The macaw, the toucan, and the manduvi

Here’s your weekly Science Matters column by David Suzuki with Faisal Moola.
The macaw, the toucan, and the manduvi
No matter how much I learn about nature, I never cease to be amazed by its mystery and complexity. That point really struck me in light of a recent study in the journal Biological Conservation about the relationship between the hyacinth macaw, the toco toucan, and the manduvi tree.
The hyacinth macaw is an endangered bird in central Brazil. It has a reputation for being picky when it comes to choosing a home: it lives almost exclusively in natural hollows in manduvi trees, which don’t grow in great numbers in the region. In an effort to help preserve the bird and its habitat, Dr. Marco Pizo and his research team at the Universidade do Vale do Rio dos Sinos explored how the manduvi tree’s seed is spread. They found that the toco toucan collects and disperses more than 83 per cent of the seeds.
So far, so good. But here’s the kicker: The toucan is the macaw’s main predator. Besides feeding on the whole seeds of the manduvi, the toucan also has a big appetite for macaw eggs. The researchers also observed toucans taking over macaw hollows and killing the nestlings.
And so, ironically, the macaw depends on its main predator, the toucan, for its survival.
This fascinating relationship has led to what the report’s authors call “a conservation biology puzzle” because “any conservation plan for hyacinth macaws must take into account the toucans, which would not normally be done because of their predator status and because toco toucans are not particularly threatened.”
It’s a puzzle that illustrates the importance of seeing the big picture when it comes to protecting the environment. Attempting to manage a single species in isolation can’t work because nature is just too complex. Take the caribou, an iconic species found throughout Canada. Caribou are in trouble across their expansive range. In British Columbia, populations of mountain caribou that inhabit the Interior rainforests have plummeted to an estimated 1,900 individuals from historic levels of about 10,000. The main threat is the destruction of its old-growth forest habitat by commercial logging, but scientists believe that predators, like wolves and cougars, may have also played a role in the caribou’s decline. Because of this, the B.C. government has initiated a plan to kill wolves and other predators, in addition to protecting significant areas of the caribou’s habitat. Such “predator control” wildlife management practices are increasingly being proposed or used elsewhere in Canada. However, because the science of predator-prey interactions is poorly understood, these methods can have severe and unintended consequences. In the case of the hyacinth macaw, killing its main predator would ensure its demise.
We must understand the broader context if we want our wildlife management plans and conservation efforts to succeed.
Governments have been talking about this “ecosystem approach” for some time, but so far they’ve been slow to follow the talk with action. The official (and somewhat bureaucratic) name for one area off Canada’s West Coast even acknowledges this broader-context approach: the Pacific North Coast Integrated Management Area, or PNCIMA. This 88,000-square-kilometre marine region next to B.C.’s Great Bear Rainforest encompasses the central and north coast and Haida Gwaii and is home to a fascinating variety of life, from basking sharks and blue whales to massive kelp forests and glass-sponge reefs. Although the federal government has committed to using an ecosystem approach for managing the PNCIMA, it has taken little action to implement the process. Environmental groups, including the David Suzuki Foundation, used World Ocean Day, June 8, to draw attention to this fact and to the lack of marine protected areas in Canada’s ocean territories.
Like the Earth’s forests, oceans are complex environments where everything is interconnected. Whether on land or at sea, large population changes (including extinction) in one species can have cascading effects throughout the ecosystem.
Good conservation planning requires efforts by local communities and governments at all levels to base decisions on an understanding not just of each species in isolation but of ecosystems as a whole. And we must keep in mind that we’re a part of that whole, even though our relationship with nature is often as complex and tricky as the relationship between the hyacinth macaw and the toco toucan.
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