Habitat of the Hector's Dolphin

Distribution

• Hector's dolphins have a very limited range. They live only in shallow waters off New Zealand's coast. There are four isolated populations. Three live off the south island and one, the Maui's dolphin, which is a distinct subspecies of Hector's dolphins, off the north island. They much prefer shallow water and seem unwilling to travel across deeper stretches, which would explain why the four populations are so genetically distinct.

Environment

• The shallow coastal areas the dolphins inhabit are rich in seaweed and fish, with often very turbulent waters. Essentially, this creates a cluttered environment, unlike the far emptier oceanic habitat. This may well affect the dolphin's navigational clicking and their behavior. Young dolphins regularly use pieces of seaweed as playthings. 2008 research from the University of Aarus in Denmark showed different frequencies used by the coastal Hector's dolphins and oceanic hourglass dolphins, possibly because of their completely different habitats.

Threats to Habitat

• Coastal habitat is vulnerable to pollution from human activities. Heavy metals in toxic waste from industry, fertilizer and pesticide runoff from agriculture and sewage are more concentrated closer to the shore. The impact on exclusively coastal animals such as Hector's dolphins is therefore serious. Hector's dolphins have been found to contain high levels of toxins including mercury, DDT, and PCBs. The dolphins are also at risk from collisions with boats and ships in coastal areas with heavy traffic.

Conservation

• Although it is uncertain exactly what effects pollution and traffic in their habitat have on Hector's dolphins, these animals are endangered. They are particularly vulnerable because their restricted distribution. Implementation of conservation measures including marine reserves has been on the agenda of the New Zealand government for decades. In 1988 the Banks Peninsula Marine Mammal Sanctuary was established because of data collected on the threats to Hector's dolphins. To continue to protect these dolphins, however, it is necessary to address the ongoing threats of pollution, damage by boats and, most critical, their accidentally drowning in fishing nets.