Eungella to Cairns: the Eastern Highlands

Consider the platypus. It has a duck-like bill covered with specialized receptors for finding its prey; a beaver-like tail covered with fur that is not used for swimming; and otter-like webbed feet for swimming (front) and steering (rear) armed with straight claws for digging (front) and curved claws for grooming (rear). Females lay eggs and nurse their young, but lack nipples. If you didn’t already know that it exists, you’d be hard pressed to believe that it does. Platypus were “discovered” near Sydney by European settlers in 1797 (of course, Aboriginal Australians knew about them for millennia). Bewildered, the local governor sent skins and drawings to Great Britain. British zoologists who examined the specimens in 1798 thought they were a hoax perpetrated by Chinese taxidermists, who were selling mummified monkeys with fish tails as mermaids at the time (link).

Platypus in Broken River, Eungella National Park

Platypus (or platypuses) are endemic to rivers, streams, lakes and ponds in eastern and southeastern Australia up to about 1,600 m (5,250 ft) and in Tasmania. They occur in about 80% of the rivers (link), but they’re not easily found. The best place to see them in Queensland (and maybe Australia) is in Broken River in Eungella National Park (link) in the mountains west of MacKay. We were there during the breeding season when platypus are more active and more easily viewed during the day.

Pioneer Valley looking east from Eungella National Park

We stayed in a cabin in the Pioneer Valley near Fitch Hatton. The owner lived across a creek flowing out of the mountains and I asked her if she had seen platypus. She had lived there for three decades and had only seen them a couple times. We unpacked and headed up the valley to Eungella National Park about 20 km (12 mi) away in the Mackay Highlands. The final 7 km (4 mi) climbs the mountain in a series of hairpin turns to over 700 m (2,300 ft), a challenge for big trucks and caravans. The park is 5 km (3 mi) beyond the summit; we parked the car and walked across the bridge over Broken River. Several people were standing on the path along the river photographing a platypus every time it came to the surface. I joined them.

Bridge over Broken River in Eungella National Park

There’s no denying that the platypus is odd, even bizarre. They’re smaller than I pictured, about the size of the stuffed platypus toys we had seen in stores. Males are 50 cm (20 in) long and weigh 1.2-2.4 kg (2.6-5.3 lbs); females are 40 cm (16 in) long and weigh 0.7-1.6 kg (1.5-3.5 lbs). I was expecting something at least twice that size. Below the bridge, a platypus made several dives foraging in the debris and sediments of the river bed for invertebrates. Their ears and eyes are set in a muscular groove on the side of the head that pinches shut when the platypus dives; the whitish spot on the side of their face resembles an eye and may discourage predators that don’t realize they forage with their eyes closed. They can remain underwater for several minutes. Males can deliver venom through a spur on their hind feet to their predators or rivals (link), which is unique among mammals [several mammals, including moles and shrews, can deliver venom through a bite] (link).

Platypus grooming

Platypus are generally solitary, although I saw two or three individuals foraging in the largest pools. They live in burrows in the river banks, which they dig with their claws, and occupy by themselves. Once we had the search image, we had no trouble finding them. Circular ripples on the surface of the water (when they’re diving) or V-shaped ripples (when they’re swimming) give them away. Early morning and late afternoon are the best times to see them. Walking slowly downstream, I saw a dozen individuals in two hours. Rande hiked farther downriver and saw a wallaby, a bush turkey and an azure kingfisher. We drove back to Fitch Hatton in the dark.

Broken River in Eungella National Park

The next morning we returned to Eungella and spent three hours hiking along Broken River. The park protects that longest, continuous stretch of subtropical rainforest remaining in Australia, which is about half of what was present prior to European settlement. Eungella is an Aboriginal name meaning land of clouds; average rainfall in the area is 2.2 m (7 ft) a year (link). After lunch, we hiked upstream through the rain forest to another section of the river. It was quite dark inside the rain forest and I needed a tripod to take pictures. We found a large, side-banded skink curled up in the sun at the base of a tree.

Broken River Trail in Eungella National Park

Side-banded skink in front of its burrow

I spent a couple hours photographing platypus late in the afternoon. I was under the bridge when a female surfaced in front of me; she was foraging in 60 cm (2 ft) of water, searching in the muck for crustaceans, worms and snails. She stirred up so much sediment, I couldn’t see her body. The platypus bill is pliable and covered with suede-like skin embedded with 100,000 mechanoreceptors (push rods that sense water movement) and electroreceptors (mucous and serous glands that sense electric fields). With the push rods (columns of compacted cells), platypus can detect the movement of prey within 10-20 cm (4-8 in). The electroreceptors sense weak bioelectric fields generated by the activity of nerves and muscles in their prey, which allows platypus to sense prey movement quicker than with their electroreceptors. By combining information from the two sensors, the platypus can judge the location of its prey in three-dimensions (link, link, link). Echidnas and dolphins are the only other mammals known to have electroreceptors (link).

Platypus in Broken River

Platypus diving

Platypus foraging on the river bed

Later I watched the same female collect long stems of grass-like vegetation from the bottom of the river and tuck them under her tail. She made repeated dives continually adding to the stems she carried. Females use vegetation to line the nest in their burrow where they raise their young (without any assistance from the male). Wet vegetation may be necessary to keep the young puggles (link) from drying out. Platypus mate from August to November. Females are receptive for 4-6 days; after mating, they prepare their nest burrow and lay eggs 2-3 weeks later. Puggles develop in the nest for 3-4 months before entering the water. Females produce milk, which is secreted onto their belly fur from two round patches of skin (they lack nipples). The average fat content of the milk (22%) is six times greater than cow’s milk, and the average protein content (8%) is about twice that of cow’s milk (link).

Female platypus collecting vegetation for her nest

Female platypus diving for vegetation

Female platypus heading off to her burrow

Where does the platypus fit in the evolutionary history of mammals (1) and how do scientists explain its unique characteristics? About 300 million years ago (mya), mammal-like reptiles diverged from the ancestor they shared with birds and reptiles. Somewhere between 210 and 160 mya, egg-laying mammals [monotremes (2)] split from the ancestor leading to placental and marsupial mammals (therians) (link).

Broken River in Eungella National Park

Ancient mammals laid eggs, so egg-laying is an ancestral, or primitive, trait that has persisted in the platypus. The duck-like bill, webbed feet and venomous spine in males are recent “inventions” (derived traits); they were not inherited from a mammal-like reptile or from birds. Scientists have sequenced the platypus genome and the story it tells confirms what evolutionary biologists had deduced. For example, platypus have several egg-development genes that also occur in fish, birds and reptiles (an ancestral trait), but not in placental and marsupial mammals (the trait was lost). Platypus venom genes are not the same genes that produce venom in reptiles; this trait developed independently from a set of genes that are part of the mammalian immune system. And the highly-evolved mechano- and electroreceptor systems platypus use to locate their prey are extremely advanced. In sum, the platypus is a thoroughly modern mammal like humans and kangaroos – all three lineages have been evolving for the same length of time (link, link).

Platypus in Broken River

The rainforest that once surrounded Eungella National Park has been cleared to create the pastures for cattle ranches and dairy farms. Only the steepest areas were left forested. An interpretive sign in the park explains that the history of the area was based on extracting resources – timber and gold – or clearing the land for agriculture (sugar cane) or grazing (dairy and beef cattle). A park sign at a Pioneer Valley lookout asks visitors to: “Take a moment to consider the valley beneath you. What do you see? A patchwork of cleared fields dotted along a lazy creek making its way to sea. See the densely forested valley walls. Why aren’t these also cleared for industry? Their slope and rockiness are unsuitable for mechanised farming so it is not considered valuable agricultural land. But does the land and forest really have no value?”

Cattle ranch near Eungella National Park

The next morning, we left for Ingham 500 km (320 mi) away, our longest drive so far. We passed a wetland with two large cranes on the Bruce Highway and stopped to watch. They were brolgas over 1 m (3+ ft) tall. Also known as Australian cranes, they are widespread in northern and eastern Australia, though generally uncommon.

Wetland along the Bruce Highway

Brolgas in the wetland

Tyto Wetlands was down the street from our motel in Ingham. In early evening, we walked around the ponds and marshes and saw whistling ducks, royal spoonbills, straw-necked ibis, crimson finches, tiny red-backed wrens and a sacred kingfisher. The mozzies (mosquitoes) were out in force and swarmed us whenever we stopped walking. Signs posted near the water’s edge warned of crocodiles in the marsh. On our way back to our motel, we passed a soccer field taken over by dozens of eastern grey kangaroos and agile wallabies grazing in the fading light.

Tyto Wetlands at Ingham

Crocodile warning sign in Tyto Wetlands

Agile wallaby

The next morning, we drove into to the Eastern Highlands to Wallaman Falls in Girringun National Park, about 50 km from Ingham. At 268 m (879 ft), Wallaman is Australia’s highest waterfall. The lowland countryside alternated between sugar cane fields and pastures with doe-eyed brahman cattle. At Tyto the evening before, we were told to watch for cattle on the road; the previous week, tourists on their way to Wallaman Falls hit a cow and wrecked their rental car. We were also told to look for cassowaries along the road in the mountains. We had hopes of seeing them, but all we saw were the yellow warning signs. These large birds can be aggressive towards people. Australia has a public information campaign to that effect; we'd seen the “Be Casso–Wary” signs on hikes where we went looking for them.

Cassowary warning sign on the road to Wallaman Falls

Wallaman Gorge in Girringun National Park

Girringun National Park (link) is part of Australia’s Wet Tropics World Heritage Area, which covers 900,000 ha (2.2 million ac) and 450 km (280 mi) from Townsville to Cooktown and contains the greatest diversity of animals and plants on the continent (link). Girringun is located in the Atherton Table Lands, a fertile plateau west of Cairns (link). We were the second car in the parking lot. The sun was barely above the horizon and the lower half of the falls was unlit. The 3-km (2-mi) trail to the base of the falls descended through open, sunlit she-oak forest that transitioned to a dark, humid rain forest dominated by palm trees. The stairs and walls along the narrow trail evidenced good trail work; this trail was better maintained (less erosion) than other trails we’d hiked. The rocks were coated with slimy algae and microorganisms and became slipperier as we descended.

Trail to the base of Wallaman Falls

By the time we reached the bottom, the sun had risen high enough to flood the narrow valley with light creating a rainbow in the mist rising from the plunge pool, which is over 20 m (65 ft) deep. We sat on the rocks and ate our lunch.

Wallaman Falls

Rainbow downstream from the plunge pool

The parking lot was full of cars when we got back to the trailhead. About 100,000 people visit Wallaman Falls each year (link) and I had to jockey for a spot to set up my tripod at the overlook. We left and slowly drove down the mountain looking for cassowaries – we didn’t see any. At the Bruce Highway we turned north for Cairns about 300 km away.

Wallaman Falls from the rim

We made another trip into the Atherton Table Lands while we were in Cairns. We had seen a show on public TV about rock wallabies in Granite Gorge and we set out to find them. From Atherton, a small city dominated by agricultural and industrial services, we took off cross country on narrow rural roads through eucalyptus forests and range lands. The eucalyptus forest at 700-750 m (2,300-2,500 ft) was quite dry compared to the tropical rainforest we passed 50 km (31 mi) back. We passed huge termite mounds in several pastures and I stopped to take pictures. The largest mounds were 1.5 m (5 ft) tall and 2 m (6 ft) wide and as hard as cement (I kicked one).

Termite mounds in a pasture near Mareeba

Granite Gorge Nature Park

Granite Gorge Nature Park is a privately-owned “bush” campground and nature park (link). We paid the entry fee ($12AUS/adult) and Rande bought a small bag of kangaroo food. The more than 100 Mareeba rock wallabies in the Granite Gorge are wild (as in not fenced in), but are accustomed to being fed by people.

Mareeba rock wallaby in Granite Gorge

Rande feeding the (habituated) rock wallabies

There are about 15 species of rock wallabies in Australia that closely resemble each other; many were thought to be races of the same species, but genetic testing has shown them to be distinct species. Rock wallabies are small kangaroos (60-70 cm, 28-28 in, tall) that live in colonies among boulders, rock outcrops and steep rocky terrain where they shelter during the day and forage at night. Their feet, which are adapted to moving quickly over rocky, often steep terrain, are wide and rough with short claws, their tail is long relative to other kangaroos and not tapered at the end, and their fur often matches the color of the surrounding rocks. Unlike other kangaroos, the young don’t follow the mother and are left hidden among the rocks until they are fast and agile enough to keep up (link).

Mareeba rock wallaby family

Juvenile rock wallaby left alone by its parents

The Mareeba rock wallaby is only found around Mareeba, a small town 12 km (7 mi) east of Granite Gorge. It belongs to a group of seven closely related species found in northeastern Queensland. We saw several females carrying joeys and unattended juveniles in the rocks. The dominant males chased other wallabies away from the people feeding them.

Male rock wallaby napping

The granite rocks of the gorge are split and rounded by weathering and floods. Marked trails wind through the boulders down to the Granite Creek. In the visitor center (really just a shack), there are pictures of Granite Creek when it flooded a couple years ago. As I walked along the creek, I saw debris still lodged in some trees higher than my head. I wondered how the wallabies fared during the flood. 

Granite Gorge

Granite Creek

We spent the afternoon in Granite Gorge and, like a lot of people before us (link), found it to be a surprising diversion.

Mareeba rock wallaby family

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(1) Creationists assert that evolution cannot “explain” the platypus (link, link).

(2) Monotremata (an order of mammals) means single hole; monotremes have a common opening, known as a cloaca, for their digestive and urogenital systems. The only extant monotremes are the platypus and four species of echidnas (link). I’ll have more to say about echidnas in future posts.