21.07.2018 – I spy with my little eye ….

It was gorgeous out on the sea, a smooth lake and four types of dolphins! And here’s the loooong list of sightings in the order of their appearance: Bottlenose dolphins (Tursiops truncatus), Common dolphins (Delphinus delphis), Striped dolphins (Stenella coeruleoalba), Atlantic Spotted dolphins (Stenella frontalis).

The pods of Bottlenose dolphins and Common dolphins were quite relaxed, here and there were little fishy snacks and Yellow-Legged gulls (Larus michahellis) and Cory‘s Shearwaters (Calonectris borealis) made funny manoeuvres while having a discussion over fish. The Striped dolphins were beautiful to watch, even if they preferred a certain distance from the boat. And the Atlantic spotted dolphins? Yes, they were as always, curious and interested in our boat.

Today we had the question, if dolphins can see well …

In the childhood game “I spy with my little eye”, memories of long car journeys may be awakened. A game that was fun and drives time out. But it also shows that we humans are visually oriented beings. 70% of the total number of our sensory cells are on the retina. The sensory eye gives us the chance to understand our world. In the course of evolution, nature produced numerous eye models.

If dolphins ride in the bow wave of our boat and turn their bodies slightly to the side in order to target us, besides the joy surely also the question arises, how important the visual sense of the animals is. Dolphins have much complicated conditions of seeing, because even though dolphins seem to be unable to perceive colors and have no visual multi-dimensionality due to their eyes being sideways, the sense of sight is well developed. For spatial vision, it is necessary that the eyes are on the front of the head, but with the use of the sonar dolphins can still create spatial images in their brain.

River dolphins are an exception, because they fish in murky waters, where seeing is almost impossible, the sense of sight is hardly or not at all pronounced. The eye of the dolphin is movable around and closed by a lid.

A secretion pulling over the eye protects against the irritation of salt water. The outer eye skin can withstand the water pressure due to its thick texture. Their softer eye lens is able to adapt to the special refraction under or over water. Here, however, there is a small restriction, because it is assumed that the animals in this case are somewhat “short-sighted” and a detection of objects only up to 15m is possible.

And now another special feature: It seems that at night it is possible to look into the “sparkling” eye of a dolphin. A thin, metallic cell layer (tapetum) behind the retina ensures, as in cats, for this special effect at night. I would love to experience THIS!! But to be in the eye of a dolphin when it is riding in the bow wave of the boat is WONDERful.

One question remains … do dolphins play in their own way “I spy with my little eye”?

By Fatima Kutzschbach

Sightings of the day

Ribeira Brava

15:00 Bottlenose dolphins, Atlantic Spotted dolphins

Stenella:

09:00 Bottlenose dolphins, Common dolphins, Striped dolphins, Atlantic Spotted dolphins