Iberian orcas' search for tuna, their main food source, is leaving them trapped in certain waters off of Spain, causing researchers to worry over this already vulnerable species, a new study says.

Until now, little was known about the movements of this small population of orcas (Orcinus orca), but thanks to a new study model and more than 11,200 sightings of cetaceans over the course of 10 years, Spanish and Portuguese researchers are coming to understand their distribution, and they are concerned.

Their findings indicate that these particular orcas, or killer whales, are swimming in waters in the Gulf of Cadiz, the Strait of Gibraltar and the Alboran Sea, directly in line with the migration of red tuna in the region.

"It is possible that this group of marine mammals travels in waters close to the migration route of the tuna," the researchers said in the Journal of the Marine Biological Association of the United Kingdom.

"This limits their distribution to the Gulf of Cadiz in spring and the Strait of Gibraltar in summer," lead author Ruth Esteban explained in a statement.

Specifically, in the summer months the population will be found in the most westerly part of the center of the Strait of Gibraltar, and in the spring the most easterly area of the Gulf of Cadiz - in shallow waters around Spain and Morocco - and in southern Portugal.

Meanwhile, during the autumn and winter months, orcas have barely been seen in the most regularly populated areas.

By limiting themselves to only a certain area, Iberian orcas - which are listed as "vulnerable" and included in the Spanish Catalogue of Endangered Species - are putting themselves at risk.

"Any reduction in the abundance of tuna could endanger this population of orcas," added Esteban.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).