Get this: spiders can “sail” on water

If, last week, you’d quizzed me about the dispersal strategies of spiders, I would have told you all about “ballooning”, how Charles Darwin, at sea on the Beagle in 1832, was stunned to see thousands of tiny, dusky red spiders come floating on board, borne on silky parachutes that trapped them in the rigging. This and other observations led him to conclude that “the habit of sailing through the air” was probably “characteristic of this tribe”.

 I would not, however, have told you that ballooning spiders can sail on water too, because I didn’t know they did until I read a paper out today in BMC Evolutionary Biology. These sailing skills, documented by Japanese research fellow Morito Hayashi and colleagues, make a lot of sense. Earth, after all, is largely water, so aerial dispersal is not a great idea unless you can cope with the presumably frequent fate of alighting on water.

Working in the “SpiderLab” at the University of Nottingham, Hayashi put hundreds of spiders from more than 20 different species “in a shallow tray filled with water to 1cm height”. When buffeted by “pump-generated air (i.e. wind)”, “spiders actively adopt postures that allow them to use the wind direction to control their journey on water,” he says. They are competent sailors even in salty and turbulent condition, the researchers find.

The paper describes five different water-related behaviours. Here they are:

1) Sailing

Sailing spiders raise their legs to create a kind of sail. “Sailing spiders smoothly and stealthily slide on the water surface without leaving any turbulence,” note Hayashi and co.

2) Upside-down sailing

This demands a “handstand-like posture”, the spider using its abdomen rather than legs to catch the wind.

3) Anchoring

Silk is released onto the surface of the water. This slows down the spider’s movement and may help tether the spider to the relative safety of a floating object

4) Walking

It’s just that, the spider rapidly propelling its legs in an effort to walk on the surface. [Re-reading Darwin’s account of the dusky red spiders he encountered off the coast of South America, it looks like he observed them walking on water: “The little aeronaut,” he wrote in his Journal of Researches, “could run with facility on the surface of water.”]

5) Death mimicry

“Death mimicry behaviour is likely to be a predator avoidance strategy, as is common to many animals.” Essentially, the spider touches the water and freezes. But owing to its water-repellent feet (see the dimples on the surface of the water), it still floats.

In a related investigation, the researchers collected data on ballooning. Those individuals and species that showed a readiness to balloon their way off a dry surface were also the ones with the greatest talent for sailing. “The sailing behaviour is almost completely associated with, and possibly a requirement for, the aeronautic behaviour,” they conclude.

“Being able to cope with water effectively ‘joins the dots’ as far as the spider is concerned,” says Sara Goodacre, head of the SpiderLab and a co-author on the paper. “It can move from one land mass to another, and potentially across huge spatial scales through the air,” she says. “If landing on water poses no problem then in a week or two they could be a long way away from where they started.”

Darwin would have loved this, a neat set of observations that helps explain why spiders are amongst the first to colonise new habitats and why many species are found all the way around the globe. They haven’t just been flying. They’ve been sailing too.

Happy birthday, Jia Jia: Hong Kong giant panda becomes oldest ever

It may not be considered a landmark birthday for humans, but turning 37 has made Hong Kong’s Jia Jia the oldest ever giant panda in captivity, and she celebrated in style.

Jia Jia is said to be still mobile but suffering from high blood pressure. Photograph: Bobby Yip/Reuters

 The equivalent of more than 100 years old in human terms, Jia Jia was presented with a towering birthday cake made from ice and fruit juice with the number 37 carved on top, in her enclosure at the city’s Ocean Park theme park.

“Jia Jia has achieved two Guinness world record titles – the oldest panda living in captivity and the oldest panda ever living in captivity,” said Blythe Ryan Fitzwilliam, adjudicator of Guinness World Records, during a ceremony at the park.

He offered her his congratulations, saying it was an “amazing longevity achievement”.

Jia Jia was born in the wild in Sichuan, China, in 1978 and was given to Hong Kong in 1999 to mark the semi-autonomous city’s handover by Britain two years earlier.

The previous record was held by a male panda called Du Du, who was also caught in the wild and died in July 1999 aged 36 in a zoo in China’s Hubei province.

Vet Paola Martelli said Jia Jia was still “moving about” though she suffered from cataracts and high blood pressure. “She is sleeping more, so is doing everything less. But she is ageing gracefully, just like your grandma,” she said.

Jia Jia. Photograph: Bobby Yip/Reuters

Because she eats less bamboo she relies on fibre supplements, Martelli added.

Jia Jia, whose name translates as “excellence”, picked at fruit slices and bamboo around the ice cake to celebrate her big day.

Although the exact birth dates of Du Du and Jia Jia are unknown because they were born in the wild, Guinness said that based on the evidence, they concluded that Jia Jia had claimed the title by a few months.

There are fewer than 2,000 pandas now left in the wild, according to the World Wildlife Fund, as their habitats have been ravaged by development. Roads and railways cut through the bamboo forests they depend upon in China’s Yangtze Basin, their primary habitat. Pandas rely on bamboo and eat almost nothing else.

Given their low birthrate, captive breeding programmes have become key to ensuring their survival.