A Nose For Navigation

Last time we were together we finished up looking at a dead grasshopper so this week we'll start with a live one. We're very much in grasshopper territory here and this is our local version of the Meadow Grasshopper, Chorthippus bornhalmi. Crickets and grasshoppers are well known for their songs and it is a common myth that they sing by rubbing their legs together. Almost true. Generally speaking crickets chirp by rubbing their wings together whereas grasshoppers rub their wings against their legs. I see that there's an old stone bridge down there crossing a small gully that gets considerably deeper as it heads southwards. Definitely worth investigating methinks.

The gully seems to be running into a bit of a ravine which is absolutely inundated with Giant Cane. Despite its massive height it is, like bamboo, a type of grass. Also, like bamboo, the young shoots are edible and you can eat the boiled rhizomes apparently. I haven't tried it myself and I've never seen any recipes for it (so I'd be inclined to take that information with a bit of caution or maybe even a pinch of salt) but I'll pass it on anyway. It also looks fairly impenetrable but we won't let a little fact like that put off intrepid explorers like us. I'm sure that we can slide our way through somehow.

OK so they were pretty unforgiving but look who's waiting for us; a Common Darter. Only he's not so common, not at this time of year anyway. It's a fairly recent discovery that certain dragonflies migrate, the same as birds do ^[1]. And how do we know that? Because some fool entomologist managed to fit a dozen of them with the world's smallest transmitters and follow them in a light aircraft for 58km over six days. Research is ongoing and I'll put in my fourpenn'orth with this set of seasonal maps which I've put together from iNaturalist. As you can see you'll only find them in Winter around the Mediterranean. By Spring they're up as far north as the Netherlands and in Summer and Autumn they're in Scotland and Denmark.

You may have noticed that these canes are getting thicker and I'm beginning to think that someone should have put an electronic transmitter on me as I'm not sure which is our best route out of here. Meanwhile we have some pretty little Clematis cirrhosa down here which is quite, quite poisonous (see Entrapment In A Virgin's Bower) and some Myrtle berries, Myrtus communis, which are most definitely edible (see Fly Feet And Lizards' Ears). All of which is rather academic at the moment as we seem to be effectively caged in on all sides and we've traced a tortuous and probably unretraceable route to get this far. All is not lost however as I am indebted to Phil Bebbington who sent me this handy little GPS tracker for our travels. As I've been marking our finds as we go along I should at least be able to track our route back by following the trail of breadcrumbs as it were. So, if I just pick the appropriate screen I get a picture of... what appears to be an earthworm in its death throes. Our route has been more circuitous than I thought. Another feature of this little gizmo is that we can combine our current position with satellite images which means, in theory, that we can see our shortest route out. I say 'in theory' because I haven't yet mastered how to do that yet. I can tell you where we are to eight decimal places of latitude and longitude but that's not exactly helpful at this moment. We will have to rely on the old naturalists' trick of escaping from river gullies: proceed in any direction you like so long as it's up.

It never fails and we seem to have emerged on the same side of the gully as we entered which is a bonus. There's a whole flock of feral pigeons sitting on a telephone wire over there and I swear that they're laughing at us. Ignoring the incongruity of a telephone wire stretching over a pinnacle of rock and dangling down into an inaccessible cave (this is Crete and it's best not to dwell on such conundrums if you wish to preserve your sanity for any length of time), the reason the pigeons are laughing is that they don't get lost in cane breaks. Exactly how they manage to navigate long distances is still under investigation but if, like me, you thought that it was all down to reading the Earth's magnetic field and/or following the sun's arc then you'd be wrong. Both are useful as compasses but not much cop if you don't know where you're heading for. Like ourselves in the cane break, without a satellite image to see where we were in relation to the edge of the canes, knowing our latitude and longitude and the direction of north was of no help. You need a map and so do the pigeons. After forty years of research^[2] it would appear that your homing pigeon probably uses olfactory mapping as a primary navigation tool. They know what home smells like and if you take them to a new location they'll sniff their way back. And on that incredible note I think we'll make our way back. Can anyone smell the car?

The Extra Bit

On the subject of navigation I would propose a study of island postmen. Here on Crete the smaller villages have no road names and no house numbers. If, like Phil Bebbington, you are kind enough to send me a piece of equipment that you have finished with and pay extra for parcel tracking then the Post Office will hand over delivery to a courier. This means that it will eventually arrive in the near vicinity of my home, having travelled across Europe in ever decreasing circles, and after a flurry of telephone calls I will retrieve the package from an exasperated man in a little white van from outside the village shop. Pop it in the regular post and my postman will (almost) invariably deliver it to my door a week or two later. How he memorises where everybody lives is a feat worthy of scientific investigation.

Thanks again for the GPS Phil, it really is a most appreciated gift and I will get to grips with combining it with satellite images!

[1] Dragonflies Migrate Like Birds

[2] How Do Homing Pigeons Navigate?

Photographic Bit

Many of you have asked me what photographic equipment I use so for details of aperture settings, shutter speeds etc. my pictures will be on Flickr within a few days and that has all the geeky stuff. Pictures were edited with FastStone Image Viewer and combined with Microsoft Paint.

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LINKS:

Share your nature thoughts, photos and comments on Naturalists (the facebook page that accompanies this blog)

Explore the region with the #CreteNature interactive Hiking and Nature Map

Cretan Flora

Flowers of Crete;

BIRDS OF CRETE

Crete Birding

Greek Butterflies and Moths

Aquaworld Aquarium

Visit Greece (National Government Tourist Office)

Fly Feet and Lizards' Ears

It’s once more into the ditch dear friends this week as we descend into the valley depths and continue our journey up the river bed. It is still dry as the autumn rains haven’t really got going yet and we’re blessed with another gloriously sunny morning for our explorations. We’ll start down here with a little bird-watching by the cane beds and just sit quietly for bit and see who turns up.

Flesh Fly, Sarcophaga

Our first visitor isn’t a bird but one of the house flies and their allies. There are about four thousand different species but they are quite recognisable from the large red compound eyes and the four dark longitudinal stripes on the thorax. This one, as you can see, is slightly larger than your average house fly and has a chequered abdomen so I rather suspect that it is an Autumn House Fly, also known as the Face Fly from its habit of feeding on eye, nose and mouth secretions of cattle and horses.¹ Oh sorry, were you just about to get the sandwiches out? It’s a bit early yet isn’t it? Put them away and have a closer look at those amazing feet. Those soft pads on the end, called pulvilli, are what enable them to walk up windows. Not only do they produce a dry glue (which we’ve only recently succeeded in emulating to make a dry sticky tape) but the pads have tiny hairs on them. Getting smaller; each hair is covered in microscopic projections which generate a molecular attraction with the surface upon which the fly is walking so they bond with the surface on a molecular level. Geckos and spiders also use this van der Waal’s’interaction ², as it is called, but one of the few things that flummox them all is Teflon, so it really is non-stick. 

Leaf Warbler, Phylloscopus

Meanwhile, back to our birds I’ve seen a Blackbird and a Robin pass through while we’ve been chatting about flies and there’s something flitting about in the canes now.  There he is; a little olive green and off yellow job doing his best to keep out of camera range. It belongs to a family of birds called the Phylloscopidae  or Leaf Warblers and, with dozens of species in only two genera, they provide ornithologists with hours of acrimonious fun debating the differences between them. Me? I’m just happy to call them Leaf Warblers and leave it at that. Anyhow, that’s enough sitting around on our backsides, let’s push on up the valley and see where it leads us.

Bracket Fungus, Trametes

This is interesting. Do you remember a fortnight ago when we found a bracket fungus with gills (see Entrapment in a Virgin's Bower) and I said that this was unusual as most have pores? Well this is the more usual structure and, rather helpfully it’s been knocked about a bit (no, not by me) so we can see inside. The bits that you can see in the middle, like a set of organ pipes, are the pores. The inner surfaces of these contain the spore forming layer called the hymenium. The spores develop and then when they are ready they drop out of the holes at the bottom. The pores are connected to the core of the fungus by an intermediate layer called the context. I was going to say that the spores in the pores which are connected to the core fall to the floor but that would be out of context. So I won’t.

It seems that we can’t get any further along the stream bed because of these infernal fallen canes so it looks as though we’ll have to clamber our way out. I’ll go first and see if it’s feasible and if it isn’t you can break my fall. Seems like a good plan to me. 

Myrtle berry, Myrtus

There, wasn’t too bad was it? Up you come. Did you happen to notice that Myrtle bush on the way up? You didn’t? Can’t think why – you spent five minutes clinging onto it for dear life. In Greek mythology it was sacred to Aphrodite, the goddess of love and also Demeter, who besides being the goddess of the harvest, also presided over the cycle of life and death so Myrtle is symbolic of both love and immortality. Love life, love Myrtle so to speak. Chinese and European herbalists prescribe it for sinus infections (although the scientific jury is still out on that one), the Italians use it as a pepper substitute in their Mortadella and Bologna sausages, and the Sardinians and Corsicans make a liqueur called Mirto from it. An interesting plant from many angles, would you like to pop back down and grab a handful of berries? No? Okay then, we’ll press on.

Balkan Wall Lizard, Podcaris

Looking back, there’s no way that we were going to get through that lot so we’ll make our way back up to the track and use that as our start point next week. Oh look, a delightful little lizard welcoming us back into the sunshine. What are you doing out and about so late in the year, eh? Actually it’s not that uncommon; this is a Balkan Wall Lizard and I often see them anytime between March and November. Can you see that little hole towards the back of his head? That’s his ear. Many people think that reptiles, particularly snakes, cannot hear. That’s not true but they pick up sound vibrations in two different ways. Lizards like this have a tympanic membrane in the ear (just like us) that picks up airborne sound vibrations and also a quadrate in the lower jaw that picks up mainly surface sound vibrations. Both the tympanic membrane and the quadrate are connected to the middle ear which processes these vibrations into something meaningful to the brain. Although snakes are ‘earless’ and don’t possess a tympanic membrane they do have a quadrate that is sensitive enough  to hear us talking like this from a distance of about ten feet.³

So, bearing that in mind, we’ll wend our way back (quietly) and until next week – happy hunting.^.

[1] I am reliably  informed by dipterist Roger Thomason that it is a flesh fly (Sarcophaga) rather than a face fly (Musca). As you can see, the two are very similar. Thank you Roger.
[2] van der Waal's force (Wikipedia)

[3] http://www.anapsid.org/reptilehearing.html

See all the pictures including insets in detail on Flickr

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LINKS:

Naturalists (the facebook page that accompanies this blog)

Cretan Flora

Flowers of Crete;

BIRDS OF CRETE

Crete Birding

Greek Butterflies and Moths

Aquaworld Aquarium

Visit Greece (National Government Tourist Office)