Mi Trappin,
The scenario matters a lot.
"Clicking" can happen when a bat is in deep torpor (sleeping) and someone dislodges or disturbs them.
Each species is a bit different, with rehab outside of all of them we deal with in houses and surveys in bridges, etc.,
silver-haired bats will often produce a "click" type sound when they are a bit cold or asleep and you are trying to pick
them up or touch them.
***One very important distinction here****
Bats produce defensive sounds to tell you, and other predators or potential predators or roost mates they aren't happy.
This is all about defense. They at their tiny size and weight aren't like a grizzly bear popping their jaws getting ready to make
a run at you.
They are simply trying to make themselves look as worrisome as possible.
Here are the simple steps with pretty much any bat species (we have 29 here and I've had at least 15 different species in hand or
the need to capture where you see or hear these sounds and see the behavior or posturing.
Step 1) Bat retracts its body to get tighter and smaller as you are reaching for it or shining a light on it.
Step 2) You keep coming with your hand and are about to grab it but haven't touched it yet, bat gapes showing all teeth and open
mouth - a clear enough sign to say if you try to pick me up I am going to bite you.
Step 3) You touch the bat even if you don't grasp or pick it up - audible distress, clicks, "screeching" for lack of a better phrase, all vocalizations
to go along with "why are you touching me, I told you I'm big and have a mouthful of teeth, I am scary!!!"
Step 4) You grab the bat to pick it up and now you are going to get any combination of all of these, biting, vocalizing, squirming and attempt to fly
away, etc...
This is the last ditch effort by them to avoid being eaten or injured severely. You aren't anything special, you are simply a large predatory mammal, they
don't view you as less dangerous than anything else in their lives that tries to eat or kill them.
I say all this to say, bats make sounds for a variety of reasons, they gape and so forth all in attempts to get you to not pick them up, take non venomous snakes,
no poison, no fangs, but they will put on a good show to make you or a coyote or bobcat think they are dangerous and maybe poisonous!
****
When bats are cold, even those we have long term for educational programs, they do not like to be grabbed, they aren't aggressive, they are at a loss for protecting
themselves and being able to fly away, so they do all those things to try to tell you don't touch me.
Simple enough, if we think about small mammals of their size, yes they hunt insects, but they are prey to literally everything that walks and crawls that is larger than them.
****
This time of year even where I am pups are weaned now and we are beyond maternity season, so any clicking or calling isn't going to be that. During pup season young pups
will vocalize to be fed, it is a very soft but constant sound till you feed them, (they can die if not fed in 3 hours so they keep calling till their belly fills).
If you are wondering about rabies as many do, I've picked up over 200 bats in the last two years, 75% were downed, low or flat on the ground. All but 1 were normal bats with
serious injuries, wing tears, cat attack victims, emaciated, dehydrated.
The 1 that wasn't was a silver haired bat, walked into the yard, bat was clicking away and vocalizing with no one near it (still could have been painfully injured), wings were fixed
out as though ready to fly, but couldn't, kept vocalizing even after picked up. Took it and left, by the time we made it to the office (20 miles away) was dead, definitely a rabies case.
But, bats vocalize for all those reasons above first and foremost, so remember when dealing with them, a vocalizing bat or one showing its teeth is largely all about self defense, simple
as that.
There are too many pics as well in our industry showing the mouth gape in attempt to make a scary animal that folks already fear even more phobic.
Hope that helps, would be interested in your scenario to know more, but ultimately what I wrote above holds true, at any given time we have 17-25 bats from 6 different species in rehab
and of course with normal work are seeing hundreds and thousands every week with inspections, survey work and exclusions.
Have only been at this since spring 2011 but have spent every day surrounded by bats both inside our home and out in the field.
Ultimately observation is key, how did you get the bat, how was it handled before you got it, etc... Is it vocalizing in utter absence of any handling or touching by you or your client?
We've had bats (many unfortunately) with compound fractures, bones sticking through the skin, still not vocalize when you and I would be lying on the ground dialing 911 praying for pain meds.
Bats seem to have a partition for survival over vocalizing which may draw predators, though that is just theory. Have seen horrible things that bats bounce right back from with rehab.
Anyway, hope that helps, your scenario would be of interest in aiding in why it was vocalizing.
Justin
