Southern-Summer School on Mathematical Biology

In the wetlands of Pantanal an endangered tropical bird relies on its nest predator for its perseverance. The tale of the hyacinth macaw (Andorhynchus hyacinthinus) involves the tree in which they build their nests (Manduvi trees Sterculia apetala) and the main seed disperser of the manduvi tree, which also happens to be the macaw's main nest predator, the toco tucan (Ramphastos toco).

Hyacinth macaws build their nests almost exclusively on the disputed manduvi trees. Taking into account macaw's threatened conservation status, Pizo et al. (2008) performed a study to investigate the natural history of its nesting tree species, specially concerning the main seed dispersers of the manduvi tree. The authors found that toco toucans are the main disperser of manduvi, responsible for more than 80% of the dispersal. At the same time, toco toucans are the main nest predator of hyacinth macaws. Most conservation actions focus only on manduvi trees and macaws; however, this study elegantly highlights how species interactions must be taken into account when performing conservation policies.

Note that this is hyacinth's macaw (also) endangered cousin – Spix's Macaw

The macaw-toucan-manduvi system clearly represents a case of conflicting ecological pressures. Propose a model to study the dynamics of this system, with special focus on conservation actions that could improve population densities of the hyacinth macaw.

• Considering the central role toco toucans play in the system, both as seed dispersor and nest predator, how does a population dynamic model allows coexistence in this system?

• As a conservation manager, you might believe that planting more trees would be a plausible plan of action to conserve hyacinth macaws. Explore the effects of such conservation action in your model. Keep in mind that fruits of the Manduvi trees are part of the diet of toucans.

• Can you think of another conservation policy that could help the endangered hyacinth macaw? How would you incorporate it in your model to learn if it would be effective?

• Hyacinth macaws need trees older than 60 years to build their nests. How would you incorporate generation time in your model? How does that change your previous predictions about the dynamics of the system?

Conservation puzzle: Endangered hyacinth macaw depends on its nest predator for reproduction Marco Aurélio Pizo, Camila I. Donatti, Neiva Maria R.Guedes, and Mauro Galetti Biological Conservation (2008) https://www.sciencedirect.com/science/article/abs/pii/S0006320708000104