Marriage isn't easy, is it? Even the closest of relationships can hit hard times. Imagine, then, seeing the same wrinkly old face over the breakfast trough day in, day out, for more than 115 years. You'd be entitled to have the odd off day, surely?
But zookeepers in Austria are now increasingly worried that the world's longest animal "marriage" could be at an end --and they have no idea why.
Poldi and Bibi, two rare giant Galapagos tortoises, arrived in Klagenfurt am Worthersee, capital of Carinthia, Austria's most southerly province, in 1976 from Basel Zoo, Switzerland. At that time zookeepers guessed they were already between 80 and 100 years old and had spent their whole lives together from just after they were born.
Owner Helga Happ, who took over Happ's Reptilienzoo & Sauriergarten in 1986 and runs it with her family, says they were always the best of friends. "They were like an old married couple," she says. "We never saw any problems." They enjoyed a contented, uncomplicated life -- sitting in the shade, sitting in the sun, eating, sleeping -- and spent many a companionable hour next to each other, shells touching, gently snoozing.
They enjoyed a full marital relationship, too, though for some reason, no baby tortoises ever materialized. Then, last November, it all changed; love doesn't live here any more.
"We had no warning," says Ms. Happ. "One minute everything was OK, the next Bibi hissed loudly at Poldi, then took a big bite out of his shell. He was bleeding."
There is soft tissue attached to the shell, so it must have hurt. The two were immediately separated and the vet called to treat the spurned and confused lover. The vet, a reptile specialist whose hobby is tortoises, had never heard of such a thing happening before.
An emergency brainstorming session was called with animal psychologists, biologists and zoologists trying to understand what could have gone wrong. But it's still a mystery. Keepers tried to put them back together, but Bibi continued to hiss and go for Poldi. Now he, too, cannot bear to be in the same enclosure as his former love.
"For no reason that anyone can discover, they seem to have fallen out; they just can't stand each other," says Ms. Happ.
Various attempts at reconciling the couple have been unsuccessful. The most elaborate was the introduction of a surrogate. An artist friend of Ms. Happ made a very visually realistic fake female tortoise out of a type of plastic. It was hoped that Poldi would think he had a nice new wife -- and, indeed, he did show her a great deal of affection for a few days. Perhaps, the thinking was, Bibi would get jealous and, fearful of losing her "husband," reform her shrewish behavior and make amends.
Sadly, Poldi eventually realized his amorous attentions were receiving an even less positive response than usual, and that his new young lover was not real. Bibi, always the couple's brighter half, was not taken in for a moment.
The stand-off continues. Zookeepers have been very gradually reintroducing the 100 kilogram (220-pound) tortoises to each other over food, making eating together a positive experience.
"They tolerate each other's presence just as long as it's not too cold, not too hot and there's plenty of food," says Johannes Happ, a paleobiologist and Ms. Happ's son.
Staff must watch them every second, though, to prevent a repeat of the love-bite incident.
Mr. Happ grew up with the tortoises -- they're part of the family, and he's sad to see them like this. "Poldi is still much more sociable and loves to have his neck scratched," he says.
"Bibi can be grumpy. She sometimes likes to be stroked, but you have to watch her body language," he says. "If her back's turned, she may be having a Greta Garbo 'I want to be alone' moment.
"Their plight has made worldwide news, with dozens of emails arriving at the zoo suggesting what the problem may be," he says.
"One was convinced that Bibi had lost her sense of smell, and therefore didn't recognize Poldi when he came close to her, so she rejected him. But she has no problem smelling tomatoes and other favorite foods, so that's not it."
Zoo officials know that it's unlikely to be anything environmental either, as Seychelles tortoises in the neighboring pen are pairing up with no difficulty. "Using artificial insemination to help Poldi become a dad could be a possibility, though," Mr. Happ says. The giant Galapagos tortoise (Chelonoidis nigra) is endangered, after all. The species can grow to a length of 1.8 metres, (nearly 6 feet) weigh up to 400 kilograms (880 pounds) and live for up to 170 years in captivity.
The number of visitors to Happ's Reptilienzoo, which houses snakes, lizards and spiders, too, has increased as curious people flock to catch a glimpse of the estranged pair.
But there is hope that the couple will soon resolve their differences. The plan is to build a grill between their enclosures, through which they can see and smell each other, but not indulge in fisticuffs. Perhaps Bibi will eventually come out of her shell, forgive whatever misdemeanor Poldi has committed and the pair will be reunited.
"We hope very much that we can find a way to bring them back together," Ms. Happ says.