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Wildlife Population Survey Methods

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40 Questions

What is the primary purpose of a census in ecology?

To estimate the population size of a species

Which type of survey design is best suited for a habitat with an abiotic gradient?

Stratified sampling

What is the advantage of using quadrats in a survey design?

They enable the detection of patterns in the distribution of individuals

What is the primary benefit of using mark-recapture surveys?

They allow for the estimation of population size

What is the purpose of using tags in mark-recapture surveys?

To identify individual animals

What is the advantage of using individual markings to recognize animals, rather than marking them?

It is a less invasive method of identification

What is the purpose of distance sampling in survey design?

To measure the distance between sampling points

What is the benefit of using transects in survey design?

They enable the detection of patterns in the distribution of individuals

What is the advantage of using a stratified layout in quadrat sampling?

It is a more effective method of detecting patterns in the distribution of individuals

What is the purpose of casting individuals in mark-recapture surveys?

To handle individual animals

What is the primary reason why small populations may experience reduced growth rates?

Because individuals are unable to find mates

What type of population model is best suited to consider individual variation in reproduction and death rates?

Individual based models

What is the term used to describe the series of rates that inform about the growth, survival, and reproduction for each stage class in a population?

Life cycle

Why is it important to track cohorts over time in population studies?

To capture the effects of environmental variability on population rates

What is the term used to describe random variation in population dynamics due to environmental factors such as weather or predator pressure?

Stochasticity

What is the primary reason why understanding population trends is valuable for conservation and management?

Because it helps to identify the risk of extinction

What is the term used to describe the situation in which increasing abundance or density is associated with increased per capita growth rates?

Allee effect

What type of population model assumes that all individuals of the same age or class category reproduce and die with equal probabilities?

Age or class structured models

What is the term used to describe the probability of moving from one stage class to another in a population?

Growth rate

What is the term used to describe fluctuations in population size that are predictable and follow a pattern?

Cyclical fluctuations

What is the main reason why forcing one single population to become multiple does not generally reduce the risk of extinction?

Because fragmentation of habitat increases the risk of extinction

What is the term used to describe the phenomenon where poor quality habitat is perceived as good by individuals?

Ecological traps

What is the main assumption of the simplest metapopulation models?

Only occupancy and movement between sites

What is the term used to describe the dynamic where high-quality patches have higher reproduction rates and individuals migrate to other patches?

Source-sink dynamics

What is the general pattern of population distribution in their geographic ranges?

Higher densities at the centre of the range

What is the main reason why organisms may not be able to choose the optimal habitat quality?

All of the above

What is the term used to describe the natural or man-made links between habitat patches?

Habitat corridors

What is the main advantage of using complex metapopulation models?

They can track changes in abundance at each site

What is the phenomenon where individuals settle in low-quality habitats because the per capita benefit equals that experienced in high-quality habitats?

Ideal free distribution

What is the main reason why metapopulation models can only use presence/absence data or have information on abundance for all patches?

Because data on habitat quality is difficult to obtain

What is the primary benefit of using photo identification in cetaceans and other groups?

To understand life history traits of individual animals

What is the major issue in sampling that arises due to differences in detectability of organisms?

Detectability

What type of population model is used when studying multiple unconnected sites?

Multiple single population models

Which type of model represents non-linear changes in growth with populations growing increasingly fast to a point at which growth stops?

Logistic model

What happens when a population grows beyond its carrying capacity?

Overshoot occurs

What are the effects that regulate growth due to interactions with conspecifics?

Density-dependent effects

What type of effect occurs at low density, where growth per capita increases?

Allee effect

What is the term for a substantial decline in density that typically goes well below the carrying capacity?

Die-off

What is the term for the maximum number of individuals that an environment can support?

Carrying capacity

What type of models are used to describe how the number of individuals changes over time?

Population models

Study Notes

Counting and Locating Individuals

  • Full count: census, partial count: survey, direct counts/indirect counts
  • Direct observation: observing/measuring the sample, e.g., number of butterflies in a meadow
  • Indirect observation: using technology to count without directly seeing/hearing the animal

Survey Design

  • Transects: linear paths in the study area, usually straight lines
  • Distance sampling: meters from transect, uniform is ideal when individuals are evenly distributed or the habitat is similar
  • Stratified sampling: best when there is an abiotic gradient or pattern in the habitat, e.g., variation in humidity or proximity to a river

Mark-Recapture Surveys

  • Using tags to mark individuals, e.g., Californian sea lions
  • Calculating total number: knowing how many individuals are marked and recaptured
  • Other means of marking animals: hot iron, plastic tags in birds, toe clipping in herps
  • Not always necessary to mark: using individual markings to recognize individuals, e.g., photo identification in cetaceans

Sampling Issues

  • Temporal heterogeneity: when to go, different times organisms may be less or more detectable
  • Spatial heterogeneity: dispersion, same methods if individuals are evenly spaced vs. clustered
  • Sampling variability: if not counting all, is the sample representative?
  • Potential biases: counting only some types of individuals, observer effects
  • Detectability: factors affecting surveyors' ability to detect individuals, e.g., habitat complexity, individual characteristics, surveyor expertise, weather conditions

Tracking Changes in Abundance

  • Population models: mathematical and statistical equations/tools aimed to describe how the number of individuals changes over time
  • Types of population models:
    • Single population models: most common, based on 1 site and 1 species
    • Multiple interconnected subpopulations (metapopulation models): multiple populations with migration among them
    • Spatially-structured models: incorporating spatial patterns and interactions
  • Exponential models: represent non-linear changes in growth, with populations growing increasingly faster or declining rapidly
  • Logistic models: represent non-linear changes in growth, with populations growing increasingly fast to a point at which growth stops, stabilizing abundance at carrying capacity

Population Models

  • Density-independent models: exponential models, no regulation of growth
  • Density-dependent models: logistic models, growth regulated by density
  • Stochastic events: unpredictable, e.g., extreme climate events, geological events
  • Density-dependent effects: factors regulating growth due to interactions with conspecifics
  • Allee effects: positive effects at low density, negative effects at high density

Types of Models

  • Unstructured models: assuming all individuals reproduce and die with equal probability and frequency
  • Age or class-structured models: assuming all individuals of the same age or class category reproduce and die with equal probabilities
  • Individual-based models: considering individual variation, each individual dies and reproduces with a different probability
  • Structured models: with defined stage or age classes, vital rates inform about growth, survival, and reproduction for each class

Metapopulation Models

  • Source-sink dynamics: high-quality patches (sources) and low-quality patches (sinks)
  • Ecological traps: poor-quality habitat perceived as good by individuals
  • Metapopulation models can use presence/absence data or abundance data for all patches
  • Complex models incorporate habitat quality and characteristics to predict future dynamics

Habitat Selection and Fragmentation

  • Ideal free distribution: individuals choose the best habitat, but per capita benefit declines as more individuals choose the high-quality habitat
  • Habitat corridors: natural or man-made links between habitat patches
  • Populations are not evenly distributed in their geographic ranges, with higher densities near the center and lower densities near the periphery

This quiz covers the different methods used to count and locate individuals in a population, including full counts, partial counts, direct and indirect observations, and survey design techniques.

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