Darling Scarp, Western Australia
Introduction
The Darling Scarp is situated east of Perth, separating the Swan Coastal Plain from Western Australia’s Wheatbelt region. Stretching across several hundred kilometres, it is part of the much larger Darling Fault, a major geological fault line that runs along the west coast of Western Australia for over 1000 kilometres. Most of the Darling Scarp is covered by vast expanses of forest and woodland that are home to a large variety of unique plant and animal species, including several endemic orchids.
Much of the Darling Scarp’s unique flora is closely associated with areas that receive plenty of water from winter rainfalls, such as creeks and low-lying flats. Another unique habitat found throughout the Darling Scarp are shallow soil pockets on granite outcrops, often covered with a dense layer of moss and lichen. They host a highly specialised community of plants that have developed strategies allowing them to survive the harsh conditions during the hot, dry summer season, when temperatures can reach 40 °C and rainfall is scarce. Several rare and unusual orchid species are known from only a handful of granite outcrops near Perth.
While the summer can be very hot, it is not uncommon for temperatures to drop below 0 °C during the winter. Overnight frost will turn the landscape into a glistening winter wonderland, coating plants and rocks in a layer of intricate ice crystals. However, this spectacle does not normally last very long, as the warming rays of the sun will melt the ice again shortly after sunrise.
Fauna
Among the animals found along the Darling Scarp is the iconic Bobtail Lizard (Tiliqua rugosa), which is one of the most common and widespread reptiles in the Perth area. Apart from their unique appearance, Bobtail Lizards have developed an unusual defence strategy. When they feel threatened they will widely open their mouth and stretch out their blue tongue to scare away any predator.
Another iconic inhabitant of the Darling Scarp is the Short-beaked Echidna (Tachyglossus aculeatus) which can be found all across Australia. Echidnas are very timid animals and will curl into a spiky ball when they feel threatened, with only their long snout still sticking out. Once the threat has passed, they will uncurl again and continue to forage for food in the leaf litter.
Among the most abundant and dominant animals of the Darling Scarp are undoubtedly the birds. The noisiest of them all are the Laughing Kookaburra (Dacelo novaeguineae) and numerous species of parrot, including several species of Black Cockatoo (Calyptorhynchus), the Galah (Eolophus roseicapilla) and the Australian Ringneck (Barnardius zonarius). A less frequent visitor to the Darling Scarp is Major Mitchell’s Cockatoo (Lophochroa leadbeateri) which usually lives in the more arid parts of Australia.
Orchids
Among the numerous orchid species found across the Darling Scarp, Sun Orchids owe their common name to the fact that they tend to open their flowers only on warm and sunny days. The Darling Scarp is home to several spectacular species of Sun Orchid, many of which are rare and endangered. Among the more common species are the beautiful Queen Orchid (Thelymitra crinita) and the Scented Sun Orchid (Thelymitra macrophylla), both of which are abundant throughout the Darling Scarp, flowering in springtime from mid September until early November.
The Vanilla Orchid (Thelymitra antennifera), also known as the Lemon-scented Sun Orchid, is one of the most common species of Sun Orchid along the Darling Scarp. The orchids are usually found on and around granite outcrops where there is sufficient moisture in soil pockets or from rainwater runoff. Vanilla Orchids often form large colonies and are sometimes found in the company of other orchid species, such as the Twisted Sun Orchid (Thelymitra flexuosa) or the Little Laughing Leek Orchid (Prasophyllum gracile).
Leek Orchids are among the tallest orchids of Western Australia, with some species reaching a height of up to two metres. The Fringed Leek Orchid (Prasophyllum fimbria) can grow over a metre tall, but rarely flowers unless its habitat got burnt by a bushfire during the previous summer. A much smaller but more commonly encountered species is the Autumn Leek Orchid (Prasophyllum parvifolium), which — despite its common name — flowers in mid winter.
Donkey Orchids are among the most common and beautiful orchids of Australia. One of the most abundant species of the Darling Scarp is the Winter Donkey Orchid (Diuris brumalis). It is particularly common in the Perth Hills, flowering during the winter months of July and August.
The genus Caladenia, commonly referred to as Spider Orchids, contains some of the most spectacular orchids found along the Darling Scarp. By far the most common is the Cowslip Orchid (Caladenia flava), which is one of the most abundant and widespread orchids of south-western Australia and can be seen almost anywhere along the Darling Scarp. Another fairly common species is the White Spider Orchid (Caladenia longicauda), which is widespread throughout south-western Australia and is known for its ability to form hybrids with several other Spider Orchids.
Among the most abundant orchids found along the Darling Scarp are the Purple Enamel Orchid (Elythranthera brunonis) and the Pink Enamel Orchid (Elythranthera emarginata). With their shiny, wax-like, purple and pink flowers they are a spectacular sight and often grow in large colonies, with the Pink Enamel Orchid generally requiring slightly moister habitats than its purple cousin. Occasionally, hybrids between the Pink and Purple Enamel Orchid are found (named Elythranthera × intermedia). Enamel Orchids are endemic to south-western Australia and found nowhere else in the world.
One of the orchids commonly associated with moist areas around granite outcrops is the Swamp Bunny Orchid (Eriochilus helonomos). Its tiny, white flowers appear early in the season, in late autumn, and are easily overlooked due to their small size and inconspicuous appearance. Another rare orchid found on and around granite outcrops is the Pink Bunny Orchid (Eriochilus sp.) with its handsome pink flowers which will only appear in the spring following a summer bushfire.
Among the most bizarre orchids of the Darling Scarp are the Duck Orchids (Paracaleana) and Hammer Orchids (Drakaea). Their strangely shaped flowers mimic female thynnid wasps in both visual appearance and scent. When a male wasp lands on the labellum and attempts to mate with the false female, a special hinge mechanism is activated that pushes the wasp against the stigma, thereby pollinating the orchid.
The most abundant species found on the Darling Scarp are the King-in-his-carriage (Drakaea glyptodon), the Warty Hammer Orchid (Drakaea livida) and the Flying Duck Orchid (Paracaleana nigrita). Although fairly common and widespread, they are notoriously difficult to locate due to their diminutive size and dull colouration. Another characteristic species found on the Darling Scarp is the Slender Hammer Orchid (Drakaea gracilis) which is somewhat less common and occasionally forms natural hybrids with the Warty Hammer Orchid that look halfway in between the two parent species.
The Slender-leafed Duck Orchid (Paracaleana gracilicordata) and the Granite Duck Orchid (Paracaleana granitica) are two extremely rare and local species that are endemic to a small, high-rainfall area of the Darling Scarp near Perth, where the orchids grow in mossy soil pockets on granite outcrops. The Granite Duck Orchid in particular is currently known from only a single population of a few dozen plants, making it one of the rarest orchids in the world.
Wildflowers
In late winter and early spring the Darling Scarp turns into a sea of colour when numerous spectacular wildflowers begin to blossom. The wildflower display is particularly colourful along the western edge where the Darling Scarp drops into the Swan Coastal Plain. A small selection of some of the most spectacular flowers is shown below. Not all of the flowers encountered on the Darling Scarp are native to Western Australia, though. Several weeds, in particular from southern Africa, have been accidentally or deliberately introduced to Australia, including flowers such as the Cape Dandelion (Arctotheca calendula) and the Cape Tulip (Moraea flaccida).
Carnivorous Plants
The Darling Scarp is home to numerous species of Sundew (Drosera). These carnivorous plants produce sticky secretions that cover their leaves and are used to both trap and digest insects. Sundew is abundant throughout the Darling Scarp and can be found in large numbers in winter-wet areas such as granite outcrops and floodplains. Many species produce beautiful flowers every winter and spring, while others will only flower in the season following a summer bushfire.
In addition to the large number of Sundew species, several other carnivorous plants can be found throughout the Darling Scarp, most notably several species of Bladderwort (Utricularia) as well as the rare and endangered Rainbow Plant (Byblis gigantea). Among the more common species of Bladderwort are the Redcoats (Utricularia menziesii) and Pink Petticoats (Utricularia multifida) which are found in moist areas on and around granite outcrops, often in large numbers.
Another common group of carnivorous plants are the aptly named Trigger Plants (Stylidium). Their common name is a reference to their pollination method, whereby an insect landing on the flower will trigger a mechanism that pushes the column against the insect to cover it in pollen. Just like their famous cousin, the Sundew, Trigger Plants are covered in numerous sticky glandular hairs that are used to trap and digest tiny insects. Trigger Plants are among Australia’s most abundant and widespread carnivorous plants, and the Darling Scarp is home to a large number of different species. They are generally very common and often grow in the company of other carnivorous species such as Sundew (Drosera) and Bladderwort (Utricularia).
