Investigation 3 - National Earthworm Survey

Worm Watch uses earthworms to help us discover soil and appreciate the importance of soil ecology in sustaining agriculture, the natural environment, and ourselves.

The National Earthworm Survey will help scientists, land managers, farmers, and people who do the research to make rules about what products are allowed into Canada, or what land reclamation practices are acceptable. We want volunteers to help us find-out how many different species of earthworms there are in Canada and where they live.

Canada is a very large country. It would take a very long time for a small team of scientists to examine all the earthworm species in Canada. That's why we need your help! Did you know that it has been assumed that most of the earthworms in Canada were killed in the last ice age, and were then reintroduced with the European settlers that came to colonise Canada. Earthworms move very slowly, so how could they have moved into so many places in such a short time?

We know that cart wheels carried mud that likely had a few earthworm cocoons attached, and hoofed animals can also pick-up and carry earthworm cocoons attached to their feet and legs. People carried worms on boats to fish and then disposed of the left-over worms on the banks of the rivers and lakes where they landed. Now people can move earthworms on heavy machinery and cars that mud attached. Maybe you have found an earthworm in a potted plant that you bought at the store.

There are native earthworms in Canada too, most of them have been found on the Pacific coast and in the far north west, where Canada was not glaciated in the last ice age. There are some native earthworms that have been found near our southeastern border that have migrated north from the U.S.A.. In the Yukon, and northern BC and Alberta we think there is an earthworm that has migrated (probably with help) across the Bering bridge from Siberia. The data you collect and file with Worm Watch will be used to compare earthworm populations and species diversity in different habitats across Canada. Then we can learn more about where the earthworms in Canada came from.

The key to this program has been the development of a set of standard sampling methods that work anywhere and can be used by anyone (scientists all over the World are using these methods). The methods range from a more casual survey to a method that is both quantitative and qualitative. We have also developed a simple taxonomic key to the more common earthworms in Canada that you can use to identify the earthworms that you find. There are procedures later on in this section that outline what to do if you find an earthworm you can not identify using the key. Our experts are only an email away if you have questions.

Challenge questions (use the library, encyclopedia, and educational internet sites to find the answers to these questions):

1. How large is Canada compared with other countries in the World?
2. When did the first European settlers move into your region of Canada, and where did they originally come from?
3. Why would glaciers have killed all the earthworms?
4. Did glaciers cover all of Canada in the last ice age?

There are approximately 23 known species of earthworms in Canada. Do you think there may be species that have yet to be discovered? Perhaps you will be the one to discover a new species of earthworm.

If you haven't already done so, complete Investigation 1: Anatomy of an Earthworm and Investigation 2: Identifying an Earthworm. These investigations are designed to give you the background information and skills that you need to identify the different species of earthworms. These exercises are for all participants!

Worm Watch requires that you use one of the National Earthworm Sampling Methods. These are standard procedures that help to ensure that your data has been collected in the same way as other participants in this program. Read the descriptions of each sampling method. Discuss the different methods with the members of your team and then decide which method to use and where you will sample. Remember to always ask permission before you sample!

National Worm Sampling Methods

Sampling Method 1 - Flip and Strip

This method is for those of you who want to do a casual survey. You could be on your lunch break, coffee break, working, or out for a walk and still identify earthworms. Some earthworm species live on or very near the soil surface. If you are in an area with lots of rocks, tree deadfall, or want a method with the least amount of disturbance: use Flip and Strip.

Earthworms live moist cool soil almost anywhere. They can also be found in many different habitats including: in, under rocks, aged dung pats, around water ways, with piles of dead leaves, under the moist bark of dead or fallen trees, and in your lawn or garden. To find these earthworms you will need to flip over rocks, logs and other bits of deadfall, and strip back the bark of the soil-side of fallen logs. Some earthworms only live in the near the soil surface and in litter, these are called epigeic earthworms. You can find these earthworms using Flip and Strip. Endogiec species that work the soil can sometimes be found under rocks, rotting wood, and aged dung pats. Anecic species that form deep vertical burrows often leave their castings (dung) at the exit from the burrow. This means you might see a hole in the ground or entrance to a tunnel (approximately the diameter of the earthworm) with a pile of casting on or near the hole. Lumbricus terrestris form middens a pile of food and castings at the entrance and exit to the burrow. So even if you don't find a worm you may be able to see evidence that earthworms are living in the soil.

There are highly productive soils around the World where earthworms do not exist, possibly because of glaciation, physical barriers to migration or for reasons that are yet unknown. You can help us understand more about earthworm habitats by recording your location, soils information, and all the other information asked for on the data sheet as accurately as possible.

• if you are not involved in long-term monitoring
• interested in biodiversity only (no need to quantify)
• if it is too difficult to dig on your site (the area is forested or rocky)
• if you are working with very young students
• if you want to do a one-time study aimed at finding the variety and number of earthworms at a selected site(s)

Click here for detailed instructions on the Flip and Strip method of sampling.

Sampling Method 2 - Modified Flip and Strip

Modified Flip and Strip (unlike Sampling Method 1- Flip and strip) requires the use of a sampling template. A sampling template is a device that standardizes the size of the area that you will be sampling allowing you to report the number of earthworms you count on a per area basis. Then you can compare the number of earthworms you counted in a habitat with those of other studies. The size of the area you sample is important: if the area is too small then the number of earthworms you find might over estimate the earthworm population in the habitat. If the sampling area is too large it is a lot of work with a lot of disturbance to find the earthworms and you might under estimate the population in the habitat. There have been studies done on the size of sampling area and the number of frames to use for studying earthworm. We have chosen a frame size of 25 cm x 50 cm based on these studies.

• if you are involved in a long-term continuous monitoring site
• if it is too difficult to dig on your site (the area is forested or rocky)
• if you want to do a one-time study aimed at finding the variety and number of earthworms at a selected site(s)

Click here for detailed instructions on the Modified Flip and Strip method of sampling.

Sampling Method 3 - Modified Hand-Sorting

This sampling method is used to determine the number and species diversity of earthworms in a given volume of soil. With this sampling method, you can study what species of earthworms live and work at different depths in the soil in your schoolyard, garden, or field.

Challenge question: How do you calculate the volume of soil you have sampled? What measurements of the sampling area do you need to make this calculation?

• if you are sampling in a more open area with reasonably deeps soils that can be disturbed
• if you want to study the relationship between earthworm populations and diversity and soil depth. (Hint: soil moisture and temperature interactions might be important)
• if you are going to split a class into groups and have each group sample an area at the same time
• if you want to do a one-time study aimed at finding the variety and number of earthworms at a selected site(s)

Note: this is not an appropriate method for long-term monitoring sites because of the level of disturbance. This is an excellent method for studying changes in earthworm populations over time or with respect to treatment in agricultural or areas subjected to intense land management practices (forestry and reclamation practices). Click here if you wish to use the Modified Hand-Sorting method of sampling.