Meso-Predator Release

 

Jebediah was a bad dog.

Jeb was one of the best dogs, in some ways, but he was bad.

At 200 pounds, he was too big to be bad.

Jeb was a free-willed guy. It was hard to be mad at him. Maybe that was the problem. 

He ate the leather couch when he was about a year old. Ate it. Gone. Pooped it out in the yard.

And the red leather chairs... both of them. The whole couch but just the arms of the chairs.

And the green corduroy recliner chair.

And the arms of the re-covered red chairs.

And the re-covered corduroy recliner chair.

 

He didn't learn.

We didn't learn.

 

Jeb loved the cats. They're his cats. They loved Jeb, too...

...Except outside.

 

When Jeb was outside, the cats wouldn't go outside. 

Something about being outside made Jeb want to play with the cats.

He would play-bow to them so they'd know he was just playing, but they didn't get it.

Jeb would play-bow, the cat would get tense, Jeb would launch at them and the cat would scram back into the house.

 

The back yard is 2-tiered. An upper yard that extends into the woods, a cinder-block wall cut into the steep slope, and a lower small yard that goes right up to the small patio and back door of the house. In the cinder-blocks and the shrubs that line the wall, and the tunnels all around the yard, live a sizable scurry of chipmunks. Tamias striatus, eastern chipmunks, are roughly midway between the size of  a meadow vole  and  a common gray squirrel.  There's only one species of chipmunk in the eastern U.S.. (though there is a Western chipmunk and a somewhat similar-looking 13-lined ground squirrel out in the prairie states); they are kind of gold or amber in color with a light stripe in between two dark brown stripes running down each of their sides. You'll know one when you see it. They're pretty common in the forrest-field interfaces of middle Tennessee where we live. They come out in the day, pick up little seeds, dig for grubs and bugs, roots and fruits.

Our chipmunks race between the block wall and the woods, jumping onto tree trunks when they get nervous. They hibernate  in the winter (well, more or less they hibernate... they go into torpor, technically), but a couple weeks before Earthday they start waking us up in the morning with their chirping, or "chipping", the sound for which they get their common name. It's not a musical, complex or even very interesting sound. You'd probably think it was a very persistent bird if you didn't know better. Just a   "chip...      chip...       chip...      chip... ".  They seem to be proud of how long they can keep up their monosyllabic message. And they are self-assured little rodents, too, because they master that one word and scream it far louder than you might think possible. One syllable, very, very loud, at a rate of one "chip!!!" every two seconds (or there about).  All morning, for hours.

 

...at least as long as Jeb is out there.

 

So, we had to get rid of Jeb because of the furniture. He was eating us out of house and home, literally. As long as we were in the house, he was fine. But if we left for more than two hours or so, it was a coin toss if we had any furniture when we got back.  Let's just say Jeb wasn't sustainable.  So, we found him a new home. Some nice folks in North Carolina with four kids, a big yard and a stay-at-home-mom.  

 

Within a couple days of Jeb's move to his new place, I noticed the "chipping" stopped in the mornings. The "chipping" song was so noticeable, so reliable that it actually woke me up when it wasn't there in the mornings.

 

It was the cats.

 

With Jeb not around, the cats moved to the yard. Now they stalk the chipmunks. They love them. They're the perfect prey for our clawless cats: slow enough to catch, big enough to fight back, they've got tunnels to dive into so it's not too easy, and the chipping gives them away. The cats have gone to work. Especially Ruby. He's a great hunter. We put a bell on his collar so the little guys would know he's coming, but Ruby is slinky and sneaky and he works overtime.  Once in a while we can catch him before he kills the chipmunk, but he's got a collection of 'em now. I estimate he gets one every other day, on average. With Jeb gone, the cats have decimated the scurry of chipmunks that were living on our little slope of edge habitat.  When we saw what was going on, we knew exactly what to call this phenomenon. It's the same thing that happened to the whole Eastern Seaboard over a 200-year period. Well, most of the Eastern Seaboard, anyway -- from the Mid-Atlantic area North through New England.  Meso-Predator Release.

 

When the Colonists came to this country in the 1500's, they didn't have a huge impact on the environment for a hundred years or so, mainly because there was so few of them, they lived in tight little villages and just tried to survive. But by the mid 1600's, the little villages became towns, and in a few areas, cities.  Colonists were encouraged to "improve the land", which of course meant cut down all the trees, plant crops, raise livestock, build a home, put up fences, kill off any wolves.  At that time, trees were so large they were commercially harvested and returned to Europe on the otherwise empty ships that had brought people over.  By the late 1600's, some Colonies were passing laws to regulate deer hunting because white-tail deer had become so scarce. By the early to mid 1700's writers were bemoaning the loss of Nature's bounty in many ways, not just the scarcity of deer.  But wolves, bear and the occasional cougar were still hunted... killed, actually. Bounties were paid for these top predators, because they were thought of as threats to livestock and people, and because the ecology behind the importance of apex predators wasn't understood at the time, these apex predators were thought to be part of the cause of the declining deer populations (a supplemental source of food for many folks and a major source for others).  

Though they were out there, skunks, mink, raccoon, fishers, otters, foxes, even large snakes - these middle sized predators, or Meso-Predators, were not usually found in high numbers. It's not that there were lots of wolves, bears and cougars, but the fact that these apex predators existed in significant numbers kept the Meso-Predator numbers reduced.  Apex predators would eat rabbits, squirrels, chipmunks, voles, mice and birds, competing with the Meso-Predators, but they would also eat a few of the Meso-Predators.  When the apex predators were removed, the numbers of the Meso-Predators would increase quite a bit (thus the name of this phenomenon: Meso-Predator Release). But, this in turn would often reduce the number of prey available causing wild fluctuations in the populations of prey and middle predators.  It's a great example of an ecological phenomenon called Top-down control, a type of Trophic Cascade. In short, the presence of a natural level of Apex predators keeps steady population levels of all the critters below them; when the apex predators are removed, complicated and sometimes unpredictable changes occur. The top predators are actually controlling, to some degree, the numbers in the trophic levels beneath them. Top Down control of an ecosystem and Meso-Predator Release.

Even though he didn't hurt the cats, with Jeb in the yard, the cats didn't hunt the chipmunks. The cats mostly stayed inside. With Jeb gone, the cats went out and hunted the chipmunks.  Good thing our   Jeb - Ruby - Chipmunk   ecological system is artificially supported by cat food.  

Certainly this is an artificial system. What's going on in our backyard isn't a natural system and it doesn't perfectly model the ecological systems that have been studied. But still, it anecdotally demonstrates the Meso-Predator Release phenomenon pretty well, even if it is artificial, overly simplified, uncontrolled (in a scientific sense) and unmeasured.  It's a cartoon, a model.

 

Though if he were still with us, I'm sure we'd be down to a couple wooden stools and the breakfast table, I miss Jeb. He was a good guy. The chipmunks miss him, too, I suspect. Though he made chaos inside the house, it seems he kept things stable outside. That's a weird thing to think about.

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James English

James English


Dr. James English serves as Academic Director for the Institute for Sustainable Practice and Associa... [More]

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