Introduction

It was the most peaceful scene imaginable. As the sun broke through the morning fog, several related families of orcas, or killer whales -mothers, fathers, youngsters, cousins and grandparents - slipped through a calm, liquid ocean, water trailing off their fins.

For weeks, a group of researchers, I among them, had spent long days travelling, with three family groups, or pods, of orcas living off Canada's northern Vancouver Island . While we grew to know them as individuals and as families, we had enjoyed watching them at rest and at play, following them on their travels. We had even given them names-Top Notch, Nicola, Sharky and Stubbs to match their distinctive dorsal fins. Now, however, a moment of truth had arrived.

On the distant horizon, we spotted some strange spouts. At first, we thought they were simply more orcas coming to join the group, but the spouts and dorsal fins of the new arrivals were smaller. As we approached in a small outboard motorboat, we cleaned the fresh spray off our binoculars and determined that two minke whales and half a dozen Dall's porpoises were swimming right into the midst of the orcas.

"Here comes a meal," someone shouted. All of us had read accounts of orcas feeding on the up-to-10 metre-long minke whales and 2 metre-long Dall's porpoises. Scientists had described in detail orcas hunting in packs like wolves, stripping the

skin off the whales and ripping out their tongues. Orcas would stun the porpoises with a flick of the tail and devour them one by one.

We expected a bloody encounter. For two hours, we waited, our small craft bobbing in the sea. Nothing happened. Instead, the three species minke whales, Dall's porpoises and the 34 orcas we had originally sighted -peacefully combed the tide rips side by side, feeding on schools of fish. We soon realized that the orcas we had been following were confirmed fish-eaters.

It was an important lesson in a summer which taught us over and over again that things are rarely as they seem at first. The real story is always worth digging for and is often far more interesting than what was assumed to be true. This is the case with all science and especially field biology. One new fact in the complex natural world leads to another and another. As the layers peel away, the world is gradually revealed.

But what were we to make of the killer whales of legend? What about the stories we had heard? One day, a wild, fierce pod of orcas appeared that did not look or behave like the orcas with which we were so familiar. Our resident pods ignored these transient orcas, as we referred to them. Silently and erratically, the interlopers swam through our study area, stalking seals and porpoises. In time, we were able to witness a successful feeding attack by transient orcas. Usually, researchers must spend many hours of observation to see such an event. Over the years, by examining the stomach contents of transients that have died, scientists have confirmed their preferred diet: marine mammals.

The science of studying wild dolphin and porpoise societies-using photography to identify individual animals -is only about two decades old. It is still young enough that cherished assumptions are overturned regularly. That is part of the excitement.

Some of the things that first attracted people to dolphins-their large brains, the possibility of communicating with them, their apparently "peaceful" societies, their friendliness toward humans in the wild and in captivity-are no longer considered to be as accurate or as relevant as was once believed. But there are lots of reasons to be curious about dolphins and porpoises.

On the following pages, we will look at the many different species of dolphins and porpoises - all of those known to live in the northern hemisphere, including the river dolphins found in the Tropics . Each species has its own peculiarities and strategies for survival. Each has particular food preferences and feeding behaviours as well as a different habitat its own niche, or place, in the water.

While most whales range throughout the world ocean, many dolphins and porpoises are limited to one hemisphere, one part of an ocean or, in the case of river dolphins, one river system. Mainly because of their limited ranges, several species of dolphins and porpoises are more endangered than are the large whales, such as the blue, humpback and gray. (These whales were introduced in an earlier companion book, Meeting the Whales, but will sometimes be referred to here, since many features of evolution and biology are the same for all whales, dolphins and porpoises.)

We will learn about the dolphins' hearing abilities, their mating and reproductive habits and the fishing-net and pollution problems that threaten their survival. We will discover the fastest swimmers and the best bowriders. We will witness examples of clever feeding behaviour - bottlenose dolphins chasing fish onto a beach, then charging clear out of the water and grabbing the fish before rolling back into the surf. We will spend time with various species in their close, long-term family groups. We will discuss experiments scientists have conducted in an effort to teach bottlenose dolphins a symbolic language.

As we find out more and more about the sea and its residents, we begin to recognize the vital importance of habitat. In the final chapter, we will examine this often-neglected dimension of research and management programmes. This book will also explore a new way of looking at these fascinating creatures and will present the results of the latest research. Good science is needed to determine the habitat requirements of dolphins and porpoises species by species -an expensive, time-consuming task. Once it is done, humans will be better able to reserve a secure home- for dolphins and porpoises, one that will allow these captivating mammals to survive into the next century and beyond.