Temperature is a critical factor for bats choosing hibernation sites. Monitoring with data loggers provides essential information for conservation research, and the provision of new hibernation sites.
The Norfolk Bat Group was formed in 1961 and was the first
county-based bat group in the UK. This small organisation
undertakes observations and records the distribution of bats in
Norfolk, and gets involved with conservation work on bat breeding
and hibernation sites.
Bats choose very specific temperature and humidity parameters
for the places in which they choose to breed or hibernate. To
monitor the temperature, the Group started using Tinytalk data
loggers back in 1994. Bats need a winter hibernating temperature
below ten degrees, and ideally less than six degrees, but there is
a variation of temperatures within the cave, tree hole or old
building for different species, and at different stages of
hibernation - i.e. as the winter progresses bats have less of their
special brown fat to sustain them, so they move within the roost to
find lower temperatures so their fat store lasts longer.
It is particularly important to understand temp/RH conditions,
as well as other parameters such as light, in order to replicate
these in terms of mitigation, or making new breeding or hibernation
sites. Bats in the UK are protected under European law as a
European Protected Species. Mitigation aims to offset likely damage
caused by development/building work/re-roofing etc., by providing
bat boxes, other new roosting sites or feeding areas to help offset
any potential damage to the species or its habitat.
For example, 22 years ago the local Fisheries Manager was having
trouble sleeping with a bat colony shuffling about in the roof
space above her head. The Group obtained a licence to block the
colony out of that roof, once they had produced their babies and
flown off to hibernate elsewhere in the late autumn. The mitigation
provided was two special new bat boxes situated near the river on
an outhouse wall. The colony took to the boxes the next spring and
has used them ever since, the longest used breeding bat box
anywhere in the UK.
An extra box was recently added to site, which was tested using
the Tinytalk data loggers to confirm the newer, lighter box design
would heat up in the sun to the same extent as the old one: the
recorded data confirmed that it did.
The Group initially chose Tinytags as at the time they were new
and unique technology: the loggers proved to be small enough to
hide in the habitat, waterproof and fully reliable.
Group Chairman John Goldsmith has used Tinytags in both his work
as an ecological consultant with Aurum Ecology, and in the
voluntary field with the Norfolk Bat Group. He has found the data
loggers to be the only reliable electronic tool for investigating
the micro-climates in which bats can breed and hibernate
John comments, "The fact that some loggers purchased back in
1994 still operate is surely a tribute to their build quality!
Staff at Gemini Data Loggers were particularly helpful in our early
days when we were learning how these instruments worked and
advising on best usage, and at that time I was told that we had
usefully contributed to the company's development work."
The image shows a bat box with a colony of approximately 300
Soprano Pipistrelles (plus 300 babies by late June) each year for
the past 22 years, which has been monitored with Tinytag data