The balance of dingoes:
Ages ago we used to speak of the “balance of nature.”  That was before we threw nature totally out of balance or anyway before we knew we had done it.  Pretty much it was thought that the numbers of any species were kept in close balance with available food and shelter, predators and diseases.  But anybody who has strolled outside in this part of the world has probably seen a squirrel or a bird and might have noticed that it wasn’t starving, so food supply is out.  You don’t see sick ones much either.  That leaves predators, and indeed depredation happens.

I have a pool cage, and once there was a squirrel that would bound insolently across the top from time to time.  I tried to shoo it away, thinking that this was a poor plan both for the screening and for the squirrel.  Then on day I noticed a squirrel sized hole along its accustomed route.  The squirrel never returned.  A hawk had seized the opportunity.  But that is rare.  The squirrel had been playing dice with the devil for many years. 

The balance of nature is accomplished by Sibly’s curve.  You’ve seen it before; here’s a rerpresentation:

from On the Regulation of Populations of Mammals, Birds, Fish and Insects, Richard M. Sibly, Daniel Barker, Michael C. Denham, Jim Hope and Mark Pagel SCIENCE vol. 309 July 22, 2005 page 609

As population size falls below the equilibrium point, fertility rises, and in the other direction fertility falls.  There is your balance.  But the message seems to have yet to sink in.  (Dingo Destruction Okay for Prey NATURE vol. 514 no. 7520 Oct. 2, 2014 Page 8  reviewing work by Benjamin Allen and colleagues at the University of Queensland in Gatton, Australia Front.Zool.11,56(2014)) They counted the animals the dingoes preyed upon both before and after the dingo population was culled and found no particular change.  The populations of prey fluctuated independently of anything done to the dingoes.

Well we knew that, didn’t we?  The Sibley curve assures a return toward equilibrium after any moderate disturbance.  That doesn’t hold where the disturbance is severe, of course.  Fell a great forest and it will be a long time before it returns, if ever.  Fish the seas to extinction and you may produce a permanent change, like maybe you only get jellyfish and nothing edible at all.  But for moderate changes, yes it not really a problem most of the time. 

There have been 109 visitors over the past month.

Home page