Bottlenose dolphins are found in most of the World’s coastal areas.
Of the dolphins, only killer whales (which really are dolphins) have a wider distribution. While bottlenose dolphins can been seen off any New Zealand coast, they are most frequently seen in the Bay of Islands, the Hauraki Gulf, Tasman Bay, Golden Bay and Fiordland.
- The Trust sponsors a long-term research programme on Fiordland bottlenose dolphins
- The Doubtful Sound population has declined substantially since the study began in 1990
- Calf survival is lower than in any other bottlenose dolphin population, including bottlenose dolphins in captivity
- Potential causes for the very low calf survival include tourism, direct and indirect effects of freshwater input from the Manapouri Power Station, and the long-term, ecological effects of fishing
- Small dolphin protection zones provide some protection from tourism
- Tourism guidelines are currently voluntary
- The ecological impacts of the power station could be reduced by releasing smaller amounts of cold freshwater into Doubtful Sound in winter and early spring
New Zealand’s bottlenose dolphins, particularly those in the far south, are among the largest bottlenoses in the world, reaching almost four metres in length, and weighing as much as a medium-sized horse. They are stocky – which is typical of cold water populations.
Bottlenose dolphins reach sexual maturity between 7 and 12 years old. Mature females give birth to a single calf every 2-4 years. Maximum lifespan is at least 40 years. In Fiordland, births are highly seasonal – restricted to spring and summer. The timing of births is really important. Our latest research has shown that calves born early or late in the calving season have a much lower chance of survival. Calves are totally dependent on their mothers for the first six months, and become progressively independent over the next two years.
In Doubtful Sound, our studies have shown that the resident dolphins have a much more stable society than elsewhere. Ties within the group are strong and long-lasting. This is unusual among dolphins, which, except for mothers and calves, typically have more casual social ties. Strong bonds in this community may be due to the habitat. Fiordland is almost as far South as bottlenose dolphins go. It may be that these dolphins need to co-operate more to survive near the limit of their distribution.
It is clear that the cold of Fiordand is an important factor in where the dolphins go. In the coldest months, the dolphins avoid the extremely cold inner regions of the fiord. By contrast, in summer they favour the inner regions, which at that time are warmer.
Bottlenose dolphins are incredibly adaptable. Ultimately, that’s why they are so widely distributed – they can modify their behaviour to adapt to almost any circumstance. Whether it is herding fish against the side of a boat, or beating their tail against a muddy bottom to create a visual barrier, these dolphins are capable of extraordinary co-operation to catch elusive prey.
New Zealand Whale and Dolphin Trust sponsorship has been instrumental in continuing a long-term research programme on the Doubtful Sound dolphins. For over 20 years, researchers have studied their habitat use, ecology, behaviour and population trends and the impact of tourism. This long-term study that has uncovered some uncomfortable facts.
Our most important work showed that this population has been in serious decline. The Doubtful Sound population gradually declined from 69 in 1994 to 56 in 2006. The decline was due to a sudden change in calf survival, which halved in 2002 and has stayed low. Calf survival in this population is the lowest of any bottlenose dolphin population. Lower even than calf survival in captivity.
Potential reasons for the extremely low level of calf survival include tourism, ecological impacts of long-term fishing within the fiords and ecological and/or direct impacts of freshwater discharge from the Manapouri power station.
The unique beauty of Fiordland supports a lucrative tourism industry. The dolphins, of course, are a key attraction. Even though the levels of tour boat activity are relatively low, in Doubtful Sound these activities can have clear impacts on the dolphins’ behaviour. While juveniles are often attracted to the boats, the adults, especially females with calves, usually avoid them. Mothers and calves usually avoid boats by “slinking” along the fiord walls or diving for longer. These reactions are most obvious when skippers ignore the rules imposed by the Marine Mammal Protection Regulations, approaching at speed, or head-on. Thankfully, skipper behaviour has improved, and the companies now follow a code of practice designed to reduce impacts.
A local power station takes water from Lake Manapouri, runs it through hydro-electric turbines and then disposes of the water into Doubtful Sound. The height difference between the lake and the fiord makes this a very efficient power station. The problem is, the water can be much colder than the ambient temperature of Doubtful Sound, especially in winter and spring. This is an important time for the local dolphin population. The females go through the final stages of pregnancy in winter and give birth in spring. The young calves have to keep their own bodies warm for the first time, and are at their physiological limits. Cooler water temperatures at this time are a challenge. Add to that potential stress from approaches from tour boats and the relatively low food availability in the fiords, which are still recovering from the impact of past intense fishing pressures. We are not yet sure which of these human impacts are most critical and how the combined effect of several human activities affects the dolphins. This is the focus of our continued research.
Research funded by the NZ Whale and Dolphin Trust has been crucial in the development of the current protection measures. Our research has raised the profile of these dolphins’ conservation problems, both nationally and internationally, to help them get the protection they need.
Dolphin Protection Zones have recently been created, in areas that our research showed to be most frequently used by the dolphins. These are a step in the right direction. The protection zones extend 200m from the shoreline, in the areas indicated in red on the map below. Boats are allowed to enter these areas for fishing, diving, anchoring etc. Voluntary guidelines request that boats travel at a slower speed (5 knots) than elsewhere in the fiord, and do not enter Dolphin Protection Zones if dolphins are seen.
Protection of the Doubtful Sound dolphins could be improved by further reducing the effects of tourism and other human impacts. For example, by increasing the size of the Dolphin Protection Zones and turning the voluntary guidelines into regulations. The amount of freshwater input into Doubtful Sound could be reduced, especially in late winter and early spring which are critical times for dolphins in the final stages of pregnancy and newborn calves. Young calves are especially vulnerable to human impact. We are interested in determining how effective these measures are.
Bennington S., Rayment, W. and Dawson, S. In press. Putting prey into the picture: adding prey data dramatically improves species distribution models for bottlenose dolphins in Doubtful Sound, New Zealand. Marine Ecology Progress Series.
Bennington, S., Rayment, W., Currey, R., Oldridge L., Henderson, S., Guerra, M., Brough, T., Johnston, D., Corne, C., Johnson, D., Slooten, E. and Dawson, S.M. 2020. Long-term stability in core habitat of an endangered population of bottlenose dolphins (Tursiops truncatus): implications for spatial management. Aquatic Conservation: Marine and Freshwater Ecosystems, 1–12. http://doi.org/10.1002/aqc.3460.
Johnston, D. R., Rayment, W. J., Slooten, E., & Dawson, S. (2017). A time-based method for defining associations using photo-identification. Behaviour. http://doi.org/10.1163/1568539x-00003455
Guerra, M., & Dawson, S. (2016). Boat-based tourism and bottlenose dolphins in Doubtful Sound, New Zealand: The role of management in decreasing dolphin-boat interactions. Tourism Management, 57(C), 3–9. http://doi.org/10.1016/j.tourman.2016.05.010
Brough, T. E., Henderson, S., Guerra, M., & Dawson, S. (2016). Factors influencing heterogeneity in female reproductive success in a Critically Endangered population of bottlenose dolphins. Endangered Species Research, 29(3), 255–270. http://doi.org/10.3354/esr00715
Brough, T.E., Guerra, M.G. and Dawson, S.M. 2015. Photo-identification of bottlenose dolphins in the far south of New Zealand indicates a “new”, previously unstudied, population. New Zealand Journal of Marine and Freshwater Research 49: 150-158.
Pirotta, E., New, L., Harwood, J. and Lusseau, D. 2014. Activities, motivations and disturbance: An agent-based model of bottlenose dolphin behavioral dynamics and interactions with tourism in Doubtful Sound, New Zealand. Ecological Modelling 282: 44-58.
Guerra, M., Dawson, S., Brough, T. E., & Rayment, W. J. (2014). Effects of boats on the surface and acoustic behaviour of an endangered population of bottlenose dolphins. Endangered Species Research, 24(3), 221–236. http://doi.org/10.3354/esr00598
Henderson, S.D., Dawson, S.M., Currey, R.J.C., Lusseau, D. and Schneider, K. 2014. Reproduction, birth seasonality and calf survival of bottlenose dolphins in Doubtful Sound, New Zealand. Marine Mammal Science 30(3): 1067-1080.
Henderson, S.D., Dawson, S.M., Rayment, W.J. and Currey, R.J.C. Missing in action? Are the resident dolphins of Doubtful Sound becoming less resident? Endangered Species Research 20(2): 99-107. 2013.
Elliott, R.G. Dawson, S.M. and Henderson, S.D. 2011. Acoustic monitoring of habitat use by bottlenose dolphins in Doubtful Sound, New Zealand. New Zealand Journal Marine and Freshwater Research 45(4): 637-639. 2011.
Currey, R.J.C., Dawson, S.M., Schneider, K., Lusseau, D., Boisseau, O.J., Haase, P. Slooten, E. 2011. Inferring trends and causal factors for a declining population of bottlenose dolphins via temporal symmetry capture-recapture modelling. Marine Mammal Science 27(3): 554-566.
Elliott, R.G., Dawson, S.M. and Rayment, W. J. 2011. Optimising T-POD settings and testing range of detection for bottlenose dolphins of Doubtful Sound, New Zealand. Journal of the Marine Biological Association, UK. 92: 1901-1907. 2011.
Rowe, L.E., Currey, J.C., Dawson, S.M. and Johnson, D. 2010. Comparative assessment of epidermal condition and calf size of Fiordland bottlenose dolphin populations using dorsal fin photographs and photogrammetry. Endangered Species Research. 11: 83-89.
Currey, R.J.C., Dawson, S.M. and Slooten, E. 2009. Conducting a regional threat assessment under IUCN Red List criteria: the Fiordland bottlenose dolphins are critically endangered. Biological Conservation 142: 1570-1579.
Rowe, L.E. and Dawson, S.M. 2009. Determining the gender of bottlenose dolphins (Tursiops sp.) using dorsal fin photographs. Marine Mammal Science 25(1): 19-34.
Currey, RJ.C., Dawson, S.M., Slooten, E., Lusseau, D.L., Boisseau, O., Schneider, K. Haase, P., and Williams, J.A. 2009. Survival rates for a declining population of bottlenose dolphins in Doubtful Sound, New Zealand: an information theoretic approach to assessing the role of human impacts. Aquatic Conservation 19: 658-670.
Currey, R.J.C., Rowe, L.E., Dawson, S.M., Slooten, E. 2008. Abundance and demography of bottlenose dolphins in Dusky Sound, New Zealand, inferred from dorsal fin photographs. New Zealand Journal of Marine and Freshwater Research 42: 439-449.
Rowe, L. E. and Dawson, S.M. 2008. Sexual dimorphism in dorsal fin size in a population of bottlenose dolphins from Fiordland, New Zealand. Australian Journal of Zoology 56: 239-248.
Currey, R.J.C., Dawson, S.M. and Slooten, E. 2007. New abundance estimates suggest Doubtful Sound bottlenose dolphins are declining. Pacific Conservation Biology. 13: 265-273.
Lusseau D. 2007. Why are male social relationships complex in the Doubtful Sound bottlenose dolphin population? PLoS ONE 2(4): e348. doi 10.1371/journal.pone.0000348
Lusseau D. 2007. Evidence for social role in a dolphin social network. Evolutionary Ecology 21(3): 357-366.
Higham, J. and Lusseau, D. 2007. Defining critical habitats: the spatio-ecological approach to managing tourism–wildlife interactions. Critical Issues in Ecotourism. (book) pp. 274-287.
Lusseau, D. 2006. The short‐term behavioral reactions of bottlenose dolphins to interactions with boats in Doubtful Sound, New Zealand. Marine Mammal Science 22(4): 802-818.
Lusseau, D. 2006. Why do dolphins jump? Interpreting the behavioural repertoire of bottlenose dolphins (Tursiops sp.) in Doubtful Sound, New Zealand. Behavioural Processes 73 (3) 257-265.
Maersk-Lusseau, S, and Wing, S. R. 2006. Importance of pelagic subsidies versus local production to the diet of a closed population of bottlenose dolphins (Tursiops sp.). Marine Ecology Progress Series 321: 283-293.
Lusseau D., Slooten E. & Currey R.J. 2006. Unsustainable dolphin watching activities in Fiordland, New Zealand. Tourism in Marine Environments 3(2): 173-178.
Boisseau. O. 2005. Quantifying the acoustic repertoire of a population: The vocalizations of free-ranging bottlenose dolphins in Fiordland, New Zealand. Journal of the Acoustical Society of America 117: 2318-2329
Lusseau D. 2005. The residency pattern of bottlenose dolphins (Tursiops sp.) in Milford Sound, New Zealand, is related to boat traffic. Marine Ecology Progress Series 295: 265-272.
Lusseau, D. 2005. The state of the scenic cruise industry in Doubtful Sound in relation to a key natural resource: bottlenose dolphins. Nature-based tourism in peripheral areas: Development or disaster. (book) pp. 246-262
Lusseau D. 2004. The hidden cost of tourism: Effects of interactions with tour boats on the behavioural budget of two populations of bottlenose dolphins in Fiordland, New Zealand. Ecology and Society 9(1): part. 2
Lusseau D and Newman M. 2004. Identifying the role that animals play in their social networks. Proceedings of the Royal Society of London. Series B 271: S477-481.
Higham J.E.S. & Lusseau D. 2004. Ecological impacts and management of tourist engagements with marine mammals. In: Environmental Impacts of Ecotourism (R. Buckley ed.), pp. 173-188. CAB International Publishing: Wallingford.
Lusseau D. 2003. The emergent properties of a dolphin social network. Proceedings of the Royal Society of London B 270 S1: S186-S188.
Lusseau, D., Schneider, K., Boisseau, O.J., Haase, P., Slooten, E. & Dawson, S.M. 2003. The bottlenose dolphin community of Doubtful Sound features a large proportion of long-lasting associations. Can geographic isolation explain this unique trait? Behavioral Ecology and Sociobiology 54(4): 396-405.
Lusseau D. & Higham J.E.S. 2003. Managing the impacts of dolphin-based tourism through the definition of critical habitats: the case of Doubtful Sound, New Zealand. Tourism Management 25(6): 657-667.
Lusseau, D. 2003. Effects of tour boats on the behavior of bottlenose dolphins: using Markov chains to model anthropogenic impacts. Conservation Biology 17(6): 1785-1793.
Lusseau D. 2003. Male and female bottlenose dolphins (Tursiops sp.) have different strategies to avoid interactions with tour boats in Doubtful Sound, New Zealand. Marine Ecology Progress Series 257: 267-274.
Lusseau, D and Slooten, E. 2002. Cetacean sightings off the Fiordland coastline. Science for Conservation 187. 42pp.
Chong, A.K. and Schneider, K. 2001. Two-medium photogrammetry for bottlenose dolphin studies. Photogrammetric engineering and remote sensing. 2001, Vol 67 (5): 621-628
Haase, P. and Schneider, K. 2001. Birth demographics of bottlenose dolphins, Tursiops truncatus, in Doubtful Sound, Fiordland, New Zealand – preliminary findings. New Zealand Journal Marine and Freshwater Research 35: 675-680
Brager, S. and Schneider, K. 1998. Near‐shore distribution and abundance of dolphins along the West Coast of the South Island, New Zealand, New Zealand Journal of Marine and Freshwater Research 32(1): 105-112.
Schneider, K., Baird, R.B., Dawson, S.M., Visser, I. and Childerhouse, S.J. 1998. Reactions of bottlenose dolphins to tagging attempts using a remotely-deployed suction-cup tag. Marine Mammal Science. 14(2): 316-324.
Williams, J.A., Dawson, S.M. and Slooten, E. 1993. Abundance and distribution of bottlenose dolphins (Tursiops truncatus) in Doubtful Sound, New Zealand. Canadian Journal of Zoology 71: 2080-2088.
Graduate Student Theses
Williams, Jami. 1992. Abundance and distribution of bottlenose dolphins in Doubtful Sound. MSc Thesis, University of Otago.
Schneider, Karsten. 1999. Behaviour and ecology of Bottlenose dolphins in Doubtful Sound. PhD Thesis, University of Otago.
Haase, Patti. 2000. Social organisation, behaviour and population parameters of bottlenose dolphins in Doubtful Sound, Fiordland. MSc Thesis, University of Otago.
Gormley, Andrew. 2002. Use of Mark-Recapture for Estimating the Abundance of Four Marine Mammal species in New Zealand. MSc Thesis, University of Otago.
Lusseau, David. 2003. The effects of tourism activities on bottlenose dolphins (Tursiops sp.) in Fiordland, New Zealand. PhD Thesis, University of Otago.
Mærsk-Lusseau, Susan. 2003. Diet of bottlenose dolphins in Doubtful Sound, New Zealand; Evidence from stable carbon and nitrogen isotope analysis. MSc Thesis, University of Otago.
Boisseau, Oliver. 2005. Acoustic behaviour of resident bottlenose dolphins in Fiordland, New Zealand. PhD Thesis, University of Otago.
Rowe, Lucy. 2008. Beyond identity: New information from identification photographs of bottlenose dolphins. MSc Thesis, University of Otago.
Currey, Rohan. 2008. Conservation biology of bottlenose dolphins in Fiordland. PhD Thesis, University of Otago.
Elliot, R. 2008. The T-POD: An innovative way to assess habitat use for the conservation of bottlenose dolphins in Doubtful Sound, Fiordland, New Zealand. Elliot, Riley. 2008. BSc hons Thesis, University of Otago.
Elliot, Riley. 2010. Passive acoustic monitoring of habitat use by bottlenose dolphins in Doubtful Sound. MSc Thesis, University of Otago.
Henderson, Shaun. 2013. Habitat use, reproduction and survival: a comparative study of bottlenose dolphins in Doubtful Sound and Dusky Sound. PhD Thesis, University of Otago.
Brough, Tom. 2013. Using photography to study the conservation biology of bottlenose dolphins in southern New Zealand. MSc Thesis, University of Otago.
Guerra-Bobo, Marta. 2013. Effects of vessels on the surface and vocal behaviour of bottlenose dolphins in Doubtful Sound, New Zealand. MSc Thesis, University of Otago.
Johnston, David. 2017. Social aspects of demographic stochasticity in an endangered population of bottlenose dolphins (Tursiops truncatus). MSc Thesis, University of Otago.
Bennington, Stephanie. 2019. Habitat use of the bottlenose dolphins (Tursiops truncatus) of Fiordland: Where, why and the implications for management. MSc Thesis, University of Otago.