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MANAGEMENT AND ANALYSIS OF WILDLIFE BIOLOGY DATA Bret A. Collier 1 and T. Wayne Schwertner 2 1 Institute of Renewable Natural Resources, Texas A&M University, College Station, TX 77845, USA 2 Department of Animal Sciences and Wildlife Management, Tarleton State University, Stephenville, TX 76402
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Introduction In wildlife biology, data analysis underlies nearly all the research that is conducted The range of statistical methods available is extensive Ultimately, good questions, study designs, and analysis are complementary topics
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First Thoughts When designing a study: Talk to a professional No amount of statistical exorcism can fix a bad study design Methods are rapidly advancing, staying in front is tough Again: When designing a study: Talk to a professional
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Study Design In scientific research, results hinge on study design Define population of interest Ecological populations Inferential populations Target populations Sampled populations Population inference requires data representing population of interest
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Data Collection Conceptual framework for ‘how’ to collect 1. Outline study question. 2. Define response variable (e.g., nest survival). 3. Define explanatory and/or descriptive variables that might affect response (e.g., vegetation cover). 4. Define steps for minimizing missing data. 5. Outline data collection approach. 6. Design initial data collection instrument specific to response or explanatory variables. 7. Conduct field test of protocols and data instruments. 8. Evaluate efficiency of data instruments. 9. Repeat steps 2–8 if necessary due to logistical difficulties. 10. Initiate data collection.
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Data Management Data types Qualitative Quantitative Data measurement scales Nominal Ordinal Interval Ratio Data files Files containing all data in rows and columns Commonly put into spreadsheets More advantageous-database management system
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Data Presentation Tables and Graphs Variety of uses
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Bar Graphs Bar Plots
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Point Graphs Point Plots
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Dot Graphs Dot Plots
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Scatter Graphs Scatter Plots
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Hypothesis Development Good questions come from good hypotheses about how a process occurs Statistical models can help evaluate strength, or lack thereof, of how a process occurs Models should inform the ecological question, not drive the question
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Hypothesis Development Good questions come from good hypotheses about how a process occurs Statistical models can help evaluate strength, or lack thereof, of how a process occurs Models should inform the ecological question, not drive the question
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Inference Descriptive Statistics Mean Mode Median Variance Standard Deviation Standard Error Confidence Intervals
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Comparative Analyses Chi-square tests T-tests F-tests ( Analysis of Variance) Correlation
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Regression Analyses Linear Regression Multiple Regression Generalized Linear Models
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Community Analysis Wildlife research has traditionally focused on the population level. Some study questions, however, address how wildlife communities: Respond to management activities or other perturbations Biodiversity is affected by various activities Change across space and time
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Species Richness Number of species in a community. Strongly influenced by sample size. Makes comparisons difficult.
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Complete Enumeration Provides the minimum number of species present. Works for simple communities. Rarely possible.
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Richness Indices Margalef’s index ► Not an estimate. ► Cannot be compared with other indices or richness estimates. ► Strongly influenced by sample size.
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Richness Estimates Estimate the actual number of species in the community Data collected as a single sample ► Rarefaction Used for standardizing sample sizes, and the resulting estimates of species richness, among samples. ► Chao 1 Method Especially useful when a sample is dominated by rare species. Requires species abundance data. Data collected as a series of samples. ► Chao 2 Method Modified Chao 1 Can be used with presence-absence data ► Jackknife and Bootstrap estimates Involve systematically resampling the original dataset.
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Species Heterogeneity Measures the degree to which individuals in a community are distributed among the species present. ► Shannon-Weiner Function Based on information theory Measures the amount of uncertainty associated with predicting the species of the next individual to be collected. ► Simpson Index The probability that 2 individuals drawn randomly from a community will be same species.
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