NRC 261 1 Lecture 8 Outline of Last Lecture II What Constitutes a Population III Population Dynamics IV Population Change a Exponential Growth b Population Crashes c Exponential Growth V Cyclic Population Change VI Biological Carrying Capacity a Density independent factors b Density dependent factors VII Cultural Carrying Capacity VIII Birth Reproductive Rates IX Death Mortality Rates X Original Questions Outline of Current Lecture II Why Count Wildlife a Easy to Count III Possible Biases IV Population Estimation a 2 main questions V Eastern Timber Wolf Recovery Plan VI Mark Recapture Estimate These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute a Assumptions of mark recapture estimates VII Indices of Abundance VIII Original Question Current Lecture Start Exam 2 Material Population Estimation Question How did we know if there were enough wolves present in the Western Great Lakes region to meet official recovery goals and thus take them off of the Endangered Species List Why count assess abundance of wildlife want to know if there are too few ex when there were 15 condors or 14 red wolves left in the world and knowing the had to increase once they get too low it becomes really difficult and important want to know if there are too many cultural carrying capacity for the most part people start wanting them gone once they think there are too many they are becoming a nuisance how to get the number down down to what is there enough ex things harvested by people like ducks if there are enough or more than enough to shoot then it offers more opportunity for hunting Is population in good or bad shape status of the population how many there are how is the population doing Easy to count some things might be fairly easy to count if they re active during the day and easy to see like the gray squirrel raccoons active at night and secretive takes more work to figure out how many there are need lots of traps in lots of places etc can t just go out and count them some things that are hunted that might be in the middle ex white tailed deer some densities they re easy to count and some densities they re harder to count If they ve eaten the entire understory of the park vegetation under trees and you could see them and count them Possible Biases ways in which you could be wrong because of the way you collected the data conditions under which you re going out and doing the survey for any animal weather affects visibility windy day makes it hard to hear birds to identify species and how far away they are accessibility some places make it easy to count things because they re easy to get to easy for wildlife to move around some places are off the beaten path ex rhino example some spots where they didn t survey because it took two weeks of walking just to get there animal density rare things are really hard to find and therefore hard to count vegetation topography some places have too much vegetation hard to count in places that are too steep etc observer effort systematic the kind of effort someone isn t trained very well may constantly miss seeing certain things you might not sample enough if you only sample a little bit you might not really know the correct population numbers ex only coming into this class once you wouldn t get a good idea of the average of students in the class timing seasons some seasons are bad to survey and some are good time of day some animals active at day some active at night if you re counting birds you have to be counting them starting half an hour before sunrise animal behavior differential observability when you set automatic cameras on jaguar trails males get photographed more often than females 2x as much but that isn t the population sex ratio Males get photoed more often because those are the trails males use and females esp females with cubs don t hang around where males are variation in distribution animal distributed differently across the landscape different densities in different areas much understand this to sample in appropriate ways to get the right count different catchability some species easier to see than others less shy of people than in other places lots of different ways that you can be wrong Population Estimation systematic representative of whatever population area you re trying to come up with estimation for statistically reliable unbiased must take into account how you could be wrong because of the factors listed above porcupine example could be under rocks could be on back side of the tree didn t turn around didn t look up didn t see 100 of the ones on the line you were walking repeatable if you or someone else came back and did it again using the same techniques you would arrive at the same answer you should be able to get the same answer given the same techniques every time 2 main questions you must be able to answer 1 How important is the information how precise do I have to be Do I have to know exactly how many animals there are a lot very few statistical amount etc census a complete exact count if you need the estimate gives you a number but is not a complete count range of what it could be index relatively a lot relatively not so many There are less today than there were yesterday etc depends on importance with endangered species might want to know exact number 2 How much will it cost will cost more for an exact count than to only get an indices if you re trying to identify the proportion of moose w radio transmitters to get an estimate it would cost a lot for radio transmitter and to get the moose lots of using a helicopter to go catch animals lots of 2 000 dollars an hour for a helicopter in Newfoundland flying in an airplane aerial survey costs a couple hundred dollars an hour to use to count animals from the air Eastern Timber Wolf Recovery Plan rules for endangered species list was solidified in the early 1970 s poster child for endangered species was the timber wolf diminished from all over the country into a small corner of Minnesota in order to recover this species they said that they needed to have survival populations in Minnesota Michigan and Wisconsin picked an area in the east where there weren t many people or livestock where they could try to bring the wolves back places in Maine and the Adirondacks in NY Recovery Goals if they could keep the population at 1200 1400 or higher wanted 80 in WI wanted 80 90 in MI if they maintained