Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Has files: YesSubject: search.filters.subject.Dolphin behaviour

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    The behaviour and ecology of short-beaked common dolphins (Delphinus delphis) along the east coast of Coromandel Peninsula, North Island, New Zealand : with a note on their interactions with humans : a dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Marine Science at Massey University
    (Massey University, 2001) Neumann, Dirk R.
    This thesis provides new insights into the behavioural ecology of free-ranging short-beaked common dolphins (Delphinus delphis), in New Zealand. A preliminary assessment of common dolphin-human interactions was also carried out as part of this 3-yr field study (1998-2001). 166 surveys were conducted in the greater Mercury Bay area, on the east coast of Coromandel Peninsula, North Island, New Zealand. These led to 105 focal group follows, with a total of 118.2 h spent following common dolphins. Seasonal movements of common dolphins were uncovered, and are apparently tied to fluctuations in sea surface temperature. Common dolphins appear to live in a fission-fusion society. Groups frequently merged and split again. The merging of groups was often accompanied by either sexual, or feeding activity. 408 individual dolphins were identified from photographs of their dorsal fins. No evidence of long-term associations between individuals was found. Resightings of identifiable dolphins indicate movement of individuals between Mercury Bay and the Hauraki Gulf, as well as between Mercury Bay and Whakatane. This study provides the first activity budget for common dolphins in the wild. Common dolphins spent 55.6% of their time traveling, 20.4% milling, 16.2% feeding, 7.1% socialising, and 0.7% resting. This proportion did not change significantly by season, or from year to year. Common dolphins were found to feed on at least six different fish species. A number of different feeding strategies were employed to capture these fish. Some of these techniques had previously been observed in bottlenose dolphins and orca, but have never before been described for common dolphins. The results of this study suggest that common dolphins can potentially be negatively affected by interactions with humans. Boat traffic appears to disturb some dolphin groups, especially those containing few individuals. However, commercial tourism appeared to have little impact on the dolphins, at this study site. Few attempts at swimming with common dolphins resulted in a sustained interaction, but unsuccessful attempts did not elicit an obvious negative response. Fishing poses the greatest threat of physical injury and possible mortality to common dolphins. Several key issues were identified, and their value in managing human-dolphin interactions is discussed.
  • Thumbnail Image
    Item
    Comparative socioecology of the dusky dolphin (Lagenorhynchus obscurus) in New Zealand : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Manawatu, New Zealand
    (Massey University, 2012) Markowitz, Wendy Jane
    Behaviour and social groupings of animals are often closely tied to habitat structure. Ecological factors (e.g., predation pressure, resource distribution) and social pressures profoundly influence behaviour and social organization. This study examined the socioecology of dusky dolphins (Lagenorhynchus obscurus) off Kaikoura, one of the most productive submarine canyon habitats in the world, supporting marine mammal populations and a thriving tourism industry. Behavioural data were collected during 332 dusky dolphin group follows from a small research vessel and onboard 174 dolphin tours during 2006-2009. Continuous and interval sampling were used to document behavioural states, behavioural events, and changes in group composition. Data from small groups (n=197) were compared with similar data collected from 67 small group encounters with Hector’s dolphins (Cephalorhynchus hectori) in the same habitat. In winter, dusky dolphins formed larger groups that ranged more widely and small groups that primarily rested during the day near shore. Although resting, small groups increased dispersion and swam in parallel formation in winter. In summer, dolphins formed small groups for calf-rearing, mating and resting. Groups with calves were the largest and most stable of these small groups, and were found closest to shore, in relatively shallow water, often near river mouths. In mating groups, rapid chases decreased intromission rates as competition among males increased. Sexual selection may favour traits improving male success in behavioural contests as well as sperm competition in this species. Apparent mechanisms for female choice included ‘escape’ strategies that prolonged chases. Hector’s dolphins formed smaller groups with higher fission-fusion rates, less cohesion, and fewer social bond reinforcement behaviours than dusky dolphins. Interactions with tour vessels had short-term effects on the behavioural state, heading, dispersion, and leaping rate of large dusky dolphin groups. Resting was disrupted during tour interactions and dolphins increased travel away from approaching tour vessels following tour interactions. Assertive approach methods reduced the duration of swimmer-dolphin interactions, particularly in summer when dolphins may be sensitised to high levels of tourism. These large-brained, highly social mammals form intricate societies that are responsive to changes in habitat, predation pressure and resource distribution. Understanding these responses is vital for protection of dolphins in the wild.
  • Thumbnail Image
    Item
    Responses of South Island Hector's dolphins (Cephalorhynchus hectori hectori) to vessel activity (including tourism operations) in Akaroa Harbour, Banks Peninsula, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Marine Biology at Massey University, Auckland, New Zealand
    (Massey University, 2010) Martinez, Emmanuelle; Martinez, Emmanuelle
    For over 25 years, tour operators have been undertaking view and swim-with-dolphin trips in Akaroa Harbour off Banks Peninsula, east coast South Island, New Zealand. Following the international exponential growth in the commercial dolphin-based tourism industry, Akaroa Harbour is now a key eco-tourism destination in New Zealand with 32 daily permitted trips targeting Hector’s dolphin (Cephalorhynchus hectori hectori). Such a high number of trips is of particular concern given that this species is not only endemic but also endangered. Our current understanding of the effects of tourism activities on Hector’s dolphins in Akaroa Harbour is far from satisfactory. To ensure the sustainability of the economically-important and rapidlygrowing dolphin-based tourism industry, there is an urgent need for sound scientific evidence on which to base management decisions. One of the challenging issues with the assessment of tourism impacts is the lack of baseline data. Prior to beginning the evaluation of the effects of disturbance on this population, data relating to the occurrence and demographics of Hector’s dolphins, as well as vessel traffic in Akaroa Harbour, were collected from land-based platforms during three consecutive austral summers (November and March), commencing in 2005. Examination of Sighting Per Unit Effort (here number of dolphin sightings per hour) and the dolphin fine-scale spatial distribution confirmed an inshore-offshore migration and, in the case of the latter, higher density patterns between the Kaik hills and the harbour entrance. However, no specific area was associated with a particular behaviour or nursery groups. The majority of groups consisted of adults only (91.2%, n = 2,000) and comprised mainly 2-5 individuals (83.2%). Group size varied with behaviour, being larger when socialising. Activity budgets within two outer bays were very comparable to Akaroa Harbour, except for socialising. In the harbour, Hector’s dolphins only spent a small proportion (14%) of their day (0600-1800 hr) in the absence of vessels. Vessel traffic in the harbour consisted mainly of recreational vessels (72.9%) although commercial vessels represented 70.4% of observed encounters and interacted twice as long with the dolphins. No displacement was evident and as a result, Hector’s dolphins might compensate for high vessel traffic levels by adjusting their behavioural budget. To determine the effects of tourism activities on Hector’s dolphins’ behavioural budget, focal-group follows using a scan sample methodology were conducted from land-based stations and analysed using Markov chain models (n = 330 sequences). Vessel presence affected the activity budget of Hector’s dolphins by changing transition probabilities, bout durations and the time taken to return to a behavioural state once disrupted. Both diving (inferred foraging) and travelling were significantly disrupted by vessel interactions. The addition of one of more vessels during an encounter further disrupted diving. Responses of Hector’s dolphins to swim attempts were assessed from commercial tourism vessel trips (n = 420). The method of approach and swimmer placement affected the dolphins’ behaviour, with a reduction in avoidance when regulations were adhered to, i.e. using line abreast and around methods. Dolphin responses to swim encounters were also correlated with the number of successive attempts, dolphin group size and initial behaviour. Although Hector’s dolphins appear to be more tolerant of the presence of swimmers over time, some level of sensitisation to seasonally high levels of vessel interactions was also detected. The effects of swim encounters could potentially be exacerbated by the use of stones as an auditory stimulant. Specifically, swimmers who used stones had a greater probability of close and sustained approaches by dolphins than those who sang or simply floated on the surface of the water. Based on opportunistic photo-identification surveys (n = 254), 46% and 44% of the 50 identifiable individuals were infrequently and occasionally recorded interacting with commercial tourism vessels, respectively. It was also estimated that individuals using Akaroa Harbour are exposed to the highest level of cetacean-based tourism in New Zealand. This implies that dolphins that are frequent users of the harbour are likely to be more exposed to intensive tourism pressure. The high resighting rate of some individuals further suggests that frequent users are unlikely to discontinue using the harbour, even though they face increased human disturbance. Data presented here reveal the nature and the susceptibility of Hector’s dolphins to tourism activities, warranting the continuation of a moratorium on new permits. Furthermore, a reduction in daily trip numbers should be considered. Ongoing monitoring of this population’s response to tourism activities, combined with an integrated and adaptive approach to management, gives the best chance of ensuring the sustainability of the industry.
  • Thumbnail Image
    Item
    Dynamics of mother-offspring common dolphins (Delphinus sp.) engaged in foraging activities in the Hauraki Gulf, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology, Massey University, Auckland, New Zealand
    (Massey University, 2010) De La Brosse, Nicolas
    This study investigated the dynamic of mother-offspring common dolphins (Delphinus sp.) engaged in foraging activities in the Hauraki Gulf, New Zealand. While previous studies have demonstrated the importance of Hauraki Gulf waters for feeding and nursing common dolphins, no previous study has systematically assessed the dynamics of mother-offspring pairs engaged in foraging activities. During 228 hr of survey time, a total of 49 independent focal groups were recorded between March and July 2009. All observations were conducted from the surface using the platform of opportunity, Dolphin Explorer, a 20 m tour boat. Variables examined included group size, composition, offspring presence, predominant behavioural state, foraging strategies employed, associated species, mother-offspring relationship, and location of offspring within groups. This study tested the hypothesis that foraging strategies employed by mother-offspring pairs would be influenced by environmental and anthropogenic parameters, group size, and associated species. It also examined the influence of associated species and foraging strategies on the mother-offspring dynamic within focal groups. Sighting Per Unit Effort (SPUE) and Offspring Per Unit Effort (OPUE) varied by month, with SPUE and OPUE being highest in March and July, respectively. Mother-offspring pairs predominantly engaged in cooperative foraging strategies (97%), and were less likely to engage in individual strategies. Cooperative feeding groups likely provide better protection to young and vulnerable dolphins, as well as a more prolific food supply to lactating females and their offspring. Water depth, sea surface temperature and group size had no influence on foraging strategies employed by mother-offspring pairs. Groups comprising immature dolphins typically altered their behaviour more frequently in presence of vessels, with presumed mothers keeping their offspring away from boats in 80% of encounters. However, a limited sample size likely impeded the statistical significance of this observation. Behavioural changes and potential vessel avoidance during foraging activity may occur as a response of perceived threat. Cooperative foraging strategies employed by focal groups had no significant influence on the location of the young. Offspring were observed in echelon position during 93.6% of the time dolphins foraged, and were never separated from their assumed mother during individual foraging strategies. Echelon position may enhance better predatory protection, as well as learning during foraging activities. Mother-offspring pairs were observed in association with Australasian gannets (Morus serrator) and Bryde’s whales (Balaenoptera brydei) during 68.4% and 8.4% of encounters, respectively. Prevalence of dolphin cooperative feeding is likely to attract and benefit associated species. While neither species were found to affect the foraging strategies employed by mother-offspring pairs, diving gannets did affect the position of motheroffspring pairs within feeding groups, with offspring typically located on the peripheral edge of the focal group. Conversely, no such affect was detected for associated feeding involving Bryde’s whales. Since mothers permit offspring in the centre of mono-specific feeding groups, it seems plausible that the use of peripheral regions maybe associated with the presence of mixed-species feeding aggregations. This apparent shift in mother-offspring position is unexplained, although may represent perceived risk by the assumed mother. Results presented here extend our knowledge of foraging behaviour and mother-offspring common dolphin dynamics in the Hauraki Gulf, New Zealand.