Bats
BATS
AT GLASGOW ZOO (Richard O’Grady)
Over the past thirty years, Glasgow Zoopark has been associated with
two types of bats:
- Exotic
bats, and
- 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! |
