Bio 120 Nature Lab 07
Estimating Population Size
Full Name: Atlas Cummins
Animal Code (password): Coyote
Mark-Recapture Data Analysis and Questions
Expand space between questions to accommodate your answers.
Sample
Black
White
Total
1
9
61
70
2
7
78
85
3
6
75
81
4
5
83
88
5
6
80
86
6
7
69
76
7
8
81
89
8
6
76
82
9
6
82
88
10
9
78
87
Total
69
763
832
Using the Lincoln-Petersen Index, calculate the beanie animal population size from data for each sample taken.
Sample 1:
778
Sample 2:
1214
Sample 3:
1350
Sample 4:
1760
Sample 5:
1433
Sample 6:
1086
Sample 7:
1112
Sample 8:
1367
Sample 9:
1467
Sample 10:
967
Using the Lincoln-Petersen Index, calculate the beanie animal population size from the TOTALS of the ten samples
Sample
Black
White
Total
Total of Samples 1-10
69
763
832
Estimate from Total of Samples 1-10:
1206
Count all of the beanie animals in your population (all black and white beans). How many beanie animals (total of both black
and white) actually were in your beanie animal population?
1,042
Questions:
1. Depending on the population and the habitat, ecologists generally claim that a sample size should be at least 30
observations --often more, never less. Describe the results of individual samples and total of all samples in light of this
claim.
When I first counted the actual total and compared it to the total I got using the Lincoln-Petersen Index my reaction
was “Oh, that’s pretty close!” (math has never been my strong suit) But upon thinking about it further, if this were a practical
field study, the numbers would be off by a lot, leaving almost 200 animals of the population unaccounted for. This lab has
spiked some curiosity in me, and I’m left wondering how much more accurate my calculation of the population would’ve
been had I had 30 samples instead of 10, and how many samples I would’ve had to take for it to get as close to the real
number as possible. I have yet to separate my bag of beans from the lab and might take the time to explore this idea further
out of my own curiosity.
2. Describe pertinent assumptions of mark-recapture theory that would not be true and might lead to less accurate results
because of the nature of each of the following populations.
a. Monarch (Danaus plesxippus)
A mark on a wing, to an untrained eye, could be a lot harder to identify than something like a band around the foot of
a bird, which is pretty hard to miss in comparison. While looking into Monarch mark and recapture, I found a website that
allows anybody to purchase a kit to allow them to partake in the collection of data. These kits have lightweight stickers as
their tagging method. This allows the general population to collect their own data, however, with multiple tagging methods
available, areas with higher Monarch migration numbers might have off data. A person tagging butterflies with the stickers
won’t be keeping an eye out for butterflies with painted marks that were tagged by another individual. This could throw off
the population estimate.
b. California Ground Squirrel (Otospermophilus beecheyi)
These squirrels are very smart, being able to recognize threats relatively easily and only foraging during certain
hours. A proper sample could be taken by setting up food traps during the hours in which they are inactive near their
burrows, then leaving and returning after their foraging hours have passed. This will limit their sight of humans, keeping
them from being overly cautious while also providing motivation to enter the trap (food).
