19-July London’s Small Mammals in Summer

Summary

Beneath London’s summer calm, a secret world of small mammals is in motion. Young moles surface and scatter, harvest mice weave nests in golden corn, and dormice tuck into honeysuckle-lined hollows. Shrews squeak and vanish, their brief lives ending quietly on paths. Bats flit over rivers and reed beds, some carrying their young mid-flight. Stoats and weasels hunt in packs, squirrels build new nests, and rats forage in open spaces.

🐾 Return on 19 July to uncover the quieter, often overlooked creatures of London’s wild spaces — from the elusive water shrew to the torch-lit ballet of bats over the Thames. It’s a rich, fleeting moment in the city’s natural calendar.

Article

Mammals

Mole

A lot of new mole hills are starting to appear this month. When young moles seek to extend their range they don’t burrow but just make a run for it on the surface. As they do this during the day as well as at night, many are killed by foxes as well as dogs and cats. It is believed as many as half of all young moles die in this way, although they are often not eaten by their predators due to their unpleasant taste.

19-July London’s Small Mammals in Summer Section Image

19-July London’s Small Mammals in Summer Section Image

Mice and Shrews

Harvest mice and dormice are making nests. Harvest mice are now moving from the edges of cornfields to build their nests within the corn itself. Here they weave grass and straw to make their tiny seven centimetres diameter nests. In less than a month these may contain five young. Dormice make their breeding nests out of dry grass, moss and strips of honeysuckle bark. They then cover and line them with dry leaves. Sometimes they will adapt an old bird’s nest, but generally prefer the hollow of a tree or a loft. Young may be born as early as May or as late as September, but they are usually busy with a family this month.

19-July London’s Small Mammals in Summer Section Image

19-July London’s Small Mammals in Summer Section Image

The presence of shrews is usually announced by their high-pitched squeaks in hedgerows and grassy banks. Once disturbed they are instantly silent and then disappear, often burrowing to escape. Last year’s males are now approaching the end of their brief, hectic lives. Having to eat twice their own weight daily, they are finding it difficult to hold on to their territories and so are often found dead on paths. They are rarely eaten due to their unpleasant, musky odour, although this doesn’t deter owls which happily swallow them whole. Finding so many on paths, it was thought they were incapable of crossing them. If one was encased in the hollow of an ash tree, the tree became known as a ‘shrew tree’ and it was then believed to have healing powers. The leaves of the tree would then be used to cure lameness. Shrews are now at the peak of their breeding season, some having already had several litters. Now is also a good time to look for water shrews, but only where the water is crystal clear. Such places are substantially less common than they were even fifty years ago, but Wimbledon Common and Thamesmead are still possibilities, with Elmley Marshes in Kent remaining a stronghold.

Another, less popular, rodent is the brown rat which may now be on its second or even third litter. This month they tend to be seen looking for food away from their usual haunts in more open areas. They like areas of low bramble at the edges of woods where it is easier for their inexperienced young to escape predators.

19-July London’s Small Mammals in Summer Section Image

19-July London’s Small Mammals in Summer Section Image

Squirrels

This is also a good time to identify young squirrels from the spring litter as they are noticeably smaller than their parents. Young squirrels disperse when their teeth are fully grown and they can feed alone. A second summer litter may be born this month and adults can sometimes be seen building a new nest.

19-July London’s Small Mammals in Summer Section Image

19-July London’s Small Mammals in Summer Section Image

Stoats and Weasels

Both are still hunting as families. With stoats, there may be up to eight in a pack, rarely reaching twenty-four if packs meet and join up. Unlike stoats, young weasels can breed in their first year, bearing litters of five or six young. This rapid increase in numbers is held in check by foxes, cats, dogs, cars and owls. They are also caught by other birds of prey, although they have been known to kill kestrels by biting the large veins beneath their wings as well as their neck. They will attack almost anything they can hold and kill it in this way, and have even been known to roll eggs out of hen houses.

19-July London’s Small Mammals in Summer Section Image

19-July London’s Small Mammals in Summer Section Image

Bats

Like most other mammals in July, bats are also breeding fast and in a good summer their numbers may have increased as much as a third. Consequently, it is worth looking for them on warm evenings at the edges of quiet rivers and lakes. Over reed beds you can sometimes see them picking off insects and spiders from the tops of the reeds, some even carrying their young as they do so. In 1767 Gilbert White mentioned “myriads of bats” flying over the Thames between Richmond and Sunbury.

19-July London’s Small Mammals in Summer Section Image

19-July London’s Small Mammals in Summer Section Image

This is not true any longer, although Richmond Park and Home Park are still good places to see them. When watching over water, it is sometimes useful to have a torch as parents may be teaching their young to catch insects, even dipping into the water as they do so. Other places recommended for individual species are the Mole Gap between Dorking and Reigate for Bechstein’s, Highgate Wood for Natterer’s, Wanstead Flats for Daubenton’s, Grand Union Canal for Noctule, Bushy Park for the brown long-eared bat and Bedford Lake County Park for Soprano and Nathusius’s pipistrelle.

19-July London’s Small Mammals in Summer Section Image

19-July London’s Small Mammals in Summer Section Image