eDNA - what is it, and how do we use it?

New surveys using eDNA are being approved all the time, learn more about them in this post.

eDNA, what’s that?

eDNA stands for environmental DNA, and it’s used to describe DNA that wildlife leaves behind in the environment. Sometimes that DNA’s obvious – bat droppings for example. Sometimes you can’t even see it’s there, like the DNA great crested newts leave behind in ponds.

So how are you using it?

Ever since it became cheaper and quicker to sequence genomes, and to run DNA samples in a lab, people have been developing identification tests to help work out exactly which species you’re dealing with. This started years ago with bat droppings. We collected bat droppings when on site, separated them as best we could into different species and sent them off, then got a confirmation of the species ID back from the lab.

Wait. You separated bat poo into different species?

Yes. Yes we did. Look, no-one ever claimed being an ecologist was glamorous. Different species of bats do different sizes and shapes of droppings, and once you’ve looked at enough, you do start to be able to separate them by species. Now you don’t have to do any sorting, you can just send off a sample and you get a list of species back.

Is it just bats?

Nope! One of the eDNA surveys we do most regularly these days is for great crested newts. Instead of needing to actually see the animals (which we did through a variety of methods, including trap and release, torchlight surveys and netting, all of which were somewhat stressful for them), now we can just take 20 water samples from around a pond, send them off, and a week later we get an email telling us whether or not great crested newts are using the pond.

You can also get confirmation of otter presence from their spraints (fancy ecology word for poo – do you see a theme emerging?), and you can get presence/absence information about invertebrates too. Tests are currently under development for crayfish, freshwater mussels and water sampling for aquatic invertebrates.

Does this mean no more lengthy surveys?

Well, no. eDNA techniques can’t give us abundance information, only presence/absence data. You need to know what size population you’ve got in order to assess the impact of what you’re proposing to do on a site, so if you get a positive result for presence, you may still need to do some more survey work.

Where can I get this done?

There are several labs which offer one or more of these services. Our personal favourite (despite their current website woes), are Nature Metrics. Other labs are available, but our experience is that the great crested newt eDNA sampling kit from Nature Metrics is much more user-friendly than any of the others we’ve tried, the app is brilliant, and their customer service is excellent.

What else should I know?

If you’re commissioning a great crested newt eDNA survey, you need to check it’s the right time of year, because there’s a very specific window when the results will be acceptable (15th April - 30th June). Also, make sure the lab has passed the current Natural England proficiency test for that year. Other surveys can be done year round.