Discovery of a new type of behaviour shows that some spiders are really good sailors.
With the exception of the coldest places on our planet, spiders are almost everywhere. From giant bird-eating tarantulas to pin-prick-sized web-builders, from solitary hunters to social colonies, spiders are versatile in more ways than one.
Some of our eight-legged friends on the smaller side of the size/weight scale even know how to fly! Now before you run off in search of an umbrella to protect yourself from an unsuspected spider attack, I should mention that the word ‘fly’ might be a bit too goal-oriented.
Rather than actively flying, some spiders let themselves be carried by the wind via a behaviour known as ballooning. They decide when to leave, but their destination is in the hands of the weather gods alone (and as we all know, those girls and guys are a fickle bunch…)
The water barrier?
This ability, ballooning, or in more technical terms, aerial dispersal, is quite an important feat. It allows spiders to colonise new habitats that are some distance away. However, water is another challenge entirely. Or is it?
Until now, it was thought that spiders weren’t able to deal with a water-landing. But then researchers affiliated with Nottingham University’s SpiderLab took a closer look. They observed spiders from two groups that were known to show ballooning behaviour and discovered that these many-legged marvels were actually pretty decent sailors.
Exploring the seas
In both groups, spiders would adopt an elaborate posture that allowed them to sail the high seas (and other bodies of water, of course). By using their legs or abdomen as a sail, they managed to stay stable even on turbulent salty water. Also, using a silk line they could anchor themselves onto a floating object or to the surface of the water itself.
Given that spiders can get by for a long time without food, an unwanted water-landing doesn’t doom them as was long thought. Spiders that balloon seem to be able to deal with it quite well. This newly discovered ability may well be an important contributor to their potential as colonisers of far-away places.
This cool study is also a great example to illustrate how much there is still left to learn about animal behaviour and how it contributes to our broader understanding of evolution and ecology.
Hayashi M, Bakkali M, Hyde A, & Goodacre SL (2015). Sail or sink: novel behavioural adaptations on water in aerially dispersing species. BMC evolutionary biology, 15 PMID: 26138616