Morning briefing: 10 stories from around the world

1 Ukrainian pilot released

During the nearly two years that she was imprisoned in Russia, Ukrainian pilot Nadezhda Savchenko became a national hero in absentia, lauded for her flinty defiance. Today she made a celebrated return to the country still embroiled in a fight against Moscow-backed separatists. Savchenko, who was captured by rebels in June 2014 and then resurfaced in Russian custody, was convicted in March and sentenced to 22 years in prison for complicity in the deaths of two Russian journalists. Prosecutors alleged she was acting as a spotter for mortar fire that killed them. Savchenko was released after a pardon from President Vladimir Putin. In turn, Ukrainetoday released two Russians who had been convicted of waging war in eastern Ukraine.

2 Ordered to shake hands

A school board in northern Switzerland said that two Muslim boys who have refused to shake hands with their female teachers for religious reasons can be required to do so, ruling that their parents could face fines of up to 5000 Swiss francs if they don't. A public school in the northeastern Therwil municipality had sought the regional school board's advice after accepting the boys' belief that they should only willingly touch the women whom they will eventually marry. The school had temporarily exempted the teens from shaking hands with teachers.

3 Hiker survived 26 days

Documents show an Appalachian Trail hiker whose remains were found last year in Maine survived at least 26 days after getting lost. During that time, her texts went undelivered because of poor cell reception. The Boston Globe reports that Geraldine Largay kept a journal in which she acknowledged that she expected to die and that it might be years before her remains were found. The Maine Warden Service released more than 1500 pages of documents today under a Freedom of Access request by several media organisations. The Brentwood, Tennessee, woman got lost after going off the trail in July 2013, presumably, wardens believe, to relieve herself. Her remains were found in October 2015 in Redington Township. The medical examiner determined she died of starvation and exposure.

4 Big cat flap

Two South African campers had a close encounter with lions who licked the tent they were in at a campsite in Botswana. Danie and Fransie Lubbe said that they were in their tent at the Kgalagadi Transfrontier Park this month when they heard a sound and looked outside to see two female lions licking the moisture off the tent's canvas. A third lioness was nearby. "My wife said 'There are lions at the tent!"' said Danie Lubbe. She closed the tent flap, but Danie quickly reopened it to see the lions right at their tent. "We were actually more excited to have them so close than being scared in their presence," said Fransie Lubbe. "I think it was a very big privilege to be in their presence, so close to nature."

5 Mugabe should 'rule from the grave'

Thousands gathered in Zimbabwe to support President Robert Mugabe, with speakers calling for him to rule for life. On buses, trains, trucks and by foot, Mugabe's supporters travelled to the capital, Harare, for the rally. Speakers said 92-year-old Mugabe should rule until he dies. His wife, Grace, went a step further and described how she would like to see him rule from the grave, prompting wild cheers from the crowd.

6 Why size matters - to fruit flies

For a long time, the debate has gone on: Does size matter to females? Biologists now say, definitively, that it does. Among fruit flies. At issue is the fruit fly sperm, which is gargantuan in the tiny world of that speck-sized insect. A fruit fly's sperm is 5.8cm long, or about 23 times longer than its body. It's about how the females genetically evolve their bodies to get the biggest and best sperm possible out of males, according to a new study by the journal Nature. Over time, female fruit flies have encouraged the production of bigger sperm by themselves developing larger organs or receptacles to store the sperm to later fertilise eggs. Smaller sperm get pushed out as the female mates voraciously with lots of males.

7 Louvre selfies with difference

French street artist JR has made the famous Louvre Pyramid in Paris disappear in an optical illusion. The artist covered the huge glass pyramid with a trompe l'oeil installation that makes it seem as if the monument at the heart of the courtyard has disappeared. Tourists jostled to take the historic selfie of the Louvre without the visible glass structure for the first time in the digital age. The black and white installation depicting the east side of the Napoleon courtyard features on the front of the once-controversial pyramid designed by Chinese-American architect I.M. Pei in 1989.

8 No new Greek crisis

It's all but official: this year's Greek crisis has been called off. After an 11-hour meeting, European officials agreed to unfreeze more rescue loans and to consider ways to lighten Greece's debt load. That means Greece stands to get €10.3 billionfrom its bailout loan package from European governments and the International Monetary Fund. The money means Greece can make debt payments coming due in July. There won't be fears of a disastrous default and forced exit from the euro currency, as there were before Greece sealed a similar deal in July, 2015.

9 Stone rings 176,500 years' old

Two mysterious stone rings found deep inside a French cave were probably built by Neanderthals about 176,500 years ago, proving that the ancient cousins of humans were capable of more complex behavior than previously thought, scientists say. The structures were made from hundreds of pillar-shaped mineral deposits, called stalagmite. They were discovered by chance in 1990,because a rockslide had closed the mouth of the cave at Bruniquel in southwest France. Using sophisticated dating techniques, a team led by archaeologist Jacques Jaubert of the University of Bordeaux, France, found that the stalagmites must have been broken off the ground around 176,500 years ago "making these edifices among the oldest known well-dated constructions made by humans."

10 Driver finds wrecked sub

An Italian diver claims to have located the long-lost wreck of the British submarine HMS P311, which was downed off Sardinia during World War II. Diver Massimo Bondone told the La Nuova Sardegna he found the P311 at a depth of 80m off the isle of Tavolara during a dive last weekend. Paola Pegoraro of the Orso diving club, which provided logistics for the dive, said the sub was positively identified by the two Chariot "human torpedoes" affixed to the outside.

- agencies