11.03.2020 – Moonlight

I always inform my guests during the briefing about the various types of data recorded during every single tour. This helps us keep track of the presence of different species in certain areas, their behaviour and the abiotic factors that may potentially contribute to their presence or absence in a certain area. One of the noted data for all tours and sighting is the current lunar phase and several members of Lobosonda have long contemplated the effect of lunar phases on the abundance of certain cetaceans. Lunar phases have been thought to affect tides, the risk of natural disasters such as earthquakes and volcanic eruptions and even is thought to induce behavioural changes in both animals and humans.

On Monday we experienced the Supermoon, a much larger and spectacular looking full moon. The technical term for this is a perigee syzygy, meaning that the moon almost gets as close as it can to the Earth in its elliptic orbit. A study on the abundance of cetaceans around the Azores has shown the occurrence of certain species being closely correlated to the lunar phases within that time frame, including Sperm whales (Physeter macrocephalus), Beaked whales (Ziphiidae) and several Delphinids.  The latter are said to display more foraging activity during full moon phases, which may be linked to the higher prey availability during certain phases.  Stronger moonlight during brighter moon phases such as the full moon is thought to reduce the vertical migration of organisms from the deep to the surface at night, causing a ripple effect through the food web.

Our skipper Filipe and I discussed the moon being the possible reason why the ocean seemed more barren today. Our spectacular spotter, however, managed to track down some Bottlenose dolphins (Tursiops truncatus) this morning and this afternoon. We also had some curious Short-beaked common dolphins (Delphinus delphis) bow-riding near our traditional boat this afternoon. So while the moon clearly affects several things in the ocean, it did not affect our crews determination and success in finding some dolphins in our waters today.

By Paula Thake

Sightings of the day 

Ribeira Brava

14:30 Bottlenose dolphins, Short-beaked common dolphins 

Stenella

10:00 Bottlenose dolphins