In Part 1, I explored the properties of the sentient mind, the special skills and the strategies employed by animals to promote not only survival and genetic fitness but also a sense of wellbeing and quality of life. Here, in Part 2, Adaptation to the Environment, I examine how sentient minds have been shaped by the special circumstances of their environments. I begin this voyage of exploration in the waters, partly because it is from the waters that so much life has emerged and partly because life in the sea, and on the seabed, has been relatively unaffected by human interference. Unscrupulous fishing practices have caused great damage to population numbers and pollution great damage to habitat. However, when we are not seeking to kill them, we leave them alone to get on with their lives (farmed fish are, of course, an exception). Their environment is essentially similar to that of their ancestors, which means that the toolkit they carry at birth is appropriate to their current circumstances.

All life needs to be fuelled by a source of energy and, for all practical purposes, that energy source is the sun. Lifeforms that capture solar energy by photosynthesis are bacteria; single‐cell organisms such as algae and plants that contain chlorophyll. Aquatic lifeforms that capture solar energy need access to light so lie close to the surface. The generic name phytoplankton is used to define those organisms that capture solar energy in the seas, lakes, rivers and ponds. There are at least 5000 recognised species of phytoplankton, which is interesting but unimportant in this context. What is important is the sheer magnitude of the food resource that it provides for animal life in the waters. It has been estimated that the phytoplankton of the oceans capture about 50% of the cardon dioxide and produce about 50% of the oxygen for the planet.

Box 6.1 presents a somewhat idiosyncratic summary of the food chain in the waters. At the bottom of the chain are the producers; organisms that may be loosely classed as ‘vegetables’ because they capture solar energy by photosynthesis. The phytoplankton are by far the dominant contributor to this category, but it also includes larger, plant‐like seaweeds and seagrasses that grow abundantly in shallow water near the shores.

Essentially all other forms of sea life are animals: an astounding variety of species ranging from the polyps that construct coral reefs to the great whales. They may be classified, rather imprecisely, into herbivores, foraging carnivores and hunting carnivores. The great majority of herbivores are the zooplankton, small invertebrates such as molluscs, jellyfish and small crustacea that feed on phytoplankton. Large herbivores include fish (e.g. carp) and mammals (dugong and manatee). The feeding behaviour of the carnivores may be described, somewhat loosely, as foraging, hunting or a combination of the two. I use the term foraging to describe behaviour that involves the relatively mindless harvesting of small creatures from the waters (e.g. zooplankton) and seabed (e.g. molluscs). Foragers, by this definition, include creatures large and small: fish, crabs, some pinnipeds (e.g. walrus) and baleen whales. Hunting carnivores are predators; animals that select their prey and kill them. This category includes fish (e.g. tuna, sharks), birds (penguins) and aquatic mammals (e.g. seals, dolphins). When we exclude single‐cell organisms, survival strategies for nearly all sea creatures depend on killing and eating other animals while avoiding being killed and eaten themselves. The question to be addressed here is how much of this behaviour is instinctive and how much may require properties of a sentient mind?

The nature and life of the open oceans has remained reasonably constant for millennia, although it is now under threat. There are, of course, large variations in the physical properties of the sea, like temperature and salinity, determined by latitude and prevailing currents, and these determine the distribution and abundance of life within the food chain. Nevertheless, the fundamentally stable character of the ocean environment, and its lack of surprises, greatly reduces the need for animals to develop new skills and better understanding in order to sustain fitness. Aeons ago, the shark evolved into a perfect killing machine and has been under no pressure to evolve further, or even give much thought to the business of life and death. However, if smaller fish, at risk of being killed and eaten by sharks and suchlike, are to achieve Darwinian fitness (the capacity to survive and reproduce) they need to develop defence strategies. As always, they are motivated by the emotional need for self‐preservation. This requires at least some instinctive notion of the concepts of pain and fear reinforced, in many cases, by some acquired understanding of actions necessary to keep out of danger.

While the oceans themselves may be relatively uniform, the environment of the seabed is complex and presents a wide variety of environmental niches that present complex challenges that encourage the development of special skills, including properties of a sentient mind. These include sheltering as a form of defence, camouflage and (perhaps) deceit as aids to attack. Further demands for navigational skills are placed on marine animals whose breeding cycle requires them to migrate between sea and land, like the sea turtle or between fresh and salt water like salmon and eels.

There is clear evidence of properties of the sentient mind in a wide range of marine animals. We are fed many tales of the intelligence and sensitivities of the cetaceans (whales and dolphins), descendants of ancestral mammals that returned to the sea to exploit an abundance of food. It is easy to empathise with these animals because they seem to be so similar to us. It may be harder to empathise with fish and marine invertebrates, but there is abundant scientific evidence to show that most fish and many invertebrates, including probably crustacea (e.g. lobsters) and certainly the cephalopods (octopus and squid) display a range of emotions and acquired skills indicative of the deeper circles of sentience (69). Here, I examine attributes of mind ranging from pain and fear through to empathy and compassion in marine animals ranging from the octopus to the whale with no attempt to pre‐classify them as inherently more or less sentient or skilled.

Pain and Fear

In Chapter 2, I drew attention to the distinction between nociception, a sensation such as an electric shock that produces an immediate withdrawal response, and true pain as a source of suffering resulting from a complex mixture of unpleasant sensation, emotion and fear of its recurrence. The extent to which pain can be more than just nociception comes from evidence of avoidance behaviour, guarding wounded sites from future trauma, changes in mood such as increased fear or depression, improved mobility and mood after administration of analgesics and, where this can be tested, self‐administration of analgesics as a conscious action intended to reduce suffering. We probably assume that cetaceans (whales, dolphins etc.) suffer pain and fear in much the same way as we do, not least because their brain development is similar to ours so there have been few serious attempts to find out for sure. In a moral sense, it is more important to discover how far the capacity to experience pain and fear as a form of suffering may extend to the fish and other marine creatures, including invertebrates, that we hunt, farm and kill for food. For many years, it was firmly believed by most fishermen and too many scientists that fish do not feel pain. Fishermen made their case on the basis that a hooked fish makes strenuous efforts to escape and claimed that it would not do this if it hurt. This argument ignored evidence of trapped foxes and mountaineers respectively gnawing or sawing off trapped limbs in order to survive. For many years, scientists argued that fish and marine invertebrates like crustacea and cephalopods could not feel pain because they do not possess the area of brain known to be associated with pain reception in mammals. Fishermen and scientists alike came to this conclusion without once asking the fish (or, indeed, the squid). There is now convincing evidence that both parties were wrong. Fish do suffer from both pain and fear.

Bony fish meet most of the criteria necessary to classify pain as a source of suffering (71,72). They avoid areas they associate with electric shocks, although (reluctantly?) will visit these areas if, after several days of starvation, they are the only source of food. The movement of injured fish (sensation) and their motivation to feed (mood) is improved by the administration of analgesics, and there is some evidence that they will select a barren environment in preference to an enriched environment if it contains an analgesic in solution.

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