Marine Mammals

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!


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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