I HAVE received many comments from visitors to our local nature reserves on how lovely it is to see our cattle grazing.

The urban locality of these sites means it is unusual to see naturally occurring large animals like deer, and most other common, large animals such as the badgers and foxes are almost wholly nocturnal. To witness our cattle casually grazing amongst the heathland scrub, or to see them emerge from the tall marshland vegetation, offers some visitors a new and novel experience.

While they offer a new dimension to the sites, their primary reason for being there is to carry out essential maintenance tasks, and are rotated around the sites when needed. In essence they act as mowing machines, controlling invasive or aggressive species without leaving the nature reserve looking like it has been mown, and instead the result is a tussocky, more varied habitat. This method is also much more sensitive to the resident wildlife. For example, a ground nesting bird is quite at ease with a cow wandering past.

As the herd moves they deposit regular piles of dung, and dung provides an excellent supply of food, warmth and shelter. These pats support a surprising array of invertebrate species, by offering a nutrient rich food for the adults, their larvae or their prey.

If you’re feeling brave, take a close look at a cow pat, and you’ll see a network of tiny holes where various inhabitants or passers-by have burrowed or fed. One of the commonest visitors is the yellow dung fly. It can frequently be seen in large numbers scurrying around on a pat, or swarming around one in the air. They are there to mate and lay their eggs.

It is the larvae of this furry yellow fly that feed and develop within the dung. The adults in fact prey upon other flies, which the dung attracts in droves. I saw this at close quarters this year, and I have to say it was quite an impressive effort on both the part of the dung fly and its prey.

I was having lunch on one of the reserves when a fly started to buzz around, probably attracted to my dinner. I was getting a little irritated by this, when I noticed the fly tumbling through the air, wrestling with a slightly smaller dung fly. It was over very soon, as the yellow assassin plunged his mouthparts into its prey.

It’s not just flies that are attracted to dung. Some beetles take full advantage of the extra food also. One in particular is the dor beetle. It is a relatively large, stocky, black beetle, which is capable of eating its own weight in dung every day (as its larvae).

Once pairs form they actively seek out an acceptable pile, under which they set-up home. The female digs a shaft beneath the dung, with channels running off. The male then brings small parcels of dung from the pat above and places them in the chambers, after which the female deposits her eggs.

There are even species of bat that rely on dung. The greater horseshoe bat particularly likes to eat dor beetles and chafers, and is thought to be declining, partly due to the use of some chemicals used to treat worms in cattle and loss of suitable habitat. The chemicals used also reduces the number of beetles.

These creatures play an important role in the breakdown of, not just cow pats, but waste from other animals also. By breaking up the pat, it provides more surface area for bacteria and fungi to populate, speeding up the decomposition process.

ADAM HAMILTON