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Bats

BATS AT GLASGOW ZOO (Richard O’Grady)



Over the past thirty years, Glasgow Zoopark has been associated with two types of bats:

  1. Exotic bats, and
  2. British native bats.

Exotic Bats


The exotic bats took the form of a breeding group of GIANT INDIAN FRUIT BATS. These were acquired from dealers Ravensden in 1973, and housed in an enclosure in our Tropical House ( where some of the Gila monsters now are).

We found them easy to keep, although we did have to invest in a humidifier because the warm air central heating tended to dry out their parchment-like wing membranes so they cracked. Although the cage measured 4 metres x 2 metres x 1.2 metres in height the bats rarely flew, preferring to clamber around from point to point. Perhaps the cage was too small and they were unable, or reluctant to fly.

In any event, this was the reason we eventually - after four years - discontinued keeping this species. A by-product of this reluctance was that bats became fairly distressed if, once on the ground, they were unable to get up the walls to join the group once again. This was solved by providing a selection of climbing holds - weldmesh, small branches, etc., nailed to the walls.

We bred the bats many times. The breeding male we found to be quite aggressive to other males, who tended to keep away from the small group of females as a result. He was noticeably larger than the females, with a bolder, heavier head. He was also extremely evidently male, which we assume is an adaptation to an arboreal or otherwise precarious habitat, as opposed to the dimensions of another mammal of similar body volume like a small rabbit or a rat.

Fruit Bats

We found fruit bats to be messy eaters - ripe fruit being the favoured food - but fastidious about their cleanliness, always grooming and preening themselves and each other. Some of this must have been to spread group smell and strengthen group cohesion, but one couldn’t fail to be impressed by their ‘delicate’ up-ending whenever they felt the need to defecate - to avoid the fur becoming soiled. Faeces and food fell straight to the floor, where it was cleaned away every day.

We were somewhat dismayed to lose animals over 2 or 3 years from cirrhosis of the liver. Veterinary advice was that fermenting fruit could have caused this, but instinct - mine - suggests this to be improbable.

British Native Bats


In 1981, in cooperation with about ten local secondary schools, we constructed nearly 200 bird nesting boxes and sixty bat boxes. The designs for the bird nesting boxes were based on the five types favoured by the British Ornithologists Union. The bat boxes were the standard design of that period (largely unchanged today).

It is said that one box can be constructed from a plank of wood about 1.5 metres in length and 10 cms in width. Be that as it may, the boxes we constructed were approximately 15 cms in height by 6 cms in depth. Entrance was from underneath, through a 1½ cms-wide slit, which ran the width of the back board. This board was 3 or 4 cms longer than the box and serrated below to provide a grip for an approaching bat landing from flight. After landing on the board, it would then scuttle up into the safety of the box.

The boxes were erected according to recommendations, in threes all at the same height. One was orientated South-West, one South-East and the other North. Bats are very susceptible to over-heating. If the sun’s rays were shining on a box for any length of time, this permitted a bat to leave the box, and creep round the trunk of the tree to the far side. That is the theory, through we have never witnessed it in practice.

Boxes were erected about 5 metres from the ground, in largish trees with a clear, unobstructed flight path. They were also, preferably, sited on trees near water - easy enough for us to do, as most of our site is near water, either the river or ‘the Webbie’, a 1½ hectare loch rich in aquatic life.

Many of the boxes were sited in near-ideal, optimum conditions. Others were not. This was largely because we were using volunteers to erect them some of whom possessed little or no knowledge of bats, or even conservation for that matter. The good bat box sites tended to be occupied quite quickly and regularly by bats. The remainder were taken over by birds. Tree creepers love bat boxes, and occupied the more isolated boxes in large old trees like oaks. Nearer the buildings, house and tree sparrows soon mastered the knack of gaining entry and used them year on year.

Those boxes which were incorrectly sited tended to stay that way, I’m afraid. Somehow we never managed to find the time to re-site them. If, however, we were to encounter a handy ‘batophile’ who would like to do this, the boxes are still in remarkably good condition, even after so many years.

With regard to the species of bats occupying the boxes, we have never had this scientifically determined. However, observations can throw some light on this. An occupied box is relatively easy to spot, even if you don’t see the bats going to and fro - the back access board has the mildew and lichen scraped clean by the bats’ sharp claws, something easily visible from the ground. Of course, this could be tree creepers, but we don’t think so.

In July, one particularly well-sited box, with clear flight lines and overlooking the Webbie, is a favoured nursery. The squeaks of the juvenile bats are audible many metres away. Probably they have been ‘parked’ whilst their mothers are off hunting.

Resident species are largely pipistrelle, to judge by the examples encountered all over the Zoo site on summer evenings. They must be hibernating close by, as I saw a flying adult near the Children’s Farm on a warmish evening in mid-November 1999. A larger and unmistakable bat seen very occasionally is the long-eared bat, though whether any of these occupy our boxes is anyone’s guess at the moment.

What is especially interesting is that on summer evenings up to forty bats can be seen hawking over the Webbie. Some of these are clearly midway in size between pipistrelles and long-eared bats. The most likely candidate is Daubenton’s bat, well-known for its predilection for roosting close to open water. Modern techniques of bat identification, by analysing the squeak as they leave their roosts, should solve that problem. We know that Andy Collins, a ranger at Calderglen Country Park at East Kilbride and a friend of long standing, has been utilising this technique in his capacity as bat recorder for the Bat Conservation Society. We really must invite him over this summer to assess our populations.

Finally, a trick which never fails to impress when conducting an evening study tour round the Zoo is to entice one of the patrolling pipistrelles almost down to your hand. Individual bats tend to patrol regular routes, probably because this makes it marginally easier and quicker to detect, then respond, to the presence of prey - or interlopers. All it takes is to pick up a stone, roughly the same size and weight as a bat, and hold it until the bat next comes round. A gently lob 3 or 4 metres into the air will cause most bats to veer off to investigate. If you have timed it right, so you catch the stone again, hotly pursued by an inquisitive - or angry - little bat, the effect can sometimes by little short of miraculous. Be warned, it takes some practice and perhaps its just further evidence of a mis-spent youth!