Thousands of Toxic Sea Hares Just Washed Up — and They Can Poison Your Dog

Are sea hares dangerous to dogs? Yes — they can be. Sea hares are sea slugs that store toxins from the algae they eat, using them as a chemical defence against predators. When a dog licks, mouths, or swallows a beached sea hare, the result can be severe poisoning. Poison experts describe contact as potentially life-threatening.

Thousands of these toxic sea slugs have just washed ashore on a beach in Australia — and councils are warning dog owners to stay away. Here’s what happened, why sea hares poison dogs, and exactly what to do if your dog encounters one.

What just happened on the beach in Eden?

On October 21, 2026, the Sydney Dispatch reported that thousands of sea hares had washed up at Aslings Beach in Eden, on New South Wales’ far south coast. Council photos showed the sand covered in the creatures — and an algal bloom remained offshore.

Bega Valley Shire Council sent contractors to clear the beach, installed warning signage, and warned that the sea hares “can pose a serious risk to dogs if they lick, mouth or ingest them” — urging owners to contact a veterinary clinic immediately if a dog is exposed.

What is a sea hare? A sea hare is a large marine sea slug named for the ear-like protrusions on its head. It grazes on algae, keeps some of the algae’s toxins as a chemical defence, and squirts an ink-like secretion when alarmed — like a squid. A beached one looks like a strange jelly-like lump on the sand: exactly what a curious dog investigates with its mouth.

Why are sea hares poisonous to dogs?

The poison is borrowed, not made: sea hares graze on algae, and as Macquarie University marine biologist Culum Brown explains, “some of the algae they eat contain various toxins which the slug can maintain, using them as a defence against predators.”

Danger varies with what each slug ate — but poison experts don’t hedge. The Australian Poisons Helpline warns that “dogs can be severely poisoned by mouthing or ingesting beached sea hares” and describes contact with them as potentially life-threatening to animals.

This isn’t a one-off. Brown noted it is “not unusual to see sea hares wash ashore in large numbers on the southern Australian coastline,” usually with rough seas and on-shore winds. In Western Australia they wash up yearly between January and March — one vet there treats about four or five dogs a year after they eat sea hares (ABC Perth, 2022).

What happens if a dog eats a sea hare?

Here’s where honesty matters: there is no published symptom list for sea hare poisoning in dogs, and toxin loads vary with what each slug has been eating — so we won’t list dramatic symptoms we can’t verify. What poison helplines and council warnings do say is that exposure can be severe and potentially life-threatening. That uncertainty is why experts treat every exposure as an emergency, not a wait-and-see situation.

What to do if your dog mouths a sea hare

If your dog licks, mouths, or eats a sea hare, do these things — in this order:

1. Move your dog away and leash them — sea hares wash up in thousands, so don’t let them go back for another.
2. Don’t treat it at home. Don’t make your dog vomit or give milk, food, or home remedies unless a vet says so — some toxins do more damage on the way back up.
3. Call your vet or a poison helpline right away — the council’s advice is to contact a veterinary clinic immediately. In the US, the ASPCA Animal Poison Control Center can help.
4. Note what your dog did (licked, mouthed, or swallowed), when, and where — a photo of the sea hare helps the vet.
5. Keep your dog calm and don’t delay the call to see whether symptoms appear.

Are sea hares dangerous to people?

No. Professor Brown confirmed sea hares aren’t dangerous to humans — just wash your hands after handling and don’t touch your eyes, since the secretions can cause irritation. Humans fine; dogs, keep away.

Beach day safety: 6 habits that protect your dog

The Eden wash-up is in Australia, but the lesson travels to every coastline:

1. Scan the tide line before you unclip the leash — that’s where wash-ups strand, and where your dog will find them first.
2. Keep your dog on a leash or long line near any stranded marine life — sea hares, jellyfish, dead fish and birds, and washed-up seaweed can all be hazards.
3. Teach a rock-solid “leave it” — it’s your cheapest insurance against strange-smelling wash-ups.
4. Carry fresh water and a bowl — a thirsty dog drinks seawater, which can make dogs sick.
5. Rinse off and check paws after beach walks — sand hides shells, hooks, and debris.
6. Save your vet’s number and a poison helpline in your phone before you go. Emergencies don’t wait for you to look things up.

FAQ

What does a sea hare look like on the beach?

A soft, jelly-like lump, sometimes mottled brown or reddish, occasionally with small ear-like flaps. Some release an ink-like fluid when disturbed. If you see lots of odd jelly blobs on the sand, keep your dog well away and check for council signage.

Can a dog die from eating a sea hare?

Poison experts describe sea hare contact as potentially life-threatening to animals, and the Australian Poisons Helpline says dogs can be severely poisoned by mouthing or ingesting them. Outcomes vary with toxin load — treat every exposure as an emergency with an immediate vet call.

I’m in the US — do I need to worry about this?

This wash-up is in Australia, but beached marine life threatens dogs on every coastline — jellyfish, dead birds, and pufferfish are hazards US beach dogs meet. Same habits apply: scan the tide line, use “leave it,” and leash near wash-ups.

My dog ate something weird at the beach. What now?

Treat it like an emergency: stop them eating more, don’t induce vomiting on your own, and call your vet or a poison helpline right away. For fast guidance on what your dog swallowed, try our free Dog-Ate-Something Toxin Checker.

What other hidden toxins should dog owners know about?

Beaches aren’t the only place danger hides in plain sight. At home, antifreeze poisoning is one of the deadliest risks dogs face. And with Halloween days away, read our Halloween safety guide for dogs before the trick-or-treaters arrive.

Sources: Sydney Dispatch, “Thousands of Toxic Sea Hares Wash Up at Eden’s Aslings Beach” (Oct 21, 2026); Bega Valley Shire Council dog-owner warning (Oct 13, 2026); Prof. Culum Brown, Macquarie University; Australian Poisons Helpline. Informational only — not veterinary advice; consult your vet for diagnosis and treatment.