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Another computer model to justify continued lion hunting?

                                                                       Catch of the day

A recent publication in Proceedings of the National Academy of Sciences by Charles Edwards and co-authors has been making the rounds on the “science explained” websites. Unfortunately, many of the reporters on such sites swallowed the hook without looking at the meat. 

The article had the unfortunate title “Data-poor Management of African Lion Hunting using a Relative Index of Abundance”   

– I would suggest the first seven words explain it all.   

Bear with me while I explain a few things relevant to this publication:

  1. Computer models have long been a favourite means of predicting future trends based on inputs of past events. As a consequence economists frequently use computer models to analyse future market trends based on what happened in the past. Like saying “given that the quarterly report from the Metals Amalgamated Corporation shows a downturn in profits, how will that affect the Copper futures market? Should investors rather buy futures in Pork Bellies?” 
  2. One of my professors in a computer modelling course said it best:  “Garbage in equals garbage out”. In other words, the predictive value of any model is only as good as the quality of information provided. His words are widely ignored as it is often not the quality of the information provided for the computer model but the output that is given greatest consideration.
  3. Craig Packer at the University of Minnesota (that institution is important, so remember the name please) came up with a computer model for “sustainable” trophy hunting of lions in 2004. He predicted, based on many years of study of lion populations in the Serengeti, that when a male lion reached six years old, his reproductive life was over. Instead of allowing this poor loveless male to wander the plains for another four or six more years, he could be shot as a trophy without any consequence. The poor lion had become an “excess” animal, no longer needed except as a rug.
  4. This was in spite of considerable other information from lion populations across Africa that a six year old male could actually just be reaching reproductive age, having reached the body size and wherewithal to challenge resident males with the assistance of his coalition.
  5. The next problem was how to age such males in the field. This was the birth of the very controversial “nose theory”. In the Serengeti it appears that lion noses change colour from pink to black with a predictable timeline. Therefore, and I’m not making this up, by the time a lion had a nose 50% black it was about six years old. As if the hunter could make an accurate assessment between 45% or 55% black and then shoot? Huge amounts of data countered this “nose theory” but it was taken seriously for a while. 
  6. Some African lion range States took the “six year” rule seriously (!). Note that it was not the hunting operators (conservation hunters) but the States that made the new rules. Mozambique first and recently Tanzania. But accurate aging remained a problem. So a strange secondary measure was imposed. Someone proposed that the age of a lion could be assessed accurately by X-ray examination of a tooth. Supposedly (you ready for this?) incremental cementum deposits in the root canal occur on a predictable timescale, so a tooth that reveals x% of the root canal closed means the lion shot was of the right age. Hmmm. Two problems here – the lion is already dead and the technique does not work. 
  7. Overall, the six year rule is nonsense, preliminary aging before the lion is shot by nose colour is nonsense, and aging via a tooth (we are not talking about rings on trees here) does not work.

So that is a bit of background. Now let’s progress to the next stage, please bear with me again for a while before I get to the “meat” of the most recent computer model about how to hunt lions. 

  1. The Proceedings of the National Academy of Science (PNAS) follows a bit of an unusual procedure for article submissions. In short, you need a “sponsor” (a Member of the Academy – actually a high honour for a scientist) to accept the paper and propose it for publication. In this case it was Stephen Polasky. Stephen is an economist and also member of the Faculty at the University of Minnesota. Stephen has a joint appointment at the Department of Applied Economics and the Department of Ecology, Evolution and Behavior where Craig Packer hangs out (told you to remember that University!). 
  2. The authors of the paper acknowledge funding from the Panthera Foundation (a long-time supporter of lion trophy hunting) and the HUNTing for Sustainability Programme of the European Union (largely about birds in the EU). The Panthera Foundation has pursued a dogged course of funding many pro-lion hunting publications over the years. Strange that, as some better balance of publication support might have been expected from an organization “dedicated to conservation of large cats”?

OK, now to the paper itself. The authors say that “Deriving robust means to set sustainable limits to exploitation is now a well developed science, increasingly applied to marine fisheries and referred to as management strategy evaluation (MSE)”. And they then go on to develop a model for lion hunting using “a control rule that is robust to incomplete knowledge of resource status or its response to harvesting, implicitly conforming to the precautionary principle of resource management”.  Hmmm.

Then they profess that lions can be sustainably harvested even in the absence of information on population size. How? Just by tracking success rates of trophy hunters – low success rates mean that there are very few lions in the area, and high success rates mean there are plenty. So no need for quotas, just gauge hunting success and all will be fine. 

This comes back to the fisheries model. There is really no way to determine how many fish are in the sea. So, as a measure of judging how sustainable fisheries are, just see how difficult it is to catch fish. If most boats come back with a poor catch, then there are not many fish left. But if the boats come back with lots of fish, then there are plenty. So adjust your fishing quotas accordingly. 

And according to the authors, the same can be applied to lion hunting.

In their defence, the authors do acknowledge (in writing, but not so much in the parameters of their model) that the “six year rule” is likely not universally applicable, enforceable, or measurable; that male lion hunting has consequences on cub survival and future reproduction within hunted populations; that hunting of lions is facilitated by setting out baits to make “lion fishing” more effective than some hunter walking around in the bush and “coming across” a huntable lion, etc. 

They also mention in passing that hunting operators “might” not be ethical in selecting lions of appropriate age for their clients to be shot. An understatement that has affected both fishing harvests and lion hunting to be sure. They do not mention that hunting operators place baits on the borders of protected areas to lure males into their fishing grounds , and that hunting operators rely on the presence of resident female lions to lure both adult males and dispersing males into the hunting concession. They do not mention that their model relies on a minimal level of age compliance that hunting operators vastly ignore. Age restrictions are not enforced in the majority of African nations where lion hunting is legal, and basically have no relevance anyway as the entire premise of the “six year rule” is wrong. 

No lion should be trophy hunted as the species is in freefall decline. Given the realistic evidence of declines to about 15,000 lions remaining on the entire continent, why bother with a flawed computer model that promotes the continued trophy hunting of lions?  

Also, is a fisheries model applicable to lion hunting? No. Is a computer model that predicts that lions can be hunted based on a “data-poor management” model relevant? No. Is this publication in any way relevant to sustainable utilization of lions by trophy hunters? No. Are computer models the way forward in sustainable utilization of lion populations by sport hunters? No. 

So why has this publication received a certain level of media attention? Doubtless because the funders of the study made the appropriate media phone calls and press releases. Certainly not because the publication has any scientifically based merit for future lion conservation.  

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Posted by Chris Macsween at 13:36

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