Behavior  Population Dynamics Behavior Directly Governs Individual Demographic Performance Indirectly Effects Population Dynamics Population Growth Implies Chance of Extinction Here, Take Behavior = Social Organization

Extinction Population extinction process Four general causes of extinction 1. Environmental stochasticity 2. Demographic stochasticity 3. Abiotic catastrophes 4. Lack genetic variation

Extinction Environmental stochasticity Random, temporal variation: exogenous factor (s) Individuals’ experience same birth, death rates Temporal fluctuations, Between-generation scale Good, Bad Years = Generations: food abundance Small population & bad year  Extinction

Extinction Demographic stochasticity Random variation among individuals, Within-generation scale Number offspring, survival Individuals’ birth and death rates independent, hence can differ Important small populations: chance extinction

Extinction Demographic stochasticity Fix time; Extinction Pr declines with Initial population ize Fix Pop size; Extinction Pr increases with time MTE = (Extinction Pr) -1

Extinction Abiotic (Physical) Catastrophes Large, sudden density reduction Environmental, anthropogenic Climate change Time scale relative to generation time

Extinction Genetic Lack variation, population fails to adapt Rarest, but [again] global climate change

Behavior  Population Dynamics Vucetich et al Effects of social structure and prey dynamics on extinction risk in gray wolves. Conservation Biology 11: Wolves: social behavior - group, pack 1 litter/year, dominant female amplify demographic stochasticity 2. Prey availability: fluctuate, source of environmental stochasticity

Behavior  Population Dynamics Gray wolf (Canis lupus) Isle Royale, MI; island in Lake Superior National Park, > 500 mi 2 Wolves feed on moose Abundance of old moose (> 9 yrs) key

Behavior  Population Dynamics Objective: Simulate wolf population dynamics Predict mean time to extinction (MTE) 1. Age-dependent mortality in wolves 1/3 pups die first year No wolves older than 11 yrs 2. Random litter size in wolves, Mean = 1

Behavior  Population Dynamics 3. Wolf packs: Some restructuring between years When prey abundance falls, smallest pack disperses, mortality cost Survivors join another pack Number packs proportional to no. old-moose

Wolf/Pack Count vs Moose

Wolf, Pack, Moose Dynamics

Behavior  Population Dynamics Mean Time to Extinction, Wolf Population Weak dependence, initial population size Standard result not observed Strong effect, initial number of packs

Simulation results

Behavior  Population Dynamics Reproductive unit is pack Number packs, not population size critical extinction process Social organization, with dominance-based breeding, amplifies effects of demographic stochasticity on extinction

Behavior  Population Dynamics No. old moose constant = 305 Wolves: MTE = 155 yrs No. old moose cycles, mean = 305 Wolves: MTE = 105 yrs Environmental stochasticity Standard result

Behavior  Population Dynamics Social group size  Individual demographic performance How might group size G influence population dynamics? Trainor, K.E. & T. Caraco Group size, energy budgets and population dynamic complexity. Evolutionary Ecology Research 8:

Model Assumptions (1)  Foragers search in groups, G individuals  Rate food-clump discovery   1/(population density) Density dependence   G  ; interference, mutualism  Energy consumption random  Number clumps, clump size

Model Assumptions (2)  Starvation  Consumption  energy requirement  Variation between groups  Predation while foraging  Random independent attacks  Increases with consumer density

Survival & Reproduction  Surviving non-breeding season  Avert starvation  Avoid predation  Reproduction: R fixed  Survivor + (R-1) offspring

Return Map (1)  n t+1 = F(n t ) n t  F(n t ): Density-dependent reproduction  F = R x p(avert starvation |G,n) x p(avoid predation |n) x p(avoid predation |n)

Stable dynamics: stable node  For α > 1, Q = 8, Vc = 1.0; G = 28 t ntnt

Stable dynamics: stable node  α > 1 (mutualism ?) Individual encounters clumps faster as G increases Mean energy intake may Increase Energy intake variance declines

Stable Cycle  For α = 1.0, Q = 10, Vc = 0.5; G = 32

Stable Cycle  α = 1.0 Individual encounters clumps independently of G Mean energy intake independent of G Energy intake variance declines

Complex dynamics  For α = 0.8, Q = 12, Vc = 0.5; G = 20

Complex dynamics  α < 1 (interference)  Individual encounters clumps slower as G increases Mean energy intake declines with G Chaotic dynamics; often near extinction

Behavior  Population Dynamics Interactions among individual group members Interference, independence, mutualism Survival through non-breeding season Complexity of population dynamics Likelihood of extinction