Nearly 5,000m away, the Gola Rainforest National Park in Sierra Leone is one of the largest remaining blocks of Upper Guinea Forest. With such a large area, biodiversity surveying can often be tricky, which is why we’re trialling using environmental DNA (eDNA). Senior Conservation Scientist Felicity Edwards explains.
The RSPB has been working in Gola for over twenty years with local NGO’s and the government. However, there’s still so much to learn about the wildlife in Sierra Leone’s first rainforest national park. And with the park being nearly 700 square kilometres, that’s a lot of ground to cover! That’s why we’re investigating how meta-barcoding, metagenomics and individual DNA can be complementary techniques for monitoring biodiversity in the park.
Gola forest (c) Caroline Thomas (rspb-images.com)
Insect soup
The first is collecting insects using malaise traps in Sierra Leone, working in collaboration with Prof. Doug Yu at University of East Anglia and Nature Metrics on this project. These tent-like traps can attract and collect a huge array of species.
Once you have a mixture of insects it is turned into mush (we call it insect soup) and the DNA is then extracted and run through a meta-barcoding machine which can identify unique species. Invertebrate sampling is extremely effective (you can collect 1000s of individuals) but it’s traditionally costly in laboratory time to identify everything that’s been caught and requires experts for each group of insects.
Meta-barcoding allows us to quickly build a broad understanding of what is present. It allows us to see how many different species are at a location and the diversity of these invertebrates, we can then compare between different sites.
DNA in samples
Environmental DNA (eDNA) is DNA that is collected from environmental samples such as soil or water, rather than directly from an individual organism. Sources of eDNA can include faeces, shed skin, hair and even carcasses.
The use of eDNA sampling can give us a snapshot of the biodiversity occurring in a local area, where normal surveying would traditionally be difficult and/or time-consuming to do.
Again working with Prof. Doug Yu and Nature Metrics, we’re also investigating eDNA, by extracting water samples from small streams in Sierra Leone to collect DNA from mammals (including small and cryptic ones!), amphibians, birds and fish.
Gola eDNA water sampling (c) H S Sathya Chandra Sagar
This allows us to work out what’s present across the landscape and with repeated sampling changes in presence over time. We’re investigating how this non-invasive survey technique can act as a biomonitoring tool in Gola. This includes both the aquatic fauna but also terrestrial species, which come down to streams to drink, as well as faces ending up in these streams.
Notably key threatened species can be noted by this sampling, which some are very hard to survey due to their elusive nature, rarity or particular behaviours/habitats (for example nocturnal or arboreal species are harder to survey). DNA in water does tend to decay quickly so results are likely to be an indication of species in a fairly immediate area over a short time frame. DNA presence will also be dependent on stream flow and volume.
It's all in the poop!
We’re also working on identifying where elephants are moving across the landscape using faecal DNA. A key thing to understand when monitoring threatened species is exactly how many individuals there might be, and which individuals have been where. This can be really tricky to find out, especially in a rainforest habitat.
Working with ELRECO (Elephant Research and Conservation) an NGO founded and run by Dr Tina Vogt and Bernhard Forster, we are starting a project which aims to try and find out more about individual forest elephants (Loxodonta cyclotis) across the Greater Gola Landscape in Sierra Leone and Liberia.
Finding elephant dung is much easier than an elephant itself (they might be big but they are very good at being elusive!), and this dung holds lots of information including DNA. Taking samples of the dung, and then processing this at a genetics lab allows us to identify individual elephants giving us both an idea of how many elephants occur in the Gola landscape and how they move across it.
Gola elephant faecal DNA sampling (c) ELRECO
Further, the more samples we get from different areas, the higher the chance to re-sample the same individual, so that we will also better understand their seasonal migration behaviour.
We’ll be releasing the results of these projects over time – so watch this space!
Continue reading
Would you like to be kept up to date with our latest science news? Email with the heading 'enewsletter' to be added to our quarterly enewsletter.
Want our blogs emailed to you automatically? Click the cog in the top right of this page and select 'turn blog notifications on' (if you have an RSPB blog account) or 'subscribe by email'.