Figure 1.
Location of the Bay of Plenty (BOP) and other places referred to in the text in relation to the North and South Island of New Zealand.
Table 1.
Definitions of behavioural states of common dolphin groups in the Bay of Plenty, New Zealand modelled on Neumannn [63] and Stockin et al. [9].
Table 2.
Different approaches of Markov chain analysis.
Table 3.
Number and duration (mean and range in min) of sequences and number of behavioural transitions during control scenarios (presence of the research vessel only) and during interaction scenarios (when in the presence of other vessels).
Figure 2.
Effect of vessel interactions on the behavioural budget of common dolphins in the Bay of Plenty.
Proportion of time spent in each behavioural state in the presence and absence of interacting vessels. Error bars represent 95% confidence intervals. Significant differences (p<0.05) between control (solid or striped black bars) and interaction scenarios (light and dark grey bars) are denoted by an (*). Results are shown following the conservative and less conservative approaches. Note: FOR = foraging, MIL = milling, TRA = travelling.
Figure 3.
Effect of vessel presence on transitions between behavioural states of common dolphins, based on differences in transition probabilities(pij(interaction)-pij(control)).
A negative value means that the behavioural transition of the control chain is superior to that of the interaction chain. The graph is composed of three parts, one for each preceding state, separated by vertical lines. In each part, bars correspond to succeeding behavioural states (see legend). Transitions with a significant difference (p<0.05) are marked by an (*). Results shown after following the conservative approach (c) and the less conservative approach (lc). Note: FOR = foraging, MIL = milling, TRA = travelling.
Table 4.
Probability of being in a particular behavioural state (πj), number of 3min time units (E(Tj)) and amount of time (min) required to return to initial behavioural states during control scenarios (presence of the research vessel only) and during interaction scenarios (when in the presence of other vessels).
Table 5.
Average bout length ( ) during control (presence of the research vessel only) and interaction scenarios (presence of other vessels).
Figure 4.
Effect of vessel traffic intensity on dolphin behaviour.
a) P-values of the difference between the cumulative behavioural budget and the control behavioural budget for common dolphin activity. The proportion of time dolphins spent with interacting vessels was artificially varied from 0 to 100%. Each curve corresponds to different behavioural states (FOR = foraging, MIL = milling, TRA = travelling). The horizontal dashed line represents the statistical level of significance (p<0.05) b) Vessel traffic intensity throughout the study period (November 2010 to April 2013). The horizontal dashed lines represent 34.0 and 56.0% of traffic intensity above which the cumulative foraging and travelling behaviours, respectively, are significantly affected. The vertical lines separate the tourism and non-tourism seasons.