As a follow-up to the previous blog on trophy hunting, Nils Bunnefeld and Aidan Keane have put together an invited Commentary (see link below) on what IPMs mean for the management of hunted populations, based on our recent paper in PNAS. In our paper, we could only very briefly deal with the wildlife management and conservation implications. There were word limitations, and we had a narrative to stick to. As a conservationist though, I am always very mindful about ‘what does it all mean?’ Surely taxpayers don’t fund our science so that we can get out bush occasionally, and work on stuff that we find interesting? Or maybe they do – and I should just keep quiet about it :]
Anyhow – thankfully Nils and Aidan have provided an outline of the challenges, and usefulness of IPMs in addressing the complex issues around sustainable harvest. I deal with their main points:
First, long-term individuals based studies take time, and are expensive – although the data are golden (see in particular Clutton-Brock and Sheldon, 2010, Trends Ecol Evol). It all comes down to resources in the end, and could these be better spent on conserving populations – or learning more about the behaviour of resource users for example? An interesting avenue of research would be to explore these trade-offs within a decision theory framework.
Second, the importance of uncertainty. They rightly point out that we use a simple, proportional harvest regime within the model – but the real world is not like that. There are issues around observation error and realised offtake (often higher than set quotas). How do we get around that? Although I have alluded to decision-theory, the authors recommend the management strategy evaluation (MSE – and see Figure, taken from the Commentary). Such an explicit framework includes a biological systems model (such as the IPM), an observation model that accounts for hunter behaviour, an assessment model that allows decision-making based on observation and a resource user model representing the socio-political-economic dynamics driving human decisions regards hunting.
Although I have little experience with such frameworks – Nils and Aidan correctly point out that the ‘biological systems model’ component has to-date been based on classic Leslie matrices, and thus the opportunity now to swap these with IPMs and thereby ‘allowing managers to examine ecological, evolutionary, and economic criteria together when making decisions on harvest strategies.’ That’s a substantial advance right there!
As a final point, perhaps a novel way of getting around lack of data would be the parameterisation of an IPM – within the MSEframework – based on allometric scaling and Bayesian priors (see for McCarthy et al, 2008, Am Nat).
See the Commentary here: http://www.pnas.org/content/111/36/12964