SEATTE, Wash. - A U.S. government agency says a killer whale that is part of the endangered southern resident population appears to have lost weight.

The whale known as K25 is a 27-year-old adult male who has been documented in aerial photos since 2008 and the U.S. National Oceanic and Atmospheric Administration says he appears thinner.

The department says his "notably poorer body condition compared with recent years" coincides with the loss of his mother last year, adding that males rely on their mothers and other family members to meet their increased energy demands.

The agency says its long-term monitoring has show adult males have an increased mortally risk following the deaths of their mothers, which highlights K25's vulnerability.

Aerial photos also show that several females in the three pods that make up the endangered southern resident population are pregnant, although the department says there's a high rate of reproductive failure.

A sickly killer whale from the same pod disappeared earlier this month after experts from Canada and the U.S. tried to save the emaciated female.