BIOL 4240 Field Ecology

BIOL 4240Field Ecology

Ecologists are often interested in spatial data…Plant ecologists, distribution of individuals.

Animal ecologists, distribution of individuals AND movements

Which way did they go?

What purpose can movement/telemetry studies serve?


* Movement patterns, migration, dispersal* Space use and home range size* Resource use and selection* Population abundance and density* Survival* Fecundity

• Movement patterns – assumed to be random through homogenous environment


N

10 Random WalksMinimum Convex PolygonObserved Movement Path

1 0 1 2 Kilometers

• Home ranges – Various models (polygons, parametric and non-parametric)








• Home ranges – 2 variables have big influence…1) How many animals

2) How many points per animal


Confidence level (%)

Bound (%)

N necessary

95 10 386

95 20 98

95 30 45

• Resource use/selection – Describe habitat with discrete categories…– Cover type– Vegetation types– Topography– Successional stage



• Population Abundance & Density –

– Use telemetered animals as “marked”– Use tagged animals to determine

visibility bias for aerial surveys… helps to minimize underestimation that is common


• Survival –

– Use computer software SURVIV by White (1983)

– Program MARK?– Various other methods…

Mayfield, Kaplan-Meier, Cox’s


• Questions necessary to determine…

– What type of study?

*Observational (descriptive or correlative)

*Manipulative



– Hypothesis testing or Model building?

*Which type of study is more appropriate for model building?



– What level of inference?• What is the population?• Time of day?• Scale?



– What is the sample/experimental unit?

*Location point/data

*Animal

* Social considerations

AVOID pseudoreplication (dependence or correlation of sample units, and artificially high estimates of precision) to minimize > type I error



– Sampling design?

– Sampling intensity?• Preliminary estimates of means/variances• Determining biological significance• Choosing desired power• Calculating necessary N



– Sampling design?

– Sampling intensity? *Studies suggest that 20-25 animals with ~50 pts

necessary for determining resource selection… AND

*50-300 pts /animal necessary for home range size(Rowland et al. 1997, 1998)



– Are Radio-marked animals an unbiased sample?*Effects of non-random capture*Marking-induced or relocation-induced changes in

behavior and survival



– Are location errors addressed?*PDOP*Remote estimation



– Are biases in observation rate identified and corrected?

*remote estimation (GPS collars etc.) important

• Preliminaries…

– How many dimensions do tracking data have?


• Coordinate Systems…Explain UTM and why it is preferred*Advantages of Lat./Long.?

*Disadvantages?


• Coordinate Systems… Explain UTM and why it is preferred*Universal Transverse

Mercator (UTM)…between 84 N and 80 S divided into 6° rectangles (zones 1-60)...


• Coordinate Systems… Explain UTM and why it is preferred* Example… zone 1 = 180 W Prime meridian = 177 W)

* What are the units in a number AND what do they convey regarding precision?0291923, 4441087 vs. 0291, 4441


• Coordinate Systems… * N or S then UniversalPolar Sterographic (UPS) used.



– What other data are important to include with location data?



– Cause and Effect can ONLY be determined through which type of experiment?



– Considerations for radio tags…– Smallest size possible– Cryptic coloration– Transmitter effects on behavior/fitness– Requisite time for adaptation– Critical life history periods to avoid– Others?


Documents

BIOL 4240 Field Ecology