Mysterious migrations of the deep!

We often think of the Straits of Gibraltar as a barrier to be overcome, a great leap of faith for the hundreds of thousands of birds that must move between the land masses of Africa and Europe. But through the eons, other vast, invisible migrations have gone almost unseen in the dark depths beneath the sparkling surface.

Here we chat to our friend Aurelio Morales, owner of family-run cetacean-watching company Marina Blue, to find out why, for marine mammals, “The Strait of Gibraltar is a vast underwater canyon – a great corridor that links the Mediterranean and the Atlantic”

Aurelio has spent twenty-two years of his life around the marine fauna of the Strait of Gibraltar. “There is something special about this place that hooks me. Two seas, two tectonic plates, two continents, two prevailing winds… Each outing is completely different. There is no one equal to the other, since the weather and light changes, the behaviour of the species varies throughout the days”

His trips are full of encounters with our local resident delphids – Common, Striped and Bottlenose Dolphins, highly-sociable Long-finned Pilot Whales, and even Orcas in summer – but he is particularly fascinated by the mysterious movements and spectacular sudden appearances of the area’s two migrant species – Fin Whales and Sperm Whales.

“We have so many experiences with these two species that never cease to amaze me. We have seen on many occasions Sperm Whales jumping right out of the water, dragging a large body of water as if it were an explosion in the sea. We have witnessed fascinating interactions between Sperm Whales, Long-finned Pilot Whales and Bottlenose Dolphins. Yellow-legged Gulls will perch on top of a resting whale and clean its dead skin. We have seen Hammerhead Sharks circling them while they rest on the surface.”

But although they are seen regularly and often with great intimacy from Aurelio’s small yacht Miamita, much remains unknown about the movements of these two peaceful giants of the seas.

“We consider Sperm Whales to be semi-residents here. They spend long periods in the Strait feeding, mostly on deep sea squid.”

“In the Strait we almost invariably see adult males of up to 15m in length – and occasionally younger males of around 7-10m. They use this underwater corridor for their movements to and from feeding and mating areas.”

Male and female Sperm Whales generally don’t hang out. The males are loners, found in higher latitude cold waters, whilst the females, calves and young adults form gregarious and relatively sedentary groups in tropical and temperate seas. They meet up only to mate, with the males performing seasonal migrations. They find each other across vast distances – their huge jelly-filled heads directing and amplifying their song to volumes louder than a jet engine.

Research in 2011 used photo-cataloguing of tail flukes – from which individuals can reliably be identified – to compare Straits whales with records from across the Mediterranean and Atlantic. Of 47 Sperm Whales identified here, fifteen could be traced travelling throughout the western Mediterranean, a straight-line distance of up to a thousand miles.

The fact that none of “our” Sperm Whales from this study were recorded in the Atlantic supports existing genetic evidence of an isolated sub-population within the Mediterranean Sea. Believed to contain fewer than 2,500 mature individuals, the Mediterranean population is considered ‘endangered’, based on IUCN Red List criteria.

However, Sperm Whale social groups, with females and calves, do turn up in the Strait from time to time. We recall an incredible experience in September 2017, watching a group of ten females and young whales. They were grouped tightly together in a “marguerite formation”, where the group surrounds a weak or injured individual with their tails pointing outward, enabling them to protect it from attackers. The gathering seemed to emanate tension and anxiety, as the sea around them boiled with curious dolphins and seabirds eyed them suspiciously from above.

The happening was during a series of strong hurricanes over the Atlantic. Could this troubled group have been Atlantic in origin, having come into The Straits to shelter?

There is clearly more work to be done, says Aurelio. “Collaborative studies are currently being carried out between different companies, associations and scientists to verify that the same species seen in the Strait are being seen in other places such as the Canary Islands and Azores.”

Fin whales, the world´s second-largest living creatures, can reach lengths of up to 25m. They used to be abundant in the Strait of Gibraltar and nearby Atlantic areas until their rapid collapse due to intense whaling at the beginning of the 20th century. They are now considered endangered.

Evidence gathered from fifteen years’ worth of photo-identification suggest that some of the Fin Whales seen in the Mediterranean are actually of Atlantic stock.  A small community of them have been observed migrating through the Strait of Gibraltar, with remarkable seasonal directionality. They head to the Atlantic Ocean in May-October and the Mediterranean Sea in November-April. Observations of young whales exiting the Mediterranean Sea mainly in May-July suggest that at least part of this community is likely to calve in the basin, probably near the Balearic Islands.

“The Mediterranean is a semi-closed sea with warmer temperatures, so it would make sense that females raise their calves there until they gain enough weight to move to cooler feeding areas.” says Aurelio.

But, he says, there are many threats to these amazing creatures as they try to navigate the busiest shipping lane in the world.

“The greatest dangers for these large cetaceans are almost always related to human presence. The Strait is the only channel that connects the Atlantic with the Med and carries massive shipping traffic. Whales are injured colliding with large ships, and noise pollution interferes with echo-location, and therefore migration. Pollution from oil spills and plastic waste is another great problem that these animals face with this unbridled progress that prevails over the conservation of Nature.”

As a wildlife tour operator, and erstwhile skipper for the Ministry of the Environment, he feels a great sense of responsibility to make sure Marina Blue’s own effects on the environmental are only positive, in line with our own #FlywayPromise.

“There are thankfully many legal requirements to operate here, in terms of good practices regarding cetacean observation and compliance with EU emissions regulations and speed limits, which we naturally comply with. But we also have our own manual of good practices, guided by our own conscience and respect for Nature!”

“Marina Blue works in and for the Strait, with small groups of no more than ten people per trip to minimise our impact. We separate and reduce all our waste. We enjoy the animals with the utmost respect, quietly, allowing them to come to us if they wish. We must always bear in mind that we do not own this planet.”

We love heading out with Aurelio and his crew during selected trips, because of the intimacy of the encounters allowed by such a small vessel, but also because of his obvious deep connection and passion for the wildlife we are hoping to observe. With each spell-binding sighting of one of these incredible animals, we learn a little more about how to protect them.