Hi, Howie, You might consider the research by David Lack (I believe) on island populations of birds that decreased their clutch size during times of resource shortage. However, if I remember the study correctly, there are a couple of caveats : Individuals breeding females decreased their clutch size (i.e., decreased resource investment at one stage of reproduction) but the result was an increase of the survivorship of the hatchlings because of reduced malnutrition and starvation. Secondly, I don't know what effect this had on total population size. Maybe it increased, or only decreased while resources were scarce.
Hope this helps. Martin M. Meiss 2016-01-21 7:11 GMT-05:00 Thomas Rosburg <[email protected]>: > 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. > > > Do you mean consciously? Then probably no. But yes for question 1 if > you consider dominance hierarchies where birth rates (matings) decrease > during reduced resource availability. And yes for question 2 if you > consider the example in some small mammals where stress resulting from > reduced resources produces pheromones in older females that delays sexual > maturity in younger females. > > > > Thomas Rosburg, PhD > > Professor and Chair, Department of Biology > > Drake Biodiversity Center and Herbarium > > Drake University, 2507 University Avenue > > Des Moines, IA 50311 > > > > 515.271.2768 > > 515.271.2920 > > cell 515.460.4468 > > Photo - finish of Leadville Silverrush 50 mile ultramarathon, with > daughter Vanessa > > > "Let the rivers run like they always do, its not up to me its not up to > you; When we reach the end, when our time is done; Let us all be still > while the rivers run" Bob Seger, *Let the Rivers Run* on Ride Out > > > ------------------------------ > *From:* Ecological Society of America: grants, jobs, news < > [email protected]> on behalf of Howard S. Neufeld < > [email protected]> > *Sent:* Wednesday, January 20, 2016 8:38 AM > *To:* [email protected] > *Subject:* [ECOLOG-L] Reducing Population Size in Natural Populations of > Organisms - A Question > > > 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 > > <http://biology.appstate.edu/faculty-staff/104> > Dr Howard S Neufeld | Department of Biology | Appalachian ... > <http://biology.appstate.edu/faculty-staff/104> > biology.appstate.edu > Our Fall 2015 featured faculty member is Dr. Matt Estep. He specializes in > Evolutionary Genetics and Genomics. His philosophy of teaching and a short > description of ... > > >
