You might also consider cases where individuals hold territories and territories are necessary for breeding success. In some cases territories simply shrink in size with higher pop. numbers, but in many there is a minimum territory size and thus a limit to the # of potential territories. Overpopulation can result in territories too small for breeding success (due to female mate selection for example) or result in some individuals not being able to maintain a territory and thus not being able to breed. As other people have mentioned, I wouldn't argue that it is conscious, but it can lead to a reduction/limit in birth rate.
Jessa Jessa Madosky, PhD Assistant Professor Biology Department University of Tampa Vice President for Membership - Society for Conservation Biology Chapters Committee Chair - Society for Conservation Biology President Elect - NA Section of SCB Education Committee Chair - NA Section of SCB On Wed, Jan 20, 2016 at 9:38 AM, Howard S. Neufeld <neufel...@appstate.edu> wrote: > Hi all - I am currently working on an abstract about global climate change > for a regional biology meeting in the southeast, and I wanted to say > something about the control of natural populations of organisms, but I am > not sure if the statement I want to make is true, so I’m asking for some > advice and counsel on this. > > > > Here’s the question: *Has any population of organisms (humans excluded) > regulated and reduced their population size by lowering their birth rate > instead of increasing their death rate*? And have any slowed their rate > of increase by raising the age at first birth? Most of the examples I > know of natural population control do so by increasing the death rate. > > > > Some further comments: If resources get scarce as populations increase in > density then behavioral changes could lead to reductions in the birth rate, > but under resource scarcity I would assume that the death rate would go up > also. I know about density-dependent and density-independent controls on > population growth, but here, I’m looking for explicit examples where > populations decrease birth rate without increasing the death rate. > > > > You may wonder why I’m asking this. It's because I’m wondering if humans > can, in the long-term, reduce their population by lowering the birth rate > without increasing the death rate. Yes, some countries are already on > that path (Japan, for example), but economists and social and political > scientists seem to have a problem with such demographic changes, > particularly in a free-market situation where an aging population, even if > sustainable, is viewed as less competitive and therefore at risk of losing > out (whatever that means) to younger, more dynamic populations. It > suggests to me that ecology and society are fundamentally at odds here, and > that future societies may require paradigm shifts in the way they operate > if humans are to actually create a sustainable society. But that’s > another story. > > > > For now, I’d be really interested to hear explicit examples if anyone has > any. > > > > Thanks. > > Howie Neufeld > > -- > Dr. Howard S. Neufeld, Professor > Director, Southern Appalachian Environmental Research and Education Center > (SAEREC) > Chair, Appalachian Interdisciplinary Atmospheric Research Group (AppalAIR) > > Mailing Address: > Department of Biology > 572 Rivers St. > Appalachian State University > Boone, NC 28608 > Tel: 828-262-2683; Fax 828-262-2127 > > Websites: > Academic: http://biology.appstate.edu/faculty-staff/104 > Personal: http://www.appstate.edu/~neufeldhs/index.html > SAEREC: http://saerec.appstate.edu > AppalAIR: http://appalair.appstate.edu > Fall Colors: > Academic: http://biology.appstate.edu/fall-colors > Facebook: https://www.facebook.com/FallColorGuy > >
