A love of the Daintree Rainforest led scientist and researcher Wren Mclean to centre her honours around Cassowaries, an iconic keystone species that’s “notoriously difficult” to study.
She has spent countless hours researching them since, and is now one of the first and foremost experts in her field. We spoke to Wren recently about the importance of these ancient birds and why their Daintree home is so worth saving.
Scientist and researcher Wren Mclean
Q: Are Cassowaries actually living dinosaurs?
A: In short, yes. Cassowaries evolved to their current form 50 million years ago. If we picture it, it would have been a much more extensive rainforest - ancient rainforest - and those Cassowaries that we see today would have been walking around spreading seeds and doing their Cassowary thing 50 million years ago. They started diverging from the greater Struthioniformes (flightless bird) group about 60 million years ago, so it took them about 10 million years to evolve to their current form.
Q: How many Cassowaries remain in Australia and where are they found?
A: A fecal DNA analysis, which I was partly involved in, involved collecting scats from different altitudes and different habitat types throughout the whole Wet Tropics. Those scats were then analysed for small traces of DNA so we could get an ID on individuals. So once you’ve identified one bird in that area, you keep collecting more scats in that area until you stop finding any new individuals and you can say that’s the number in that area. Four thousand adult birds was the estimate in the Wet Tropics, from below Cooktown to north of Townsville.
Then we have isolated subpopulations across Cape York, and we don’t know how many are there. It’s currently under investigation and [something we’re working on].
Cassowaries in Australia are all the same species, Casuarius casuarius, and that species also extends to southern Papua New Guinea. In Papua, there are two other species of Cassowary - the Dwarf Cassowary and the Northern Cassowary.
The endangered Southern Cassowary
Q: You've observed many Cassowaries in the wild. Are they as dangerous as some people think?
A: They’ve earned their reputation; they are the most dangerous bird in the world and the only bird that has killed people. So yes, they are dangerous, but in every case of an incident with human beings, it’s either been that the cassowary is defending itself, its eggs or its chicks, or it’s been hand fed. In the case of hand-feeding, it drastically alters behaviour and of course cassowaries are not really supposed to eat most things that humans eat. They get very imposing, they’ll stand above you and have been known to chase people away from picnics and all sorts of things. We certainly do not want to be hand-feeding Cassowaries, it always leads to trouble.
I’ve had a couple of encounters which have been very memorable - one in particular when I was doing solo field work for my honours thesis in the Daintree lowlands. I startled a Cassowary and it startled me so we both got a fright. It ran off making guttural coughing noises as they do, and then I heard it making a new deep growling sound I had never heard before, so I looked around for a tree to climb. That Cassowary paced around me for a good 10-15 growling - a pretty big warning. I just ended up taking my time with it and walking slowly away. There is always a chance of encountering a dominant wild Cassowary when your off track in those forests and it’s very exciting when you do.
Q: Why is the Daintree Rainforest important for Cassowaries?
A: Cassowaries are our largest frugivore, - dietary analysis has found 99% of what they consume is rainforest fruit - and they’re a seed disperser of those rainforest species as well. The rainforest provides the majority of their food but they will also use habitats adjacent to rainforests such as mangroves. They’ve been known to eat crabs, and will use other types of closed forests such as monsoonal vine thickets, but rainforests are their stronghold. While they may target fruits that are seasonally available in adjoining vegetation types, they are dependent on rainforests and spend most of their time in them.
The Daintree Lowlands retains the largest tract of unfragmented lowland tropical forest in Australia. It has been shown that lowland rainforests support the highest densities of Cassowaries due to the high availability of fleshy rainforest fruit they provide.
Fruit of the Cassowary Plum (Cerbera floribunda)
Q: What are the main threats to Cassowaries?
A: As we know, a lot of that lowland area in the tropics has been cleared for sugar cane and also for urban and residential development. The Daintree has retained a lot of its ecological integrity as a lowland forest. Probably the only other site that’s comparable is Mission Beach and that location is being increasingly developed. We see a lot of Cassowaries getting into trouble there - car hits are rife, dog attacks are rife and just the general destruction and fragmentation of their habitat due to the amount of development going on in Mission Beach.
Even small residential lots within the rainforest fragment what’s available to Cassowaries, especially when people who’ve settled there are not aware of the sensitivities of this ecosystem, have large dogs, put up fences and introduce foreign plants to the area which can then become weeds further threatening Cassowary habitat. There are a lot of issues around that kind of development within an ancient rainforest. Tropical rainforests are hot, humid, closed canopy systems and new residents often find this oppressive and start clearing around their houses to let in the light and air. This will have serious long-term consequences for the stability of these delicate rainforests under future climate stress.
The Daintree has managed to retain a lot of its natural vegetation, and historically there’s been a lot of effort to protect the area, but those efforts did not complete the job. That's why groups like the Save the Daintree program have been really focused on finishing the job. Buying back those last lots and ensuring as much of that irreplaceable lowland forest is protected as possible.
Q: The buyback of land in the Daintree began in 1992. How has that benefited Cassowaries and where would we be if it hadn't happened?
A: The more people that move to the Daintree lowlands, the more people start to lobby for development, and it is so important to keep the population of resident humans to a minimum. These residents have an invaluable opportunity to promote and benefit from global fascination with this rainforest through sustainable eco-tourism. This will ensure a sustainable population of cassowaries, which is one of the main reasons visitors are attracted to the area. If we start to see more of these blocks developed, there’s going to be more pressure for bridges, for mains power which will make further development more attractive and it just snowballs from there. If the buyback hadn’t happened, we wouldn’t have an area with such integrity. It would be fragmented, full of risks and threats to the biodiversity there.
Ecosystem connectivity is really important to Cassowaries. Young cassowaries get hounded out of their territory as soon as they reach adolescence, which is probably a strategy to stop inbreeding. But if there’s nowhere safe for those young ones to move to, they wander through developed areas and are really vulnerable to all those threats. Having the connectivity is just so important. It’s absolutely integral to long-term survival of the species.
Wren Mclean in the Daintree
Q: What are the next steps for protection of the Daintree?
A: It’s a 34 km stretch of rainforest; it’s not even a large area so surely, we need to be able to protect all of this remaining integral habitat for its connectivity values, from the Great Barrier Reef to up to the high altitude mountains. If you’re supporting Save the Daintree and Rainforest 4 Foundation, you are supporting biodiversity into the future and a legacy that we can all be a part of. This ancient rainforest is irreplaceable and, if it’s developed, fragmented and degraded it will be irrevocably damaged. Now is the time and we are the people. We are the humans to do this - if everyone chips in a little bit it adds up to a lot in the long term, for the long term survival of Cassowaries and all the species they cohabit these rainforests with.
Act now to help us protect and purchase Lot 26 Ronald Road in the Daintree and ensure vital habitat for the endangered Southern Cassowary is conserved. Time is running out for us to buy this property and the situation is becoming urgent. We only have until June 30 to raise the funds needed. Please, donate today.