BIOL2108H - Predator-Prey Dynamics

endotherm and ectotherm (metabolic rate)

-endotherm: metabolic rate goes up as external temperature drops

-ectotherm - metabolic rate drops as external temperature goes down

optimal foraging theory

predators should choose the prey that maximize net energy gain (calories gained - calories lost)

prey switching

switching to the next best prey item when a preferred item becomes rare

main idea 1 summary

predators use foraging strategies that optimize energy gain based on prey availability and energetic value

we can use mathematical models to describe how predators and prey affect each other’s population growth

N = number of prey; P = number of predators

recall

-we can describe how populations grow or shrink over time

-deltaN/deltat = rN

-r = per-capita population growth rate

change in number of prey over time formula to describe prey population growth including effects of predators

deltaN/deltat = rN - aPN (aPN = predators kill prey)

when will prey populations grow over time (words)

-the prey population will grow if the number of predators is less than r/a

-higher r or lower a → can handle more predators

when will prey populations grow over time (formula values)

-deltaN/deltat = rN - aPN > 0

-rN > aPN

-r > aP

-r/a > P

-r = prey population growth rate with no predation

-a = the rate of predation per prey and per predator

change in number of predators over time to describe predator population growth (including effects of prey)

-deltaP/deltat = baNP - mP

-baNP - prey feed predators

-mP - rate of predators dying

-aN- rate of eating prey to reproduce (bP)

when will predator populations grow over time (words)

-the predator population will grow if the number of prey is greater than m/ba

-higher ba or lower m → can handle fewer prey

when will predator populations grow over time (formula values)

-deltaP/deltat = baNP - mP > 0

-baNP > mP

-baN > m

-N > m/ba

what do these equations tell us about how prey and predator populations will change over time (N = m/ba line)

-prey above line = predators increase; prey below line = predators decrease

-prey and predator populations cycle above and below these critical thresholds (fluctuating equilibrium)

what do these equations tell us about how prey and predator populations will hange over time (P = r/a line)

-predators above line = prey decrease; predators below line = prey increase

-prey and predator…

no

yayy

other impacts of predators on prey

the ecology of fear (example on slides not sure if need them)

herbivores…

are capable of decimating primary producers