mark and recapture lab
methods of mark and recapture
*complete census of individually identifiable organisms* -involve tagging trees in a forest plot, or making all animals of a species living in an area at a particular time -catalog or photos that show unique markings of individuals -tagging with markers visible from a distance *quick and dirty method- estimates of abundance* -counting birds alongside route by car -counting number or butterflies passing a point
assumptions: the accuracy of this mark-recapture method rests on a number of assumptions being met
1. between the preliminary marking period and the subsequent recapture period, nothing has happened to upset the proportions of marked to unmarked animals (that is, no new individuals were born or immigrated into the population, and none died or emigrated). 2. The chance for each individual in the population to be caught are equal and constant for both the initial marking period and the recapture period. 3. Sufficient time must be allowed between the initial marking period and the recapture period for all marked individuals to be randomly dispersed throughout the population 4. Animals do not lose their marks
mark and recapture example 1000 mice
For example, suppose you took 200 mice out of a forest having an unknown number of mice, put leg bands on them, return them to the forest and let them mix thoroughly. If you then take 250 mice from the forest and find 50of them to be have leg bands, then M = 200, T = 250, R = 50,
effort 1 methods
Obtain a population of white beans, a large habitat beaker, colored beans, and one small beaker. The white beans will represent the population to be sampled. 2. Marking: Using the small beaker as a "trap", push through the white bean population once, filling the trap with beans to the 10 ml line. Count the number of white beans caught and for each white bean caught, substitute a colored bean and record that number as: Number marked = M 3. Thoroughly mix the marked and unmarked bean population. 4. Recapturing: Now sweep through the mixed bean population with the trap once, filling the trap to the 10 ml line. If you recovered at least one colored bean with this sweep, record the number of marked beans (recaptures) as R. Record the total number of beans caught as T, ( i.e. marked + unmarked). 5. Now calculate the bean population size using the formula N = M*T/R
Mark and Recapture Technique formula
R (marked recaptures) ------------------------- T (total in second sample) = M (marked initially) ----------------------- N (total pop size) M*T N= ------- R
Mark and Recapture Technique
best method commonly used by fish and wildlife managers to measure pop before hunting season marks individual and returns to population
purpose of mark and recapture lab?
understand how different physical and biological factors influence the distribution or abundance or species, usually need to measure changes in population abundances over space or time
how to best estimate the size and population of organisms in the field?
usually not possible to obtain a complete count or census of a natural population of animals generally have to rely on some kind of estimate of abundance or density
