sheep, or wheat or barley or rice or potatoes – none of which are native to many of their current habitats around the world.

No, we mean animals like the albino California kingsnakes (Lampropeltis getula californiaeon the Spanish island of Gran Canaria, the progeny of escaped pets which are now decimating the native birds and lizard populations.

Or the voracious demon shrimp (Dikerogammarus haemobaphes), a Black Sea native that has been discovered in UK waterways, and whose impact on native species is as yet unknown.

As of April 2014, the European Parliament has approved new legislation aimed at controlling and eradicating non-native species that are considered damaging enough to be considered ‘invasive’ and dangerous to the survival of native species.

Albino California Kingsnake

Albino California Kingsnake

Originally planned to be capped to fifty species, the blacklist will be now be unlimited, because there are simply too many species having a negative impact on native European biodiversity.

But what about the common rhododendron (Rhododendron ponticum)? While it’s not native to the United Kingdom, it has been widely used in hybrids, and is a well-liked botanical addition to gardens. And like many non-native garden favorites, it can be wildly successful at escaping and carpeting indigenous habitats.

If it makes the black list, will all varieties be banned? And how would that affect gardener’s preferences and choices – or the nurseries that breed rhododendron hybrids? Pet or plant, we always want what we want, when we want it.

Non-native species might be beloved as a domesticated varieties, but only as long as they obey our arbitrary rules of life, reproduction and geographical spread. Which they don’t, and almost never do.

Rhododendron ponticum, native to southern Spain, covers a hillside in Snowdonia, UK Photo: M Williamson

Rhododendron ponticum, native to southern Spain, covers a hillside in Snowdonia, UK
Photo: M Williamson


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