Discovery of the Rare Sea Hare
A dogwalker on Anglesey beach made a remarkable discovery when she found a giant marine slug stranded nearly 20 metres from the water's edge. Emma Leese, the dogwalker, initially puzzled by the bizarre creature, later learned it was a sea hare—a type of marine snail commonly referred to as a 'sea slug'. While smaller sea hares are native to the UK, this particular specimen is believed to be a much rarer depilatory sea hare, typically found in the Mediterranean Sea.
Rescue and Behaviour
Concerned that local dogs might harm the creature, Leese returned it to the sea. 'When back in water, it sort of unfolded,' she said. 'It began wriggling – slug-like – and its stalks began going back up.' Sea slugs cannot absorb atmospheric oxygen, so they usually die quickly if stranded. When disturbed in water, they release a dramatic cloud of purple ink derived from red algae they consume. Similar to octopuses, this ink is thought to confuse predators.
Expert Identification
Frankie Hobro, owner and director of Anglesey Sea Zoo, identified the creature as a depilatory sea hare. He noted, 'This is still a rare UK species, found occasionally in southwest Britain. However, it’s a species we’re likely to see more of in the future as the seas warm and they keep moving north.' According to the Global Biodiversity Information Facility, the Isle of Man has three confirmed sightings of the depilatory sea hare, and north Scotland has one. Wales has no confirmed sightings, though anecdotal reports exist in Pembrokeshire.
Physical Characteristics
As a mollusc, sea hares are related to common garden snails. Instead of an external shell, they have a thin, transparent internal shell. Their fleshy mantles have evolved into large, wing-like flaps, which they use to swim gracefully through water—described as surprisingly agile. The native spotted sea hare, commonly found in the UK, is usually around 7 cm long but can grow up to 20 cm. In contrast, depilatory sea hares can reach 40 cm, dwarfing their British cousins, and are much bulkier.
Safety Advice
Hobro advises anyone finding a sea hare not to touch them without gloves, as their skin stores noxious chemicals from their algal diet. 'They are quite revolting to touch. As they have quite strong suction, they should never be prised off a rock, as this may damage them,' he added. 'I always say it’s best to leave marine creatures alone, as it might not always be what you think they are.'
