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Lion's mane
Jellyfish and dogs on Cape Ann beaches
Lion's mane jellies bloom in Massachusetts waters far more in some years than others, and a big one stranded at the tide line is easy for a dog to nose. Our beach hazards page covers the wrack line in general. This one is about the jellyfish itself: when it turns up, what a sting does to a dog, and which first aid is settled and which is not.
When and where
Lion's mane jellies bloom from spring, travel on wind and current, and strand on beaches and rocks
WHOI scientists describe the lion's mane life cycle. In late summer and early fall, larvae settle near estuaries and river mouths and become small polyps, and each polyp can produce many jellyfish, which grow into a bloom the following spring. After that, jellies are weak swimmers, so wind and currents decide where they go. Some years bring very few; 2020 brought reports of record sizes and numbers from Maine to the Massachusetts south coast. Lion's mane jellies float along rocky shorelines and sandy beaches, the same places people and dogs walk.
For a Cape Ann dog the overlap is narrow but real. Gloucester's public beaches are closed to dogs from May 1, Good Harbor from April 1, through September 30, and Rockport's from June 1 to September 15, at the time of writing, so summer meetings happen on rocks, breakwaters and Crab Beach, which the city opens to off-leash dogs all year. Whether any jellies are still washing up when the beaches reopen depends on the year, so look before you unclip. WHOI also notes that clinging jellies, a different species that prefers marshy areas, give a painful sting.
- Spring: blooms grow from polyps that settled the previous late summer, per WHOI
- Wind and current decide which beaches get them
- Stranded jellies and loose tentacles still sting
- Clinging jellies prefer marshes and sting harder
What a sting does
A sting hurts the skin, a mouthful is worse, and some dogs drool or struggle to breathe
The ASPCA says a jellyfish sting causes pain, redness and skin irritation in pets, much as it does in people, and that eating certain kinds can cause stomach upset and muscular, cardiac and neurological effects. Cornell's Riney Canine Health Center adds the beach-specific warning: even a dead jellyfish on the sand can sting, causing mouth irritation, drooling or even breathing trouble in a dog that sniffs or licks it. Cornell's advice is to call your vet if a dog shows unusual symptoms after contact with sea life.
Dogs meet jellies face first, which puts the sting on the lips, tongue and muzzle, or on the paws of a dog that pounced. The tentacles are the hazard, and WHOI points out that they can be hard to see in the water and that the stinging cells stay active after a jelly washes ashore or is broken up by a boat. A beach with no visible jellyfish can still hold stinging fragments in the wrack, which is why the first pass along the tide line belongs on a leash.
What to do now
If your dog is stung, get it away, keep tongue and paws off the spot, and phone your vet
You will hear that a sting should be rinsed with seawater, never fresh water, and that is what public health guidance in the UK tells people stung around the British Isles. The evidence is less tidy than the advice. A 2017 laboratory study of lion's mane stings found that rinsing with seawater increased the venom delivered while vinegar did not, that hot packs cut venom activity sharply and ice did nothing, and its authors called for first aid guidance to change. None of that work involved dogs.
For a dog, the parts everyone agrees on are the safe ones: no rubbing, no bare hands and no home remedies such as urine. Lift off what you can see, keep the dog calm and still, and let your vet tell you on the phone whether to rinse and with what. If the vet is closed, Massachusetts Veterinary Referral Hospital in Woburn is open 24 hours, and ASPCA Animal Poison Control at (888) 426-4435 can advise if the dog ate part of a jelly; a fee may apply.
- 01
Leash the dog and move it up the beach, away from the jelly and any loose tentacles
- 02
Stop it licking or pawing the sting; a towel over the spot helps
- 03
Lift off any tentacle you can see with gloves, a towel or the edge of a card, never bare hands, and do not rub
- 04
If the dog mouthed the jelly, look at the lips and tongue without prying the jaws open
- 05
Call your vet, say where the sting is and how the dog is acting, and ask before you put anything on it
- 06
Go straight to the nearest emergency hospital for trouble breathing, a swelling face, vomiting or collapse
Prevention
Look before you unclip: scan the tide line and the shallows, then let the dog run
WHOI's advice to people is to stay far enough from jellies that you are in no danger of being stung, especially in the water, where tentacles are hard to see. With a dog that means a look along the tide line and into the shallows before the leash comes off, a leashed pass by any stranded jelly, whole or in pieces, and no fetch into water where you have seen them. A dog that drops a find on cue is safer still, and our beach hazards page covers the cues that help most.
Most summers the question solves itself, because nearly all of Cape Ann's public beaches are closed to dogs through the warm months. For the dog that needs its miles anyway, Dogtown's at-home walks start from your door: solo walks of 20, 30 or 60 minutes for $25, $35 or $55, with a photo and a note after each one. Ask us whether we cover your address. In the fall, the Cape Ann dog beach calendar has every reopening date in one place.
- Scan the tide line and shallows before the leash comes off
- Leash past any stranded jelly, whole or in pieces
- No fetch where you have seen jellies in the water
- Practice drop it on the sand before you need it
At Dogtown
Walks while the sand is closed
Solo at-home walks led by Dogtown staff, and Academy days that make leave it hold on the beach.
Asked and answered
Questions people ask about this
Short, complete answers you can act on today. More in the full FAQ.
Do loose tentacles on the sand still sting?
Should I rinse a jellyfish sting with seawater or fresh water?
What are the signs of a serious reaction in a dog?
What if my dog eats part of a jellyfish?
When do jellyfish turn up on Cape Ann beaches?
More questions? Read the full FAQ
Sources
- WHOI: jellyfish on Massachusetts beaches
- ASPCA: beach day the safe way
- Cornell Riney Canine Health Center: dogs at the beach
- Toxins (2017): evaluation of lion's mane sting management protocols
- nidirect (UK): jellyfish and other sea creature stings
- Gloucester beaches, detailed information
Rules and dates change. We re-check every beach, licensing and ordinance page each spring and fall; the source above is the current word.
Keep reading
Next step
Summer miles, no stings.
Book the free evaluation on a weekday between 6:30 and 9:30 AM, then set up at-home walks for the months the sand is closed to dogs.
- 01Free evaluationWeekdays 6:30 – 9:30 AM
- 02Book a dayOnline, in the app or by phone
- 03Play, rest, repeatReport card at pick-up
