Trapline Math

Use this simple equation to figure out what is working
By Brad Lindblad

ost capitalist trappers will eventually ask themselves this question: “How can I trap more fur?” He sees pictures from other trappers in Internet discussion forums or sees pickup beds stacked to the cab with fur, and asks himself what those people are doing that he isn’t? Most trappers realize that there are no grand tricks to making extraordinary catches in the trapping game; there is just perseverance, careful attention to detail and spousal understanding. Beginning trappers and many seasoned veterans will make the mistake of thinking that their more successful peers have a secret lure that accounts for their higher-than-average catch rate. How else would they make such large catches?
First of all, there is no secret lure or set out there that magically outperforms the rest. There are currently dozens of companies selling more lures than ever before, and a good majority of those catch fur. But there is a not so secret discipline that masters use to out-trap you: careful record keeping and simple math formulas. Fortunately, anyone can learn one of the most useful of these formulas: the Trap/Days ratio.
The previously mentioned aspiring and capitalist trapper has already seen some success and catches fox occasionally, but wants to catch more. He knows that his dirt-hole sets are on point, and he has access to thousands of acres of prime farmland, so lack of territory isn’t holding him back. He figures that if he used the same lures as some of his trapping heroes he could make bigger catches. He asks around, tries out some new stinky potions, and finds that he catches more fox when he uses the new lures, and he attributes the success to the new lures alone. The painful truth is, no matter how much he wants to believe that the new lures were the reason for his success, any number of reasons could have increased his catch: better weather, higher animal numbers, etc. This is what we call “muddy science,” because our trapper assumes that his success is coming from one thing when in reality it could be coming from many things.
Great trappers take a scientific approach to their trapline. One of the keys to this thinking is to keep your sets consistent; we cannot measure the effectiveness of a lure (the dependent variable) if we are putting out different types of sets in an otherwise inconsistent manner. These trappers use the same one or two set types consistently across their whole lines, and when testing lures, they will apply the new lure equally with their old lure, so they can measure how well one lure performed against the other. By changing one variable at a time (in this case, the lure) they can measure and find which lure works best.
But how do you measure just how effective a lure, location or set is? The Trap/Days ratio. By using very simple math anyone can keep track of their success from season to season.

Trap/Days Ratio:

(number of traps in the field) × (number of days traps are out) / (number of animals caught)

To calculate you simply multiply the number of traps you have out in the field by the number of days that they have been out, and divide that number by your total catch. For example, if you have two traps out for a week and catch two fox, you multiply two by seven, which is fourteen, and divide by your catch which is two, this gives you seven. This is the number you want to keep track of. To think of it in a different way, this number tells you that if you had only one trap out in the field, in order to catch one animal the trap would have to be out for seven days.
My Trap/Days ratio on my coyote line is around 30, so if I were to use only one trap I would be waiting about a month to catch an animal. You can use this number in your lure test by keeping track of your catches for the sets using the new lure and your traps using the old one. If your trap-to-days days ratio is lower for the new lure, you can safely and scientifically conclude that the new lure is more effective than the old. But don’t stop there, if you take careful records you can compare this ratio for a number of variables that you can change, such as location and set type.
Many trappers may scoff at the idea of using fancy notebooks, phone apps and ratios to keep track of their trapping shenanigans, arguing that Jeremiah Johnson surely didn’t need any algebra to trap griz, or similar old-school whining. But take heart, the mountain men of old were no dummies; if they knew that all it took was a bit of “cipherin” as they called it, to out-trap their rivals, you bet they would have taken advantage of it. Learning and applying the trap-to-days ratio is one of the easiest and cheapest ways to add more fur to your stretchers.


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