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Journals 2003/2004

Elizabeth Gibbs
Thompson Middle School, Newport, Rhode Island

"Impact of human activities on dusky dolphin behavior and population biology"
Field Station, Kaikora, New Zealand
July 13 - 25, 2003

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Monday, July 14, 2003

I got up before sunrise (but not so early - it was 7:30) and went for a run in the beautiful morning light with clouds scattering the sky into oranges and yellows. Some fur seals were swimming, extending their pectoral flippers in the air. A man on the beach photographed them. The sun finally appeared at about 7:55. I terrified the cows as I ran through their pasture so that I had to stop and walk and talk soothingly to them.

After breakfast, Tim, Jenny, and Anita prepped us with basic information on the dolphins and on our research. Here are some of the things we learned.

Behavioral Ecology
Humans have the largest brain in comparison to their bodies, followed by dolphins, then chimpanzees. The sperm whale has the largest brain of all. Because big brains are metabolically "expensive," what are they for? What makes them worth all the energy input? It seems to be the formation of complex societies. But insects such as ants and bees may have complex societies and they don't have big brains. The difference is that insects are considered to be "hard-wired" for their social structures, while humans, dolphins, and chimps can adjust their behavior in sophisticated ways depending on the situation. For example, they may form alliances, or long-term relationships or shorter-term coalitions to accomplish goals. They may have dominance hierarchies in which social status becomes important. Or they may engage in cooperative foraging to get food.

Dusky Dolphins

  • They are small - adults grow to 1.7 meters and weigh 40 to 80 kilograms (88 to 176 pounds).
  • They are gregarious, sometimes associating in pods of 1000 or more.
  • They may move up to 40 kilometers (25 miles) a day or hundreds of kilometers per season.
  • They inhabit the waters of the continental shelf to the continental slope.
  • They are famous for leaping. This is probably often done to signal other dolphins.
  • They are found in the waters of New Zealand, South Africa, Peru, Argentina, and Chile.
  • Individuals are identified using photo identification of dorsal fins, looking for marks caused by play and bites from other dolphins.

In New Zealand, duskies inhabit the waters over the edge of a canyon over 1500 meters (4875 feet). In this location, there's a subtropical convergence zone where currents come together creating an upwelling of nutrient-rich water, which leads to excellent feeding. Here, the dolphins feed at night on lanternfish and squid, which come closer to the surface after dark. In the daytime, the dolphins rest, socialize, and mate in waters closer to shore. They are found in large groups of hundreds to thousands of animals.

Research objectives
The Earthwatch program's research objectives are to:

  1. Compare behavior in groups
  2. Record dolphin movements
  3. Estimate abundance. (There are thought to be tens of thousands of dusky dolphins in New Zealand)
  4. Identify association patterns, or groupings
  5. Determine human impacts, especially from dolphin swim boats
  6. Determine genetic relatedness and populations

We learned that aboard the Punua Aihe, we will be measuring environmental parameters as well. We'll use an anemometer to clock wind speed a compass for wind direction and, a refractometer to measure salinity, a thermometer for water temperature, and lower a secchi disk into the water to measure turbidity, or water clarity.


Kaikoura does good business from ecotourism, including dolphin swimming and whalewatch tours. About 20,000 people per year-as many as 100 a day-book dolphin swims with Dolphin Encounter. Direct revenue from both dolphin swims and whalewatching in 1999 was $28 million per year and indirect was estimated at $36 million per year. Ecotourism operations employ 330 local people full time and create about 50 new jobs a year. The Earthwatch project works cooperatively with the ecotourism businesses, providing research information to help make the tour operators ensure sustainable use of the resource. For example, research results that found that the dolphins rest more midday led to a decision by the tour operators to institute a three-hour midday break during the summer months. A three-boat limit has also been established for vessels viewing the marine mammals.

The tour boats also have allowed researchers to collect data aboard the tours themselves, learning that 90% of the dolphins viewed are in large pods, the boat is stationary 60 percent of the time during swims and the engine off 48 percent of the time. The average trip includes three "drops" of swimmers into the water and the average length of each drop is eight minutes.

Mating and young
Dusky dolphins mate all year, but the behavior is mainly for social, not reproductive reasons in the winter. Females are in estrus in the summer and calves are born in the summer. They form small groups of mothers and calves in the summer. These groups rest more and are more sensitive to disturbance by people. They have been found to have higher respiration rates and to swim more slowly. They leap less and stay closer to shore, probably because they are less likely to be attacked from depth. In these groups they can also defend against male harassment and prepare the calves for life in dolphin society.

Large groups of dolphins usually comprise smaller groups of individuals. In the summer, there may be hundreds of animals in a groups, while in the winter there may be thousands.

Seasonal migration and residency

The dolphins we saw in Kaikoura in the winter traveled from the south to spend the winters there, while those seen in Kaikoura in the summer move north in the winter to the Marlborough Sounds, on the north end of the South Island. The interesting thing is that the dolphins in the sounds, such as Admiralty Bay and Queen Charlotte Sound, act more like those seen by Bernd Wursig and other researcher in Golfo San Jose in Argentina. The continent does not seem to matter as much as the local environment. The Texas A&M researchers have learned that there about 250 dolphins in Admiralty Bay in the winter, many of them adult males. They travel in group sizes that average five or six animals and they feed during the daytime on schooling fish such as mullet and pilchard.

Punua Aihe

Next we were briefed on safety information and life aboard the research boat, the 5.5-meter (18-foot) inflatable Punua Aihe (Dolphin Calf). We learned how to use the radio in an emergency (Channel 16 - the international distress channel) and conversationally (Channel 80). The Earthwatch team has a good relationship with the dolphin tour operators. We went over some common sense things that might be the first forgotten in an emergency - remember to tell your potential rescuers where you are first, and also don't forget if you use a flare to aim it away from the boat!

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