Desert Oaks; beautiful desert giants

If I were to ask you to nominate Australia's most photographed tree, I wonder what you'd suggest? Perhaps the Cazneaux Tree (a River Red Gum in the southern Flinders Ranges, made famous by Harold Cazneaux's 1937 photograph The Spirit of Endurance, and rephotographed numerous times since)? Or maybe the Curtain Fig at Yungaburra on the Atherton Tablelands of north Queensland, a massive Strangler Fig visited by every tourist bus in the area, and there are many of them!

A segment of the Curtain Fig Ficus virens, Yungaburra, a massive tree.

You'll probably have other suggestions, but my bet is on a tree that most people don't even realise they're photographing. 

Every day hundreds of people gather in central Australia at set areas to watch the sun going down on mighty Uluru, previously known for a while to English speakers as Ayer's Rock. The viewing areas are extensive, so there's no real sense of crowding, and the tour buses use a different area from private cars. A couple of weeks ago we joined them. Here is a selection of photos, taken over a 40 minute period from before to after sunset - just five of 18 that I ended up keeping.

So, if every one of the people there on just that one evening took that many pictures - and many would have taken far more - that's thousands of pictures a day, and it's not peak visiting season yet.

And, you see the tree? I suspect that most photographers don't even really notice it. Here it is again closer up, the shots taken just 10 minutes apart - the light changes are truly stunning.

This tree - my nomination for the title of Most Photographed Tree in Australia - is a Desert Oak, Allocasuarina decaisneana. It is my favourite tree species of the Australian central-western deserts, limited to an area of eastern Western Australia, south-western Northern Territory and a tiny bit of north-western South Australia. They are the only casuarinas in central Australia, most of the family being near-coastal in distribution. (Some time ago the genus Casuarina was controversially split into two, creating the genus Allocasuarina based on minor differences.)

It has adapted to life in the sandy dune country, where spiny spinifexes (hummock grasses of the genus Triodia) dominate the understorey.

Desert Oaks, Chambers Pillar, Northern Territory.

Unlike many other casuarinas, adult Desert Oaks are largely fireproof, recovering from epicormic shoots in the crown; at the same time seedlings sprout in the wake of the fire.

Stand of Desert Oaks south of Alice Springs.

In the photo above the beautiful adult trees appear to be growing above another bottle-brush-shaped species, but this is an illusion. The seedlings don't resemble the adult trees at all.

Desert Oak seedlings, Uluru - Kata Tjuta National Park.

Close to the ground the young trees are a spiky tangle, resisting grazing. The crown doesn't form for years; during this time the emphasis is on sending a tap root deep into the soil. When it strikes ground water many metres down, the crown finally develops and the side branches wither. 

The timber is hard and heavy and was used by the desert peoples for tools and weapons but, perhaps fortunately, it doesn't hold its shape after cutting and drying, so wasn't harvested by European settlers.

The species name honours a Belgian botanist, Joseph Decaisne, who spent his working life - much of the 19th century - working in Paris, especially at the Muséum d'Histoire Naturelle, where he began as an apprentice gardener. He never visited Australia, though he described some species from French expeditions returning from there. He rose to become regarded as the leading French botanist of his time, though it is often said that it was his studies into fruit varieties which were his main achievement. It was the great German-Australian botanist Ferdinand von Mueller who honoured Decaisne with the name.

There are separate male and female flowers but, unlike in many casuarinas, they occur on the same tree. The seed cones are magnificent, and can be up to 10cm long.

Desert Oak seed cones.

One day I'll do a posting on casuarinas in general, but for today I wanted to focus on this one beautiful species. 

Meantime, do you have another nomination for most-photographed tree? I'd love to hear.

There will be more postings inspired by the wonderful arid lands we've just visited; thanks for waiting for me!

BACK ON FRIDAY

The Song of the Butcherbird

The song of the Pied Butcherbird Cracticus nigrogularis is without doubt my favourite bird song of all. If you click here you can enjoy it while you read the rest of this brief post. (Andrew Skeoch is unquestionably one of Australia's foremost wildlife recorders and you could do worse than go on to his site after you finish here; and no, I've only met him once, by chance, and he doesn't know me!)

A bold hunter, the Pied Butcherbird is a bird of the dry inland, one of the reasons for my passion for it. And for the next month, I'll be hearing it, and you won't be reading me, as we head up through central Queensland, across the Donohue and Plenty 'Highways' (no bitumen, lots of dust and corrugations) to Alice Springs in the central deserts, and ultimately home via the Andamooka Track and the Flinders Ranges, definitely heart country for me.

I'll doubtless come back with lots of material for future postings, so please don't forget me! I'll be checking in when internet access allows (ie not very often) and would be glad of your comments.

BACK ON TUESDAY 28 MAY

The Blues; nature's trompe d'oeil #3

This is the final instalment of my discussion and celebration of blue in nature - which in turn is part of a sporadic series on colour in the natural world. As foreshadowed, this one focuses on plants. Unlike in animals, blue pigments are quite common in plants - flavonoids, indigoids, phytocyanobilins and anthocyanins can all produce blue flowers. Anthocyanins are interesting in that they can produce red, violet or blue depending on the acidity of the cell sap - some gardeners alter soil pH to influence the colour of their hydrangeas. 

However it seems that structural blues in plants may be more prevalent than hitherto recognised; this article gives an interesting overview of what is - and isn't - known about it. As far as I can determine though, this has scarcely been investigated for Australian plants.

There is another aspect that I must mention too, in that it affects my choice of photos. I have trouble sometimes deciding if a colour is blue or mauve; my partner and I differ, sometimes significantly, in how we interpret these shades. The other side of this coin is that cameras are notoriously unreliable when it comes to reproducing blues accurately, and some of the pictures below look a lot less blue to me than I recall their subjects being!

Anyway, that's enough introduction; let's just celebrate some delightful flowers.

Tall Bluebell Wahlenbergia stricta Campanulaceae, Canberra, with pollinating wasp.
Insects see best at the short wavelength end of the light spectrum - yellows, blues, purples and on into the ultra-violet - so these are the colours of insect-pollinated flowers.

Wandering Sailor Commelina cyanea Commelinaceae, Murramarang National Park, south coastal New South Wales.
With no supporting evidence, the striking blue of this flower makes me wonder if underlying pigments are not being amplified by structural features.

Blue Pincushion Brunonia australis Goodeniaceae, north of Perth, Western Australia.

Dampiera stricta Goodeniaceae, Namadgi National Park, Australian Capital Territory.
This rare and threatened species appeared in good numbers on rocky slopes a few years after the intense fires of 2003; a couple of years later they had died back again.

Hand Flower Cheiranthera cyanea Pittosperaceae, Wee Jasper, New South Wales.
The common name refers to the oddly-positioned anthers (the genus name means 'hand-anther').

Narrow-leaved Squill Chamaescilla spiralis Anthericaceae, Esperance, Western Australia.
A delightful lily, which can grow en masse from pure sand.

Nodding Blue Lily Stypandra glauca Phormiaceae, Canberra.

Blue Tinsel Lily Calectasia grandiflora Dasypogonaceae, Moore River National Park, Western Australia.
One of those which looks bluer in my mind than it does in this photograph.

Smooth Flax Lily Dianella longifolia Phormiaceae, Canberra.

Blue Lechanaultia Lechanaultia biloba Goodeniaceae, north of Perth, Western Australia.
One of the most breathtakingly blue flowers I know; quite stunning.

And a few orchids....

Blue Fingers Cyanicula caerulea, Canberra.

Waxlip Orchid Glossodia major, Canberra.

Bluebeard Pheladenia (Caladenia) deformis, Alligator Gorge, South Australia.

Two sun orchids; Thelymitra media and T. ixioides, Ulladulla, New South Wales.

Mountain Beard Orchid Calochilus montanus, Canberra.
The shiny blue smooth plates on the labellum seem very good candidates for a structural blue,
formed by layers of cells over a dark background.

Tasman Flax Lily Dianella tasmanica, Namadgi National Park.
It seems that blue berries get their colour from a waxy layer scattering blue light.

Lastly, the article I mentioned in the second paragraph discusses some blue foliage at some length, though its purpose is not at all clear.

Bluebush Maireana sedifolia, Gawler Ranges, South Australia.
Here the blue is from a waxy leaf coating which helps protect from water loss in a harshly arid environment;
perhaps the colour is an incidental byproduct of this.

Lilly Pilly Acmena smithii Myrtaceae, south coast New South Wales.
The article referred to above discusses a multi-layer blue iridescence in the leaves of some
rainforest understorey species (which this small tree is), as a possible protection against unexpected high-intensity
light exposure in leaves not otherwise adapted to it.

A very silly song that I recall expresses the hope that "these pretty flowers chase the blues away". It's too corny and inappropriate to mention here so I won't...

BACK ON WEDNESDAY

Natural History Book Reviews

This is an 'out of session' post to draw your attention to another project of mine, a periodic series of reviews of natural history related books, which I email, but which are also posted on the National Botanic Gardens Botanical Bookshop website. You'll find the most recent one, as well as all previous ones, HERE.

Meantime, here's a small offering for your trouble.

Young Marine Iguanas on jetty, Isla Isabela, Galapagos.

BACK ON SUNDAY

A Tale of Two (Ant) Cities

This is the story - or rather two stories - of two very different groups of tropical rainforest ants, in two continents, which have in common only that they do remarkable things with leaves, and are the basis of two pretty good yarns. 

Leafcutter Ants, Yasuni National Park, Ecuador.
There are over 40 species of leaf-cutters in the genera Atta and Acromyrmex, found from southern North America through Central America to much of South America; the differences between the genera (not to mention the species) are really only available to laypeople with a good lens and an immobilised ant!

Green Tree Ant Oecophylla smaragdina, Litchfield National Park, south-west of Darwin, Northern Territory of Australia.
This species (as currently recognised) is found across the coastal tropics of Australia and through south-east Asia to India. Only the Australian ants have the green abdomen; elsewhere they are known as Weaver Ants.
There is also an African species, O. longinoda.

Anyone familiar with the Australian tropics is very wary of Green Tree Ants; it is easy to inadvertently annoy them by leaning on their tree, and it's something you don't do twice. They don't have a sting, but they can bite hard enough to break the skin - after which they make sure they have your attention by spraying the wound with formic acid. It works too. On the other hand there seems to be no consensus about the stinging capabilities of the Leafcutters; different sources are equally adamant that they either do, or cannot, sting - perhaps it varies between species, or genera. There seems to be an agreement that they can bite however, though I've never had a problem with them, and the lodges in the Amazon which have trails of them on the paths don't see the need to warn guests about them.

They both utilise leaves, but in entirely different ways and for quite different purposes. The Green Tree Ants glue living leaves to make a magnificent nest. 

Green Tree Ant nest, Darwin. The 'glue' can be seen as white material at the bottom of the nest.

I've never seen the beginning of construction, but it's commenced by a few ants reaching across from one leaf to another to pull them together by sheer force. If the process looks like being a success, more ants join in - the more ants that are involved, the more likely it is that others will assist. If the gap between leaves is too wide the ants will form a living chain to bridge it. Once the leaves are in contact something even more remarkable happens. Other workers bring mature larvae, and with their antennae signal them to start releasing their silken threads from glands below their jaws; they move the larvae back and forth like glue guns.

A colony may number half a million ants, and maintain well over 100 nests in 20 or more trees. Green Tree Ants are voracious scavengers and hunters, streams of workers bringing back a variety of animal food for the queen and larvae; workers lay chemical trails to lead others to a good source.

Green Tree Ants dismembering a dragonfly, Litchfield National Park.

Leafcutter ants on the other hand do not eat meat - but despite the evidence of our eyes, they do not eat leaves either!

Leafcutter Ant trail, Manu, Peru.
These trails of ants carrying leaf segments above their backs as long as the sun lasts
are an integral part of South American rainforests.

Given their ability to cut leaves all day into manageable pieces, it's not surprising that they're reputed to be able to give a respectable nip if molested. The leaf material is taken to the nest, cleaned and taken to the underground fungus farm, where they are used to feed a remarkable species of fungus, which has lived in ant nests for so long that it has lost the power to produce spores to reproduce (according to at least one source anyway). The entire ant colony lives on the nutritious fungus.

Nor do all leafcutters restrict themselves to leaves!

Some plants produce leaves which are inimical to the ants, which avoid these trees. If they do bring an undesirable leaf home they are able to monitor the fungus' reaction and remove the offending greenery again.

The nests are enormous and may cover tens of square metres of forest floor, which the colony keeps clear of vegetation.

Leafcutter Ant nest, Manu, Peru.
A big colony can house millions of ants.

 When a queen leaves to start a new colony she takes a fungal sample with her to start the new farm. These young queens emerge in vast numbers, a resource large enough in Ecuador to attract the Quechua people to collect them, wrap them in leaves, and sell them in markets. 

Leafcutter Ant queen, Sacha Lodge, Ecuador.

I am always fascinated by ants, but the activities of Green Tree Ants and Leafcutters constantly astonish me, and they are one of the first things I look out for when I get back to the tropics. If you've met them, I hope this brings back good memories; if you haven't, that's something for you to look forward to!

BACK ON SUNDAY

Lake Mburo National Park

Lake Mburo National Park was the last park I visited in a very memorable trip to Uganda (mostly birding, though by no means just that) a couple of years back. It wasn't the most dramatic place I saw, but I have good memories of it, along with a tiny frisson when I think of the pre-dawn walk on my own to breakfast, wondering how far the lions had moved on!

It is in the far south-west of Uganda, in the savannah country, focussed on big Lake Mburo, part of an extended wetland system.

The accommodation was relatively simple, in comfortable permanent tents on wooden platforms, perhaps my favourite of the trip - I always sleep best in a tent!

My tent; note the shower system to the left. On request it is filled with warm water; the flow is regulated from
inside by pulling chains to turn it on and off. Very sophisticated I thought!

My verandah; a most pleasant place to sit, read, write and contemplate.

The view from the verandah. over the low woodland to the distant lake in front of the hills.

Uganda's parks suffered terribly in the Amin years, with most big mammals being shot by troops for food and entertainment. They are recovering very well now though, and we were warned to be wary of buffaloes wandering the unfenced camp. Seeking some reassurance, if I'm truthful, I asked Alex, my 'house attendant', "When I go to breakfast in the dark tomorrow [a 300 metre walk on paths through the scrub] is it dangerous?". "No, it is not dangerous." "Are there no buffaloes then?" "Yes, there is buffaloes." There seemed nowhere for the conversation to go after that...

We had been told that neighbours had shot out the lions from Mburo, but were pleased to hear distant roaring on the first evening.Then at about 4am I heard a party of lions coughing and growling nearby; the tent suddenly felt very flimsy. It was not a totally relaxed walk to the nice open-air dining room a scant couple of hours later.

Camp dining room.

A highlight was a boat ride on the lake, where Finfoot was a high priority for me. Bingo, as soon as we arrived!

African Finfoot Podica senegalensis, early morning Lake Mburo.
This is an intriguing species whose only relatives seem to be the Masked Finfoot of south-east Asia
and the South American Sungrebe.

African Fish-Eagle Haliaeetus vocifer Lake Mburo.
Their pulsing whistling duets are one of the most evocative sounds of Africa.

Malachite Kingfisher Alcedo cristata; no matter how often I see this little jewel - and it is widespread across Africa - it is never enough.

Parks staff washing vehicles in the lake - and yes, there are crocodiles here!

A walk in such areas is not the same as a walk in Australia, where nothing is likely to stand on or gore you with malice aforethought. As we ventured into the edge of a swampy area (putting our faith solidly in the hands of our Ugandan guide) a distant group of buffalo and we viewed each other suspiciously, but we each kept our respectful distances.

Swampy habitat, Lake Mburo.

Saddle-billed Stork Ephippiorhynchus senegalensis, a magnificent big hunter of fish and frogs, and a close relative of the Australian and Asian Black-necked Stork.

Greater Blue-eared Starling Lamprotornis chalybaeus; the magnificent glossy starlings of Africa constantly delight me.
In southern Australia the only starlings are two highly destructive exotic species,
which can't provide much satisfaction here.

Mburo's mammals are another source of great pleasure, with zebra and antelopes prominent.

Plains Zebra Equus quagga, common in Lake Mburo. A small group accompanied us into camp on the first night, perhaps nervous of lions and glad of our temporary protection. The extinct Quagga and the Plains Zebra are now considered the same species, and as the Quagga was named first its name takes precedence.

Impala Aepyceros melampus, truly a most elegant antelope.

Waterbuck male Kobus ellipsiprymnus; another typical Lake Mburo resident.
A powerful antelope, rarely found far from water.

Lake Mburo is a highly recommended part of your visit to Uganda, a country famously described as 'the pearl of Africa' by Sir Winston Churchill. Certainly recommended by me anyway...

Sunset, Lake Mburo National Park.

BACK ON WEDNESDAY