Lately we have been dealing with a few damaged ponds here in Southeastern Wisconsin. Through the years, I’ve been impressed with the durability and resilience of the eco-system ponds that we install. For the most part, these ponds can withstand all sorts of abuse and come out unharmed. You can walk, jump, run or swim in your pond without the fear of wrecking anything. Your dog or dogs can use our ponds as swimming pools and drinking troughs and never do any damage. Deer can walk through and stand in these ponds and I’ve yet to see a rip in the liner from a deer hoof. I’ve driven over the pond bottom with a skid steer and an excavator. I’ve rolled huge rocks around on the rubber liner and even dropped a few huge rocks on the liner. All of these things and usually no damage. Granted, you need to be cautious and know what you’re doing to drive equipment and maneuver huge rocks on top of the rubber, but for the most part, clients ponds just don’t get damaged very easily.
The only real damage that we see is from teeth. Every spring we get a few calls from pond owners whose ponds are suddenly leaking. Most of the time this is from a hole in the rubber liner somewhere in the stream or the pond edge and it’s usually located on a vertical surface. It seems that mice like to crawl in between the rocks of our ponds and try to make themselves a little burrow for the winter. I’ve seen holes the size of oranges and tiny little holes the size of a dime. Some of the holes are clearly leading to a burrow and others simply appear to be chewed on. Either way, it is a good thing to look for if your pond has a sudden leak as soon as you fire it up in spring.
Sure, this mouse hole business is definitely damage, but it is not really the damage that I was refering to when I started this post. The damage that I was refering to is similar but on a much larger scale. Instead of orange or dime size holes, I’ve seen long holes large enough to pass a party sub sandwich through, sideways! I’ve seen multiple holes the size of a grapefruit in one pond. I’ve seen ponds with an entire wheelbarrow’s worth of dirt in them. Damage to this extent, here in Ozaukee county Wisconsin, I’ve only seen done at the hands (or should I say teeth) of the pond spoiling MUSKRAT!
These toothy little critters can really mess up your pond in a short time!
It seems that the Muskrat likes to swim in ponds and eat the various aquatic plants that we pond owners like to keep in our ponds. Once they find a pond full of tasty food then they start to think about moving in to stay. This is when the real trouble starts. Like the mice, they find a gap between the rocks and they also burrow into the rubber to make a nest. The difference here is that the mice usually do it in winter and usually do it in the stream or in an edge above the water line. The Muskrat does it any time of the year and does it well below the water line. They want to create a burrow that is only accessible from under the water to discourage their predators from joining them I would imagine. So, they dig and dig and dig. I’ve seen holes that start one or two feet below the water line with burrows that go for ten feet into the pond bank. At my house we had one make a burrow that twisted and turned and ended up under my stream. They want to access it from the water and then create a burrow above the water line to stay dry. I’ve seen where they, for whatever reason, burrow just behind the rocks in the pond tearing up the rubber all along their path. This is where the party sub effect comes in. I’ve seen long holes about six inches wide that stretch for six to eight feet! Talk about a lot of patching work. Of course, when tunneling, the spoils must go somewhere. That somewhere is in your pond. These pesky creatures push all of the excavated soil into your pond. So now, not only do you have a pond that is losing water at an alarming rate, but you also have a big pile of mud in your pond.
What to do, what to do? Well, you definitely want to get these pests out of your pond as soon as possible. If you ever notice chewed up plant material floating in your pond, you probably have a Muskrat. At this point you had better act quick. I’ve heard of people shooting them or trapping them. I suppose the most humane method would be the live trap, but the Muskrat is a prolific breeder and one female can have up to four litters a season of up to four to eight young each, so I wouldn’t worry about the population. There is a legal muskrat trapping season in the fall here in Wisconsin.
The patching and clean up from a muskrat can go on for a day or two. Obviously you need to pump down the water to a level below the holes, or maybe the pond is already at this level due to the gaping hole in the liner. Find the hole by looking for the telltale pile of mud in the pond or by looking for the chucks of chewed up rubber scattered about the pond floor. Look in between rocks anywhere that a Muskrat head would fit. Most of the time you will need to remove all of the rock from the area where you found the first hole. Moving all adjacent rock will oftentimes reveal more holes. Once you feel that you have located all of the holes, you can patch them and try to remove as much of the mud as possible from the pond. If the holes are too large to patch, you may need to seam in an entirely new piece of rubber. When all of this is done, put the rocks back in place and fill the pond to test your patches. Keep your fingers crossed, there might be multiple holes in multiple areas. If you’re not careful, you may need to drain the pond again to find the missing hole.
Luckily, I’ve only seen muskrat damage in five lined ponds since I’ve started installing them, so this doesn’t happen too often, but when it does it is a real mess. I have seen natural bottom ponds drained by muskrats also, it is very similar, except they just burrow through the side of the pond. Sometimes they do this simply to create their burrow, other times they want an underground passage from the pond to an adjacent wetland area. This can be a very hard problem to fix and I’ve heard of people trenching around their ponds with deep trenching machines so that they can fill the trench with heavy clay or concrete hoping to stop the burrowing.
I am currently working on a pond that is rubber lined and was damaged by a Muskrat last fall. We went in to try to patch it in late fall, but we didn’t find all of the holes, so the pond still leaked. The homeowner took all of his fish into the basement for the winter and kept them in huge tanks. We are now in the process of removing all of the rock from the pond and replacing the liner. Once the new liner is in, we will line the pond with stainless steel screening to prevent any more burrowing. I have never tried this approach before, but the homeowner found the screening and wants to give it a try. I guess a winter with a basement full of fish will inspire one to go to great lengths to avoid this in the future. The pond is about 18′ x 25′ x 3′ deep and the stainless steel screening cost about $3000. Wow, what an expensive repair job. I feel really bad about the disruption of the yard, the pond eco-system and the homeowners pocket book, but hopefully he’ll never have this problem again.
We did have one homeowner request protection a few years ago and we installed a galvanized hardware cloth on top of the rubber on only the first shelf level. The mesh was about 1/4″ squares and was quite rigid. It wasn’t much fun to work with and we really needed to protect the rubber from it’s sharp protruding wires. We haven’t been back to repair any holes, but I don’t know if that is because of the mesh or because there just haven’t been any more Muskrats in the pond.
I sincerely hope that you never need to deal with this type of pond damage, but if you do I wish you the best of luck with your repairs.
Doug
27 Comments
Yes, heavy stones and gravel will help to deter the muskrats. Good luck with patching. Big holes are never fun to patch.
Thanks for your fast reply. Muskrats are brought in Europe one hundred years ago, since then they have invaded the continent according to Wikipedia. Personally never seen any before. For me every rodent seems the same. The place is in a remote area, with valleys and fishing lakes, so it can be easily a muskrat. But nothing makes me surprised. I have found so many strange animals, plants and algae, with zero chance to appear there, but they are there and feel ok. Still, I can not see any hole in the protecting fleece underneath the lining. The owner did not anchored the liner in a trench, so it can easily be a space between stones and wrinkled lining to travel in and out the lake. What scares me the most is that hole which is big enough for me to go through. After patching we’ll try to cover with stones ans feel the gaps with gravel . Hope it helps.
Hi Attila,
From my experience here in Wisconsin, USA if I find holes that are below water level, they are always caused by muskrats. Muskrats like to burrow holes below the water level to make a nest underground somewhere outside of the pond. There is usually one hole going in and at least one going out. They make big holes, a huge mess and they push mud into the pond also. It is likely that mice or rats created the holes above the water line.
Dear Doug. Thanks for advice. I am from Romania and had to install a filtration system in a pond by a monastery, filled with swans and ducks. Realizing that the water level falls rapidly i recommended to remove the stones as there was no protecting geotextile between liner and stones, so I was thinking that the stones punctured the liner. After removing the stones i started to find orange sized holes at water level above and below, then two huge ones, over one feet in diameter. These holes were found mainly close to the bird feeding areas, where grains are served. I see no harm in the geotextile below the liner. Could be caused by swans or just rodents? I have seen last evening a rat,(but not sure) feeding from the bird food and running away. There is a pony and donkey stable next to the pond. Did rats eat the liner under water level too?
Jo
I had same pond problem last year. I received some help advices from Doug. I located holes and patched these holes with pond patch kit. After the holes were patched, I placed ultrasound mole/mouse repelent stick plunged in the area closed to the holes. Till now everything is ok for my pond. You may try my method and it saves you tons of money.
Sorry this took so long to reply. We’ve had some success deterring the smaller rodents by simply covering all rubber with heavy pond gravel or rock.
We live in VA and have discovered chipmunks chewed holes in our pond–one a small desert plate sized hole, and the other golf ball sized. There is a small hole going straight down about 2 feet into our clay soil just near this evil hole, evidencing its those darn chipmunks….
What’s the solution?
-Wire mesh (hardware cloth) will deteriorate when in contact w/ chipmunk/rodent urine, risking poking holes in liner.
–mothballs, I’ve put down moth balls, but they risk going into pond.
–castor oil. I’ve found the mole/vole chemical repellent I’m using contains castor oil, which apparently deters chipmunks, but one must re-apply frequently.
–Lime mixed w sand. I’ve read somewhere that lime mixed with sand put behind pond liner may deter chipmunks due to smell…but won’t that change to mortar?
–Traps. I’m going to try to trap the chipmunks, but they are like hangers in the closet–always reproducing overnight…
any suggestions to prevent future chewing of pond liner?
Marcy, just do it as Doug said. Doug is a real pond expert.
Hi Marcy,
We would never ever recommend emptying a pond for the winter. In fact we always recommend that your pond be as full as possible going into winter so that the mice can’t get to your rubber. Best of luck.
Okay… my first time with a blog. I have pond problems. We drained our pond last year and it was empty for a year. This year we cleaned it up and our liner looked like Swiss cheese. The pond is large and covered with huge rock…. very heavy. We got some help, moved all the rock, purchased a new liner and installed it. We found burrowing holes. Decon went into the holes before the liner went back in (over the old liner). Now winter is approaching and I am afraid to drain the pond again. We do not have fish. Do we have to drain it? If we keep water in it, will it prevent the mice/chipmunks from eating the liner…. help! We are too old to go through moving all the rock again.
My pleasure, best of luck.
Thank you, Doug. Your help is in time and appreciated. You are a real pond expert.
If the pond can sit full without the pump running then the faceplate must not be leaking. Usually when that starts to leak the pond will lose water right down to the bottom of the faceplate and then stop. If it loses with the pump running it is usually an edge leak in the stream, sometimes mouse holes, rarely a cracked pipe and even more rare would be a leak at the biofalls lip or I have seen a cracked biofalls twice in my career.
Doug, I fixed the mice holes on my pond waterfall bank, the results is good. The fixing material I used is the patch. I have a question to ask you. When water pump is not running, water level in the pond is not dropped, the skimmer faceplate should not be the reason for leaking, correct?
Dear Doug
Thank you for your in time response! I have punched this sonic mole stick repellent near my pond water stream. I will give you update later after I try it for sometime.
Have a good holiday!
I really don’t have any experience at all with ultrasound repellents, but I’d say it’s worth a try.
Dear Doug
Thank you very much for your in time response. After I patched the hole, I put the ultrasound stick mole repellent near the stream area. Does it work?
Yes, mice can definitely cause a great deal of damage. Every year we need to patch holes in ponds. The mice seem to like to make nests in between the rocks for the winter and chew little holes in the rubber. It is important to keep your ponds and wetland filters as full of water as possible over the winter months to discourage the mice. Although that doesn’t help with your stream and waterfall that may sit dry all winter. Be careful what you use to repel the mice. Mouse poison and pesticides will kill fish.
My pond liner was also chewed by mice/rats I guess. Should I place some repellent on the liner after I patch the holes and pack the liner back?
“Once the new liner is in, we will line the pond with stainless steel screening to prevent any more burrowing.”
Interesting approach to solving that problem, please update us (when you can) if that idea worked out for your client.
We have a few clients each year that have mice chew through the rubber in their streams and waterfalls. These holes are usually about the size of a quarter and can be hard to find. Look for wetness along the edge and then feel underneath the rubber if possible to pinpoint the leak before you start removing rocks.
Question. Have been having a problem lateley with something eating through the liner
in my stream?? I have a waterall that drops to a stream about 15ft long than drops to
a 1500 gallon pond. This is the third time in a two month period this has happened.the sreat is about 2″ in depth and the system runs 24/7, any guess what animal might cause this type of problem.
I really enjoyed the article. I had no idea a mouse could get in there and cause damage.
We’ve had some issues with a ground squirrel eating liner on a pond Idlywild, California this year otherwise we haven’t had issues wildlife messing with our ponds.
Thanks for sharing.
why would you want damaged liner pics?
does anybody have pictures of damaged pond liners?
Great Article! Many pond owners don’t realize how badly a muskrat can damage a pond.