An experiment that hung rhinoceroses upside down to see what effect it had on the animals has been awarded one of this year's Ig Nobel prizes.

Other recipients included teams that studied the bacteria in chewing gum stuck to pavements, and how to control cockroaches on submarines.

The spoof prizes are not as famous as the "real" Nobels - not quite.

The ceremony couldn't take place at its usual home of Harvard University in the US because of Covid restrictions.

All the fun occurred online instead.

The science humour magazine, Annals of Improbable Research, says its Ig Nobel awards should first make you laugh but then make you think.

And the rhino study, which this year wins the award for transportation research, does exactly this. What could seem more daft than hanging 12 rhinos upside down for 10 minutes?

But wildlife veterinarian Robin Radcliffe, from Cornell University, and colleagues did exactly this in Namibia because they wanted to know if the health of the animals might be compromised when slung by their legs beneath a helicopter.

It's an activity that increasingly has been used in African conservation work to shift rhinos between areas of fragmented habitat.

However, no-one had done the basic investigation to check that the tranquillised animals' heart and lung function coped with upside-down flying, said Robin.

He told BBC News: "Namibia was not the first country to move rhinos upside down with helicopters, but they were the first to take a step back and say, 'hey, let's study this and figure out, you know, is this a safe thing to do for rhinos?"

And so, his team, in collaboration with the Namibian Ministry of Environment, Forestry, and Tourism, suspended 12 tranquillised black rhinoceroses by their feet from a crane, and measured their physical responses.

It turns out, the animals coped very well. In fact, there was evidence the rhinos did better in this usual position than simply lying chest down or on their side.

"I think the reason for that is, when a rhino is on its side, you have positional effects of blood flow. So in other words, the lower parts of the lung are getting lots of blood flow for gas exchange, but the upper part of the lung, just because of gravity, is not getting perfused well, so when a rhino is hanging upside down, it's basically like it's standing upside up; the lung is equally perfused.

"We've also seen that rhinos that are on their side too long, or on their sternum, especially - they get muscle damage, they get myopathy, because they're so heavy. And there's no pressure on their legs, other than the sense of the strap around their ankle," Robin explained.