As crime waves go, there’s something very fishy about a series of thefts taking place at the London Aquarium. As the mating season begins, ‘criminal’ Gentoo penguins have been stealing pebbles from rival nests. This is not the Penguin Posts first encounter with penguin pebble thieves and we’re sure it won’t be the last, as with a stealthy glance over their shoulders, the fiendish birds quickly waddle to their neighbors’ unguarded nests, steal a stone and run back to their own nest. In many cases it won’t be long before the ill-gotten stones will again be stolen by another bird or even the original owner. You can blame this circular crime wave on hormones more than anything else, but it’s a crime none the less. But as the number of break-ins increase, the Gentoos have become suspicious of their fellow colony members, and no one is beyond suspicion. If they notice a rival moving in to plunder their pebbles they quickly run back to defend their nests, keeping everyone on their webbed toes. The colony of 10, which arrived at the attraction last year, are in the middle of their first mating season at the aquarium. Males declare their interest in a female by selecting and presenting a ‘love token’ in the form of a pebble to their chosen female. If it is accepted, the couple then begin collecting more pebbles to line their doughnut-shaped nest. The birds build their stone nests to elevate and protect their eggs. Smooth pebbles are ‘like gold dust’ because they are easy to pick up and comfortable to lie on, according to those who tend to the birds. Hayley Clark, aquarist at the Sea Life London Aquarium, said extra pebbles had to be put into the enclosure after burglar Vladimir has conducted daily robberies on surrounding nests. She said: ‘Some of them are a little bit more tricky than the others, they keep an eye out for the owner of the nest before stealing. A couple of them will just run straight to a nest and will be chased off straight away. ‘They just prefer a certain type of pebble. Pebbles are like gold dust to these guys. ‘The male works out where he wants his nest and that is when he starts collecting pebbles. The female will join in as well after he has given her a few pebbles to place in the nest how she wants it. ‘It is like giving your girlfriend chocolate.’ Ms Clark added that there has been ‘a few tiffs’ over pebble thefts. ‘They will run over pretty sharpish and tell them where to go,’ she said. ‘It can get a little bit aggressive but they generally back away very quickly.’ No eggs have been seen yet but breeders are hoping that a few will turn up in the next few weeks. The pilfering activities of pesky penguins were also featured in the BBC’s Frozen Planet when crews captured Adelie penguins performing a similar thefts while filming in Antarctica.