Natural RegulationNatural RegulationBiotic TheoriesClimateFoodComprehensiveSelf-regulationBiotic FactorsHoward and Fiske 1911ClimateBodenheimer 1928Uvarov 1931Comprehensive schoolThompson 1929Nicholson 1933Control = Regulate about stable densitySmith 1935Instan- taneous RatePopulation DensityBirth RateDeath RateDensity IndependentDensity DependentKDensity-dependent factorsSchwerdtfegger 1941Outbreaks of forest insectsSchwerdtfegger 1941Pest InsectWeatherDiseasesPredatorsFoodParasitesOther SpeciesAndrewartha and Birch 1951Classify factors:WeatherFoodOther animals and pathogensA place to liveLimitation may occur:Shortage of material resourcesInaccessibility of material resourcesShortage of time when r is positiveAndrewartha and Birch 1951Worked on insects in very dry climates - Australia - harsh environmentSpatial Aspect - MetapopulationsIs it applicable to vertebrates?Denali Sheep - Haber 1977Quail in SouthwestCalifornia Quail - Leopold 1977Forbs in late winter-spring; Complex modelResidual soil moisture on April 30Percent adults in femalesr2= 96%Gambel Quail - Gallizioli 1965Latest: Natural compounds in forbs mimic estrogens and produce physiological changes in hens.David Lack 1954Natural Regulation of Animal PopulationsArgues for food as primary factor in birds because:1. Few birds die of disease or predation2. Birds are more numerous where food is abundant3. Each species eats different foods in same habitat; otherwise lives in different habitats4. Birds fight for food, especially in winterComprehensivePopulation abundant Environment favorable Density-dependent factorsEnvironment extreme Numbers change Density-independentBoth biotic and abiotic (climate) valid but for different types of environment4. Self RegulationIntrinsic factors or intrinsic changes Two types:PhenotypicGenotypicE. B. Ford 1931Dennis Chitty (1955)If find a population decreasing, must consider the hypothesis:Individuals in population have changed and now are more susceptible to same environmental mortality factors.He was studying microtines which are highly irruptive or cyclic Chitty’s Hypothesis (1960)“All animals are capable of regulating their densities without destroying the renewable resources of their environment or requiring enemies or weather to keep them from doing so.”SELF-REGULATIONMechanisms of self-regulationV. C. Wynne-Edwards (1962)Social behaviors are mechanism1. Animals have tremendous potential for dispersal.2. Food is generally ultimate limiting factor.3. Rather than fighting for food, animals participate in ritualized contests.4. Defended territories contain more than required amount of food, so that population stabilizes at density below what is set by food limitation.Group selectionTerritoriesPrime HabitatMarginal HabitatDo territories really limit reproduction?Behavior limits breeding population Watson and Moss (1970)Must show:1. A substantial part of the population does not breed.2. Such non-breeders are physiologically capable of breeding if the more dominant or territorial animals are removed.3. Breeding animals are not completely using up some resource.4. This mortality or depressed recruitment changes to just compensate for changes in other sources of mortality or depressed recruitment.Behavior limits breeding population Watson and Moss (1970)5. If 1-4 true and numbers change following changes in food, then both food and behavior are limiting population.Red Grouse (Lagopus lagopus scoticus) Red Grouse Habitat and FoodAbundant on moors in ScotlandMain food is heather (Calluna vulgaris)Total quantity of heather vastly exceeds requirements at all timesFew signs of grazingLess than 5% removedBut they sometimes select heavily for nitrogen and phosphorousRed Grouse Food SelectionCollected Red Grouse and compared crop contents to heather clipped in area.Placed grouse in portable pens and compared diet quality to current years and tips of current growthGrouse selected heather higher in nitrogen and phosphous than available when N and P low.Red Grouse Nutrition ExperimentsRed Grouse populations on areas over base-rich rocks are more dense than in areas with poorer (less productive) soilsExperimental treatments: (overhead)TerritoriesEach cock is exclusively dominant over all other cocks on a fixed territory of heather moor.Here he courts and pairs with one (or two) hens & she nests in springTerritoriesChange from year to yearOverheadTimingTerritories distributed annually in Oct.-Nov.Held till late May3 categories of individuals:Territory holdersFloatersOthersSize of territoriesBigamous cocks have significantly larger territories than cocks with one hen whose are larger than unmated cocks.More aggressive cocks have larger territories.Tests of territoriesHow would you test what determines size of territories?Androgen implant makes cocks take a bigger territory.Estrogen implant -> lose hen, less territorial behavior, loses territoryDoes territorial behavior limit population size in grouse?1. Many birds fail to get territories in the fall. - They all die before spring. - Thus do not breed.2. These birds can breed if remove territory holders.3. Food limiting? - Difficult - Birds take less than 5% of annual production of heather.Does territorial behavior limit population size in grouse?3. cont. But they are highly selective. They take only the tips of new shoots and somehow pick these with high nutritional value.4. Mortality seems to be compensatory.5. Nutrition and territories are interrelated, but complex.Why cycle?Territorial cocks from year class hatched during a decline took bigger territories than cocks from other year classes.They survived better and were more aggressive.This introduces a lag.What determines territory size?Quantity of food?Number of competitors?Quality of food?Paul Ehrlich’s Checkerspot ButterfliesEuphydryas editha30 years studied at Jasper RidgePlantago erecta on serpentine outcropsStudied evolution, population structure, survival and dynamicsKey feature missed until recentlySummary Where to now St.