Around 250 long-finned pilot whales live in the Strait of Gibraltar and stay there every month of the year. Photo identification work has matched the same individual dorsal fins season after season since the late 1990s, which is what makes them residents rather than passers-by. Here is the part that catches our guests out. The boats leaving Ocean Village and Marina Bay work the Bay of Gibraltar, and the pilot whales spend most of their time out in the Strait itself, off Tarifa. Same water on a map. Different trip, different animals, different price. [firmm, the Tarifa research foundation that has recorded sightings in the Strait since 1998](https://www.firmm.org/en/whales-dolphins/pilot-whale), puts adults at 4 to 7 metres and 1.8 to 3.5 tonnes, with calves born at 1.5 to 2 metres and about 75 kilograms. The same source gives a maximum recorded dive of 824 metres, dives of up to 20 minutes, and a daily intake of roughly 27 kilograms, mostly squid. The social numbers matter more than the size. Gestation runs about 15 months, nursing about 27 months, and a pilot whale can live around 60 years. Families in the Strait have historically averaged roughly 14 animals. A population that breeds that slowly does not bounce back from a bad year. It had one. A morbillivirus epidemic swept the western Mediterranean in 2006 and 2007, and researchers who track these families reported the Strait population falling by roughly a quarter in the five years that followed. The published figures do not all line up, and we would rather show you that than smooth it over. A photo identification study put summer numbers between 147 in 1999 and 265 in 2003. The epidemic knocked about a quarter off. Recent work describes a resident population of roughly 250 again. Treat 250 as a working figure, not a census. What is not in doubt is the listing. The Strait of Gibraltar subpopulation is Critically Endangered, alongside the Strait's orcas, in the [2018 to 2021 round of IUCN Red List assessments compiled for ACCOBAMS](https://accobams.org/wp-content/uploads/2022/11/MOP8.Inf26_Information-note-on-the-IUCN-Red-List-status.pdf). The Strait is 14.2 kilometres across at its narrowest, and the [seabed under it is a set of sills rather than a trench](https://en.wikipedia.org/wiki/Camarinal_Sill). The shallowest, the Camarinal Sill, sits about 280 metres down and roughly 25 kilometres west of the narrows. That shape does the work. Atlantic water flows in on top, denser Mediterranean water flows out underneath, and the tide dragging those two layers across the sill throws up internal waves that can be traced for as much as 100 kilometres. The usual explanation for the wildlife follows from that: the mixing keeps prey concentrated in a strip of water you could swim across in a day. Squid for the pilot whales, tuna for the orcas, small fish for the dolphins. That is also why the same 14 kilometres attract the raptor migration overhead. If you have read our [guide to watching the raptor crossing](/blog/gibraltar-raptor-migration-strait-watching-guide), it is the same geography doing the same trick, in a different medium. Seven cetacean species are seen with any regularity. Four of them are here all year, which is the single most useful fact for planning a trip, and three are seasonal. The status column is from the ACCOBAMS note above, and it is the assessed subpopulation rather than the species worldwide. |Species|When it is in the Strait|Where you realistically see it|Local subpopulation status| |Long-finned pilot whale|Every month|Strait proper, off Tarifa|Critically Endangered, Strait of Gibraltar| |Common dolphin|Every month|Bay of Gibraltar and the Strait|Endangered, Inner Mediterranean| |Striped dolphin|Every month|Deeper water in the Strait|Least Concern, Mediterranean| |Bottlenose dolphin|Every month|Bay of Gibraltar and the Strait|Least Concern, Inner Mediterranean| |Sperm whale|Mainly spring, into summer|Deepest water in the Strait|Endangered, Mediterranean| |Orca|Mainly July and August|Strait, wherever the tuna are|Critically Endangered, Strait of Gibraltar| |Fin whale|In transit, mostly warmer months|Open water, crossing between two seas|Endangered, Mediterranean| Read that last column carefully. Only the pilot whale and the orca are assessed as Strait of Gibraltar subpopulations. The other five listings are Mediterranean ones, and the Strait sits on the boundary between two seas. For those, the label is indicative rather than a verdict on the animals in front of your boat. The orcas are the ones people ask about, and they are also the ones with the shortest window. They follow Atlantic bluefin tuna, which means the Gulf of Cadiz in spring and the Strait in high summer. firmm only runs its longer three hour trip when there is a realistic chance of orcas, which tells you how narrow that window is. One line in that table deserves a footnote. Fin whales are usually described as passing through. But a drifting hydrophone recording made near Bar