Tourism affects the behavioural budget of the common dolphin Delphinus sp. in the Hauraki Gulf, New Zealand

Abstract

Common dolphins Delphinus sp. are frequently targeted by tourism operations in New Zealand waters, yet there is a paucity of data on potential impacts faced by this species. Transition matrix models, used widely in population ecology, have recently been applied to behavioural transitions in order to provide successful management guidelines. We detail the use of Markov chain models to assess the impact of tourism activities on the behavioural state of common dolphins in the Hauraki Gulf, New Zealand. First-order time discrete Markov chain models were used to describe transition probabilities in both control and impact scenarios. The effect of boat interactions was quantified by comparing transition probabilities of both control and impact chains. Foraging and resting bouts were significantly disrupted by boat interactions to a level that raises concern about the sustainability of this impact. Both the duration of bouts and the overall time spent in these 2 behavioural states decreased. Foraging dolphins took significantly longer to return to their initial behavioural state in the presence of the tour boat. There was also an increased preference to shift behaviour to socialising or milling after tour boat interactions. Impacts identified in the present study are similar to those previously reported for bottlenose dolphins, a coastal species typically considered to be more susceptible to cumulative anthropogenic impacts.

Distance does matter: close approaches by boats impede feeding and resting behaviour of Indo-Pacific bottlenose dolphins

“…Accordingly, management strategies can be modified depending on the habitat scale of the targeted animals, for example, resident versus non-resident populations, and/or the intensity of interactions with vessels (see e.g. Bejder et al 2006b;Stockin et al 2008).…”

Marine vessels alter the behaviour of bottlenose dolphins Tursiops truncatus in the Istanbul Strait, Turkey

“…Recorded behavioural states were identified as travelling, diving, surface-feeding, milling, resting, or socialising (Table 2). Previous studies combined diving and surface-feeding behaviour under either a diving or foraging state (Neumann 2001, Lusseau, 2003, Constantine et al 2004, Stockin et al 2008, Meissner et al 2015. However, due to the uncertainty of determining if dolphins were actually foraging during the diving state, we separated these 2 behavioural states into diving and surface-feeding (Table 1).…”

“…Definition of each behavioural state (Lusseau 2003, Constantine et al 2004, Christiansen et al 2010 the behavioural states to be assessed (Lusseau 2003, Stockin et al 2008. Therefore, the preceding and following behavioural states were recorded for control and impact situations in order to create the transition probability matrix for the Markov chains.…”

“…Dusky dolphins Lagenorhynchus obscurus (Barr & Slooten 1999, Dans et al 2008, common dolphins Delphinus delphis (Stockin et al 2008, Meissner et al 2015, Indo-Pacific humpback dolphins Sousa chinensis (Van Parijs & Corkeron 2001), sperm whales Physeter macrocephalus (Gordon et al 1992), minke whales Balaenoptera acutorostrata (Christiansen et al 2013), Hector's dolphins Cephalorhynchus hectori (Bejder et al 1999) and bottlenose dolphins (Nowacek et al 2001, Hastie et al 2003, Lusseau 2004, Christiansen et al 2010, Pirotta et al 2015, Perez-Jorge et al 2017, have demonstrated both short-and longterm behavioural changes in response to marine vessels within a wide range of ecological settings. Such changes can take on various forms, with the most frequent being variations in vocalization, an increase in dive intervals, both vertical and horizontal avoidance behaviour, an increase in swimming speed, and a decrease in foraging and resting behaviour (Lusseau 2004, Stockin et al 2008, Christiansen et al 2010, 2013, Meissner et al 2015. By contrast, cases exist whereby habituation may be particularly advantageous to the population as a whole.…”

“…Various authors (e.g. Saulitis et al 2000, Lusseau 2003, Stockin et al 2008, Christiansen et al 2010, Meissner et al 2015 have utilized behavioural budgets via the creation of Markov chains as a tool to assess disturbances in various cetacean populations, with particular focus on marine vessel pressure. However, it is important to keep in mind that studying the effect of marine traffic can involve some limitations, given that cetaceans spend most of their time underwater and some of their behavioural reactions might be elusive to the observer (New et al 2014, Pirotta et al 2015.…”