Department of Anatomy, University of Otago, Dunedin, New Zealand.
PLoS One. 2012;7(7):e41969. doi: 10.1371/journal.pone.0041969. Epub 2012 Jul 23.
Commercial viewing and swimming with dusky dolphins (Lagenorhynchus obscurus) near Kaikoura, New Zealand began in the late 1980s and researchers have previously described changes in vocalisation, aerial behaviour, and group spacing in the presence of vessels. This study was conducted to assess the current effects that tourism has on the activity budget of dusky dolphins to provide wildlife managers with information for current decision-making and facilitate development of quantitative criteria for management of this industry in the future.
METHODOLOGY/PRINCIPAL FINDINGS: First-order time discrete Markov chain models were used to assess changes in the behavioural state of dusky dolphin pods targeted by tour vessels. Log-linear analysis was conducted on behavioural state transitions to determine whether the likelihood of dolphins moving from one behavioural state to another changed based on natural and anthropogenic factors. The best-fitting model determined by Akaike Information Criteria values included season, time of day, and vessel presence within 300 m. Interactions with vessels reduced the proportion of time dolphins spent resting in spring and summer and increased time spent milling in all seasons except autumn. Dolphins spent more time socialising in spring and summer, when conception occurs and calves are born, and the proportion of time spent resting was highest in summer. Resting decreased and traveling increased in the afternoon.
CONCLUSIONS/SIGNIFICANCE: Responses to tour vessel traffic are similar to those described for dusky dolphins elsewhere. Disturbance linked to vessels may interrupt social interactions, carry energetic costs, or otherwise affect individual fitness. Research is needed to determine if increased milling is a result of acoustic masking of communication due to vessel noise, and to establish levels at which changes to behavioural budgets of dusky dolphins are likely to cause long-term harm. Threshold values from these studies would allow managers to set appropriate operational conditions based on quantifiable criteria.
在新西兰凯库拉，观赏和与暗色斑纹海豚（Lagenorhynchus obscurus）一起游泳的商业活动始于 20 世纪 80 年代末，研究人员此前曾描述过船只存在时海豚发声、空中行为和群体间距的变化。本研究旨在评估旅游业目前对暗色斑纹海豚活动预算的影响，为野生动物管理人员提供当前决策的信息，并为未来该行业管理的量化标准的制定提供便利。
方法/主要发现：使用一阶时间离散马尔可夫链模型评估了旅游船只目标的暗色斑纹海豚群体的行为状态变化。对行为状态转移进行对数线性分析，以确定海豚从一种行为状态转移到另一种行为状态的可能性是否取决于自然和人为因素。由 Akaike 信息准则值确定的最佳拟合模型包括季节、一天中的时间和 300 米范围内的船只存在。与船只的相互作用减少了海豚在春季和夏季休息的时间比例，而在除秋季以外的所有季节中增加了闲逛的时间。海豚在春季和夏季（受孕和幼崽出生的季节）更多地进行社交活动，在夏季休息时间最长。下午休息时间减少，旅行时间增加。
结论/意义：对旅游船只交通的反应与其他地方描述的暗色斑纹海豚的反应相似。与船只相关的干扰可能会打断社交互动，带来能量成本，或以其他方式影响个体的适应能力。需要进行研究以确定增加的闲逛是否是由于船只噪音对通信的声学掩蔽所致，以及确定暗色斑纹海豚行为预算变化可能导致长期伤害的水平。这些研究的阈值值将允许管理人员根据可量化的标准设置适当的操作条件。
