09.04.2025 – Under their skin

Cetaceans have various physiological adaptations to their environment and a few of the most remarkable concern the largest organ of their body; their skin. Cetaceans live at the interface of sea and sky, leaving their skin subject to the effects of multiple environmental aggressors, so it comes as no surprise that their skin has been the subject of research for decades.

First off, the outer layer of skin, the so-called epidermis, is extremely thick, ranging between 2 and 4mm. This is 10-20 times thicker than human skin or than the skin of any terrestrial mammal. While the epidermis is generally smooth to the touch, it is covered in tiny channels that add to its hydrodynamic properties and optimises swimming. Below the epidermis is a thick layer of blubber which offers additional protection and prevents heat loss.

The skin of cetaceans is also fascinating because it can be so beautiful and even provide information on social dynamics. Atlantic spotted dolphins (Stenella frontalis) offer clues on their age class through the spots/freckles on their skin while Short-beaked common dolphins (Delphinus delphis) and Striped dolphins (Stenella coeruleoalba) never fail to dazzle our guests with their beautiful flank patterns.

While the skin is a strong barrier to many aggressors, it can be subject to discolouration. Mutations causing the over- and underproduction of the pigment melanin can lead to albinism and melanism in cetaceans, the latter being frequently observed in common dolphins visiting both the Azores and Madeira.

Skin discolouration can also occur for other reasons. Blainville’s beaked whales (Mesoplodon densirostris), the species that was seen later this afternoon, often have golden patches covering their light grey skin. These discolourations are thought to be caused by diatoms, micro algae that settle on the cetaceans skin giving it a distinct golden tint.

Another incredible characteristic is the incredibly quick healing of the skin and even the regeneration of blubber. Apart from their unique immune mechanisms, this is largely due to the presence of stem cells and natural antibiotic substances in the skin (that also help prevent infections allowing wounds to fester) as well as rapid skin turnover. In the morning we had a few spotted dolphins meandering between a few Portuguese Man O’Wars (Physalia physalis) and, while they definitely are not immune to the sting, we can be rather certain that the effect it has on their skin will be far less severe than on ours!

No matter the colour, the skin of cetaceans remains an incredible adaptation of these fine animals to aquatic life ands the more we learn about it, the more fascinated we are!

By Paula Thake

Sightings of the day

Stenella

09:30 Atlantic spotted dolphins, Striped dolphins

12:30 Atlantic spotted dolphins, Short-beaked common dolphins

16:00 Blainville’s beaked whales