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I've been a Canberran since moving here from Adelaide on the first day of 1980. I now live in suburban Duffy with my partner Louise Maher, ABC 666 radio and on-line journalist. Among my early memories is following Sleepy Lizards (Shinglebacks) around the paddocks north of Adelaide, guarded by the faithful bull terrier. I have always been passionate about the natural world, trying to understand how it works, how the nature of Australia came to be, and sharing those understandings. My especial passions are birds, orchids and mammals. For much of my life I have been a full-time naturalist, running bush tours, writing books etc, doing consultancies, presenting a regular radio slot on local ABC, chairing a government environment advisory committee and running adult education classes. Recently I have eased back somewhat, but am still writing, teaching, doing some radio work and running overseas tours - as part of my fascination with our Gondwanan origins I've been running tours to South America for the past decade. I was awarded the Australian Plants Society Award in 2001 and the Australian Natural History Medallion in 2006, both for services to education and conservation.

Friday, 7 March 2014

Camouflage; hiding in the open

Much has been written on the topic of camouflage in nature, and I don't have the access or the equipment to show you some of the truly marvellous examples in nature that I'm sure you've seen on the telly. However, maybe you'll enjoy some of the examples that have come my way over the years; they represent some of the most wonderful - and I use that word both advisedly and often with regard to nature - examples of evolutionary adaption imaginable. 

Several approaches to camouflage are recognised. (The word incidentally comes to us straight from the French camoufler, simply 'to hide' or 'deceive'. It only appeared in English, for reasons unclear to me, during the First World War, referring to military applications.) The two most widespread in nature involve firstly breaking up outlines by use of bold and irregular patterning, and secondly blending into the background by matching colours, minimisation of shadow, and/or an overall posture and shape resembling an 'uninteresting' object.

And camouflage works remarkably well for big animals as well as small ones; there is nothing quite like the shock of realising - preferably from within a vehicle - that that movement is the flick of an elephant's ear, and that it is attached to an elephant, and that there is a whole herd all around. (Not that I can suggest why an elephant needs camouflage!)

Context is critical. An animal which disappears into its environment is entirely conspicuous out of that context, as the following examples demonstrate.
Sumatran Tiger Panthera tigris sumatrae, Adelaide Zoo.
No missing it here, but in dappled shade among grass and shrubs, it can disappear as its outline vanishes.
Coiled among foliage, this green tree snake Thrasops batesii (Limbe Botanic Gardens, Cameroon)
would not be nearly so obvious.
Titan Stick Insect Acrophylla titan,  Nowra, New South Wales south coast.
Among foliage or twigs this superb monster - some 20cm long - would effectively vanish.
For the rest of this posting I am going to focus on vertebrates; don't be too exasperated, this is merely because I have too much material for one posting, and I will make sure our invertebrate friends get their full due next time!

The examples above represent two predators and one potential prey; both roles can require camouflage, for evident and complementary reasons.

Most of the following examples employ their camouflage with the intention of not becoming someone's dinner, though in the case of the lizards and frogs for instance (and the tree snake above) they play the role of both dinner and diner in different situations.

One group of animals which needs effective camouflage comprises nocturnal birds, many of which roost in the open during the day. As such they are certainly vulnerable to direct predation, but owls in particular are also unmercifully harassed by diurnal birds, who know perfectly well that at night the owl is a very dangerous neighbour and would rather it slept and woke somewhere else entirely. Tree-roosting species have evolved some superb resemblances to tree bark, with perfect patterns of cracks and fibres.
Tawny Frogmouth pair Podargus strigoides, south of Canberra.
While they have chosen to roost by an inappropriately smooth trunk, they match the branch they're on.
If concerned - and these weren't - they will stiffen and pull in the feathers to look remarkably like a broken branch.
Tawny-bellied Screech-Owl Megascops watsonii, Amazonia Lodge, Rio Madre de Dios, Amazonian Peru.
Again, perhaps not the ideal situation, but imagine if that underside was alongside a tree trunk,
rather than in the bamboo clump that it has chosen.
Note the slightly open eye, just checking on me...
And while looking at creatures wanting to be mistaken for lumps of tree, how about the sloths, which are permanently at risk in the canopy from large eagles?
Brown-throated Three-toed Sloth Bradypus variegatus, Puerto Maldonado, Peru.
Had I not zoomed in and centred on her, this animal (two actually, if you look closely at her belly)
would not be at all obvious.
 OK, so maybe these examples aren't convincing you, though I can promise that in the right situation they are remarkable, but the ground-roosting nightjars are something altogether else! Try this one - a Standard-winged Nightjar Macrodipteryx longipennis at Ngaoundaba Ranch, central Cameroon - before looking at the clues in the caption.
How did you go? If it weren't for the extraordinary wing standards (resulting from a hugely elongated central feather shaft, much of which is bare) this would be impossible. The dark patches are the standards - look closely and you can see the bare shafts. In front of the one on our left is the bird's head, looking to the left. Now you can fill in for yourself!
Some frogs are pretty good at it too.
unidentified tree frog, Manu National Park, Peru.
This a night photo, when the frog doesn't need to hide, but in the day imagine those remarkable skin patterns
against a mottled tree trunk.
Engystomops freibergii Tambopata Research Centre, southern Peruvian Amazon.
This one is superb!
 Lizards, like frogs, are both hunters and hunted and many adopt camouflage accordingly.
Lined Earless Dragon Tympanocryptis lineata, Bladensburg NP, central Queensland.
Beautifully hidden among the ochre and rust colours of its arid environment.
The dragon lizard family, Agamidae, is also widespread in Asia and Africa; unsurprisingly, agamids in similar habitats in these continents adopt similar camouflage.
unidentified agamid, north of Maroua, northern Cameroon.
Common Gliding Dragon Draco volans, Gomantong Caves, Sabah.
The matching of its pattern to the lichened tree trunk is remarkable.

In the Neotropics there are no agamids, but there are plenty of Anolis lizards (family Anolidae or Iguanidae, depending on your taxonomic preferences). Here the priority is more likely to be towards hiding in the greenery.
Green Anole Anolis chloris, Mindo Valley, Ecuador.
Young animals are especially in need of camouflage, especially before they are able to accompany their parents or, in the case of birds, able to fly.
Common Potoo chick Nyctibius griseus, Sacha Lodge, Ecuadorian Amazon.
In this case it really isn't obvious where branch stops and chick starts!
Dusky Woodswallows Artamus cyanopterus (family Artamidae, nothing to do with 'real' swallows), east of Canberra.
They nearly always nest in such a situation, in tree forks or hollow stumps or spouts,
where bark-like camouflage is also important.
But even before the chicks, eggs and even nests must be hidden from predators.
Patagonian Tyrant Colorhamphus parvirostris on nest, Alerce Andino National Park near Puerto Montt, Chile
We can just see the parent peeping over the top of this beautifully disguised nest; this nest, I am told, is not often seen, not least, I am sure, because of the lovely camouflage of mosses and lycopods.
Egg of Red-capped Plover Charadrius ruficapillus, Comerong Island, south coast New South Wales.
Many ground-nesting shore birds have done away with nests altogether, as being too conspicuous.
Here the egg resembles a stone to a remarkable extent.

Next time, I will conclude this mini-series by looking at some pretty impressive invertebrate disguises.

BACK ON TUESDAY

1 comment:

Flabmeister said...

Possibly the reason the word appeared during WW1 was covered by Sir Humphrey Appleby. It was about the first time the Poms were on the same side as the French!

Martin