1. Population Dispersion of Spider Webs

2. Spiders Spinnerets Webs to catch food Draglines Webs vs. Burrows
Ballooning
Living conditions
Common Names
Nesting
Eggs
Life cycle

3. Spider Species
Sheet-web weavers
Orb Weavers

4. Data Collection Jewell Moore Nature Reserve
Random directions from central point
1 meter radius circles
Limited to Forest
Count # of webs in trees

5. Data Mean= 1.233 Variance=1.840 SD=1.357
Number of Cobwebs
Frequency of cobwebs
Observed
P(x)
Poisson 11
0.367
0.301 1 10
0.333
0.361 2 3
0.1
0.217 4
0.133
0.087
0.033
0.026 5
0.006 6
0.001
Table 1

6. Results
In the Jewell Nature Reserve we surveyed thirty plots and found 37 spider webs, averaging 1.23 webs per plot.
We expected 4 plots to contain 0 spider webs, but found 11 (see Table 1).
The chi-square value, 43.28, suggests a borderline random, contagious dispersion pattern (refer to Figure 4C.6 in lab manual).
Our variance to mean ratio, 1.46, is somewhat close to 1 which suggest random dispersion, but it is also above one which suggest contagious dispersion. This is consistent with our chi-square value.
The number of individuals found in all the plots were close to the number of individuals predicted by Poisson which suggest random dispersion (see Table 1 and Figure 1).

7. Figure 1

8. Conclusion
Why might our data be borderline between random and contagious?
Old webs
Different species

9. Conclusion Main Hypothesis:
1. The spider webs will be randomly dispersed because of food competition.
Alternative Hypothesis:
2. Randomly dispersion occurs to prevent cannibalism.
(see text page 253)