The devil hiding in the detail

Debates about wildlife are fertile with misinformation about the size and growth, or decline, of their popuatlions. Exaggeration grows with the competition of claims and counter claims by opposing groups.

If a claim is not accompanied by a verifiable measurement – one that could be repeated because you can know how it was achieved – treat it sceptically and ask for supporting documentation. Claims are more valuable if they can be evaluated because the where, how, who and when they were achieved is documented and available to all to see.

But my concern here isn’t with making sure that all of us who care about wildlife and their better management discriminate between substantiated and unsubstantiated claims because that is a transparently good and simple task. Challenging wild claims and focussing your attention on those that can be substantiated is just plain good practice whatever your purpose and prejudices.

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My concern is with helping people discriminate between the good and the bad of ‘official’ claims because they are more difficult, or made more difficult, to evaluate. Even though, or probably because, official claims are supported by documentation, evaluating their quality requires some experience and insight.

Transparency and simplicity is necessarily sacrificed by detail. No one, for example, takes a large financial risk without the apparently opaque complexity of a legal document. But there-in is the opportunity for a ‘devil’ to also hide in the detail. Flaws unintentional, unintentional but intentionally hidden, or intentional can be devils in the detail of official claims about population size and how it migth be changing, that is growing or declining.

I am concerned that the history of official, sometimes referred to as ‘scientific’, estimates of feral horse population growth revealed more about expectations of those conducting or reporting the estimates than the truth.

Horse & Pony coverSometimes, the official reports of population growth have been so flawed that guesses from amateurs lobbying against population control can be closer to the truth. In New Zealand, for example, at the height of debates about how the Kaimanawa Mountain population the Department of Conservation released estimates that the population was growing at 16%, or as high as 24%, each year [1] – a rate that would be alarming if it were true. Such rapid growth rate would be cause for immediate population control to avert ecological catastrophe and animal suffering on a massive scale. It is fairly safe to assume, therefore, that it met the expectations and intentions of those in the government agency promulgating the extraordinary rates.

Around the same time, however, a representative of the International League for the Protection of Horses, Elizabeth MacFarlane, was reported in New Zealand Horse & Pony disputing the extraordinary rates and suggesting that the population was growing no more than 9.4% a year [2] – a value later found to be closer, remarkably close, to the truth [3].

It is possible that Ms MacFarlane achieved a degree of insight that escaped much more experienced wildlife managers, or she just made a good guess – we may never know (I have tried since to track down Ms MacFarlane but without success. If you know her please put her in touch). It is certain, however, that official claims were seriously flawed. Unfortunately, the official claims were made opaque with documentation and authority. They were not found to be flawed until after they had been used to justify a particular course of population management. Critique did not happen soon enough.

In the following weeks’ posts I will describe the several ways that official, apparently well substantiated, reports of feral horse population size and growth have been misleading. I will provide some simple ways of detecting hyperbole and being sensitive to bias in ‘scientific’ and official reporting.

I will discuss how animal immigration and population adult sex ratio need to be considered when interpreting and applying estimates of feral horse population growth.

I will describe the techniques for estimating population size and growth and how they vary in their reliability. I will identify those techniques that are inherently flawed and should probably not be used or, at least, not used as if they are infallible.

Lastly, I will highlight the several research groups working hard to improve estimates – like the United States Geological Survey.

Lessons from feral horses could be usefully applied to controversies about other wildlife populations where their size and growth rate is disputed.

Bibliography

1. Department of Conservation, 1995. Kaimanawa Wild Horses Plan. Wanganui, New Zealand: Department of Conservation, Wanganui Conservancy.

2. Smith, S. 1994. Army sets wild horse numbers at 200. In: New Zealand Horse and Pony, p. 24 & 46.

3. Linklater, W. L., Cameron, E. Z., Minot, E. O. & Stafford, K. J. 2004. Feral horse demography and population growth in the Kaimanawa Ranges, New Zealand. Wildlife Research, 31, 119-128.

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