Bats Wilson Reserve 14 March 2015
Another fine, windless afternoon and a good-sized team
assembled. Steve and Stanley checked the Burke Rd
tubes first and captured two Gould’s males, then did the
last few boxes at Wilson Reserve, with Emily helping.
Katrina’s daughter wanted to get up very close to see
what her mum was doing. Katrina works at Biosis. She
assessed several Gould’s, and the one Broadnose before
her little girl’s attention span was exhausted.
Kristin had a broken ulna and radius from a fall, but
wouldn’t miss batting anyway, and we had a new
recruit in Katrina Sofo, with her husband and little
daughter
Maddy made good progress in overcoming beginner’s
nervousness by the end of the afternoon, and was very
pleased about it.
There were bats in six boxes, and we had a couple of
escapees, possibly recaptured later. Jessica Whinfield
joined us with a university friend, Maddy Woodruff,
who has been vaccinated and was eager to start learning
bat-handling skills, as was Katrina. Helen Reilly has
been having her vaccinations and is keen to start next
month. So Jessica helped Maddy get started while I
helped Katrina, whose little daughter very much wanted
to pat a bat and feel its soft fur, and even hoped she’d
be allowed to hold one (which she wasn’t). Stanley
went off to release his two bats once they’d been done,
so missed the news that another Burke Rd bat had
emigrated to a Wilson Reserve box. There were two
unbanded bats, so Steve dealt with them.
One of the 2-year-old Gould’s females, banded in Dec
’13, and captured 11 times by now, had a serious band-
ing injury: the band had slipped far down her arm and
cut through the wing membrane. Steve removed it and
put a new band on the other arm. It is unusual for a
banding injury to occur so long after banding. 93288
struggled in her first year to put on adult weight, but
went through her first pregnancy last spring, had two
healthy pups and is now a healthier weight.
Most Gould’s females get to 15+ grams before their
first winter, but 93288 was well below that. She had a
severe abdominal injury last March, so wasn’t weighed,
and had two attached young in November.
She’s having a tough time with adulthood.
The one Broadnosed bat is our 21st of this species, so
there are now 10 females and 11 males, with nearly all
the repeat visitors being males. This is a big contrast to
the Gould’s whose colony is dominated by the females.
Jessica was keen to be involved in releasing the bats
after dark, so she, Maddy, and mother Brigitte all came
along and Maddy opened most of the bags to let little
bats fly off into the night. I got many photos of white
bags, and one of a bat leaving.
Box Bats Species
Adult
Esc
M
F
2
10
1
B19
12 Gould’s
Broadnose
1
1
Gould’s
1
8
2
B12
9
Gould’s
3
2
B05
5
Gould’s
2
B01
2
Gould’s
1
B06
1
Gould’s
1
B16
1
31
Total
7
24
3
For Burke Rd:
Tube Bats Species
Adult
M
F
Gould’s
1
T04
1
Gould’s
1
T07
1
33 Total
9
24
Over eleven years, March captures have fluctuated
quite a bit, peaking in 2006 then settling between 40
and 60 most years, but down in 2013 and again this
year to little more than 30 bats.
having been through pregnancy and succeeded in
catching enough insects to maintain their own weight
and also produce milk for growing young, tend to be
heavier.
Eleven of the Wilson Reserve bats were post-lactating
females and there were 16 other Gould’s, so some must
have died already from the probably 22 young born in
October. The remainder of the year’s young will
probably emigrate in search of breeding colonies in
May.
Which boxes do they prefer in March?
Some of the boxes are in shadowy woodland, others out
in the open meadow edges, three are narrow-chambered
and one is made of thicker timber. Generally in March
the meadow boxes are favoured, but not this year. The
woodland and narrow-chambered boxes had the bulk of
the 31 bats this March.
But there is a fair bit of overlap – some young bats
grow fast, some mother bats still struggle to keep their
weight up. So this month we had a 16-gram young bat
and a 14-gram post-lactating mother. Bats are variable
in their life skills and their inherited predispositions.
Community structure
The 31 bats captured this month have been members of
our colony for variable lengths of time, some just
arrived, others around nearly 4 years.
What happens to group size in autumn?
Each month we get some solitary bats, some in quite
small groups and sometimes we get big groups of over
40. The mix of big and little groups varies through the
year, the big groups far more prominent in the breeding
season, when the females gather in maternity groups.
The chart shows the typical change from summer to
autumn, with fewer bats in big groups and more in
smaller groups. This shift continues to the end of
winter.
Life experience and a bat’s weight
Young bats take a few months to become experienced
insect hunters and reach adult weight. Mother bats,
The three “old ladies” who have been in the colony
over 40 months have been joined by some of their
daughters who didn’t emigrate, and some immigrants
who became long-term stayers. And there is a very
large group of this year’s young in the first column,
present for up to 5 months since banding. Most of these
are likely to emigrate by May to seek breeding opportunities elsewhere. But the long-term structure probably
has several generations plus several immigrants who
dispersed from other colonies elsewhere.
Next box check: Saturday 18 April 2:30 p.m.