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Tell-Tale Signs of Pond Predators

Awareness, Detection & Avoidance


Robert Fenner



            One of your absolutely necessary jobs as a pond-keeper is the guarding of your livestock from would-be predators. Mortalities can come from several quarters: snakes, toads, fishing birds, raccoons, opossums and other mammals…. including humans. Here I will share with you my many years of experience in playing Sherlock Holmes in consulting with owners and associations concerning these depredations.

            It is my hope that by reading what I’ve posted here, you will become more aware of the potential from predation losses; be able to recognize when they’ve occurred, and even better be better prepared to avoid such losses.  

In General: Avoiding Predation by System Design, Walls & Fences

            Planning ahead for warding off pond predators is better than battling them after they’ve become acquainted with your system. The usual arrangement of the basin/s is of critical importance; the sides should be steep, not gradually sloped, to discourage animals entering the water, as well as give your mobile livestock depth to dive immerse from the edge, out of harm’s way.

            Depth of basins figures in here as well. Systems of less than a few feet deep are going to have troubles from predators as well as seasonal to daily over-vacillation in water quality.

            The pond, fountain, lake berm should also have a solid edge to it; this need not be rock or formal masonry, but some substantial working up above grade of concrete or mortar will serve as a barrier of entry psychologically to many animals.

            Fencing around the yard, including the water feature will deter most four-legged animals that can’t get over, under or through it.

            Shading the water with cloth, interlaced anti-bird screen, or crisscrossed stout wire or cabling raised on tall poles is usually sufficient to discourage large fish-eating birds like herons and egrets.

            Lastly, there are higher technology approaches, including motion detectors, electrical fencing, and tied in noise and bright-light alarm systems that can be automated.

Detection: In General:

            Missing livestock, trounced and torn plantings; water everywhere and signs of carnage are sure-fire indications of unwanted visitors. Again, motion detection devices can be easily and inexpensively employed with small digital cameras to catch culprits in the act.

Pond Depredation: Possible Culprits:

The Neighbors (and Your) Cat and Dog/s:

            When it comes to tallying up the most likely source of trouble; domestic canines and felines easily rank the highest. If and when it comes time to don your Sherlock Holmes cap and pipe; do therefore consider first and foremost that these pets “did it”. Cats of all kinds for sure enjoy consuming fishes; and they and dogs will dive into ponds to seize them, as well as turtles…

            The best way to keep out unwanted pets is ironically by having one or more of your own that doesn’t molest your pond life. A dog of size can be trained to chase off cats, dogs, birds, and possible human challenges.          

Other Mammal Visitors:

            What to list here? Possums, skunks, raccoons and more seek out ponds for water, habitat and food. Rigging up cameras that are actuated by motion detection I have recorded these animals over and over “foraging” in domestic ponds. Once they become aware and accustomed to visiting your/their watering hole, it will become necessary to take drastic action. My and our company that installed and maintained biological water features preference here was the use of “Havahart” traps. http://www.amazon.com/Havahart-Professional-One-Door-Chipmunk-Squirrel/dp/B000BPAVCG

            These non-kill type trap door devices really do work. The more than trapping difficult part is what to do with said mammals once they’ve been confined. If you intend to try re-locating them, be prepared to drive several miles out of the area; else surely they will return. Be aware that there are likely more than one of a given species (they do chat regarding where the getting is good); and so you’ll need to be diligent with trap use. Also, do look into local laws concerning trap use and relocation of offenders.

            If you suspect, and especially if you confirm that there is a large animal… like a Bobcat, involved, do contact the pest control agency in your local government rather than trying collecting the animal yourself. And do remember to not handle these animals with bare hands. They do bite, can often claw deeply, and are carriers of human-susceptible pathogens.

The Bird IS the Word:

            After kitties and woof woofs, likely fish-eating birds come in second in terms of mass and numbers of animals lost in neighborhood ponds. And some have HUGE appetites. The big herons and egrets can consume fishes of more than a foot in length; and several of them at a sitting! I have seen this two groups of avian fish feeders eat so much they regurgitated the food and went back to catch more.

            There are fish hawks, eagles and smaller non-raptors like Kingfishers that will visit ponds if hungry and there’s access.


Did you think that gulls and other sea-birds might visit your town? Some fly and live very far from the sea; and yes; they do eat pond fishes. Here’s a California gull on a roof, espying possible snacks.


What’s that poem re the Pelican?
“The remarkable bird the pelican.

His beak can hold more than his belly can”…

This salty denizen will sample freshwater ponds as well.

And then there were ducks… of oh so many types. Most of these leave fishes of size alone (but not all), but they do consume aquatic plants; and make an incredible mess with their droppings.


            Again, the best approach in thwarting pond predators is masking the presence of your pond. Secondly by screening, shielding it against easy access. Lastly by utilizing drastic means that damage or destroy indigenous wildlife.

            The most innovative anti-bird technique I’ve personally encountered was in a gorgeous coastal residence with very expensive Koi. Here the folks had tried shading, electrified wires and even a good-sized Labrador with no success.

            What did work was arranging a series of interlocked “photo” eyes around the pond; such that when the light beam was crossed, loud disco music and flashing strobe lights were actuated. This of course did not delight their neighbors, but after a few weeks resulted in eradication of their flying visitors.

Amphibians & Reptilia; from the Greek, Meaning “to Crawl”:

            Where are frogs, snakes, turtles going to come from? Mother Nature will obviously supply them.


Frogs, particularly the larger Toad species (Family Bufonidae) are undesirable on a few counts. They’re noisy with their croaking; eat smaller fishes, and some produce noxious materials in their skin.


Be on the look-out for them and remove frogs before they reproduce!


Turtles and ponds seem to be naturals together; but like ducks, they are messy and can be trouble in scratching your fishes even if they can’t catch to eat them. IF you stock turtles, keep their numbers low; and purposely feed them through the warm months of the year per their needs as determined by water temperature.



A REAL Surprise:

            Southern California has had some great Koi, Goldfish, Water Lily and general Pond Clubs over the years. During the early years of the recent iteration of the San Diego Koi Club, I had the good fortune to meet Terry Hollingsworth. Terry was a businessman with huge skills in handling backhoes and skip loaders; very useful for folks as ourselves in the trade; as excavating any but the smallest of volumes by hand is hard, dirty work; the ground in many places being composed of mostly rock and clay.

            And as a bonus, where Terry lived, out in the almost coastal resort town of La Costa in northern San Diego; his neighbor with a shared driveway was a very famous person of interest. I’ll mention that this fellow had a fabulous mailbox that was a perfect replica of the USS Enterprise and leave his name unmentioned.

            At any length, the pond that Terry built was a Japanese traditional beauty; replete with extensive surrounding landscape and elements of the pond that one finds in the orient. One such feature involves a garden path that leads down to a purposely shallow area; a boon for the times one needs to get in and out of the basin for work.

            I’d been out to this pond a few times with the KCSD group, but got a call from Ter one day; he asking if I could stop on out for a look/see and help him detect what or who was stealing his large prize koi (Nishikigoi). I first suspected that a person had done this, as all of his fish were quite large, near two feet and larger.

            On inspection of the pond however, I was sobered to find some very large and long claw marks in the shallow entry area of the pond; from… what turned out to be the apex predator in our area; the national mammal, Felis concolor, commonly named the cougar or mountain lion.

            I suggested that Terry try installing an electrified fence around the ponds perimeter; but in the meanwhile, to provide a tray of alternate food….

Homo sapiens:

            Unfortunately, there are two-legged critters that can cause pond losses; and these varmints can be the hardest to catch. Again, a good canine companion may do more than spoil such thievery by barking, or biting would-be intruders.



            Yes, the list of potential and real pond predators is indeed long; and it pays to be aware of which are likely probable potential suspects in your area. Forewarned is fore-armed: know who these foes are and defend your pond livestock against attack. Walls, shading cloth and wire covers; high tech. electronic fences, motion detectors and even strobe lights and disco music (have mercy!) are the best available, more appropriate means to preclude damage and losses.


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