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For me, it all started in a room in Ruthin in 1984, along with fellow members of the North Wales Naturalists Trust.

We spent a day having lectures on aspects of bat biology, identification, conservation and licensing and in the evening we each had an opportunity to catch a pipistrelle in a hand net and examine it.

After that our licences were signed off and participants were urged to form new county Bat Groups. In our case it was the Clwyd Bat Group, but the same process was taking place over much of the rest of Wales.

The Bat Groups started to survey the status and distribution of their resident species, often starting from scratch. In Wales, with its abundance of natural caves and disused slate and lead mines, the easiest and most productive way of gathering this information was to survey hibernation sites.

Subsequently, many of these surveys have developed into long-term studies, highlighting national changes in bat distribution.

In the early 1990s, Montgomeryshire Bat Group reported a greater horseshoe bat hibernating in the West Llangynog Slate mine, even though previous records had been restricted to the southern Wales.

Initially it was suspected this was a single vagrant animal, but over the following winters the species was reported from other underground sites across the border in Clwyd and then as far north as the Conwy Valley.

Greater horseshoe bats are now recorded as summer residents in North Wales and it seems only a matter of time before breeding colonies are found in the area.

(Image: Dr Henry Schofield)

Another species that appears to be on the move is the serotine. Serotines are large bats that forage low over grassland feeding on dung beetles. Although there had been tentative sightings in south-west Wales, the first substantiated record of the species was in central Powys in 1984, where four animals emerged from the roof space of a large house.

One of them was caught and proved to be a juvenile serotine. It was viewed as an extraordinary discovery at the time but over the following decade there were records of individuals caught in mist nets and small colonies discovered in churches and other buildings.

Amid increasing evidence of a shift to the west in its range, it was perhaps not unexpected to have the odd one turn up in North Wales, as one did in 2011.

This might also have been regarded as a vagrant had it not been for the efforts of Sam Dyer and his colleagues, who established by radio-tracking the presence in North Wales of the fifth largest breeding colony in the UK, located 100km north of the nearest known roost.

It’s hard to believe that the species would have been overlooked back in the 1980s – they are noisy and make their presence felt in roosts, and they produce copious amounts of very distinctive shaped droppings.

They are also easy to pick up on a bat detector – but then bat detectors have changed too.

(Image: Dr Henry Schofield)

In the mid-1980s the only easily and cheaply available bat detector was made by Queen Mary’s College London, which bought in cheap transistor radios and modified them with a transducer microphone so they could detect ultra-sound.

It was not until the late 1990s that computer technology and electronics had progressed to the point where bat echolocation calls could be recorded in the field and subsequently analysed on a home computer.

This development continues to this day: it would have been impossible back in the 1980s to imagine a bat detector linked to a mobile phone, which displays sonograms of bat calls to you in the field as you watch the animal foraging for prey.

One species we have been able to detect more easily is the barbastelle. Rarely recorded in Wales during the 1980s and 1990s, they are now known to be widespread here, although they are still regarded as one of our rarest bats.

(Image: Dr Henry Schofield)

The new bat detector technology has not only allowed us to look at bat echolocation calls but also their social calls.

Bats use these calls to communicate things like territoriality and to attract mates during the breeding season. The calls vary between species and they are often quite complex and can consist of sharp frequency sweeps and trills.

When slowed down so that we can hear them, they are often quite beautiful and sound like bird song.

The past 30 years has seen some huge changes and our knowledge of the distribution and status of our bats has improved dramatically.

Protective legislation means that Wales is now home to one of the largest lesser horseshoe bat colonies in western Europe, with 1,000 resident bats.

New threats will undoubtedly emerge, but so too will advances in technology and survey techniques: we can look forward to GPS tags that are small enough to fit to bats, and maybe hand-held portable devices for confirming species identification using molecular techniques.

It seems likely the next 30 years will be as challenging and changeable as the past have been.

The author of this abridged article is Dr Henry Schofield, conservation programme manager for The Vincent Wildlife Trust

A longer version appears in the Winter edition of the quarterly magazine Natur Cymru – the Nature of Wales.

Annual subscription is £18 (or £17 by direct debit). See www.naturcymru.org.uk or 0300 0654867.