Population Ecology (W6) Flashcards
Ecological niche?
= involves an organism’s tolerances (conditions) & requirements (resources).
Eg of conditions? (3)
• Heat.
• Acidity.
• Windiness.
Egs of resources? (4)
• Food.
• Soil.
• Nutrients.
• Sunlight.
Niche dimensions?
= habitat factors.
Egs of niche dimensions? (2)
• Acidity.
• Salinity.
Habitat?
= the combination of resources & conditions that promote occupancy by individuals of a particular species.
Habitat attributes? (3)
• Species-specific (eg habitat for meerkats).
• Spatial locations associated with resources like food, water, shelter, security from predators/parasites.
• Serves a particular function (eg. feeding habitat).
Promoting factors?
= increase the likelihood of occupancy.
Restricting factors?
= decrease the likelihood of occupancy.
Egs of Promoting factors from House discussion? (3)
• Price.
• Space.
• Close to shops.
Egs of Restricting factors from House discussion? (3)
• Crime.
• Near a coal power plant.
• Neighbouring properties are dodgy.
Habitat use?
= pattern of individual locations with respect to habitat factors, which are linked to an individual’s movement.
What does habitat use depend on?
The ability of the individual to access the habitat.
Tool used when understanding an individual’s use of a habitat?
Home range (HR).
HR properties to know? (2)
• Overlap in HR between individuals.
• Spacing of HR/between HR.
What does overlap in HR between individuals tell us?
Tells us whether species are gregarious or territorial.
What does spacing of HR/between HR tell us?
Gives us spatial perspective on changes in the population abundance over time.
Lots of overlap of HR between individuals means…?
Gregarious individuals.
Eg of gregarious species?
Sable antelope.
No overlap of HR between individuals means…?
Territorial individuals.
Eg of territorial individuals?
Prides of lions.
Full landscape of HR means …? (2)
• Population is territorial.
• Population is at ED.
Still more room landscape means…?
Population is growing & not yet at a population density (middle of sigmoid graph).
What do we use to estimate HR?
Spatial field data.
Spatial field data attributes? (4)
• GPS collar used.
• Data are collected at intervals (daily, hourly).
• Variation in lengths of “steps” between locations.
• Most of an individual’s time is spent in a small fraction of the available area.
Why use a GPS collar?
Placed on animal to track its movement & location.
Downside of collecting data at intervals (daily, hourly)?
We only see a subset of where an individual occurs & not the full picture.
What does the variation in lengths of “steps” between locations tells us/help us with?
Gives us an idea of what an animal might be doing as it moves from one location to another.
“Most of an individual’s time is spent in a small fraction of the available area”, what does this mean/what can you deduce from this?
Animals appear to show preference for some patches over others.
Goals of estimating HR? (3)
• To characterize the overall pattern of use on the landscape.
• To measure the extent/size of the area over which individuals traverse as they do their life activities.
• To relate location & search paths to variables in the environment.
What information does relating location & search paths to variables in the environment provide? (2)
• Tells us what factors in the environment affect where we find locations & where steps occur.
• Gives us information about the biology of the species we are studying.
HR estimators? (3)
• Minimum convex polygon (MCP).
• Kernel method.
• Local Convex Hull (LoCoH).
HR method criteria for a good method? (2)
• Must give us HR size & location.
• Must give us utilization distribution (intensity of use).
MCP method attributes? (2)
• Easiest.
• Most common.
Importance of MCP? (2)
• Gives us extent/size of the HR.
• Gives us location of polygon (HR) using GPS.
Con of MCP?
Doesn’t provide utilization distribution.
Types of Kernel method estimators? (3)
• Bivariate kernel.
• Adaptive kernel.
• Brownian bridge kernel.
Bivariate kernel attributes? (3)
• Fits a 3D normal distribution around a set of points.
• X & Y coordinates measure extent of area used by the individual.
• Z coordinate measures intensity of use by individuals.
What do the X & Y coordinates of the Bivariate kernel method measure?
The extent of area used by the individual.
What do the Z coordinate of the Bivariate kernel method measure?
The intensity of use by individuals.
Cons of Bivariate kernel estimator? (2)
• A lot of areas are not a nice oval shape & you need that to use the Bivariate kernel method.
• Spread of location is in one patch.
Sections of 3D normal distribution? (3)
• Core area.
• Isopleth.
• Periphery.
Core area of 3D normal distribution?
= has high use by the animals.
Isopleth section of a 3D normal distribution?
= contour that tells us the density of use of the habitat.
Periphery section of a 3D normal distribution?
= less use by the animals.
Pros of Adaptive kernel? (2)
• More flexibility in its shape.
• Spread of location is in 2 pockets.
Gap in between 2 pockets attributes? (2)
• Not a lot of resources & intensity of use.
• Could be a moving area to & from resources & shelter/resting.
Axes/Coordinates of 3D normal distribution? (3)
• X coordinates.
• Y coordinates.
• Z coordinates.
What are the Bivariate & Adaptive kernel estimators based on?
The location of the GPS points coming from the animal’s GPS radio collar.
What does the Brownian bridge kernel estimator focus on?
On the steps between the locations.
LoCoH attributes? (3)
• How it works.
• Many overlapping polygons/hulls.
• Fewer overlapping hulls.
How does LoCoH work?
Works by drawing polygons around certain points & seeing within the HR how many polygons overlap with each other.
Many overlapping hulls =…?
High intensity of use.
Fewer overlapping hulls = …?
Low intensity of use.
How do we estimate habitat use & habitat availability?
We look at the characteristics within the HR where the animal occurs & where it doesn’t occur to get an idea of which parts of the HR are important than other parts.
Types of vegetation? (4)
• Streamline/Riparian vegetation.
• Open woodland.
• Closed woodland.
• Grassland.
Importance of estimating habitat use & habitat availability?
Allows us to relate the intensity of use to vegetation types occurring in the homeland.
How/What we use for estimating the habitat use & habitat availability? (3)
● Individual locations from GPS collar which gives us “used” habitat.
● Vegetation map from GIS by covering HR with random locations which give us availability.
● Compare proportions of use & availability to judge selectivity of vegetation types.
Properties of using GIS to estimate/model a habitat for a species? (4)
● Computerised maps are represented as a layer.
● Accuracy of data that goes into GIS layer/map must be assessed.
● Resolution of a layer might not be sufficient to address the question of interest.
● GIS/its layers may not be able to capture the changes of landscapes over time & space.
Types of HR? (5)
• Total HR.
• Seasonal HR.
• Breeding HR.
• Migratory HR.
• Annual HR.
Total HR?
= HR throughout an individual’s lifetime.
Kinds of Seasonal HR? (2)
• Dry season HR.
• Wet season HR.
Habitat assessment?
= measures of availability where we cover polygon with random points.
Steps of assessing selective use of habitat? (4)
● Observed locations from a GPS collar (use)
n = 378.
● Random locations (availability)
n = 378 (different colour).
● Use these to determine how many location points fell into each vegetation type:
• Grassland
- USE = 28.
- AVAILABILITY = 57.
• Stream vegetation
- USE = 227.
- AVAILABILITY = 95.
• Closed woodland
- USE = 102.
- AVAILABILITY = 151.
• Open woodland
- USE = 21.
- AVAILABILITY = 76.
● Estimate strength of selectivity (S) for each vegetation type via using USE & AVAILABILITY ratio:
S = USE/AVAILABILITY
• Grassland (S) = 0.49
• Stream vegetation (S) = 2.40
• Closed woodland (S) = 0.68
• Open woodland (S) = 0.28
S < 1?
Organisms avoid vegetation type.
S > 1?
Organisms favour vegetation type.
Interpretation of vegetation type?
This organism uses grassland at about half its availability, uses stream vegetation at 2.4 times its availability, uses closed woodland at about two thirds of its availability & uses open woodland at about a quarter of its availability.
What can we do with this data? (2)
• Gives us a picture about what is important for an animal.
• We can do a statistical test for how important the selectivity is (χ² test) & test whether O & E are equal.
χ² test formula?
χ² = Σ (O–E)² / E
O & E symbols in χ² equation? (2)
• O –> use.
• E –> availability.
Elaborate χ² equation in our vegetation type example? (3)
● Input use & availability in equation
χ² = Σ (O–E)² / E
= (28–57)²/57 + (227–95)²/95 + (102–151)²/151 + (21–76)²/76
χ² = 274.64
● Information obtained:
df = 4; χ² = 276.64; p<0.01 (very small)
● There is strong evidence that USE is unequal to AVAILABILITY.
Resource Selection Function (RSF) attributes? (3)
• Works with environmental factors that are continous.
• Relationship between a continuous predictor variable and habitat factor & a degree of use.
• Similar to simpler linear regression.
Simple linear regression equation?
y = βo + β1 x
Eg of an environmental factor that is continuous?
Elevation.
Simple linear regression equation symbols? (4)
• y —> amount of use.
• x —> elevation.
• βo —> y-intercept.
• β1 —> strength of the relationship between elevation & use.
Things that contribute variation in habitat use? (3)
• Scale of habitat use.
• Effect of availability.
• Effect of density.
Scale of habitat use as a contributor to habitat use variation?
= looking at habitat use at different scales, temporal & spatial.
Scales of selection? (4)
• Type 1.
• Type 2.
• Type 3.
• Type 4.
Effect of availability attributes as a contributor to habitat use variation? (6)
• Influences the strength of selection.
• x-axis = amount of resource (Q) [little to lots].
• y-axis = strength of selectivity (S).
• Resource Q is scarce is at top of line graph.
• Resource Q is plentiful is at bottom of line graph.
• Decreasing line graph.
When resource Q is scarce = …?
High strength of selection (S).
When resource Q is plentiful = …?
Low strength of selection (S).
Habitat functional response?
= where the strength of selection varies depending on how available a particular resource/habitat is.
Effect of density attributes? (2)
• Deals with IFD.
• Deals with IDD.
IFD attribute?
Distribution should be proportional to the quality of the environment.
IDD attributes? (2)
• Not free.
• Individuals have to deal with territorial behaviour & competitors.
Important aspects of Habitat selection? (2)
• Habitat selection is linked to movement (you can only get access to habitats if you can move to them).
• Consider movement within the HR & how it influences availability.
How do we estimate movement & HR? (2)
• Movement within the HR.
• Movement among the HR.
Movement within the HR attributes? (3)
• Gives us an idea of the behaviour of the animal.
• Uses ¹ step length & ² turning angle.
• Use hourly GPS locations to look as patterns over time & figure out what animals are doing as they are moving.
Components that Movement within the HR uses? (2)
• Step length.
• Tyrning angle.
Short step lengths & tight turns = …?
Organism is using an important patch.
Long step lengths & few turns = …?
Organism travels between patches.
Step selection analysis?
= involves looking at the environmental characteristics where the steps occur.
Importance of Step selection analysis?
Gives us a sense of what sorts of environments facilitate movement & what sorts of environments impede movement (eg, protected animals for conservation).
Movement among HR attributes? (3)
• Deals with migration between non-overlapping, seasonal HR.
• Nomadism.
• Residents.
Nomadism attributes? (4)
• Movement is unpredictable.
• Characterize the HR at small scales.
• No fixed HR in one location or other locations.
• Unpredictable HR from one season to the next.
Eg of Nomadic animals?
Elands.
Residents attribute?
Have the same HR annually.
Eg of Resident animals?
Serengeti wildebeest.
Explain Serengeti wildebeest? (6)
• Move in a cyclic movement.
• Seasonal HR.
• Meet at a location in one part of the HR & in another part of the HR.
• Depends on rainfall.
• Characterize those 2 HR.
• Migrate between Kenya & Tanzania.
Pros of Serengeti wildebeest being residents & moving in a cyclic movement? (2)
• Get access to better resources.
• Helps with predators as wildebeest move seasonally, which predators cannot due to them being territorial.
Benefit for predators in Serengeti wildebeest example?
Predator swamping.
