RISC Fundamentals

Question 1

Why are standardized methodologies important?

Answer 1

• Historically, lack of data to allow resource managers to evaluate the status of BC’s biological diversity or to make scientifically based land use decisions
• To understand what species/ecosystems and how much are at risk – there must be high-quality data collected by well-documented, proven methods that allow comparisons from place to place and year to year

Question 2

What is the most critical phase of implementing and completing an inventory project? Why? ( 3 points)

Answer 2

The most critical phase of an inventory project is SURVEY DESIGN. Careful design will:

• Increase effectiveness
• Reduce cost
• Produce more reliable information

Question 3

What is the 1st critical step in developing an effective survey design?

Answer 3

1° step is to establish clear objectives from the very beginning. Objectives dictate level of intensity. For example:

• To obtain baseline data?
• To monitor changes in abundance / composition /distribution?
• To measure the direction and extent of above changes?

Question 4

What are the 3 levels of intensity of wildlife surveys? How do these levels relate to intensity, resource requirements, and information gained?

Answer 4

The levels of intensity are:

1. Presence/Not detected
2. Relative abundance
3. Absolute abundance

The levels of intensity increase in the order listed above, along with resource requirements and information gained.

Question 5

What is the objective of Presence/Not Detected surveys?

Answer 5

To determine species occurrence in area (presence/not detected, distribution)

Goals:
Species list (Species richness)
Species range
Species habitat associations (distribution and associations)

Question 6

What is the objective of Relative Abundance surveys?

Answer 6

To provide indices of population size (unit time, unit area, or distanced travelled). Usually can not be converted to an estimate of absolute population size

Question 7

What is the objective of Absolute Abundance surveys?

Answer 7

To estimate total number or density of a species for a specific area

Question 8

What are the assumptions of Presence/Not Detected surveys?

Answer 8

Assumption: you can detect presence with some reliability given minimum effort. The truth of this assumption depends upon the species and the techniques used.

Question 9

What are the assumptions of Relative Abundance surveys?

Answer 9

Assumed that the true population is related linearly to the estimates/measures. Other assumptions:

• Identical or statistically comparable methods are used when comparison between areas or monitoring trends in one area over time is an objective.
• Environmental, biological, and sampling factors are kept as constant as possible to minimize differences in survey bias and precision between surveys.
• Surveys are independent; one survey does not influence another.

Question 10

What are the assumptions of Absolute Abundance surveys?

Answer 10

Mark recapture/population estimation assumptions:

• Tags are not lost
• Population is mixed
• Animals behaviour doesn’t change when caught
• Sample is a random sample of all individuals (doesn’t hold because trap doesn’t move, but neither do all the home ranges)

Question 11

State the 3 critical assumptions related to survey bias in relative abundance surveys?

Answer 11

• Identical or statistically comparable methods are used when comparison between areas or monitoring trends in one area over time is an objective.
• Environmental, biological, and sampling factors are kept as constant as possible to minimize differences in survey bias and precision between surveys.
• Surveys are independent; one survey does not influence another.

The most important assumption is that survey bias, as reflected by the proportion of a population observed is, on average, constant across surveys.

Question 12

What is ‘survey bias’?

Answer 12

“Survey bias” is a source of systemic error introduced into the data as a result of the sampling method chosen - and so can be controlled via careful choice/refinement of sampling method

Question 13

How does edge effect affect area when using area-based surveys?

Answer 13

In area based surveys, edge effect interacts with the size and shape of the survey area.

For example, in a heterogenous patchy area, a long rectangle will encounter more patches than a circle which covered the same amount of area.

Likewise, the shape of the sample area (e.g. square vs rectangle) will change the amount of perimeter. A larger perimeter is more likely to capture mobile species.

Question 14

Why are relative abundance surveys used more than Presence/Not Detected and Absolute Abundance? (3 points)

Answer 14

• majority of ecological problems can be tackled through the use of relative abundance indices rather than absolute abundance estimates
• Absolute abundance are usually more costly and difficult to measure, data has limited range in space and time

Question 15

What is a key question to ask before you finalize your survey design?

Answer 15

Key question to ask about a survey protocol – will my estimate be representative of the WHOLE target population?

Question 16

How do Simple Random Sample (SRS), Systematic Sampling (SYS), and Stratified Sampling (STS) vary with respect to randomization?

Answer 16

SRS - occurs when all sample units in a population have an equal chance of being selected. This procedure emphasizes randomization.

SYS - Employed when the population of interest can be sampled along a line. Random starting point is selected along the line and then systematically thereafter.

STS - Breaking the sample population into strata, and then using SRS or SYS within strata. Each strata is homogenous within, but different from others. Sampling effort is focused on strata of higher interest . Not random in the sense of choosing strata and sampling accordingly, but randomized because SRS or SYS are then used within the strata.

Question 17

How does the physical layout of SRS, SYS, and STS vary?

Answer 17

SRS - Random points placed within an area of interest.

SYS - Line is placed through the area of interest, and sampling is done along the line.

STS - Area of interest is broken into strata based on habitat/expected density/home range, and then SRS or SYS done within the strata.

Question 18

What are the advantages and disadvantages of SRS, SYS, and STS?

Answer 18

SRS - Emphasis on randomization reduces the potential for bias. Provides a large amount of data because large number of sample points are required to reduce variability.

SYS - Produces good coverage of an area while costing less than SRS. Relatively easy to do and less subject to site selection errors by field staff

Question 19

What are the advantages and disadvantages of SRS?

Answer 19

Pros:

• Emphasis on randomization can reduce the potential for bias.
• Lots of sample points

Cons:

• difficult to control for variability,
• difficult to conduct because plots may be difficult to get to
• not cost effective

Question 20

What are the advantages and disadvantages of SYS?

Answer 20

Pros:

• Produces good coverage of an area while costing less than SRS.
• Relatively easy to do and less subject to site selection errors by field workers

Cons:
- Potential concern of naturally occurring variation that occurs at the same frequency as the sampling methodology, but probably not an issue in most field studies

Question 21

What are the advantages and disadvantages of STS?

Answer 21

Pros:

• Can be cost efficient because less time spent surveying areas where species is likely absent.
• Stratification produces a tighter confidence interval especially if strata are homogenous
• Cost per observation is reduced
• Separate estimates of population parameters can be obtained for subgroups of the population

Cons:

• Requires an established understanding of the appropriate stratification of an area. May not be possible if stratification parameters are not known for species of interest (e.g. home range is not known).
• Inaccurate stratification will produce inaccurate data

Question 22

How does effective trapping area vary from actual trapping area?

Answer 22

How the size and shape of the sampling area interacts with the dynamics of the species in question. You may be “effectively” sampling more species than your “actual” sampling area would indicate if the species is very mobile.

True sampling area vs. actual sampling area…
 2 grids 9 ha in size: 1 square and 1 rectangle
 Square 300 m X 300 m = 1200 m perimeter
 Rectangle 100 m x 900 m = 2000 m perimeter
 Effective sampling area for mobile species is significantly larger for the rectangle

Question 23

Can you declare a species as ‘not present’ if you failed to find/observe it during your survey? Why?

Answer 23

No, because there are a number of factors that can influence whether or not a species is successfully observed. A species may be present in an area, but is not observed due to:

o Poor sampling technique
o Animal rarity
o Unskilled observer
o Weather
o Seasonal absence

Question 24

How do ‘encounter transects’ vary from ‘fixed-width transects’ (or ‘line transects’)?

Answer 24

In an encounter transect, there is a line where observed species are counted continuously or at fixed points. Area isn’t measured, so population size estimate is not possible (although accurate mapping may allow for this later e,g. spcs per km)

In fixed width or line transects, species are counted within a fixed distance from the transect center or only if they fall on the transect line. Density can be calculated using these methods because the area of the transect is a known factor for both.

Question 25

What is the primary objective of an inventory project?

Answer 25

1 objective of an inventory project is to make inferences about the population from information contained in a sample. Typically the desired inferences are population estimates (mean, total, proportion)