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In the Eyes of the Dolphin

Cetaceans have extraordinary eyesight.

Dolphins can use their sonar to detect complex shapes and identify them visually. Captive animals have been known to throw frisbees and catch fish without using their sonar. And at any oceanarium it is common to witness dolphins demonstrating their amazing ability to leap out of the water and touch a small target many feet above the surface. These same dolphins repeatedly sail over tightropes and through hoops without touching them, often times in unison. All demonstrating that cetaceans are capable of seeing, not only underwater, but also in air and from water to air. The combination of their visual acuity and sonar abilities makes dolphins well equipped to evaluate any and all objects in their environment.

When the ancestors of the modern dolphin re-entered the water, so many eons ago, their eyes and eyesight went through some major transformations.

On land, eyesight is primarily challenged by dust and the threat of physical harm. These problems are counteracted by hairy eyebrows and lashes and eyeballs that are located in deep sockets of the skull for protection. Tears help wash away dust and clean the eyes. In the sea, the challenges to the eye are more associated with salt and particles in the water, as well as the massive pressure associated with deep dives. Cetacean eyes are encapsulated to protect the shape and integrity of the orb from pressure during dives. There are no dolphin tears, instead special glands secrete oil that continuously wash the surface of the eye to prevent irritation from salinity.

Land animals depend on detection of movement, position, color, detail and sharpness as visual cues. Dolphin vision is more dependent on brightness. The cetacean eye is adapted to perform at depths where light is minimal. At thirty feet, as much as 90% of sunlight is lost and color disappears. The dolphin pupil is capable of opening enormously wide to enhance brightness. The eyes are also lined with a highly reflective substance that concentrates light, similar to the silver of an old traditional headlight. The eyeball has an oval shape, and the lens is positioned to prevent even the weakest ray of light from escaping the retina.

On the other hand, dolphins must see not only at lightless depths, but also at or just below the surface, where it is the brightest. Due to water movement and its effect on sunlight, it can be more than seven times brighter just below the surface than it is above the water. The eye is equipped with a flap like structure that closes over the restricted pupil. It can look as if the dolphin has two tiny pupils at times. Even so, the ability of the dolphin to go from near complete darkness to extreme brightness is one of the miracles of the dolphin eye.

The position of the dolphin eye on each side of the head not only provides additional protection from the onslaught of ocean particles as the dolphin swims forward through the water, but also allows for a nearly complete field of vision. This position of the eye provides some stereo vision directly below them, but also creates a blind spot directly in front of the dolphin. This is one of the places where the sonar comes in handy as they can virtually “see” anything in this blind spot… with sound.

Dolphins don’t just use their eyesight to locate food. The structure of dolphin societies suggests a strong use of visual cues in communication. It makes perfect sense that in an environment where danger can come from any and all directions, silent communication is important. Body posture and subtle swimming techniques can effectively give the others a warning. They can also express irritation, initiate romance and/or provide comfort. An S-shaped body posture by an individual is thought to represent some degree of annoyance, an inverted swim under a female by a male suggests courtship, and companions often swim side by side, eye to eye and rub pectoral fins, possibly during new or unique situations.

Since the dolphin body has adapted to be optimum in the aquatic world, they have lost the ability for facial expression common in terrestrial mammals. They cannot smile with satisfaction, nor grimace in pain. Therefore there must be a lot to be seen in the eye of the dolphin. As many of us here at the Palm Beach Dolphin Project can attest, dolphins are not only capable but sometimes insistent on making eye contact. Not only with each other but with us as well. Here’s looking at you kid!

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We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world.  Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective.  The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

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The Objectives of Marine Mammal Research

The aim of marine mammal research is to develop progressive knowledge and understanding of their biology, adaptations, behavior and ecology, which will lead to better protection of species and their habitats, contributing to biodiversity in such a way that a sustainable use of the sea becomes possible.  Furthermore, such research strives to understand how we affect their lives and how we can gain from them, e.g. through tourism.

If you understand dolphin echolocation and how it works, then you have the tools to apply that knowledge.  If you are a conservationist and are concerned about dolphin entanglement in nets, the knowledge allows you to build better fishing nets that will not harm them.  The application of the knowledge depends on what you value: for an academic, to further knowledge and understanding; for an applied researcher, to be able to provide information to managers on the implications of a range of management options, for a conservation biologist: to find ways of ensuring the health of populations.

In the end, all this will contribute to a better understanding of the impact we have on our planet.  You can’t have seven billion people growing and running around on a planet without having some major impacts.  Right now we are making choices we don’t even understand; better to make an informed choice don’t you think?

There are various tools that can be used to achieve this goal, including expanding the knowledge base through biological inventories, research, monitoring, training of professionals, planning (environmental impact assessment), action plans and integrated area management, regulating threats to marine species and ecosystems, establishing protected areas, and ensuring active involvement of citizens in government decision making.  Public education is very important in all conservation efforts.

 

Most of science consists of answering very small questions.  Each one may not have much value in and of itself, but when the whole picture is to be seen, each of the many small pixels of knowledge will be required.  So in the long term, we can expect to truly understand some of the things that are affecting cetaceans and their behavior.  In the short term, however, one cannot expect too much.  Important results in this field are usually gained through long-term research, which will then constitute the wisdom and the power to make the best possible decisions about the future.  Research aimed only at solving a specific, well-understood short-term problem is not going to provide us with the answers we need ten or twenty years from now.  We need to commit some fraction of our resources, our dollars, to basic science, understanding that it is a risk-taking investment; not all science hunches pay off, but when they pay off, they pay off big.  And this investment of resources should not be done because it is `en vogue’ to be concerned about the animals, the oceans and the planet, but because it is intellectually and morally the correct thing to do.  By better understanding one group of marine creatures, with which we compete for resources – prey and habitat -, we may be able to better manage our affairs on this planet.

In sum, excellent research provides several results: Firstly, it leads to a deeper understanding of the world and its basic mechanisms of function, or in other words, an increased appreciation of the world in which we live.  Secondly, it provides a baseline of data against which we can measure changes and information that can be put to practical use, thus reducing our impact on these animals and their environment.  And third, the advancement of knowledge usually entrains an increase in public awareness and then support from the general public, which is a crucial determinant for maintaining biodiversity, the survival of the variety of species and their habitats and a wise resource use by man.

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We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world.  Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective.  The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

Read more

Threats to Whales and Dolphins

Whales and dolphins are a vibrant part of the global ecosystem and their populations have been severely affected in various ways.

Many species have been over-hunted in the past, and several populations are reduced to a small fraction of their original levels. They are vulnerable to entanglement in fishing gear and incidental catch in gillnets is one of the most serious threats to marine mammals.  These fishery operations may well cause the extinction of several small cetacean populations within the next few decades, including the Vaquita and Chilean dolphins. Collisions between larger whales and ships (ship strikes) occur with regular frequency and represent a significant cause of death and traumatic injury.  Because toothed whales and dolphins are top predators and thus at a higher tropic level in the food chain, they are especially prone to bio-accumulating toxins, such as heavy metals, persistent organic pollutants (POPs) and endocrine disrupting chemicals (EDCs). However, as recent research has demonstrated, such toxins and pollutants also negatively impact baleen whales.

Another threat to the health of whales and dolphins comes from the petroleum industry. Seismic surveys, which are used to discover oil and gas field situated below the seabed are, at a minimum, suspected to damage the complex hearing system of these marine mammals. Once the oil extraction processes is under way, the negative impacts shift habitat loss and exposure to hydrocarbons, lubricants and outright pollutants and toxins used in the process.

Loss of whale and dolphin habitat is directly linked to increasing human activity in and along marine environments. The aggregation of wastes we allow to flow into our streams and estuaries, and ultimately into the oceans, is a biochemical soup carrying thousands of different chemicals. Rainwater and snow melt, that run off from congested urban areas, collect street oil and chemicals as well as many metals. Runoff into streams and rivers adjacent to farmlands carry tons of suspended particles of soil. This is not only damaging to fish but can also choke-out submerged oxygen-giving grasses in coastal woodlands, bays or estuaries. Runoff from timber harvesting activities, especially clear cutting, deprives the exposed land of thousands of tons of soil and has caused the pollution of some of the most valuable spawning grounds for trout and salmon in the Pacific Northwest. Runoff of the nitrogen and phosphorus components of fertilizers leads to an oxygen depletion in the water. This depletion has caused massive fish die-offs and can wipe out whole areas of marine habitat necessary to maintain the life cycles of myriads of species of aquatic life.

Marine debris is a visible expression of human impact on the marine environment. Debris is more than an aesthetic problem, it poses a real danger. Ocean currents carry milk cartons, toothbrushes, cigarette lighters, and other familiar plastic items around the world. In some areas, such as the Central Pacific Gyre, plastics outnumber plankton seven to one.

The number of marine mammals that die each year due to ingestion and entanglement of debris approaches 100,000 in the North Pacific Ocean alone. Worldwide, 82 of 144 bird species examined contained small debris in their stomachs. Plastic is the most far-reaching man-made threat facing many marine species. Over time, it reacts with sunlight and turns into small plastic polymer molecules. It turns out that these plastic polymers are sponges for DDT, PCBs and other toxins that don’t dissolve in seawater. Plastic pellets have been found to accumulate up to one million times the level of these poisons that are floating in the water itself. These pellets are consumed by baitfish, which in turn are consumed by larger fish, eventually finding their way into the stomachs of large predators, such as dolphins and toothed whales, and our own.

Other human activities, such as the construction of shipping channels and marinas, and the recreational use of coastal areas, including resort development, are likely to have a negative impact on the lives of whales and dolphins using the same areas.

Last but not least, climate change, with its changes of sea temperature, sea level rise, changes in salinity, just to name a few, will undoubtedly change the socio-ecology of whales and dolphins. Species inhabiting the high latitudes, such as bowhead, narwhal, beluga may be the first to feel the impact due to diminishing food resources, such as krill. But other species, such as humpback whales and killer whales will likely experience significant changes in their food supply, resulting in changes of existing migration patterns and a shift of home ranges.

Whales and dolphins are facing enormous challenges and threats. They are the ocean canaries, warning us about the disastrous effects of pollution and habitat destruction, and they can be our guides to where to look for answers about how our oceans work. If we have any philosophical leanings towards preserving these wonderful creatures and the oceans, either for future generations or for its own value, than learning enough to prevent any further damage is crucial.

 

We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world.  Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective.  The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

 

Read more