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snake head out the water in a koi pond

Koi Ponds and Snakes

Probably the most worrisome part of cohabitating with snakes is the fear of being bitten. But for koi owners and their koi ponds, it’s the idea that they can lose some to predation by snakes. Especially in those states where snakes are commonplace visitors.

There are 160 species of snake in North America. Only 20 are considered venomous, and every state (except Hawaii and Alaska) has one venomous varietal. But for koi enthusiasts, any snake, venomous or not, can pose a definite threat to their living jewels—the smaller ones in particular. Snakes are good swimmers, and if there is a meal to be had, by and large, they will have it.

Water snakes, cottonmouths, garter snakes and racers are the more commonly mentioned snakes that make off with pond koi and goldfish. But it’s not all one-way traffic. This man captured one of his koi eating a garter snake. The prey becomes the predator!

How Do Snakes Eat Koi?

Snakes that can eat koi have a bone between the top and bottom jaw (the quadrate bone). This double-hinged jaw allows the mouth to open 150º. Additionally, the lower jaw is split in the front and is connected by muscles and ligaments allowing it to widen, too.

Snakes are adaptable and efficient predators. Here is a video of how a garter snake can hunt smaller fish.

Depending on what you read, anecdotal evidence suggests that larger fish-eating snakes can make off with koi that weigh more than themselves. This is rare, however. In most instances, the prey (in this case, your prized tosai kohaku) will need to be no more than 20% of the snake’s body weight. In this video, you can see a garter snake trying to eat a larger koi. 

In most cases though, a snake’s eyes aren’t bigger than its stomach. With flexible skin and stomachs, they can fit something bigger than their heads into their mouths. This post on livingalongsidewildlife.com has some pretty revealing evidence as to the capabilities of some snakes in hunting fish.

To Kill or Not To Kill

To many koi owners, the only good snake is a dead snake. Especially where cottonmouth (water moccasins) are about. The investment that an owner makes in the koi they buy and feed, as well as the time and effort in maintaining a pond, makes losing a fish to snakes a bitter pill to swallow. So most snakes get the ax.

Unlike the Blue Heron (another koi pond scourge), it is not illegal to kill snakes. More intrepid (and reptile-friendly) koi enthusiasts will try to catch the snake and release it a safe distance away from their pond (a mile or more is recommended). Many pond folk will tell you that they will come back.

Or you could call in experts and have them dispose of it. Some pest control companies offer the service. There are some listings that deal with snake removal as a primary business.

You can also opt for a snake trap. The two main types are:

  • Minnow traps

Minnow trap that can be used to catch snakes in koi pondsThis is a cylindrical, mesh trap with openings on either end. It allows the snake into one end, but it can’t get back out. The mesh is tight enough that the snake can’t escape out of the side. You can submerge it, too, leaving one end of the trap above water. Release in this method can be a dicey proposition, though.

  • Glue traps

Like mice traps only bigger. The glue will secure the snake. To release it, pour vegetable oil over the snake and it will wriggle free once you are a safe distance away.

In both instances, the potential exists for also trapping creatures that you weren’t after at all.

Deterrents

How do you keep snakes away? You could try Samuel L. Jackson. But here are some other ways.

Yard Maintenance

This is perhaps the best preventative measure anyone can take in keeping snakes out. A well-kempt and debris-free yard tell snakes they aren’t welcome. Things to clean up:

  • piles of leaves
  • unused stacks of bricks
  • grass clippings
  • thick grass
  • overhanging foliage
  • large wood piles
  • rock piles

If you don’t, then you are creating an environment perfect for snakes to hide or find shelter.

Home Maintenance

Keeping your home rodent-free is another way to force any squatting snake to move elsewhere to look for a meal. Sealing up cracks and holes that snakes can use for refuge is another means of saying “no vacancy.”

In-pond Hiding Spots

Not a deterrent per se, but providing your koi some places to take refuge from predators can help to give them an advantage and make it just difficult enough for the snake that it moves on.

Cats

Outdoor cats are handy to have around. They help to control the rodents (a food source for snakes) in and around the house. There are plenty of stories about cats bringing in dead snakes—both venomous and non-venomous.

Predator Urine

Diluted fox urine, mongoose urine, and kingsnake musk are all available at hardware stores. It is believed snakes are put off by the scent of these predators.

Mothballs

If you go into forums about the efficacy of using mothballs as a snake deterrent, you will get answers from “absolutely!” to “I saw a cottonmouth coiled up in mothballs” and a lot in between.  

One theory is that the mothballs drive away snakes’ food sources and as a result, the snakes too. As to whether it will stop koi snatching, it might not have the same effect.

The smell of mothballs, however, is one of the main factors that make koi keepers reluctant to use them. There is also the potential for harm to the keeper (with hemolytic anemia, liver damage, and neurological damage listed) and their pets.

Snake-a-way (and Other Snake Repellents)

Spread around the perimeter of a yard or living space, this pelleted product uses Naphthalene as its main ingredients—which is also one of the main components of mothballs! These formulas are alleged to work on non-venomous and venomous snakes—but to varying degrees based on the type of snake.

These products also divide sentiment. Some users have had the success they were looking for with it while others consider it to be, well, snake oil salesmanship.

Sulphur

This seems to be universally given the thumbs down. It is in the category of old wive’s tales. It DOES NOT work.

Human Hair

Yes, this has been suggested. Hair clippings are alleged to be unpleasant for snakes.

There are a lot of creatures that might not have the same appreciation of the hard work you put into keeping koi. As much of a threat and a nuisance they are, keeping would-be koi killers at bay is part of the experience. But it is worth it.

One Response to Koi Ponds and Snakes

  1. Keith Wiedmar May 18, 2017 at 1:05 pm #

    As my pond has aged I have had the pleasure of seeing lizards run around my pond and waterfall. My two dachshunds enjoy chasing them as well. Blue tail skinks are the most common reptile. Honeybees, dragonflies, and frogs also make appearances because of the water. I have not had the pleasure of watching a snake take a swim. Maybe this year…

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