Rats on Boats

Rats are Just Bad News on Boats

We ended up with a rat on our boat just a couple of weeks ago when I was headed out to crab fish – had to throw away the mattress,
sleeping bag, and bedding in our bunk in the wheelhouse. I thought I’d closed up all possible entrances on the boat
a year ago, when I found chewed wires that I had to replace.      – 
Dutch Harbor Crab Fisherman, January 2007

Rats aren’t just creepy; they are destructive. Being rodents, they need to constantly chew to wear down their teeth. Your wiring, fuel lines, foam, fabric, wood, nets, and cargo are all fair game for these busy little chewing machines. Chewing on wires can cause fires. What they don’t chew they foul with urine and feces (40 droppings a day). They contaminate food storage areas and can even spread disease by inhabiting crew quarters and introducing fleas and mites.

You Could Cause Harm

What’s more, if your vessel unwittingly carries rats to a location they don’t currently inhabit, you could cause the infestation of towns, maybe even your home town. Should a hitch hiking rat from your boat jump ship on a remote bird refuge, you could cause untold wildlife destruction. St. Paul Island in the Pribilofs by city ordinance does not allow boats with rats aboard to enter city waters or tie up at the dock.

It Could Happen to Any Boat

Young rats who need to find new territories may hop onto your vessel no matter how clean it is. Under the astonished eyes of biologists, a rat streaked down the Dutch Harbor dock and leapt onto the U.S. Fish & Wildlife Service’s M/V Tiglax during the Selendang Ayu oil spill. Smellier boats will draw more rats but no boat is immune. Cargo ships and ferries have special risks in that rats could come aboard with freight, vehicles, and containers. Boats left unattended in ratty ports until the next fishing opener or through the winter are at particular risk for significant damage. Keep traps set!

Run a Rat Free Boat

  • When tying up in port, look for ways rats could board your boat, and take steps to stop them. Rats are excellent climbers, jumpers and swimmers.
  • Use rat guards on tie-up lines where appropriate.
  • Since they are nocturnal, lighting up gangways and ramps at night can discourage them.
  • Seal entry points to the vessel’s interior, such as cable chases, and put screens or louvers over windows and vents.
  • Inspect and shake out fishing nets and lines, before taking them aboard. Rats particularly like to nest and shelter in trawl and seine nets and coils of groundline. Most gear storage facilities do NOT have rat control programs. Rat control experts say soap does not work to protect stored nets from rat damage.
  • Inspect cargo for rat sign. Rats can hide in containers and in pallets.

Be Knowledgeable and Ready

  • Know what ports you need to be on guard in – see the map of Alaska ports on our home page and assume any lower 48 port has rats.
  • Good sanitation is a key to prevention; keep food and garbage in tightly sealed storage areas to avoid tempting rats to board.
  • Familiarize yourself and crew with rat sign, such as chewed materials, hair, rub marks, feces and urine. Periodically search dark and concealed spaces for sign.

Kill Any Rats That Get Aboard

  • Learn more about rat identification and impacts.
    When tied up in ratty ports, deploy traps or poison bait stations near any possible spot a rat could board.
  • Use multiple approaches. Deploy snap traps, sticky boards and poison. Put traps where sign is found, in dark and concealed spaces and near food or garbage.
  • Use fresh bait, and be patient. Rats are wary of new items in their environment and often will not take the bait for days or even weeks after it is introduced.
  • If you catch one rat, don’t assume it is the only one. Re-deploy traps.
  • As a last resort you may need to have the vessel fumigated.
  • Never throw a live rat overboard. They are good swimmers and may reach land.

Speak Up and Spread the Word

  • Tell the harbormasters in the ports you patronize that you expect effective rat prevention as part of the service you pay for.
  • Report rat sightings and especially a rat invasion of your boat to the harbormaster.
  • Ask about rat control where you store your gear.
  • Spread the word to the fleet. Tell others how to get our rat kits.
  • Tell us your rat stories and share your prevention tips on our Blog page. (Free gummy rats for every story fit to print!)

You Can Make a Difference

Rats may have spread around the world on boats but it doesn’t always have to be that way. People who work on boats are in the best position to make a difference. Help us draw the line in the sand. No more ratty ports. No more wildlife destruction. Bristol Bay, Kenai Peninsula, Prince William Sound, the Alaska Peninsula and the Pribilofs are still rat-free. Help us keep our communities, our wildlife and our boats safe from rats.