For a while now, we have been noticing squeaks coming from within a boxed in gap in the fascia board surrounding the back deck.  We’ve suspected there may be a few bats living in this gap and over the last two weeks we have been trying to monitor their habits.  Right on the point of darkness, about 9:10pm tonight, but last week it was 8:45pm, the bats begin to emerge from a space no larger than 75mm x 50mm.   We have counted up to six bats, but there seems to be a lot of squeaking going on inside their roost after this, so perhaps there are still baby bats in there waiting for parents.

I’ve done a bit of reading on this, and it seems that the female bat will set up a roosting spot separate from the main colony to breed.  Most of the bats found in our area only have one or two young, so if there are five or six adult bats leaving the roost each night, does this suggest it is a number of females?

Tonight while I tried to take photographs, with my camera protesting about taking shots in the dark, one bat did return to enter the roost.

So, while I don’t have very good photographs, hopefully I have enough clues to identify the species of bat.  We’ve narrowed it down to four potential species, but don’t have sufficient expertise to know which of these it would be. If you can help out, we would love to know which one it is.

We have Leonard Cronin’s “Cronin’s Key Guide  to Australian Mammals‘. Putting the observed details together with entries in the field guide, we came up with this shortlist of possible species. It is  possible we may have overlooked some species if they were not included in our field guide.

Eastern False Pipistrelle:  This species is dark brown to reddish-brown on top, and paler beneath – one of the few that mentions colour change in the fur on the back, however, at 50 mm to 70 mm the size may rule it out Also large pointed ears with rounded tips doesn’t quite fit.

Gould’s Wattle Bat: This species also has a colour gradation, but from the description it is from very dark brown/ black to a lighter brown.  It also has a wattle at the side of the mouth. At 46 mm – 60 mm the size seems to be a better fit.

Common Bentwing Bat:  Probably the best match colour-wise for the photographs I have taken.  The fur is chocolate-brown above, and can show patches of bright rufous fur in times of moult. The field guide also indicates that older bats can appear gingerish in colour. The size is 47 mm to 63 mm, making this species probably the most likely candidate.  However, the description mentions an exceptionally long tip on the third finger – I don’t really know if that applies to our bats.

Little Forest Bat:  We briefly considered this bat, which is very small at 34 mm to 50 mm in size.  However the description of the fur mentions it is predominantly  dark to mid grey (not brown or red) but sometimes can be flecked with brown or white.  So while the face could match the photograph, the rest of the description doesn’t seem to match up.

I love Cronin’s Key Guide because they give detailed descriptions, and also show a distribution map, so I know all of the above four species are found in our area.  My guess is we have Common Bentwing Bats,  so if you can confirm this or if you think it is a different species, please let me know via the Comments box below.