The easiest way to prevent mudsnails from spreading is to avoid water contact when possible. However, if your activities include water contact, you can follow these simple steps to reduce the chances of spreading this invader to another stream:

The Basics:

  • 1: Don't be a carrier!
  • Avoid transferring anything wet (especially, waders, boots, and gear) from stream to stream.
  • 2: Keep it DRY!
  • After every trip to a stream or lake, remove all mud and debris, visually inspect, and completely dry your belongings. If you can, put your wet things in the dryer on high heat for a minimum of 2 hours. Air drying your belongings at temperatures of at least 85°F for 24 -48 hours will also kill mudsnails.

These are the easiest, and most basic things you can do to prevent the spread of New Zealand Mudsnails and prevent the introduction of other invasive species into our local waterways.

Visit more often?

If you frequently visit lakes and streams, (e.g., you are a stream researcher, monitoring crew, watershed survey group, and others who access streams and lakes regularly), you should refer to "How to Prevent the Spread of New Zealand Mudsnails through Field Gear" produced by Oregon Sea Grant.

This guide provide more detailed information on currently accepted methods for treating gear and preventing the spread of mudsnails.

It only takes one snail to infest a waterbody! Please help protect our creeks and streams!


McKinney, Dennis. "Destructive Mudsnails Found." The Gazette. 4 Apr. 2005

National Invasive Species Information Center.

Oregon Sea Grant. 2006. "New Zealand Mudsnails: How to Prevent the Spread of New Zealand Mudsnails." [Brochure]

Perras, Kriss and Melina Watts. . "Significant Portions of Malibu Creek Hit with Invasive Species." PCH Press. 28 June 2006

Schreiber, E.S.G.; Quinn, G.P.; and Lake, P.S. (2003). Distribution of an alien aquatic snailin relation to flow variability, human activities and water quality, Freshwater Biology 48: 951-961

Shinn, D.C. 2001. New Zealand Mudsnail in the Middle Snak River, Idaho. In: Chavez Writing and Editing, July 9 and 10, 2001. In: New Zealand Mudsnail in the Wester USA Conference 2001. Minutes of the First Annual Conference. Cheever Hall, Montana State University, Bozeman, Montana.

Sohn, Emily. "Alien Invaders."


This website was created to provide information about New Zealand Mudsnails and the threat of invasive species to creeks, streams and lakes in Southern California. Below are answers to some frequently asked questions about the mudsnail and what you can do to prevent its spread.

What is the New Zealand Mudsnail?

New Zealand Mudsnails are tiny INVASIVE snails that have now been found in certain creeks in the Santa Monica Mountains area.

They may be small, but don't be fooled! In large numbers, these small snails can completely cover a stream bed and wreak havoc on local stream ecosystems. Introduced from New Zealand to the Western United States in the 1980s, New Zealand Mudsnails have already invaded many Western rivers in California, Idaho, Montana and Wyoming including Yellowstone National Park. They have now been found in eleven streams and four watersheds in the Santa Monica Mountains.

Local and state agencies and environmental organizations are now enlisting the help of local hikers, horseriders, anglers, and others who use the creek, in preventing the spread of the New Zealand Mudsnail waterways in Southern California.

Photo: D. McKinney, with thanks to

New Zealand Mudsnails on a wading boot. Mud snails hitch hike on gear such as boots, waders, bike tires and even pets. "These mudsnails behave rather differently as snails go... They are almost aggressive in the way they motor around and seek new things. If you are walking around in a stream, these snails are going to be checking out your feet. And if you stand in one place very long, some of them are going to come onboard." - Pete Walker, Colorado Division of Wildlife Senior Fish Pathologist (from McKinney, Dennis. "Destructive Mudsnails Found." The Gazette. 4 Apr. 2005)

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What are invasive species?

In a day and age of global trade and international travel, it is not surprising that plants and animals are also traveling by hitching a ride. Today, you can find Japanese oysters in Ensenada, Mexico, or in your backyard! However, some non-native plants and animals get out of control-when they reproduce very rapidly and crowd out other, native species, they are considered INVASIVE. Every year, 1.3 BILLION dollars are spent in the United States to battle invaders.

In fact, half of all endangered species in the United States are being threatened by invasives who eat them, eat their food, crowd them out, and destroy their natural habitats.

Photo: R. Draheim, with thanks to Center for Lakes and Reservoirs

New Zealand Mudsnails on a small rock, with penny for size comparison. Mudsnails create dense colonies-often 100,000 mudsnails can be found in an area the size of a large kitchen sink. "Where they have been found, they make up a large proportion of the living material that's in the ecosystem. But they are a dead-end, in terms of the food chain. They consume, but can't be consumed. They can out-compete and reduce the number of native aquatic invertebrates that fish and amphibians rely on for food. This reduction in food supply can disrupt the entire food web with drastic consequences." - Marc Abrahamson, Heal the Bay

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What makes the Mudsnail invasive? Why is it a problem?

In some ways, the New Zealand Mud-snail is the perfect invader. Mud-snails reproduce parthenogenetically-that is, by cloning themselves. It only takes a SINGLE snail to produce an invasion. In fact, a single snail can result in a colony of more than 40 million snails in just one year! New Zealand Mud Snails can completely cover a streambed, crowding out the native aquatic insects that provide food for native creek animals, including local endangered species like steelhead, tidewater goby, and the red-legged frog.

Photo: Miwa Tamanaha

Located just 25 miles from downtown Los Angeles, Malibu Creek flows through the Santa Monica Mountains to Malibu Lagoon, offering residents and visitors opportunities for hiking, fishing, bird watching and horseback riding. “These creeks and streams are incredibly sensitive systems. Anything that messes up that balance can have a grave impact. Changes we, as humans, create in the system are not always easy to change back. We should recognize that the more we alter the system, the more difficult it is to turn the clock back.” –Gary Busteed, National Park Service

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That sounds bad. What can I do?

Well, there is good news and bad news. Unfortunately, once a creek or stream has been invaded by mud-snails, the invasion is irreversible. There is no known way to eradicate mud-snails once they have been found in a water body.

The good news is that there is A LOT we can do to prevent mud snail invasions. And the things we do to prevent mud snail invasions will also help protect our local lakes and streams from other kinds of dangerous invaders�other invasive plants and aquatic animals that can also spread from place to place. While mud snails have been found in certain portions of Malibu Creek and Lake Piru, there are many of other places where we do not have mudsnails, and hopefully never will!

Remember, mud snails are tiny. They can be as small as a grain of sand, and only get up to 1/8 of an inch long. As you go from place to place, these tiny hitchhikers can easily attach to your wet boots, clothing, sports gear, pets, horses, and bikes, and spread from one stream to another.

You can help protect our local creeks by NOT SPREADING the New Zealand Mud-snail.

  1. Follow the tips on the left when visiting streams and lakes in your area. Don�t carry mud snails from place to place.

  2. Learn more about mud snails and invasive species. Click here for more resources.

  3. Spread the word! If you have friends and family who visit streams and lakes in your area, tell them about the threat of New Zealand Mudsnails and other invasive species. Encourage them to do the right thing and stop the spread!

  4. Creeks with poor water quality and degraded habitat quality are MOST susceptible to invasions-by mudsnails and other aquatic invasive species. Simple actions-like picking up litter and pet waste-can go a long way towards protecting creeks and streams. Click here to find some easy things you can do to improve water quality in our watershed.

We are fortunate, in an area as highly urbanized as Southern California, to have natural areas with truly beautiful lakes and streams. These places are home to many important native creatures, such as the endangered Southern Steelhead Trout, Arroyo Chub, Western Pond Turtles, Pacific Tree Frog, California Newt, Arboreal Salamander, Western Toad. Let's protect our natural heritage sites! Prevent the spread of New Zealand Mud-snails and other invasive plants and animals!

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Mudsnails are brown or black in color and can be as small as a grain of sand and reach lengths of up to an 1/8 of an inch.

To find the NZMS research website at Montana State University for more information on how to identify New Zealand Mudsnails Click here

Useful Publications

How to Prevent the Spread of New Zealand Mudsnails through Field Gear

Photo 1: D. Gustafson
Photo 2: Jamie Reinhart, with thanks to the City of Calabasas