Sperm whale research expanding beyond Kaikōura

Steve Dawson and Liz Slooten, both Professors at Otago University, started the sperm whale research programme in Kaikōura in 1990. Since then, the NZ Whale and Dolphin Trust has supported research on population dynamics, behaviour, ecology, and response to anthropogenic and environmental impacts, as well as the development of new techniques to measure the body size of sperm whales.

Over the last few years, several postgraduate students, working along Dr Will Rayment as supervisor, have carried out research projects on sperm whales at Kaikōura. Funding and support from Whale Watch Kaikoura for a three-year project starting in 2015 enabled the research to be kick started after a pause in the programme, and has been ongoing since then. When the Kaikōura earthquake hit in 2016, our team was able to draw from the long-term monitoring data to carry out the first dedicated study on the impact of earthquakes on marine mammals.

In 2021, the team received funding in collaboration with the Centre of Research Excellence ‘Coastal People Southern Skies’ to continue research at Kaikōura and expand to new areas including the Otago canyons (just off the coast of Ōtepoti Dunedin) and offshore of Te Tai Tokerau Northland.

Further below are the summaries of the research projects and findings from the last few years, and the exciting next steps for our research.

But first, let’s take a look at the star of the show: the sperm whale (‘parāoa’ in Te Reo Māori).

Sperm whales – key facts about one of the most extraordinary marine creatures:

  • Animals of extremes: sperm whales are the largest of the odontocetes (toothed whales and dolphins), perform some of the deepest dives, produce the loudest biological sounds underwater, and have the largest nose in the animal kingdom, due to their highly specialised echolocation organ.
  • Deep dark dinner: sperm whales are deep-diving predators of mesopelagic ecosystems in the deep ocean. They feed on deep-water squid and fish, and hold an important ecological role as top predators. At the depths that sperm whales forage it is completely and utterly dark, so they can’t use their vision to find prey. Like all other odontocetes, sperm whales produce powerful clicking sounds to find prey and navigate their way around. When foraging, sperm whales produce echolocation clicks at a rate of about twice a second. We use these echolocation clicks to track the whales, by using a directional hydrophone.

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Photo: Tamlyn Somerford using a directional hydrophone to acoustically track whales.

  • Sperm whales are a taonga species, and hold great cultural significance for Māori. They are often associated with qualities of strength, endurance and chieftainship, and feature in many important stories and as tohu (signs) of the environment.
  • Who is who? Each whale has a unique combination of nicks and scallops in the trailing edge of their tail flukes. By taking photographs of the flukes when the whale dives, we can identify each individual. Each individual has a unique identifying code and nickname. We’ve known some individual whales for 30 years now!

Photos: sperm whales can be identified by the unique combination of nicks and notches on their flukes.

Sperm whales of Kaikōura:

  • Kaikōura is one of the few places in the world where sperm whales are found close to shore year-round
  • Only males visit Kaikōura, which is a productive foraging ground. Females live in warmer waters in tropical and subtropical latitudes.
  • The population of parāoa visiting Kaikōura has huge importance for the community, as it supports a thriving whale watching industry, and the whales are a key element of the local history and culture.
  • Sperm whales feed on deep-water squid and fish, foraging mostly at depths between 400 and 900 m. The hunt for prey in the water column, but also in proximity to the seafloor.
  • The diet, diving behaviour and distribution of sperm whales varies between summer and winter, due partly to a seasonal change in diet. Sperm whales target demersal fish more often in winter than summer.
  • The number of sperm whales visiting Kaikōura during spring and summer is declining. The causes remain unknown, but may be related to a change in their wider movements and distribution, possibly linked to changes in ocean conditions affecting the Kaikōura Canyon ecosystem
  • In New Zealand, sperm whales are classified as ‘Data Defficient’, while the globally designated conservation status of the species is ‘Vulnerable’

Current research

‘Parāoa of the South Pacific‘ is a new three-year project which started in November 2021. This project is part of the ‘Coastal People Southern Skies’ Centre of Research Excellence, which is funding the work and supporting the research team. We will assess how the health of the sperm whale population at Kaikōura is related to changing ocean conditions, and investigate the connectivity of sperm whales around Aotearoa and with Polynesia. We are extending our work to areas beyond Kaikōura, conducting surveys off the coasts of Otago and also off Northland, in collaboration with the Far Out Ocean Research Collective. We will look for individual movements among sampling locations using photo-identification and comparisons of acoustic dialects, as well as gene-flow, using state of the art sequencing and genotyping techniques on non-invasively gathered sloughed skin samples. In addition, our current perspective on parāoa is limited by being derived almost exclusively from investigations framed by western science, and by focusing almost entirely on a single region, Kaikōura. An essential part of the project will therefore be understanding historical and contemporary distribution and movements of sperm whale populations in a co-led process with hapū and tohunga parāoa, by interweaving mātauranga and Pacific traditional ecological knowledge with insights from this study. Our aim is to empower and learn from communities that have important relationships with parāoa, and therefore foster connectivity among coastal people in Aotearoa and neighbouring Pacific nations. This process will be driven by the desired outcomes for the respective and collective communities. We hope that the result will be an improved understanding of parāoa and the impacts they are facing, so that traditionally important connections may persist and thrive into the future.

Recent Projects

Impacts of the Kaikōura earthquake on sperm whales. In 2021, MSc student Stella Simpson carried out a research project to evaluate the ongoing effects of the 2016 Kaikōura earthquake on the whales, after previous research from our team (Guerra et al. 2020) suggested short-term changes in behaviour and distribution. Stella’s research used a multi-year data set that encompassed three years before and five years after the earthquake, with data on whale behaviour and diving locations. Analyses of diving behaviour showed that surface intervals were significantly longer during three years after the earthquake, suggesting decreased foraging efficiency. The location of high-use areas shifted to areas further down the canyon and further offshore, with a recovery to pre-earthquake distribution taking place only in winter. Overall, the study suggested partial recovery of sperm whales in response to the Kaikōura earthquake, and that recovery may still be ongoing.

Measuring sperm whales using drones. In 2020, Toby Dickson completed his MSc, which focused on estimating the size of sperm whales via aerial photogrammetry using unmanned aerial vehicles (UAVs, also known as drones) and on studying size structure of the population. The study was the first research to measure sperm whales using drones. Aerial photogrammetry was used to test and improve the accuracy of acoustic estimates of whale length, which are obtained from acoustic recordings of the whales’ echolocation clicks. The pulse structure of the clicks can be related to the size of the whale’s head, because clicks echoing inside the head are more spaced in time if the whale’s head is longer (amazing, isn’t it!?). Drones can measure the full length of the whales directly from full body images taken from above. By measuring lots of whales simultaneously through acoustic recordings and drones, we can get a very good equation to translate acoustically derived inter-pulse intervals of recorded clicks to full body length. Analysis of whale lengths over a period of 25 years (based on acoustic recordings) revealed a significant increase in mean length in whales during summer, suggesting an aging population with fewer new recruits.

A sperm whale as seen from above from a drone.

Foraging ecology of sperm whales at Kaikōura. In 2019, Marta Guerra completed her PhD, which focused on studying the food web and diet of sperm whales, their habitat use (where do they feed an why?) and the variability in whale abundance at Kaikōura in relation to changes in oceanographic conditions. Stable isotope analyses of whale skin (which is sloughed naturally and collected with a small net) were used as a tool that identifies the chemical composition of whales, which in turn reveal things about their diet, in a demonstration of “you are what you eat”. The results suggested that the whales change their diet seasonally, with demersal fish becoming a bigger part of the menu in winter than in summer, and pelagic squid being more predominant in summer than winter. Stable isotope analyses also showed that whales that were seen more frequently at Kaikōura had a particular local signature, and that the food web of the whales was mostly supported by pelagic phytoplankton rather than by coastal kelps. The whales foraged in different areas in summer than winter, with specific habitat features being important in each season: in summer, for example, whales looked for food in deeper areas where the seafloor slopes were steeper and the temperature gradients in the water column were stronger. Lastly, the decline in abundance of whales at Kaikōura may be related to climate change, with Marta’s research showing that when sea temperatures were higher and the cold currents flowing into the area were weaker, there were fewer whales visiting Kaikōura in summer.

Trends in population size and sociality of sperm whales. In 2018, Tamlyn Somerford completed her MSc on population dynamics at Kaikōura. Her research investigated improved methods for estimating the abundance of whales, to account for their comings and goings in and out of the Kaikōura area. The refined method showed that the decline in the number of whales visiting Kaikōura had persisted since it was last investigated in 2007, and that the trend was driven by a decline in numbers during summer but not winter. The number of This research was key for better understanding the potential causes of the decline. Tamlyn’s work also investigated social associations between male sperm whales, revealing that although males forage mostly on their own and are typically ‘solitary’, they have long-lasting bonds with other males, providing new insights into the social lives of sperm whales.

Research Papers

These articles can be found online (for example, through Google Scholar) or you can email us at info@whaledolphintrust.org for a pdf copy.

Guerra, M., Dawson, S.M., Somerford, T.R., Slooten, E. and Rayment, W.J. (2021) Fine‐scale habitat use of foraging sperm whales is driven by seafloor topography and water column structure. Marine Mammal Science.

Somerford, T., Dawson, S., Slooten, E., Guerra, M., Childerhouse, S., Richter, C., van der Linde, M., & Rayment, W. (2021). Long-term decline in abundance of male sperm whales visiting Kaikōoura, New Zealand. Marine Mammal Science.

Dickson, T., Rayment, W. and Dawson, S. (2021). Drone photogrammetry allows refinement of acoustically derived length estimation for male sperm whales. Marine Mammal Science, 37(3), pp.1150-1158.

Dickson, T., Rayment, W., Guerra, M. and Dawson, S., (2021) Multi-decadal observations of the size structure of sperm whales at Kaikōura, New Zealand. New Zealand Journal of Marine and Freshwater Research, pp.1-12.

Guerra, M., Wing, L., Dawson, S., & Rayment, W. (2020). Stable isotope analyses reveal seasonal and inter-individual variation in the foraging ecology of sperm whales. Marine Ecology Progress Series, 638, 207–219

Guerra, M., Dawson, S., Sabadel, A., Slooten, E., Somerford, T., Williams, R., Wing, L., & Rayment, W. (2020). Changes in habitat use by a deep-diving predator in response to a coastal earthquake. Deep Sea Research Part I: Oceanographic Research Papers, 158, 103226.

Guerra, M., Hickmott, L., van der Hoop, J., Rayment, W., Leunissen, E., Slooten, E., & Moore, M. (2017). Diverse foraging strategies by a marine top predator: sperm whales exploit pelagic and demersal habitats in the Kaikōura submarine canyon. Deep Sea Research Part I: Oceanographic Research Papers, 128, 98–108.

Miller, B.S., Growcott, A., Slooten, E. and Dawson, S.M., (2013). Acoustically derived growth rates of sperm whales (Physeter macrocephalus) in Kaikoura, New Zealand. The Journal of the Acoustical Society of America, 134(3), pp.2438-2445.

Miller, B., Dawson, S. and Vennell, R., (2013). Underwater behavior of sperm whales off Kaikoura, New Zealand, as revealed by a three-dimensional hydrophone array. The Journal of the Acoustical Society of America, 134(4), pp.2690-2700.

Growcott, A., Miller, B., Sirguey, B., Slooten, E. and Dawson, S.M. (2011) Measuring sperm whale body length from their clicks: the relationship between inter-pulse-intervals and photogrammetrically measured lengths. Journal of the Acoustical Society of America. 130: 568-573.

Richter, C., Dawson, S.M. and Slooten, E. (2006) Impacts of commercial whale-watching on male sperm whales at Kaikoura, New Zealand. Marine Mammal Science. 22: 46-63.

Douglas, L., Dawson, S.M. and Jaquet, N. (2005). Click rates and silences in sperm whales at Kaikoura, New Zealand. Journal of the Acoustical Society of America 118(1): 523-529.

Rhinelander, M.Q. and Dawson, S.M. (2004) Measuring sperm whales from their clicks: stability of inter-pulse intervals and validation that they indicate whale length. Journal of the Acoustical Society of America. 115(4): 1826-1831.

Letteval, E., Richter, C.F., Jaquet, N., Slooten, E., Dawson, S., Whitehead, H., Christal, J. and McCall Howard, P. (2002) Social structure and residence in aggregations of male sperm whales. Canadian Journal of Zoology. 80: 1189-1196.

Jacquet, N., Dawson, S.M., and Douglas, L. (2001) Vocal behaviour of male sperm whales: why do they click? Journal of the Acoustical Society of America. 109 (5): 2254-2259.

Jaquet, N., Dawson, S.M. and Slooten, E. (2000) Abundance, occupancy and seasonal distribution of male sperm whales off Kaikoura, New Zealand. Canadian Journal of Zoology. 78: 407-419.

Childerhouse SJ, Dawson SM, Slooten E (1996) Stability of fluke marks used in individual photoidentification of male sperm whales at Kaikoura, New Zealand. Marine Mammal Science 12:447-51.

Childerhouse SJ, Dawson SM, Slooten, E. (1995). Abundance and seasonal residence of sperm whales at Kaikoura, New Zealand. Canadian Journal of Zoology 73: 723-731.