Mammal Week 2020 - Freshwater

National Mammal Week 2020: Day 6: Freshwater

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PhD student Holly Broadhurst writes about Swimming Through Freshwater Habitats....

Hi, I am Holly Broadhurst, a PhD student at the University of Salford. I am investigating if environmental DNA (eDNA) can provide a real-world application for monitoring mammals. During my fieldwork I get the privilege of walking along riverbanks, slow-flowing streams and smooth lakes to collect water samples that could contain the genetic material or eDNA of mammals living in or around those freshwater habitats.

Those walks are arguably the most exciting aspect! You could spot an otter entering off the banks or hear a distinctive ‘plop’ of a water vole. If you are really lucky, you could spot the elusive water shew swimming through the water predating on aquatic insects. Freshwater creates a unique habitat, providing different opportunities for the mammals living in and around them.

These mammals have developed special features that have allowed them to adapt to a semi-aquatic lifestyle in our freshwater systems. Otters have perfected their swimming technique with webbed feet and the ability to see underwater, electing them the top predator in our watercourses. Water voles live in burrows within the grassy banks of slow-flowing rivers and streams, that can sometimes have a secret underwater entrance for a quick getaway and water shrews have stiff hairs on their tail and back feet making them an excellent swimmer.

Beavers are also making their way back into our water courses after a near global extinction. They are ecosystem engineers that can transform a freshwater habitat into a completely new ecosystem. They dam narrow water courses and cut down trees to create a wetland environment like no other. Freshwater allows semi-aquatic mammals to express behaviours that cannot be performed in any other type of habitat. Unfortunately, these habitats are under immense pressure from human development, pollution, habitat loss and the spread of invasive species. These pressures can have a major impact up the food chain, from the invertebrates that water shews feed on, fish that otters predate on and the buffet of lush vegetation that water voles indulge in.

Monitoring Mammals

Knowing where mammals live is important for conserving them and their habitat, we can identify these areas by looking for field signs. Whether that be footprints on the muddy banks or in between grassy tussocks, a feeding station of a water vole containing nibbled grass cut at a distinctive 45˚ angle or the best kind of field sign ecologists love to find: faeces. Water vole latrines and otter spraint are both signs of territory markings and are a great identifier that the species are nearby.

As semi-aquatic mammals swim through the water, they leave behind traces of their DNA in the form of faeces/urine, skin cells or saliva. When I collect water samples, I am also collecting eDNA. After applying specialised laboratory methods such as eDNA metabarcoding, we can find out what species are living in and around those habitats, including terrestrial mammals!

The use of eDNA metabarcoding is a non-invasive method and you don’t have to know what species are already there in advance. This makes it a potential method for the early detection of invasive species such as the American mink. Environmental DNA has become a vital tool for determining the distribution of a wide variety of species in different environments, revolutionizing wildlife surveys.

I work with a brilliant team at the University of Salford that works towards using non-invasive genetic techniques to monitor mammals. If you would like to know more about what we are doing to monitor our mammal communities, please head over to our website for more information.

You can find out more about Holly's group on the Lab website here 

How Can You Help?

You can help build knowledge of the mammals in and around Britain's freshwater systems by recording your sightings on our Mammal Mapper app. It's free to download, and if you register during Mammal Week you'll be entered into a prize draw too! Read more about how Mammal Mapper works here

Don't have a smartphone? You can still submit your recordings through our online form found here