Bryan Hummel

Ecology 3434

Ribble; 8:30 TR

March 16, 1999.

 

The Effects of Human Land Management Practices on the Small Mammals of Friedrich Park.

 

Introduction:

A question was raised about the reaction of small mammal populations in areas where humans have changed the habitat of Edwards Plateau woodlands by various clearing techniques. A study was developed to estimate the population of these mammals in the various treated areas and then compare these to the numbers in the untreated areas.

 

Methods:

An area of Emilie and Albert Friedrich Park was selected near the Vista Loop Trail because of the close proximity of three different types of habitat. There were untreated areas composed of Ashe Juniper and Oak woodlands next to areas treated by the clearing of the Junipers without fire and also next to areas that were cut then treated with fire. There were ten transects divided between the three habitats. Ten live-catch Sherman traps were set up on a ten-meter interval for each transect. Transects C and F were set up in the untreated Juniper and Oak woodlands and used as the control. Transects D, G, I, and J were set up in the cut unburned areas while A, B, E, and H were set up in the cut areas treated with fire. The Lincoln Peterson mark and recapture method was used estimate the population for each area. The results were then compared to find which types of habitat were preferred by the areas most commonly caught small mammal, Peromyscus pectoralis.

Results:

The populations of each of the ten transects were calculated individually then they were grouped together by habitat. The results of the transects combined by habitat are more conclusive, because several of the individual transects had insufficient captures to get good population estimates.

Transect

Origional (M)

Total # in 2nd (n)

Recapture (m)

Total Population (N)

Std. Error

(+/-) 95% Confidence

A

1

1

1

1

0

0

B

0

0

0

#DIV/0! ( 0 )

#DIV/0!

#DIV/0!

C

1

1

1

1

0

0

D*

0

2

0

#DIV/0! ( 2 )

#DIV/0!

#DIV/0!

E

2

1

1

2

0

0

F

1

1

1

1

0

0

G

2

2

1

4

8

15.68

H

0

0

0

#DIV/0! ( 0 )

#DIV/0!

#DIV/0!

I*

2

2

0

#DIV/0! ( 4 )

#DIV/0!

#DIV/0!

J

4

4

2

8

16

31.36

 

 

 

 

 

 

 

Totals

13

14

7

26

48.28571

94.64

"Native"

2

2

2

2

0

0

Cut *

8

10

3

26.66666667

165.9259

325.2148148

Burned

3

2

2

3

0

0

 

 

 

 

 

 

 

Cut Habitat with P. pectoralis only

8

8

3

21.33333333

94.81481

185.837037

 

Table 1. March 1999 trapping results from Friedrich Wilderness Park, Bexar County, Texas. The results are by transect and also by habitat for the original number of rodents marked and captured the first day, the total number caught the second day and the number of rodents recaptured the second day. The total population was calculated using the Lincoln Peterson method. The standard error and 95% confidence interval were calculated. The #DIV/0! symbol is shows where the model proposed dividing by zero which is mathematically impossible and thus no conclusive data can be gathered in these cases. Transects D and I both contain species other than Peromyscus pectoralis in the totals for the second day, (Peromyscus atwatteri and Sigmodon hispidus respectively). The last row takes this into account and provides the information on Peromyscus pectoralis only.

 

The information collated in Table 1 shows that because of the large standard errors and 95%confidence intervals, the data cannot be considered statistically different for any of the three areas.

 

Discussion:

The assumptions of the Lincoln Peterson index were satisfied at Freidrich Wilderness Park even though the data obtained was not conclusive. The individuals were randomly sampled and because of the short (24 hour) time frame there was little if any migration or mortality, and little time for the rodent to lose its tag. To decrease the possibility for error, several things can be done such as setting more traps in each transect or adding more transects in similar habitats. With larger numbers of mammals captured and most likely more recaptures, the possibility for errors decrease and so too may the standard error. A larger sample size may allow for better analysis of the data.

                            

The Effects of Human Land Management Practices on the Small Mammals of Friedrich Park.

  

Bryan Hummel

Ecology 3434

Ribble; 8:30 TR

March 16, 1999.

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