Mark and Recapture

HOW WOULD IMMIGRATION AFFECT ESTIMATE OF N?

IMMIGRATION = DECREASED #R= INCREASED N = OVERESTIMATE

HOW WOULD MARKED ANIMALS LOSING THEIR MARKS AFFECT THE ESTIMATE OF N?

IT WOULD DECREASE #R WHICH WOULD INCREASE N AND LEAD TO OVERESTIMATE

HOW WOULD MARKED ANIMALS BEING TRAP HAPPY AFFECT ESTIMATE OF N?

IT WOULD DECREASE THE RATIO (INCREASE RECAPTURE #) AND LEAD TO UNDERESTIMATE

HOW WOULD MARKED ANIMALS BEING TRAP SHY AFFECT ESTIMATE OF N?

IT WOULD INCREASE THE RATIO (DECREASE RECAPTURE) WHICH WOULD CAUSE OVERESTIMATE OF N.

COMPARE WHEN IT WOULD BE GOOD TO USE MARK AND RECAPTURE VS. CAPTURE

MARK AND RECAPTURE= LIVING, MOBILE POPULATION CAPTURE= USE COUNTS TO GET IDEA, INDIVIDUALS ALREADY DEAD

WHAT IS THE FIRST OF 2 ASSUMPTIONS OF THE LINCOLN (OR PETERSON) INDEX?

No change can occur in the ratio of marked to total animals between the time of release and recapture. a. No immigration b. Marked animals must not have different mortality than unmarked. c. Marked and unmarked animals must have the same likelihood of being caught. d. Marked individuals cannot lose their marks.

HOW WOULD EMIGRATION AFFECT ESTIMATE OF N?

DOES NOT AFFECT N AT ALL; PROPORTION SHOULD STAY THE SAME (M/N=R/C)

Lincoln (or Peterson) Index estimates population density by _____. The Equation is ________.

by taking a random sample of a population , marking individuals captured, releasing those individuals back into the population and then taking another random sample. In that second random sample the number captured and the number of those captured with marks are counted (Recaptures) and recorded. This is used to estimate the density of that population. Equation: N=(M*C)/R N= # indvdls in population M= # marked in population C= # captured R= # recaptured example- random sample 5, mark all, return to pop, sample again capture 5, 1 marked N=5*5/1=25

WHAT IS THE 2ND ASSUMPTION OF THE LINCOLN (OR PETERSON) INDEX?

must be random mixing of the marked individuals throughout the population during the interval between captures to insure an unbiased estimate of the ratio of marked to total animals.

Mark and recapture methods are used to measure the _______ of ________

population density; mobile populations