Sea Hare

Fast Facts

Latin name: Aplysia punctata

Notable feature: ‘Bunny ear’ tentacles, a pair of fleshy ridges on the back.

Conservation Status: Not Evaluated

Where in the UK: Widespread in shallow coastal waters across England, Wales, Scotland and Northern Ireland


Sea Hare (Aplysia punctata) eggs © BareFoot Photographer

The Sea Hare (Aplysia punctata) is a native, sea snail found in weedy coastal waters around the UK.  Although they look more like slugs, they have a small shell embedded in their back with fleshy frills either side called parapodia, used for breathing; this internal shell is around 4 cm in length and is transparent and pale amber in colour

Named for their ‘bunny ear’ tentacles, known as rhinophores, the Sea Hare is one of our larger more easily identifiable coastal sea creatures; measuring up to 20cm in length, but usually about 7-8cm. Their tentacles, rhinophores, are used to detect scents in the water.

The Sea Hare’s body colour is variable ranging from olive, green, brown, red or purplish black.  Feeding on seaweed, it is thought that this is what gives each Sea Hare its colour, e.g. green Sea Hares are eating green seaweeds like Sea Lettuce whilst the reddish-maroon sea hares are eating red seaweeds, like Dulce.  This also helps to keep them camouflaged amongst their chosen food.

The Sea Hare is a hermaphrodite, but must come together to breed; sometimes mating in chains, with an individual acting as both male and female. They lay eggs in long pink strings, which look a little like pink spaghetti.

    • Size: 7-20cm in length
    • Life span:  Annual life cycle; approximately one year with mating occurring from May to October
    • Diet: Algae (seaweed); consuming up to one-third of their body weight of algae per day!
    • Reproduction: Sea Hares do not self-fertilize and engage in mating behaviour that can involve multiple individuals, or chains.  Laying pink spaghetti like eggs which hatch in to a larval stage where Sea Hare young become temporary members of the plankton community
    • When to see:  All year round, but easier to spot due to large numbers during mating season
    • Population Trend:  Unknown
    • Threats: Loss of habitat, as a result of recreational activities, pollution, climate change and changes in sea temperatures and pH levels
    • Fun Fact:  Despite being soft and slow-moving, Sea Hares have an explosive defence. If one is pestered by a predator, it can eject a cloud of ink and a milky chemical called opaline. The ink helps to surprise and distract the predator, whilst the opaline coats it in a sticky mess which can clog up the antennae of crustaceans such as Lobsters. With the predator left surprised and senseless the Sea Hare can make a getaway.

How you can help: 

When rockpooling, be sure to leave everything as you found it – replace any rocks you turn over, put back any creatures where you found them, don’t scrape or kick anything off rocks and change the water in your buckets regularly to prevent overheating.

Join a recording scheme and log your finds – join the Wildlife Trusts’ Shoresearch citizen science network (whether organised or flying solo) or download the iRecord app and get recording!

Do remember that we rely on donations to continue our work.  If you have searched, found and learnt about our incredible invertebrates on our website, please do consider Making a Donation, Becoming a Member or maybe even making a purchase in our shop.  For more ideas on how to support our work find out how to Get Involved.  Thank you 🕷