Three Dolphin Species Share the Bay of Gibraltar, and Almost Never the Same Water

24 September 2026 Last checked 2026-09-24

Four years of surveys logged 2,410 dolphin sightings in the bay. The three species were rarely in the same water at once. What that means for a boat trip from Marina Bay.

Four years of survey work in the Bay of Gibraltar logged 2,410 dolphin sightings across 593 days at sea. The three species that live here were rarely recorded in the same water at the same time.

That result was published on 2 June 2026, and it changes how you should read the ticket you buy at Marina Bay. You are not going out to see three species. You are going out to see one of them, and which one depends on where the boat goes and what month it is.

What four years of counting found

The study ran from 2017 to 2020, off the back of a long running monitoring programme worked from a licensed dolphin watching boat. Observers used 7 by 50 binoculars and logged every sighting by species, age class and GPS position. Total effort came to 25,610 kilometres over 1,690 hours of navigation. The paper is open access in the Journal of Marine Science and Engineering.

The short beaked common dolphin was the most frequently sighted, with numbers climbing from summer into autumn. The bottlenose was the least, at 102 records in four years. A chi square test found no significant seasonal variation in bottlenose occurrence across years and seasons, which is a statistician's way of saying they are around all the time and never in numbers.

Here is the part that matters on a boat. When the researchers measured the gap between a bottlenose sighting and the next sighting of either other species, the distances ran from 261 metres to 12 kilometres, and the time gaps from 33 seconds to 5 hours 38 minutes. Overlaps of 300 seconds or less were infrequent. In the sequences analysed, not one mixed group involving a bottlenose and either other species was recorded.

We are going to be straight about the limits of this, because most write ups of a paper are not. The authors ran logistic models and found no statistically significant relationships. They say so plainly, call their own results descriptive rather than explanatory, and point at uneven sampling effort and missing variables such as depth and prey distribution. The pattern is there in the data. The mechanism behind it is not established.

Telling the three apart in the four seconds you get

A dolphin is above water for about a second at a time, and size will not save you: a common dolphin runs 1.9 to 2.5 metres and a striped one 1.8 to 2.5, so on the water they are the same animal. Learn one marking per species instead. The field marks below follow the standard reference accounts, including the striped dolphin's distinctive blaze and flank stripes. The group sizes are the ones actually recorded in this bay.

Two habits help as much as the markings. Common dolphins here move in loose, fast, noisy groups that often include calves and neonates, and they will ride a bow wave. Striped dolphins leap, and in winter and spring their small juvenile groups of five to twenty animals were often found mixed in with the common dolphins. The bottlenose kept away from both.

There is a canyon under the bay

The Bay of Gibraltar is about 10 kilometres long and 8 kilometres wide, some 75 square kilometres of water with Algeciras on one shore, La Linea at the head and the Rock on the other. Reference works give its depth as around 400 metres. The survey papers are more specific and a little deeper: one submarine canyon runs north to south across the bay in what the researchers call a specular S, bottoming out at 450 metres in the 2026 paper and 460 metres in the same team's 2023 one. We cannot reconcile those two figures and we are not going to pretend they agree.

The canyon is why any of this is here. A 2023 study in the Journal of Environmental Management mapped three years of common dolphin sightings and found the pods strung along the canyon's vertical axis, feeding, mating, breeding and rearing calves in a well defined area the authors call critical habitat.

The water does the rest. Atlantic water pours in through the Strait on the surface, denser Mediterranean water slides out underneath, tides drag the two layers about, and a local upwelling sits at the mouth of the bay. The result is a small patch of sea that keeps producing food. It is also under heavy pressure. The 2026 paper lists what shares the bay with the dolphins: one of the busiest commercial shipping routes in Europe, heavy port operations, fishing, and a growing whale watching sector, all of it close to the animals.

So when your boat clears the marina and heads for open water instead of following the shoreline, that is not the skipper padding out the trip. That is where the fish are.

Billie

In 2006 a solitary juvenile female bottlenose turned up in the bay and started swimming with common dolphins. Researchers named her Billie. She has been recorded with common dolphin groups ever since, even though there are other bottlenose in the same water, and the 2026 paper treats her as a category of her own because she does not behave like her own species.

On 11 August 2016 she was photographed pushing a newborn to the surface with no other dolphin nearby. The calf carried foetal folds, the creases a newborn keeps from being curled in the womb. The team published the case in PLOS ONE in April 2019 as the first recorded hybrid in the wild between a bottlenose and a short beaked common dolphin.

The caveat is in the paper itself. There is no genetic confirmation. The researchers judged a biopsy on a calf that young too risky, and rested the case on photo identification and the animal's shape and markings. It is a strong case built on ten years of watching one female. It is not a DNA test, and they do not claim it is.

Mixed groups of both species had never before been recorded locally. That is what made a calf with both sets of features worth a paper.

Local coverage at the time put its finger on the oddity: these two species usually keep away from each other. The same team then went and measured how far apart they actually stay. That is the 2026 paper, and it is why one strange calf is worth 2,410 sightings of context.

The 99 per cent, and what it is actually measuring

Operators here advertise sightings on about 99 per cent of trips. We have no reason to doubt the number, and it answers a question you did not ask. It means you will see a dolphin. It says nothing about which one, or how close, or for how long.

The research boat, working the same bay with binoculars and people paid to look, still had blank days. The paper names 25 March, 16 April, 24 April and 29 May 2018 as survey days with no dolphins at all in conditions that were otherwise fine. Those are given as examples rather than the full list. That is the paper's wording, not ours.

The variable that actually decides your afternoon is wind. A hard levante turns the bay into a washing machine and trips get pulled, sometimes for days together. If the Rock is wearing its levanter cloud, ring the operator before you walk down. Mornings are usually flatter than afternoons. Go early.

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What the boats do, and the rules meant to stop it

This part is not on the ticket. A 2025 study in Marine Environmental Research, same team, same bay, sorted sightings into regulated and unregulated boat encounters and tracked six behavioural states. Feeding and resting were significantly altered. The authors conclude that the presence of boats, and non compliance with the approach protocol, were the main causes.

Gibraltar's rules are strict on paper. Every whale and dolphin is protected under the Nature Protection Act, and the Cetacean Protocol introduced in 2014 draws a 60 metre exclusion zone, a 300 metre separation where adults have young with them, and a 500 metre radius inside which a vessel does no more than four knots. The Department of the Environment reissued the reminder on 31 May 2026, with 58009620 to call for an animal in distress. Our guide to the Strait's pilot whales sets out the full geometry, including the 20 minute limit on one vessel and the 30 minute rest after two.

The 2023 paper names the pressures it found: collisions with small vessels under 15 metres, and sport fishing, specifically popping, ballooning and trolling, on top of noise. Gibraltar banned popping inside its Dolphin Protection Zone in 2018. A canyon does not stop at a line on a chart, and the researchers' conclusion is that a cross border micro sanctuary is needed, with proposed coordinates and a delimited area set out in the paper.

Gibraltar already protects a lot of sea. The Southern Waters of Gibraltar are designated as both a Special Area of Conservation and a Special Protection Area, running three miles east and south of the Rock and west to the median line in the bay. What does not exist is a single regime covering the whole canyon on both sides. That is the gap the 2023 paper is aimed at.

Where these three animals actually stand

They share a bay and they carry very different labels.

The common dolphin's Mediterranean subpopulation has been Endangered on the IUCN Red List since 2003. The Alboran Sea next door holds most of what is left, with the most recent estimate at 19,082 animals, coefficient of variation 4.7 per cent, in the northern third of that sea alone. The bay you are looking at is the doorway to it.

The bottlenose is in a better position. Its Mediterranean subpopulation was reassessed in 2021 and moved from Vulnerable to Least Concern, and the striped dolphin sits at Least Concern as well. Plenty of material online still prints the old Vulnerable listing for the bottlenose, so check the date on whatever you read. For the Strait itself, OSPAR carries a 2010 photo identification estimate of 297 bottlenose dolphins, 95 per cent confidence interval 276 to 332.

Set 297 animals in the Strait against 102 bottlenose sightings in four years of survey work in the bay and the picture makes sense. There are not many of them, they are spread across a lot of water, and they do not queue up alongside the common dolphins.

Booking it from here

The tourist board lists Gibraltar's licensed dolphin watching operators. They work out of Marina Bay and Ocean Village, trips run roughly 75 to 90 minutes, and in season the boats go out morning and afternoon.

We are not quoting you a price. The figures we could find sat on resale sites in dollars and euros rather than on the operators' own pages, and we would rather say that than print a number that is wrong by the time you read it. Walk down to the kiosks and ask, or phone.

Take binoculars. The 60 metre rule means a fair amount of what you watch will be at a distance, and that is the law working rather than the trip being short changed. Take sun cover, and something warm even in June, because the bay runs windier than the town. Children do well on a 75 minute trip and badly on a rough one.

One thing guests get wrong every week. A bay trip is not a whale trip. Pilot whales, sperm whales and the Strait's orcas are out past Tarifa, and they need a different boat and half a day. If you want the water without a boat at all, our guide to snorkelling Camp Bay covers what you can reach on foot.

Victory Suites runs 100+ apartments in Gibraltar, on Devils Tower Road, about 15 minutes on foot from the Marina Bay and Ocean Village berths. Ask the team which operators are sailing that week and what the wind is doing. We hear about cancellations before the websites update.