The great Irish mammal watch

CITIZEN SCIENTISTS are being encouraged to help build a national picture of the dozens of mammal species with which we share this island. Sightings of mammals are being recorded, with more than 5,000 logged so far, to compile an Atlas of Mammals in Ireland.

Members of the public, amateur naturalists and scientists are asked to send details of mink, bottlenose dolphin or whatever else they see to the National Biodiversity Data Centre. It will help track non-natives such as mink and Irish species such as stoat.

The centre chose mammals for its first atlas project because, though common and often observed, “there is no or little data in terms of their distribution”, says Liam Lysaght, director of the centre, which has just released its annual report.

The task now is to see where our terrestrial and marine mammals live, plot them on the online atlas and promote mammal recording among the public.

“We now have a system in place where we can plot the distribution of say the blue whale and the pygmy shrew,” says Lysaght. Existing and historic data is also being collated to get a picture up to 2010.

In future, anyone who observes a wild mammal can submit details via an online form. Some unusual ones have rolled in. “We have had sightings of wild boar, muntjac, ferret, even chipmunks. They would all be verified before being accepted,” Lysaght explains.

It is surprising how little we know about some species. It was thought hedgehogs might reside more in suburban areas, as this is where people most frequently encountered them, but not so, says Lysaght. “The project is showing that they are widely distributed, but probably avoiding the uplands and wetter areas.”

Some introduced species, notably American mink and brown rats, can devastate nesting freshwater birds and seabirds, especially on islands, says Niall Hatch of Birdwatch Ireland.

We don’t know much about mink distribution, which zoologist Ian Montgomery of Queen’s University Belfast says is best described as scattered.

“It is difficult to estimate the abundance of species such as mink, which are quite secretive. They live along rivers in fairly thick vegetation so you can easily overlook them,” he says.

“They eat small mammals and birds as well as aquatic material, so they’ve a plentiful food supply. There is no reason why they shouldn’t be present in any part of the island. They’ve had time to spread everywhere.”

With recorded sightings, the atlas may fill in some blanks in mink distribution when the catalogue is completed – planned for 2016.

Each of Ireland’s 60-plus mammal species has been assigned a “champion” – a designated phone-a-friend expert for the centre. Zoologist Paddy Sleeman of University College Cork is confident that the project will tell us more about Irish stoats, which he champions.

We can say “absolutely nothing” definitive about the distribution of this small carnivore in Ireland, he says. “They seem to be abundant at rural rubbish dumps, in coastal deciduous woodlands and where there are a large number of rabbits.”

The last nationwide study of stoats was carried out in 1985 by Sleeman. “They are extremely difficult to study. They are not easy to trap, because you don’t know where they are,” he says. Stoats hunt small mammals and birds.

“This project will quantify the number of sightings in an area and give us some idea of where they occur. It is great to have somebody collating records in a systematic way. It’s a breakthrough,” Sleeman says. For May and June, many reports have been of stoat families – mum with two or three kits in tow.

Visitors to the atlas site can see recent confirmed entries. For example, an Irish stoat was seen on April 14th on sand dunes near Kilmore Quay in Co Wexford. Around the same time, a pine marten was recorded in a hedgerow near Timahoe, Co Laois, while an American mink was seen in Tomnafinnoge Wood, Co Wicklow. Red and grey squirrels are the most commonly reported species, which should help identify trends in their distribution.

Montgomery does have some reservations about the public’s ability to correctly identify wild mammals, however. “You would have to use the data with a certain amount of caution,” he says. “How many people know the difference between a red and grey squirrel? They may only see the backend of the animal.” Lysaght says the centre does have a quality control system.

Since the launch of the Atlas of Mammals in Ireland in April 2011, 5,363 records have been added to the database and made available through the centre’s biodiversity maps. The centre’s database, which compiles details on many more species, continues to grow. Thirty additional datasets containing half a million observations were added during 2011, according to the centre’s annual report.

Voluntary organisations have helped a great deal in the case of bats (Bat Conservation Ireland, batconservationireland.org) and marine mammals (the Irish Whale and Dolphin Group, iwdg.ie) by submitting their own records.

A deer database added last year showed the spread of sitka deer, a concern to foresters. So far there are no muntjac records this year, says Colette O’Flynn, a researcher at the centre. This dog-sized deer could become a high impact invasive species, so all sightings go through a strict verification procedure.

“There are verified sightings of muntjac in the National Invasive Species Database for counties Down, Armagh, Meath, Kildare, Wicklow and Cork. There have been additional unverifiable sightings in many other counties,” says O’Flynn, who adds that there is no evidence that it has successfully bred here or is established in the wild. If they do start breeding, the population will grow and “probably have a detrimental impact”, says Lysaght.

Wild boar has been seen in the countryside and has bred here, but young were removed. Experts say it is best to deal with invaders early. Montgomery reckons eliminating mink from the countryside would require a colossal undertaking in terms of manpower and funding. Effectively, it’s too late.

The same could be said for bank vole and a newly arrived shrew species (see panel). These new rodents may shrink the range of our native pygmy shrew. The new atlas should illustrate how the story unfolds.

“The primary value of what we are doing is to bring all existing databases together and so have contextual data for more detailed studies. If someone wants to do a study on squirrels or hedgehogs, at least they will have some distributional data to work from,” Lysaght concludes.

Visit the National Biodiversity Data Centre at biodiversityireland.ie

Wood mouse and pygmy shrew under pressure from non-native rodents

Scientists report that the wood mouse and pygmy shrew in Ireland are under pressure from two non-native rodents, the bank vole and greater white-toothed shrew. The effect is cumulative. When both invaders are present, native shrew and wood mouse are hit harder.

“The pygmy shrew disappears. It just goes completely where bank vole and greater white-tooth shrews are present. So they are putting this species in danger,” says Ian Montgomery from Queen’s University Belfast, who has studied the impact of these invaders. The number of mice falls to one-sixth what they would have been when the two species are about.

Experts questioned whether the continental shrew would survive an Irish winter, but Montgomery trapped plenty of them during the harsh winters of 2010 and 2011.

“It is very unlikely that the greater white-toothed shrew and bank vole will do anything other than spread throughout the country and there is not a great deal we can do to actually eliminate either species,” he concludes.

The mammal atlas currently being assembled with the help of citizen scientists should at least show us where the invaders are and highlight any future trends in our native small mammals.

Montgomery says we can manage the landscape to extend our indigenous wildlife species a helping hand toward survival. Planting more woodland in every county is one way of keeping the environment more in tune with their needs. “Allowing hedgerows to become a little bit overgrown is a good thing for wood mice but not so good for bank voles and greater white-toothed shrews,” he adds. The mammal atlas could help track the impact of changing habitat.

The bank vole arrived here from Germany, probably in the late 1920s. It now occupies the southwestern third of Ireland.

The greater white-toothed shrew was discovered here in 2007, but probably established a beachhead in Tipperary over a decade earlier. It likely hitched a ferry ride over from France in wrapped roots of trees. The bank vole is numerous throughout the southwest, while the French shrew reaches high densities wherever it occurs, says Montgomery.