Learning to See

This isn't so much a post about ecology, but a couple of times now in both my hobbies and whilst out on bat walks and such I've noticed that people assume that they can't see in the dark.

I've been guilty of it in the past.  For years I was told by my mother that I was night blind.  I had this all but confirmed by both a doctor and an educational psychologist when I was diagnosed with Irlen Syndrome.  Irlen Syndrome sounds terrible, but it's just a perceptual disorder that means I see after images a lot.  It also means that I'm a bit clumsy, I like low contrast lighting conditions and I suck at reading graphs, music or anything that's lined or with high contrast patterning.  It can also mean that you are night blind.

About five years ago, I started doing hobbies that meant that I had to be outside at night, without artificial light and for long periods of time.  It was really difficult at first, I won't lie.  I felt unable to do much and even a bit helpless on occasion.  But in time, I learned how to see and it made me realise something -- sure, I struggle in the dark at night, but I wouldn't call it blind (anymore).  I've had to learn how to see in the dark though; it's not been easy and sure, I still have some problems that other people don't.  It still takes me several minutes more than my friends to adjust to the lighting levels, for example; but I can do it if I hang in there and I use the following coping strategies:

• Peripheral vision!  I all but ignore most of my central vision at night.  If you're looking for movement in the dark, you'll see it in the peripheral vision first.  You'll also see things like trees and branches in your periphery first.  This can be demonstrated pretty well with stars -- there are several stars that are so faint that you can't see them if you look straight at them.  If you look with your peripheral vision though, you suddenly can. 
• Lose the torch or go for a torch with a red light option.  Red light means you can still see to write without losing your night vision or affecting anyone else's.  Carry a white light torch though in case you really need it (emergencies, ID purposes, etc).
• If you're cordoning off an area for safety with glowsticks, use red spectrum glowsticks for the same reason.
• Don't just assume that because it's dark, you can't see!!!  On a night with a moon -- especially a full moon -- it can be bright enough to cast shadows.  Sure, there are some nights that are moonless, where you are out in the middle of nowhere, with no city light glow or perhaps there is no cloud cover to reflect light down from neighbouring cities.  Maybe you're in a wood and it's too dark to move.  Fine.  But give your night vision a chance first.  Give it 10 minutes.  Move slowly.  Your own eyes will surprise you.  Only use a torch if you really need to. 
• If someone is blinding you,  politely say something.  Usually they'll be pretty apologetic.  And don't hesitate to preserve your night vision by looking away or shielding your eyes.  Edit:  A friend of mine suggested the pirate trick of covering your dominant eye in order to preserve night vision.  I forgot that I do this too as it's now fairly instinctive.  He also suggested closing your eyes for 60 seconds in order to acclimatise to the dark.  It works for him, but I know I'd fall over!

Night vision can be really quite an important thing to have if you're doing nocturnal surveys.  Some bats actively avoid light (even the red lights) and you've little hope of looking at that moth if you shine a torch at it.  I've seen folks do this and the moths usually fly into the torchlight.  Use a jar to collect the moth and then bring it into the light -- you'll have much more success with your ID.

As I said, learning to see in the dark is a learned skill for me.  It probably is for a lot of people, whether or not they've got night vision issues.  Keep an open mind about it.  Sure, I still stumble often and it takes me a while to get going in the dark, but if I can do it, so can others.

Bats at Delamere

This last weekend was pretty busy as I went along to Chesire Wildlife Trust's Bat & Moth evening as well as taking a day out at Yorkshire Sculpture Park.  On the upside, that makes for quite a few articles.  On the downside, that makes for no time in which to write them, especially when you consider that I work part-time as a lecturer and it's enrollment week!

Friday's Bat & Moth evening was pretty nifty, split into a bat watch and walk, as well as an introduction to moths and moth trapping, so I'm going to do a few entries on it in a similar way.

The bat watch & walk was really interesting and informative, though a bit more technical information about the frequency ranges of the bats we were picking up on the bat detectors would have been more helpful -- but you can't have everything.  We did an emergence watch and saw quite a few brown long-eared bats (Plecotus auritus) leaving their roosts in one of the older buildings at Delamere.  They were really loud at the 43 kHz range on the bat detectors, which is no surprise as their call range is 27-56 kHz.  However, it's really worth noting that you'll see these critters before you hear them usually as the detectors only work on their quiet calls up to a distance of 6m, hence their other name, whispering bats.  A good daylight indicator of these chaps being around is moth wings under the roost (most favoured moth being the Yellow Underwing) and of course, bat droppings on the wall.

As soon as they left the roost, they immediately headed for the closest tree to feed.  They are gleaning feeders, meaning that they eat the insects that alight on leaves and tree bark.  Unfortunately, as it was a bit dark and the bats were a bit far away (who'd've thought, eh?) I wasn't able to get any pictures of any bats that evening, however, here's a picture from wikimedia commons of what a brown long-eared bat looks like:

They look far more charismatic as a species when they're moving and not stunned.  Bad photos even happen to bats, apparently!

The next bats we fleetingly saw and certainly heard were the pipistrelles.  There are two types of pipistrelle -- the common pipistrelle (Pipistrellus pipistrellus) and the soprano pipestrelle (Pipistrellus pygmaeus).  The main identifying difference if you're spotting using a detector is that the common pips have a call with most energy at 45kHz, whereas the soprano pips have a higher echolocation call at 55kHz.  We also heard a few social calls down in the 20kHz range.  Social calls are the bat world's version of a male bat calling out "hey, ladies!", especially when you bear in mind that bats have harems. 

The calls of these bats are interesting to listen to as you can actually hear them hunting.  When they dive to catch an insect, it sounds like someone has just blown a raspberry.  When it stops, chances are that the bat is having dinner.

I'm fairly certain I also heard a Natterer (Myotis nattereri), though as the pips were around at the time and were being pretty loud, it was hard to tell.  However, it wasn't the same sound and the frequency went as high as 70kHz before suddenly stopping rather than fading out.  The lovely folks from the local bat group seemed to think it was a good possibility though.

Either way, they were amazing to watch and to hear.  It's just a shame their body-clocks are so antisocial!