Methodological Prelude

Recapitulation: Groups B and C had been subjected to a switch in visiting regime; the subsets are presented as datasets B₁ (1 P, L&F), C₁ (1 P, S&S) and B₂ (1 P, S&S), and C₂ (1 P, L&F), respectively. Visiting regimes for groups X (3 P, S&S) and Y (3 P, L&F) had not been changed, resulting in a total of six datasets from four focal groups (tab. 5.1-1)

Behaviour and posture were transcribed in four nest rows of increasing distance to the source of human disturbance (fig. 5.1-1).

Figure 5.1-1: Recapitulation: Assignment of rows. The screenshot taken at the beginning of each data transcription served to assign nests to rows of increasing distance from the source of human disturbance (R1 - R4). Conspecifics (C) currently not engaged in incubation were also identified in the screenshot. In each row, nesting penguins were marked from left to right (here: R1-1, R1-2, etc.). The white arrow indicates the direction from which the human visitor(s) approached. © K.Schuster 2001

During primary transcriptions (from tape onto paper), two time sampling methods (chapter 4.2.2.1, tab. 4-3) had been combined for maximum efficiency: Instantaneous-Scan Sampling (ISS) had assigned the incubating birds’ behaviours to six behaviour states (alert, agonistic, flippers-up, preen, manipulate, or rest&Co) and two postural states (prone or up) every 30 s, while All-Occur-rences Sampling¹ (AOS) had served to count the number of headshakes performed by each bird (behaviour event) during the 30 s-interval preceding the scan sampling point.

5.1.1.1 Secondary Transcription of Behaviour/ Posture

For secondary transcriptions, data from the (hard-copy) transcription sheets were entered into Excel spreadsheets (Microsoft, 1997/ 2003; see exemplary matrix in appendix 5.1-1). Instantaneous-Scan Sampling data (behaviour states and posture) were matricised the way they had been originally transcribed (i.e. numbers of incubating penguins per row assigned to each category).

1 Given that headshake reactions are of short duration (event, rather than state), their occurrence would have been inaccurately represented by Instantaneous-Scan Sampling.

All-Occurrences Sampling data (occurrence of headshakes) were modified as follows:

For each individual it was noted whether they had performed at least one headshake per interval². Although this effectively reduced the information gathered to the level generally obtained by One-Zero Sampling, this method was considered to yield more appropriate results, as it directly reflected the number of penguins reacting, rather than representing a mixture of ‘more penguins’ and ‘the same penguin more often’ – and thus permitted OZS-results to be compared to those obtained by Instantaneous-Scan Sampling.

While All-Occurrences Sampling is highly useful when examining individual differences among the penguins, at this stage, row/ group reactions were in the focus of the analyses.

5.1.1.1.1 Penguin-Unit-Index (PUI)

Rendering group reactions comparable³ across sessions, as well as between different rows and datasets, required a proportionalisation procedure. For this reason, a ‘penguin unit’-index (PUI) was devised. This index corrected not only for differences in the number of penguins per dataset or row, but also for differences in number of sampling units (points or intervals).

For each period (before, during, after human visitation), the number of penguins that could be unequivocally assigned to a given behaviour/ posture category per sampling point or interval was summed up over all sampling points or intervals included in the period, and divided by the sum of birds observed at all sampling points or intervals included in the period⁴.

‘Penguin unit’-index per row (= R1, R2, R3, R4) – PUI-R

2 For each penguin, the exact number of headshakes was noted in the primary matrices, but occurrence (yes/ no) of headshakes within a given interval was entered into the secondary matrices and used for evaluations. Thus, sums per interval give information on the number of penguins performing at least one headshake within a given interval, NOT on the number of headshakes.

3 Due to slight day-to-day differences in camera angle and zoom, the total number of nests varied across sessions.

4 N.b.: In the following equations, the 5-sign is merely used as shorthand for ‘sum of’.

∑ ∑

+

… + +

+

… + +

n) R1, R1,2

(R1,1 period per points sampling

n) R1, R1,2

(R1,1 period per alert

∑ ∑

+

… + +

+

… + +

n) R4, R1,2

(R1,1 period per points sampling

n) R4, R1,2

(R1,1 period per alert

‘Penguin unit’-index for entire focal group (= R_tot = R1+R2+R3+R4) – PUI-G

e.g. for focal group, ‘alert’

e.g. for R1, ‘alert’

The proportionalisation procedure described above results in values ranging from 0.00 to 1.00, with larger values indicating a greater proportion of penguins assigned to the respective category.

5.1.1.2 Secondary Transcription of Disturbance

5.1.1.2.1 Human Visitation – Point Performance Indicator Value for Human Disturbance (PPIV-H)

Table 5.1-2: Categorisation of Disturbance during Human Visitation (Focal-Group Analyses). At each sampling point, the sum of applicable code-values constitutes the Point Performance Indicator Value for Human Disturbance (PPIV-H).

Example: For loud and fast conduct (code value = 4) of one visitor (= 2) at 5 m distance from the penguins (= 4), PPIV-H would total 10 at any sampling point for which these conditions applied.

If a transition between distances (e.g., approach from 15 m to 5 m) had taken place within the preceding sampling interval, the proportion of time the visitor(s) had spent at each distance was taken into account by assigning the point to the distance the visitor(s) had held during the greater proportion of the interval. PPIV-H was entered into Excel and SPSS matrices for correlations with focal-group behaviour/ posture.

5.1.1.2.2 Conspecific ‘Disturbance’ – Point Performance Indicator Value for Conspecific Presence (PPIV-C)

Categorisation of conspecific total ‘disturbance’ considered the number of conspecifics present in six predetermined areas from ‘outside colony’ to ‘between fourth and fifth row’ of nests. While separate transcription had served well as a guard against losing track of numbers, only the sum of conspecifics was used in analyses: As the exact location of each conspecific will be close to some birds in the focal group and more distant to others, their total number, rather than their specific position, was considered to represent the potential impact on groups.

Total conspecific presence was thus used as an approximation of total ‘disturbance’ at a given point and constituted the Point Performance Indicator Value for Conspecific Presence (PPIV-C). PPIV-C was entered into Excel and SPSS matrices for correlations with focal-group behaviour/ posture.

For secondary transcriptions, the components of human visitation identified previously (distance, conduct, number) were categorised and coded as shown in table 5.1-2.

Total human disturbance at a given sampling point was then calculated as the sum of applicable code-values. The resulting sum at a given sampling point constituted the Point Performance Indicator Value for Human Disturbance (PPIV-H).

Visitor Distance Code

no visitation 1

approach to 15m/ at 15m 3 approach to 5m/ at 5m 4 approach to 3m/ at 3m 5

retreat 2 Visitor Conduct (Type) Code

no visitation 1

silent and slow (S&S) 2 loud and fast (L&F) 4

Visitor Number Code

no visitation 1

one visitor (1 P) 2 three visitors (3 P) 4

5.1.1.2.3 Predator/ Aircraft Disturbance

Ad libitum sampling notations in the ‘remarks’-column of primary transcriptions were entered into a corresponding column in the Excel matrices. While systematic evaluation was impossible due to rare and ‘erratic’ occurrences, these notes helped to gauge whether changes in the focal group’s behaviour were likely to result from sources of disturbance other than human or conspecific (chapter 4.3.4.7, q.v.).

5.1.1.3 Presentation of Results

5.1.1.3.1 Absolute and Magnitudinal Results

Whenever there are distinct between-row or between-dataset differences prior to human visitation (pre-), however, it is misleading to simply compare absolute results during or after human visitation across rows or datasets, because absolute penguin-unit-values make no distinction between ‘a leap and a crawl’.

Example: The scenario ‘few birds were standing prior to human visitation’ (e.g., absolute penguin-unit-value_pre: 0.02), and then ‘many more got up during visitation’ (resulting in, e.g., penguin-unit-value_dur: 0.13)’ differs strongly from that of ‘many birds were standing right from the start’ (e.g., penguin-unit-value_pre: 0.11), and then ‘a few more got up during human visitation’

(equally resulting in, e.g., penguin-unit-value_dur: 0.13)’, but the difference between the scenarios is not reflected in the absolute penguin-unit-values.

In those cases, differences were assessed by comparing the magnitude of the change. This was done by subtracting the absolute penguin-unit-values of the respective period from those of the previous period (i.e., ‘during visit’ minus ‘pre-visit’, ‘post-visit’ minus ‘during visit’) so that positive values indicated an increase relative to the previous period, while negative values pointed to a decrease.

5.1.1.3.2 Friedman-Test

Friedman-test was performed to examine whether differences in the behaviour of penguins nesting in different rows of increasing distance from the human disturbance were statistically significant. In case of significant results, pair-wise Friedman-tests (and sequential Bonferroni adjustments, q.v.) were calculated to detect between which rows the significant difference existed.

5.1.1.3.3 Colour Codes

The colour codes used to facilitate visual discrimination of significance levels (tab. 5.1-3) as well as r²-values (transformed correlation coefficients; tab. 5.1-4) have been introduced in chapter 4.4.

They are repeated here.

Table 5.1-3 (= Table 4-20): Colour Codes for Significance Levels for áF = Overall Significance.

Table 5.1-4 (= Table 4-19): Colour Codes for and Informal Interpretation of r²-Values, Modified Following SPRINTHALL

(1987).

4 0.0001 < p < 0.001 very highly significant 3 0.001 < p < 0.01 highly significant 2 0.01 < p < 0.05 significant

1 0.05 < p < 0.1 tendentially significant

5 0.810 < r² < 1.000 very high correlation, very dependable relationship (not in these datasets) 4 0.490 < r² < 0.810 high correlation, marked relationship

3 0.160 < r² < 0.490 moderate correlation, substantial relationship 2 0.100 < r² < 0.160 low correlation, definite but small relationship 1 0.001 < r² < 0.100 slight correlation, almost negligible relationship

5.1.1.3.4 Order of Presentation

The first section on period differences on the group level demonstrates the extent to which parameters differed before, during, and after human visitation.

Results on row differences in the following section are used to examine a possible influence of distance from the disturbance stimulus. Results of Friedman-tests serve to gauge the statistical significance of differences found.

In the last section, results on the relation between intensity of response and type of disturbance are presented for selected parameters of each behaviour aspect.

Results on correlations of focal-group responses to conspecific presence before and after human visitation are followed by those on partial correlations between focal-group responses to conspecific presence during visitation, and to human visitation itself.

Within chapter 5.1, the following order of presentation has been adhered to: Results in each section are presented first for behaviour states (‘alert’, ‘agonistic’, etc.), then for the behaviour event (‘occurrence of headshakes’), and finally for postures (‘prone’, ‘up’).

In each of these ‘packages’, results on predominance of categories (i.e., which category was shown by most penguins most of the time) are presented first, followed by an overview on differences between periods and/or rows. Subsequently, more detailed results on differences between groups (before human visitation), and differences between regimes (during and after visitation) are mentioned. The ‘package’ closes with a description of effects of the switch in visiting regime – or their absence (groups B and C only).

Im Dokument Impact of Human and Other Disturbance on Behaviour and Heart Rate of Incubating Adélie Penguins (Pygoscelis adeliae) (Seite 180-184)