16.06.2018 – Moments of silence

The most impressive moments during today’s tour have been some minutes of silence. We were on our way back from outstanding encounters with two big pods of almost 100 playful short-beaked common dolphins (Delphinus delphis) when we stopped – no voices or traffic sounds, no phone ringing, no camera clicking. We were out on the ocean. Only some Cory´s Shearwaters (Calonectris borealis) lightly discussing and small waves gently passing by. We all scanned the surrounding surface intensively when suddenly a few pale brown curvatures appeared a few boat lengths off our bow. The elongated shapes turned out to be equipped by little fins towards their ends. They were moving in our direction: a pod of rarely seen Blainville´s beaked-whales (Mesoplodon densirostris) came along our way.

Our captain had maneuvered us in a good position. Without any own movement, we awaited the animal’s decision to either come closer and give us a nice view or continue in another direction. We were lucky and witnessed six or seven adults and a calf coming up to the surface just a few meters to our port side. The calf turned around and gave us a curious look before an impressive male came along. Similar to all the other animals the broad and long snout came up to the surface first, but now we could even see two spiky teeth sticking out from the end of the lower jaw. This is a characteristic feature to distinguish between the sexes in beaked-whales. Only males have these tusks which are used as effective weapons in fights against rivals. Also, the specimen we saw showed some battle scars along the flanks. With up to six meters in length and a weight of around one ton, the male harem leaders are also slightly bigger compared to the female beaked-whales.

There is not much known about this extremely rare deep-sea specie. During long dives, which can last up to one hour, they can reach a depth of more than 1000 m. They go down to hunt little fish species and squid in their deep-water habitats. After longer dives, they rest and recover on the surface or just below. Interesting is the fact about their very dense bone structure which is even denser than ivory. What we know for sure is that these animals also enjoy the silence. And even more, they depend on it. Too many distracting noises disturb their communication and result in disorientation. Very loud sounds cause fatal injuries.

Noise pollution is a serious threat to Blainville´s beaked-whales, but our oceans are getting louder and louder. Ship traffic, coastal and offshore construction as well as military activities are only some causes. Oceanic noise needs to be regulated and reduced in order to conserve cetaceans and enable them to enjoy what we all appreciate: moments of silence.

by Jan-Christopher Fischer

Sightings of the day

Ribeira Brava

17:00 Blainville´s beaked whales, Short-beaked common dolphins, Loggerhead turtles