MANAGEMENT AND ANALYSIS MANAGEMENT AND ANALYSIS OF WILDLIFE BIOLOGY DATAOF WILDLIFE BIOLOGY DATA

Bret A. CollierBret A. Collier11 and T. Wayne and T. Wayne SchwertnerSchwertner22

11Institute of Renewable Natural Resources, Texas A&M Institute of Renewable Natural Resources, Texas A&M University, College Station, TX 77845, USAUniversity, College Station, TX 77845, USA

22Department of Animal Sciences and Wildlife Department of Animal Sciences and Wildlife Management, Tarleton State University, Stephenville, Management, Tarleton State University, Stephenville,

TX 76402TX 76402

IntroductionIntroduction

In wildlife biology, data analysis underlies nearly all the In wildlife biology, data analysis underlies nearly all the research that is conductedresearch that is conducted

The range of statistical methods available is extensiveThe range of statistical methods available is extensive

Ultimately, good questions, study designs, and analysis Ultimately, good questions, study designs, and analysis are complementary topicsare complementary topics

First ThoughtsFirst Thoughts

When designing a study: Talk to a professionalWhen designing a study: Talk to a professional

No amount of statistical exorcism can fix a bad study No amount of statistical exorcism can fix a bad study designdesign

Methods are rapidly advancing, staying in front is toughMethods are rapidly advancing, staying in front is tough

Again: When designing a study: Talk to a professionalAgain: When designing a study: Talk to a professional

Study DesignStudy Design In scientific research, results hinge on study designIn scientific research, results hinge on study design

Define population of interestDefine population of interest Ecological populationsEcological populations Inferential populationsInferential populations Target populationsTarget populations Sampled populationsSampled populations

Population inference requires data representing Population inference requires data representing population of interestpopulation of interest

Data CollectionData Collection Conceptual framework for ‘how’ to collectConceptual framework for ‘how’ to collect

1. Outline study question.1. Outline study question. 2. Define response variable (e.g., nest survival).2. Define response variable (e.g., nest survival). 3. Define explanatory and/or descriptive variables that might affect 3. Define explanatory and/or descriptive variables that might affect

response (e.g., vegetation cover).response (e.g., vegetation cover). 4. Define steps for minimizing missing data.4. Define steps for minimizing missing data. 5. Outline data collection approach.5. Outline data collection approach. 6. Design initial data collection instrument specific to response or 6. Design initial data collection instrument specific to response or

explanatory variables.explanatory variables. 7. Conduct field test of protocols and data instruments.7. Conduct field test of protocols and data instruments. 8. Evaluate efficiency of data instruments.8. Evaluate efficiency of data instruments. 9. Repeat steps 2–8 if necessary due to logistical difficulties.9. Repeat steps 2–8 if necessary due to logistical difficulties. 10. Initiate data collection.10. Initiate data collection.

Data ManagementData Management Data typesData types

QualitativeQualitative QuantitativeQuantitative

Data measurement scalesData measurement scales NominalNominal OrdinalOrdinal IntervalInterval RatioRatio

Data filesData files Files containing all data in rows and columnsFiles containing all data in rows and columns Commonly put into spreadsheetsCommonly put into spreadsheets More advantageous-database management systemMore advantageous-database management system

Data PresentationData Presentation Tables and GraphsTables and Graphs

Variety of usesVariety of uses

Bar GraphsBar Graphs Bar PlotsBar Plots

Point GraphsPoint Graphs Point PlotsPoint Plots

Dot GraphsDot Graphs Dot PlotsDot Plots

Scatter GraphsScatter Graphs Scatter PlotsScatter Plots

Hypothesis DevelopmentHypothesis Development Good questions come from good hypotheses about how Good questions come from good hypotheses about how

a process occursa process occurs

Statistical models can help evaluate strength, or lack Statistical models can help evaluate strength, or lack thereof, of how a process occursthereof, of how a process occurs

Models should inform the ecological question, not drive Models should inform the ecological question, not drive the questionthe question

Hypothesis DevelopmentHypothesis Development Good questions come from good hypotheses about how Good questions come from good hypotheses about how

a process occursa process occurs

Statistical models can help evaluate strength, or lack Statistical models can help evaluate strength, or lack thereof, of how a process occursthereof, of how a process occurs

Models should inform the ecological question, not drive Models should inform the ecological question, not drive the questionthe question

InferenceInference Descriptive StatisticsDescriptive Statistics

MeanMean

ModeMode

MedianMedian

VarianceVariance

Standard DeviationStandard Deviation Standard ErrorStandard Error

Confidence IntervalsConfidence Intervals

Comparative AnalysesComparative Analyses Chi-square testsChi-square tests

T-testsT-tests

F-tests (F-tests (Analysis of Variance)Analysis of Variance)

CorrelationCorrelation

Regression AnalysesRegression Analyses

Linear RegressionLinear Regression

Multiple RegressionMultiple Regression

Generalized Linear ModelsGeneralized Linear Models

Community AnalysisCommunity Analysis Wildlife research has traditionally focused on the Wildlife research has traditionally focused on the

population level.population level.

Some study questions, however, address how wildlife Some study questions, however, address how wildlife communities:communities: Respond to management activities or other perturbationsRespond to management activities or other perturbations Biodiversity is affected by various activities Biodiversity is affected by various activities Change across space and time Change across space and time

Species RichnessSpecies Richness Number of species in a community.Number of species in a community.

Strongly influenced by sample size.Strongly influenced by sample size. Makes comparisons difficult.Makes comparisons difficult.

Complete EnumerationComplete Enumeration Provides the minimum number of species present.Provides the minimum number of species present.

Works for simple communities.Works for simple communities.

Rarely possible.Rarely possible.

Richness IndicesRichness Indices Margalef’s indexMargalef’s index

►Not an estimate.Not an estimate.

►Cannot be compared with other indices or richness Cannot be compared with other indices or richness estimates.estimates.

►Strongly influenced by sample size.Strongly influenced by sample size.

Richness EstimatesRichness Estimates Estimate the actual number of species in the communityEstimate the actual number of species in the community Data collected as a single sampleData collected as a single sample

►RarefactionRarefaction Used for standardizing sample sizes, and the resulting estimates of species Used for standardizing sample sizes, and the resulting estimates of species

richness, among samples.richness, among samples.

►Chao 1 MethodChao 1 Method Especially useful when a sample is dominated by rare species.Especially useful when a sample is dominated by rare species. Requires species abundance data.Requires species abundance data.

Data collected as a series of samples.Data collected as a series of samples.►Chao 2 MethodChao 2 Method

Modified Chao 1Modified Chao 1 Can be used with presence-absence dataCan be used with presence-absence data

► Jackknife and Bootstrap estimatesJackknife and Bootstrap estimates

Involve systematically resampling the original datasetInvolve systematically resampling the original dataset ..

Species HeterogeneitySpecies Heterogeneity Measures the degree to which individuals in a Measures the degree to which individuals in a

community are distributed among the species present.community are distributed among the species present.

►Shannon-Weiner FunctionShannon-Weiner Function Based on information theoryBased on information theory Measures the amount of uncertainty associated with predicting the Measures the amount of uncertainty associated with predicting the

species of the next individual to be collected.species of the next individual to be collected.

►Simpson IndexSimpson Index The probability that 2 individuals drawn randomly from a community The probability that 2 individuals drawn randomly from a community

will be same species.will be same species.