Many people think of otters as charismatic critters who provide lots of entertainment when observed naturally in the wild or in captivity at a zoo. But for the home aquatic gardener, they can be quite a pest – they are voracious carnivores and eager fish hunters!
Read on to learn more about otter natural history, and for some tips about how to humanely discourage otters from visiting your garden and how to protect your pond.
How to Get Rid of Otters In Ponds
1) Physical Barriers
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Physical barriers can be effective at keeping predators from invading your garden. Installing fencing, or keeping your pond covered with netting or covers, especially at night, are potential easy solutions to predation. Since otters visit from the direction of larger wetlands, lakes, or rivers where they will make their dens, understanding which direction the otters come from can help you create more effective barriers.
2) Predator Decoys
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While animal decoys may help deter some species, most otters are highly intelligent, so decoys don’t always work best for keeping them away (especially if they’re already used to the environment!). However, If you want to use decoys, the best would be predators that may hunt otters or their young, such as coyotes, wolves or even bobcats. At the very least, a wandering otter mother may think twice before bringing her young to a new pond with potential predators around!
3) Electronic Deterrents
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Some people have had success with using motion-sensing cameras or lighting as a warning system to pond owners when a predator arrives at the pond, but this can be an expensive and disruptive option. Another option is to get some fish shelters, large enough for your fish so that they can hide from predators but not so large that otters could get into them.
4) Humane Traps (Or Professional Help!)
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As a last resort, humane trapping and relocation may be used, but it is best to hire a professional for this task if needed. This is more often used as a solution for larger fish hatcheries, which are more appealing for otters to return to.
Relocating any animal risks stressing the animal, as well as potentially endangering its life as it will likely be moved outside of its lifelong home range and into new, unfamiliar territory where it will have a much harder time finding the resources it needs, or may be attacked by individuals who have already claimed that area.
Are Otters Good for Ponds?
Otters are active, playful, and undeniably cute, and wildlife watchers consider themselves fortunate to encounter one! Because they are threatened in some areas, it can be positive just to see one because it is evidence of a recovering population. They are also considered ecological indicators so their presence signifies a healthy wetland/aquatic habitat. This is why it is especially important to consider non-harmful ways of deterring otters from personal property.
Unlike beavers, a visit from otters will usually not cause any major structural changes to an existing pond.
Due to their predatory nature, the presence of otters might also keep pests such as rodents away from your property, or even deter other predators.
Are Otters Bad For Ponds or Dangerous?
Otters can quickly and easily eliminate entire prized fish populations from a pond. They are very efficient predators and consume large amounts of food daily. Many slower-moving domestic fish such as carp and koi can make easy prey, especially in smaller ponds.
Otters will leave very strong smells – olfactory signals are a primary form of communication for them, and they have a few different ways of leaving their mark. They will roll around and groom themselves in strategic locations, which rubs their scent glands across surfaces and spreads a musky odor. They will also leave markings through their urine or their feces mixed with scents from their anal glands, which is known as spraint. In fact, a common and somewhat easy way for scientists to monitor otter populations is by tracking otter markings and latrine sites, which they can use both for population estimates and to collect DNA.
Otters can also be dangerous towards domestic pets who encounter them. Although otters will not attack pets on their own, there have been some news incidents in which overly curious dogs were injured when an otter acted in defense. However, otters tend to stay away from humans and do not pose a threat to us – as with any animal, respect them by giving them space, and nature will respect you in return!
Are Otters Eating My Fish? (How to Tell)
Whatever method you might try, keep in mind that pond inhabitants such as fish and amphibians that may attract otters can attract other predators such as foxes, raccoons, birds, and domestic/wild cats, so it is important to consider multiple potential threats when protecting your pond – the culprit may not be an otter. Check for droppings, tracks, or utilize a camera if possible.
You can also tell if an otter is indeed visiting your pond by checking for scat, pictured above, or for their oily-looking spraint markings on rocks. Both of these will have a strong, musky scent. Sometimes raccoon scat can look similar, but is usually more regular in shape and has smaller bits as raccoons chew more thoroughly than otters. Often, raccoon scat will have seeds and grains; otters are completely carnivorous, and do not feed on these items. If you see any seeds or other vegetative matter in the scat, it’s not an otter. Sometimes, cat scat can also look similar; cat droppings are often dry, have hair, and are regularly shaped, while otter scat won’t have as much hair (since they don’t groom themselves like cats do) and tend to be irregularly shaped and more loose.
How Do Otters Hunt? Can They Communicate?
Both species have webbed feet, a thick paddle tail, and the ability to close their ears and nostrils underwater, which makes them excellent swimmers. They are highly mobile on land as well, and can travel long distances walking, running, and sliding. They have thick fur which provides insulation for enduring colder waters in far northern ranges and over the winter.
Otters also rely on sharp senses to thrive as hunters. Like all otters, vocalization is extremely important for communication. Smell and scent markings help them recognize each other’s territories and search for food. Finally, they have long, sensitive whiskers which help them navigate their surroundings underwater and seek out prey. Both species exhibit sexual dimorphism, with the males growing larger than the females.
Diets for both species are similar. Their diet mainly consists of fish, but they will also eat crustaceans, amphibians, reptiles, and have even been observed consuming birds and small mammals.
Otter Species You May Find in Your Ponds
Otters are mammals of the family Mustelidae, which also contains weasels and badgers. They are in their own subfamily, Lutrinae. There are 13 otter species around the world, and in this article, we’ll focus on just two freshwater semiaquatic species that may affect aquatic hobbyists; the North American river otter and the Eurasian otter. While these two species have several similar physical features and natural adaptations that help them thrive as freshwater predators, they are not often confused for each other because their ranges never overlap.
Other common names for this species are the European otter and the Old World otter. The Eurasian otter is the most widespread species of otter, though it’s considered a threatened species on the decline in most areas. It is distributed throughout Europe, Asia, and Northern Africa. They have adapted to occupy all types of freshwater bodies, and some even live in coastal areas, spending some of their time in salt water. Eurasian otters are the larger of these two species, typically reaching an adult size between 15-30 pounds and up to 5 feet long (including their tail).
Eurasian otters are most active at night, and are generally solitary and highly territorial. While individuals will mark and guard their territories against others of the same sex, male and female territories may overlap, though close interactions mainly only occur for breeding. Mating can occur anytime during the year and usually takes place in the water. Females build their own dens, called a holt, usually on the banks of a river where they will birth and care for young.
After a gestation period of about 60 days, females bear a litter of two or three pups at a time. Males do not have any parental role, and pups stay with their mother for about a year while they learn the skills needed to become independent. This species’ average lifespan is 4-5 years, but some individuals can live into their late teens.
As mentioned above, an otter’s sense of smell is very important in helping it navigate its territory. An informal study found that Eurasian otters may be able to use bubbles to smell underwater, which is a rare ability for mammals.
It is unfortunately endangered in some areas, mostly due to human actions such as pollution, habitat loss from development over wetlands, and hunting. In Europe, many populations are recovering thanks to the banning of harmful pesticides and, subsequently, increased water quality.
This species is also known as the northern river otter or common otter. Populations range throughout most of the United States, Canada, and as far north as Alaska. In the 1700’s, the North American river otter was first classified into the genus Lutra with the Eurasian otter. It was somewhat recently reclassified as Lontra, the genus of New World otters. This otter averages around 20 pounds and 3 feet in length, but can be as small as 10 pounds or as long as 5 feet.
North American river otter social behaviors are unique compared to other mustelids. While they devote a lot of time to scent marking, it is more for communication than defining territories. They also spend time in cooperative groups, which even consist of multiple males. These groups have been observed engaging in play activities, which is believed to strengthen social bonds and practice hunting skills.
Breeding in this species usually occurs in winter or spring, and the gestation period is also about 60 days. The females generally do not build their own dens, but instead find empty beaver lodges to occupy. North American river otters generally live an average lifespan of 12 years.
Like the Eurasian otter, the North American river otter’s populations have decreased over time due to factors such as pollution, habitat loss, and hunting. Protection of wetlands has allowed some populations to recover.