Jennifer Marohasy

a forum for the discussion of issues concerning the natural environment

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The Cumulative Impact of Rainforest Research

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In the late 1990’s, a scientific ‘pig-exclosure’ project was established in the Cape Tribulation section of the Daintree National Park. The project involved the construction of an 80 metre square fence, anchored aggressively to the ground with steel trimmer bar and pegs. The site selection encompassed much of the very restricted, endangered and previously studied laurel, Endiandra cooperana.

The purpose of the project was to collect comparative data, inside and outside the exclosure, to quantify the adverse impacts of feral pigs upon seedling recruitment rates of an endangered plant species.

Criticisms of the project at the time included the accessibility by piglets into the exclosure through the mesh squares, the obstruction to cassowaries in a known corridor, proximity to two roads and the contention that even blind Freddy could see that pigs were damaging to seedling recruitment rates.

Despite these concerns the project proceeded and there it remained for many years. Eventually, the land manager agreed to remove the construction, but was so under-resourced it dismantled only one corner section and middle panel on each side, leaving around eight 30-metres sections of fence in the rainforest, where they remain to this day.

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In around the year 2000, another scientific study was carried out in the vicinity of the pig-exclosure project. This one sought to capture the primitive rainforest macropod, Musky-rat Kangaroo Hypsiprymnodon moschatus. The methodology required the placement of several hundred metres of plastic barrier through known habitat, stretched to form walls with strategic openings every thirty or so metres. The animals would familiarise themselves with the openings and after a period of adjustment, cages would be placed at the openings into which the animals would be herded by the research scientist. Once caged, they would be analysed and genetic material collected from hole-punched tissue from the ears of specimens.

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More recently, another similar project was transferred to the same locality from rainforest in the Cyclone Larry affected areas. Different plastic barriers were constructed, for the same purpose, but this time the project sought to map the liberation of captured animals by gluing a cotton reel to the released subjects so that the thread would leave a variety of passages that could be compared relative to the adjacent roadway, to determine whether roads had a quantifiable impact on evasive mammal behaviour.

All very interesting projects, but why are the researchers abandoning their materials in the forest?

Prue’s Unidentified Anomoly

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In the year 2000 I posted an image on wikipedia of a growth that I found on a Ryparosa javanica hoping to get it identified.

Seven years older, but no wiser, I thought it worth giving it another shot.

I think it’s part of the growth of the tree. The stem looks similar, but it is not the normal fruiting body and with hundreds of trees to look at daily, I have not seen it again.

I am asking Neil, most humbly, if he will post my image on the blog, since I remain unempowered in the blogging process.

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Something Rotten in the Daintree

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Step into the rainforests of the Daintree lowlands at the moment and you’re likely to whiff the pervasive scent of the rare Javan Ash (Ryparosa javanica). The abundant flowering emits a sweet, slightly off-smell, like five-day-old socks or raw hamburger mince.

The Javan Ash is found in both Java and Australia. This forms evidence of the mixing of the continental biota of the Australian and Asian plates, which are believed to have collided about fifteen million years ago, in the vicinity of what is now the Timor region.

As a defence against herbivores, these plants emit the poisonous gas Hydrogen Cyanide (HCN), through a process called ‘cyanogenesis’.

HCN is poisonous, not only to animals that the eat plants, but to the plants themselves. To prevent poisoning themselves, the plants limit the production of HCN through the strategic storage of both cyanogenic glycosides and an enzyme in adjacent vacuoles of the cell. When the cell is damaged the compartment walls are breached and the reaction takes place. In this way, HCN is produced only when needed.

Greenwashing River Red Gums

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Ecotourism Australia has thrown its weight behind the Victorian Environmental Assessment Council’s River Red Gum Forest Draft Proposal, claiming that it will open up important new ecotourism opportunities for the region.

However, another NGO, Timber Communities Australia, argues that as many as 400 families, whose livelihoods are dependent on access to these forests, will be adversely affected by the proposals.

Ecotourism Australia’s foray into the debate represents an expression of its mission to contribute to conservation solutions and projects; involving and providing benefits to local communities, but will those 400 families be the targeted beneficiaries?

My dubiousness reflects the pre-existing capacity of genuine ecotourism to access an already existing superb environment. Change of tenure to National Park is not prerequisite. What is does provide though, is subsidisation of the full costs of conservation and commercial operator relief of the requirement to improve the well-being of local people.

Genuine ecotourism is internationally defined as:

Responsible travel to natural areas that conserves the environment and improves the well-being of local people.

Ecotourism Australia is a membership-based organisation that is strongly representative of protected area managers and holders of commercial activity permits. It has adopted a different definition to the international standard:

Ecologically sustainable tourism with a primary focus on experiencing natural areas that fosters environmental and cultural understanding, appreciation and conservation.

The Oslo Statement on Ecotourism was recently produced at the Global Ecotourism Conference held in Norway 2007.

‘Ecotourism’ was recognized as being widely used, but also abused, as it is not sufficiently anchored to the definition. The ecotourism community, therefore, continues to face significant challenges in awareness building and education and actively working against greenwashing within the tourism industry.

Frogs and Snakes

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When Stoney Creek treefrogs (Litoria lesueuri) mate, hundreds of males congregate around three or four females. In contrast to their normal olive drab, the much smaller and more numerous males display their state of excitement by becoming brilliant bright yellow.

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I have never seen any any nocturnal snakes avail themselves of these veritable smorgasborgs; perhaps the treefrogs are poisonous. The Keelback or Freshwater Snake (Tropidonophis mairii) however, is diurnal and can tolerate the toxins of young cane toads (Bufo marinas) and also Stoney Creek treefrogs, if captured during the day.

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In this media release from Sydney University, strategic behaviour of frogs and snakes reveals an unexpected sophistication:

When dinner is dangerous

Normally, when a snake meets a frog it is the frog that must fear for its life. But in the tropics of Australia there are several frog species that can turn the tables on their attacker.

The marbled frog produces a strong glue when bitten by a snake, making the frog difficult to handle. Dahl’s aquatic frog uses a different tactic, producing a potent poison that can kill a snake attempting to swallow it.

In a recent article in The American Naturalist Ben Phillips and Richards Shine from the University of Sydney show that one species of Australian snake has developed an ingenious trick for dealing with these dangerous prey items. The northern death adder is a highly venomous front-fanged snake native to the same floodplains inhabited by these dangerous frogs. By examining snake feeding behaviour, Phillips and Shine found that death adders not only know that these frog species are dangerous, but they recognize which species they are attacking and deal with them appropriately.

How do the snakes deal with these toxic prey? The answer is simple: by biting and then waiting. The adders simply bite then eat non-toxic frogs, but dangerous frogs are bitten, envenomated and then released. By waiting for the toxic frogs to die, and then waiting for the toxin to degrade, predatory snakes can effectively dodge the toxic frog bullet.

Intriguingly, the snakes recognize which kind of prey they are dealing with: the glue of marbled frogs takes about ten minutes to lose potency and so snakes wait about 12 minutes after biting this frog before eating it. The toxin in Dahl’s aquatic frog takes longer (about 30 minutes) to lose potency. Thus, adders delay swallowing for 30-40 minutes after biting and releasing these frogs.

In evolutionary terms, the snake’s strategy of “bite, release, and wait” is unbeatable by the frogs. Although prey often evolve ways of overcoming predator tactics, the frogs can’t do so in this case – because the snake’s strategy only becomes effective after the frog has died. Natural selection ceases to operate on an individual after that individual’s death, so frogs will probably never evolve toxins that last longer in response to the snake’s tactic. Thus, this waiting strategy is likely to be stable and unbeatable over evolutionary time.

“The common assumption is that snakes are pretty stupid, and to them a frog is a frog. But here we see a snake that effectively discriminates between frog species and then deals with each species in an appropriate manner. If dinner can kill you, you have to be careful,” said Dr Phillips.

Mossman Sugar Trials

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It has been my observation that the little-known prehensile-tailed rat (Pogonomys mollipilosus) loves the sweet gel around the seeds of cocoa beans and I have wondered how cocoa can be protected from their adverse economic enthusiasms.

The notion may well come to a head, with Mossman Agricultural Services helping to develop a cocoa industry with a $199,000 Sugar Industry Innovation Fund grant. In partnership with Cocoa Australia and Mossman Central Mill, the project seeks to diversify the income stream for the mill, by manufacturing sugar-based products needed for cocoa and chocolate production. Part of the grant will be used to help establish a cocoa processing factory.

Plummeting world sugar prices have encouraged the development of value-adding in Mossman Mill, through organic chocolate production and also the world’s first batch of low glycemic-index (GI) sugar, which could help people with diabetes.

Damage Mitigation Permits are processed by Queensland’s Environmental Protection Agency, after non-lethal strategies have shown to be unsuccessful, but the little-known prehensile-tailed rat has not been previously identified as a pest and neither has it been listed for its vulnerabilities.