Lab 12: Population Ecology

What is Population Ecology? Ecology: study of interactions between organisms and their environment Population: group of conspecifics living in the same area Population ecology: how the environment influences a population and vice versa

What is Population Ecology? Population Ecology Topics: population growth endangered species (conservation) effects of habitat fragmentation on the population

Population Growth & Demography Demography: Study of populations How many? What’s the age structure? Growth rate determined by: Birth rate Death rate Immigration and emigration

Population Growth & Demography Demography: Study of populations How many? What’s the age structure? Growth rate determined by: Birth rate Death rate Immigration and emigration

What can affect Population Size? Stochasticity random events such as drought, severe winter, fire, etc. Demographics – age distribution of population How many are of reproductive age? Pre-reproductive age? Post reproductive age? How can we tell if a population is growing or shrinking?

Life Tables Used to estimate age-specific fecundity and survival rates Fecundity = reproduction Look at Table 12.5 on page 202 You’ll be filling this out in lab today Made for females – too difficult for males Cohort life table Follow individuals born at the same time for their whole lives Static life table Random sample of individuals, marked at the same time

Life Tables – what’s in them? x = age class s x = survival in age class l x = survival to age class x b x = age-specific fecundity R 0 = net reproductive rate 0-1 years, 1-4 years, etc. proportion in age class that are alive all the s x up to that age class multiplied # of female offspring produced by female in that age class # of female offspring produced by a female during its lifetime You’ll have to do these calculations – look at pg 187!

How do we estimate population size?

Mark-Recapture Method (you’ll be doing this today) 1.Animals are trapped, marked for ID, and then released In birds, we mark them by putting colored bands on their leg 2.Later, a second set of animals is trapped (or observed) from the same population Some of these animals will be from the first, marked group 3.The total number of animals within the population can then be estimated (pg. 188)

Total in population Total that were banded in the 1 st round Total observed this time # observed this time that were banded

Radio Telemetry Place transmitter on animal – use receiver to pick up signal Uses Find animals to observe Track activities Determine home range size Look at dispersal Look at migration Etc. Mortality

Triangulation (you’ll be doing this today) Used to find animal from far away Use receiver to get directional readings at 2 locations Use map and compass to draw lines Where lines cross is location of transmitter

Plan for today 1.Take a look at lab report BEFORE starting lab There are some things you will need to do before leaving 2.Go out and find owls 3.Work on computers 4.Lab report

Hints and tips For table 12.7 – only change one parameter per age class – don’t change it too much Find living owls (won’t take too long) For the discussion in the lab report – read page 195 carefully Will need to discuss biology and conservation concerns Think about which age class is having trouble – is there something we can do to help that age class? Think about old growth vs new growth forests