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The Road Runner will always win

Posted: January 22, 2018

Wile E. Coyote will never catch the Road Runner and we will never catch him.

We are all familiar with the tale of Wile E. Coyote.  His life’s mission: to catch the Road Runner.  He’s been at it since 1949 and has yet to be successful.  While we are always entertained by his endless creativity in pursuit of his prey, it’s a bit sad.  I mean, almost 7 decades of failed attempts of your life’s work.  Yikes!

But nevertheless, he persists.  

Humans are akin to good ole Wile E.  We’ve made this comparison before.  For decades, we’ve blamed coyotes for taking “our” deer but coyote control programs have failed to increase fawn recruitment in deer populations and yet we persist.  In a previous post, Duane noted that if we are to ever have any hope of devising an effective coyote control program (i.e. conventional wisdom actually holding a chance against Mother Nature), we need to understand the relative importance of coyote reproduction and immigration in relation to culling.

Well, guess what.  Research from South Carolina was recently published titled Reproductive characteristics of a coyote population before and during exploitation.  They must read our blog.

Researchers in the Southeast examined reproductive tracts of female coyotes trapped over a 3 year period as part of a control effort.  The number of coyotes trapped was similar among years suggesting the population recovered following the trapping period.  It did, however, shift to a younger age structure.

Reproductive output was relatively low prior to control efforts with 39% of adult females breeding and an average litter size of 5.4 with no breeding among juveniles.  Following the trapping period, there was weak evidence of compensatory reproduction with mean litter size increasing to 7.0 and adult pregnancy rate jumping to 63%. 

However, this increase in reproduction did not increase population fecundity.  Why?  There was a decrease in the number of adult females in the population (24% to 7%).  Adult females contribute the most to reproduction. The modest increase litter size and pregnancy rates were not enough to replace those lost to trapping and hunting.


Before coyote control During coyote control
Percentage of adult females in the population
24% 7%
Percentage of females breeding 39% 63%
 Avg. pups per litter 5.4 7.0 
 Immigration Equaled emigration
Much greater
than emigration 
 Population Trend Stable Stable

How then could the population recover each year? The clue was in the shift to a younger age structure.  Immigration of juveniles from surrounding areas vying for vacant territories stabilized the population.

So why not just expand the area of coyote control to limit available juveniles?  Did I mention the size of the study area was 78,000 ha?  For those of us not good at the metric system, that’s over 300 square miles.  

Here’s what the authors concluded:

“Thus, given the impossibility of implementing a trapping program over hundreds of square kilometers, which would be necessary to limit the regional pool of immigrants, control efforts are unlikely to reduce coyote populations in the Southeast for longer than a few months. Managers should be aware of this limitation when considering coyote control.”

There is no reason for us to think that coyotes in Pennsylvania would be any different.  Population parameters in this study were similar to those found in other studies and are well within the norm for coyotes.  

It is time we stop chasing that Road Runner. 

-Jeannine Fleegle
Wildlife Biologist
PGC Deer and Elk Section

 

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