Is the monk seal returning to shores? The new pilot that may save one of the world's rarest marine mammals

The Mediterranean monk seal population has shown an impressive recovery in recent decades, but its concentration in just three caves off the coast of Mauritania is causing concern among researchers, who are now proposing an ambitious solution

Good news: The population of Mediterranean monk seals (Monachus monachus), one of the rarest marine mammals in the world, is no longer considered under immediate threat, and now, a new pilot project may even help the population expand further.

Despite the impressive recovery of this population, which numbered only about 450 individuals in the early 2000s and now numbers about 1,000, about half of the population is now concentrated in the Cabo Blanco region of Mauritania and Western Sahara - which is a cause for concern among researchers. A single extreme event - a disease, a cave collapse, marine pollution or an unusual storm - could affect a significant portion of the global population.

Map of Mediterranean monk seal population concentrations. From the article "On sightings of (vagrant?) monk seals, Monachus monachus, in the Mediterranean Basin and their importance for the conservation of the species"

What happened in Cabo Blanco?

The Western Sahara War at the end of the last century left the shores of Cabo Blanco with a small population of seals numbering only about 320, after many of them were injured by mines placed along the coast. In 1997, the population suffered another blow: a mass mortality event during which over 100 seals were found dead along the beaches - most of them adults and one pup. Within a few months, about two-thirds of the seals had disappeared, and after the disaster only 108 individuals remained.

Since then, thanks to international collaborations, habitat protection, and long-term monitoring, the population has gradually recovered and now numbers over 350 individuals and dozens of new cubs are born each year, all in three caves located along one kilometer of coastline.

Sign on the coast of South Africa. Photo: Olga Ernst

The new pilot: establishing new seal colonies

A new study published this month explores an ambitious possibility: relocating young pups from the source population in Cabo Blanco to areas in the Atlantic Ocean where Mediterranean monk seals once lived, such as Madeira, the Azores, and the Canary Islands, with the aim of establishing new colonies, increasing genetic diversity, and reducing the risk of regional extinction.

The researchers used demographic models to test whether the source population could “withstand” the transfer of cubs without being harmed. The results were encouraging: Even after transferring six cubs each year for five years, the population in Cabo Blanco is expected to continue to grow.

In addition, the researchers assessed the feasibility of establishing new populations and returning seals to places where they previously lived, weighing biological and human data: the coasts of Cabo Blanco benefit from estuarine currents that support a rich food web, while the Madeira Islands, for example, are known for relatively low primary production and low prey availability. When choosing a new location for the transfer of pups, the characteristics of these marine and coastal habitats must be carefully assessed - which can affect the reproduction and survival rates of monk seals, and thus also the rate of population growth and its viability. Furthermore, social, economic and cultural factors must also be considered and addressed when choosing sites for seal reintroduction, as these may affect the survival rates of a newly established Mediterranean seal population.

Why open beaches?

One of the interesting insights in the study is related to the place of birth. Today, most monk seals give birth in isolated sea caves - probably as a result of human pressure over centuries. But in these caves, many pups are affected by floods and storms. According to the researchers, a return to giving birth on open beaches - as was the case in the past - may actually improve the pups' chances of survival.

Yulia the Mediterranean monk seal, during her visit to Israel in May 2023. Photo: Maor Siboni

What does this mean about Israel?

In recent years, monk seals have also been spotted off the coast of Israel, after an absence of decades. The hope is that the recovery and growth of populations throughout the Mediterranean Sea and the Atlantic Ocean will allow the rare species to gradually return to areas from which it previously disappeared.

Dr. Mia Elasar from Delphis, who leads the project to bring monk seals back to Israel: “Although personally it is difficult for me to think about separating and relocating young seals from their natural habitat, I am glad that the population’s condition has improved to the point where steps are being considered to help ensure the future survival of Mediterranean monk seals. Knowing the group of researchers involved, I am confident that every step is being considered with great care and sensitivity.”

In parallel with Delphis' activity to restore caves for seals in the Rosh Hanikra area, the association continues to work these days to raise awareness of the importance of reporting sightings. In recent months, Delphis has received several reliable (undocumented) reports of seal sightings, and researchers continue to monitor and verify each report.

One of the best ways to protect marine mammal populations off the coast of Israel is to report sightings. Have you seen a seal or any other marine mammal? Keep a distance, take pictures, and report!