WLF 448: Fish & Wildlife Population Ecology
Lab Notes, Fall 2004

Problem Set #5

Distance Sampling

Analyses

Description: This problem set involves a hypothetical population of cottontail rabbits (Sylvilagus floridanus) on an old field. These data are different from the In-class data because there are 2 treatments areas (fertilized and mowed) and 1 control area.  These data are to be evaluated by estimating mean density and 95% confidence intervals among control and treated areas within the old field.  Do either of the 2 treatments influence the density of cottontail rabbits on the old field?  There is a dataset that can be found at K:/WLF/448/2004/Lab2004/distance2004.  It is called alltreatments.xls.  This file is similar to the In-class data except the strata are now between treatments (i.e., control, fertilized, and mowed).  Each treatment area is 80 ha in size and there were 4 transects run within each treatment.  All transects were 4 km long and perpendicular distances were measured in meters.  Import these data into DISTANCE as a single text delimited file to obtain estimates of density and 95% confidence intervals.  Use the same models that were used in the In-class exercise, however feel free to explore other models.  Find a set of estimates based on optimal model fit and parsimony.  In your report, justify the model selected. You will need estimates of density and confidence intervals for each stratum. 

Write a short scientific paper to report your findings (Body of text [items 1-4] should be a maximum of 4 pages typed double spaced; not including the table).  It would be wise to review your information provided in lecture on scientific writing.  Your lab should have these sections:

1.  Introduction -  Provide background on the topic by briefly describing distance sampling.   State the objectives of the lab.  

2.  Methods - Briefly describe how you analyzed the data.  Mention the models and series expansions you used.  Also include any data filters you might have tried (i.e., truncation or intervals).  Note: We did not thoroughly discuss data filters in this lab, but feel free to use them if you deem it appropriate. 

3.  Results - Create a table that compares all the method/strata combinations.  Report the key function and series expansion chosen, density, f(0) or p(0), and effective width/radial distance.  Include each estimate's 95% CI.  Report any other relevant results from this lab.

4.  Conclusions - Compare estimates obtained for each strata (i.e., 2 treatments and control) and the total density estimate.  Make sure to comment on all information listed in the results section.  Include any relevant assumptions, possible violations to those assumptions, and consequences of violating those assumptions.  Are the rabbits impacted by either of the 2 treatments?  Why or why not? 

5.  Literature Cited - Background information that you include should be cited here.  Remember to follow the citation format for the Journal of Wildlife Management. 

6.  Appendix - Copy all relevant output from distance into this section.  Don't include all of the output, only the parts that are applicable.

Note:  It will be helpful for you to review the material covered up to now regarding scientific writing.

Note:  See Lab 5 Help/Hints for some helpful tips.

For this week's lab on distance sampling and next week's lab on mark-recapture you will need a basic understanding of statistics.  To help you gain a better understanding and prepare you for these labs give a brief definition for the basic statistical terms and/or concepts listed below.   Hand this in next week in addition to your scientific paper on distance sampling, but do not attach your definitions to your Lab 5 problem set.  This additional assignment is worth 5 points.

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Revised: 29 September 2004