Comparison of photographs of endangered Western gray whales obtained from the Sakhalin Island, Russia feeding grounds with photo-identified individuals from the Baja California Peninsula, Mexico breeding lagoons resulted in 14 matches between these two locations. These included six males, six females and two whales of unknown sex. Thirteen of these endangered Western whales were observed in Laguna San Ignacio and one in Laguna Ojo de Liebre, indicating that some Western gray whales migrate from their summer Russian feeding grounds to North America in the fall and migrate with Eastern gray whales to winter breeding areas off Baja California Sur, Mexico.
UPDATE: As of 2014 there have been 23 photographic matches of “Western gray whales” in the breeding lagoons of Baja California, including breeding females in Laguna Ojo de Liebre and Laguna San Ignacio, confirming that some “Western” gray whales visit the winter aggregation and breeding areas of the North Eastern Pacific population during the breeding season.
Researchers previously thought that Western gray whales migrated along the Pacific coast of Asia to breeding areas off of Korea and China. Recent incidental catches, sightings and strandings of gray whales off Japan and China suggest that some Western gray whales do migrate to winter off China, however, it is now clear that others join the larger Eastern North Pacific population and spend the winter off of Baja California Mexico where they may interbreed with Eastern gray whales.
Three of the whales were sighted the same day in Laguna San Ignacio suggesting that these animals were traveling in association with each other, and perhaps with other Western whales. Three of the five females with calves sighted in the winter in Mexican waters were seen the following summer off Sakhalin without their calves suggesting that these females had either separated from their calves as part of the normal weaning process, or that their calves did not survive due to predation by killer whales or other causes. The mean time between the last sighting in one season and the first one in the next season was 195.4 days (n=11, 141-255) during the summer-winter migration, and 165.6 days (n=13, 131-213) during the winter-summer migration.
The matches made between whales sighted off Sakhalin and the Mexican Pacific are the first results of the multinational collaboration “Pacific Wide Study on Population Structure and Movement Patterns of North Pacific Gray Whales” initiated under the coordination and support of the International Whaling Commission last year. Additional comparisons and analyses of photographs from the Western and Eastern gray whales are ongoing and will include photographs from Laguna San Ignacio and Bahia Magdalena winter aggregation and breeding areas, obtained during the 2012 winter.