The habitat needs of dolphins and porpoises vary by species and by population. To establish real needs, we must map their movements and understand their basic biology and social behavior. Where do they travel? is it mostly to the same places and along the same routes from year to year? Where do they give birth? Where do they socialize, rest and play? Do these activities require protected habitats?
In general, the closer dolphins live to shore and to people, the more problems they face. Many harbour porpoises and bottlenose dolphins raise their young and eat fish near shore. They are much more affected by ship traffic and pollution - runoff from agricultural land and dump sites - than are the dolphin herds that live and feed in the deep waters off the continental shelf. Atlantic humpbacked and other tropical species are losing their food supplies with the cutting of the mangroves that serve as fish nurseries.
The greatest impact on dolphin habitat has been felt by the river dolphins and vaquitas, found in the Gulf of California, Mexico. These are the most threatened of all whales and dolphins. In China, baijis have been killed by fishing hooks and only about 300 remain. The bhulan, with fewer than 500 left, is now restricted to limited areas between irrigation barrages in the Indus River system of Pakistan, where some illegal hunting persists. And on the Amazon River, dams, industrial developments and extensive logging are reducing dolphin habitat.
For orcas off the west coast of Canada, some of the key habitat questions have been answered. After more than two decades of studying orca behaviour, we know that they return to the same waters years after year and that they prefer certain places to others. A favorite area is around Robson Bight, off northern Vancouver Island. Here, in the clean water near the stuary and along the shore, orcas spend a few minutes to a few hours most summer days resting, playing and rubbing on the special smooth- pebble beaches that are found only here. They also feed on salmon that school along the shore before spawning.
In 1982, Robson Bight became a marine ecological reserve - the first orca sanctuary in the world. Public protest halted the creation of a log port that had been planned for Robson Bight. But the whales needed some land protection as well, and 505 hectares - including 10.7 kilometers of shoreline - were set aside in the late 1980s. Still, logging activities in the Tsitika River Valley at Robson Bight have pushed the clear-cuts to within four kilometers of open water. The wilderness character of the area is quickly disappearing. The water quality of the river may change, and the salmon runs could be harmed.
In order to save dolphins and porpoises, we need to learn much more about their movements and habitat needs. Then there must be public pressure to convince governments to establish reserves. Sometimes, this involves buying the surrounding land from industry or private individuals. It may also require rerouting oil tankers and other ship traffic. Only if we reserve safe homes for dolphins and porpoises and then protect them can we count on the wonder of their company in the future.
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