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Born Free?

Posted: January 29, 2018

Wildlife may be born free but humans are cramping their style.

If you are a long-time follower of The Deer-Forest blog, you know we talk about deer movements A LOT.  Buck movements, doe movements, seasonal movements, breeding season movements, hunting season movements, weather event movements.  You get the picture.  

We, of course, focus on our tiny slice of the planet and a single species.  There is plenty to talk about even if it is rather myopic (from a world view perspective).  But what if our humble Pennsylvania deer could add to the collective knowledge of science on a global scale?  I mean that is what science is really all about. 

Well, guess what.  They did.

Marlee Tucker and a slew of coauthors (including our very own Duane Diefenbach and Chris Rosenberry) just published Moving in the Anthropocene: Global reductions in terrestrial mammalian movements in Science.  Analyzing the movements of 803 individual animals across 57 species, they found that mammals in high human footprint areas moved half to a third the extent as compared to those in low human footprint areas.  Humans activities have modified 50-70% of the earth’s land surface and apparently that’s a real downer for wildlife. 

human footprint graph

Long-distance movement of 624 individuals from 48 species are greater in areas where human impact is low (HFI = 0) compared to areas with a high footprint on the landscape (HFI = 40). 

The authors attributed these reduced movements to (1) habitat change and fragmentation and (2) enhanced resources.  Indeed, we have seen this with deer in Pennsylvania.  Fragmented landscapes caused deer home ranges to become smaller.  For deer in Gettysburg, both fragmentation and enhanced resources (crop fields and maybe females for males) contribute to smaller home range size and therefore reduced movements.  For deer in the Big Woods, that pipeline is an imaginary boundary not to be crossed.  Direction and distance of male dispersal is also influenced by the human footprint.  

The effect of reduced individual movements has different effects on populations.  Increased resources benefit populations but fragmentation has the opposite effect on others.  However, these reductions in movements go beyond individuals and species and affect entire ecosystems.  Seed dispersal, food web dynamics, resource cycling, and disease dynamics are all affected.  Another plug for the “circle of life” and “everything in nature is connected” mottos. 

It’s important to remember that human activities affect more than physical landscape features.  More and more our behaviors are “taming” the movements of wildlife.  Anyone else hearing Roy Rogers singing “Don’t Fence Me In”?

If we value coexistence with wildlife and our own health, then wildlife needs to remain “free” for their benefit as well as ours. 

-Jeannine Fleegle
Wildlife Biologist
PGC Deer and Elk Section

 

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