Researchers studying the endangered southern resident killer whales have made an alarming observation regarding the rise of skin disease within this population.
In a recently published study in PLOS ONE, it was noted that there has been a notable rise in the occurrence of gray patches and gray targets on the whales’ skin from 2004 to 2016. Although the exact cause remains unknown, the researchers express their concern about this finding.
Environmental factors, such as changes in water temperature or salinity, were carefully examined and ruled out as potential causes. Instead, the study’s authors propose that an infectious agent is the most likely explanation, suggesting that the increasing presence of lesions might indicate a weakening of the whales’ immune systems in fighting off diseases.
This distressing finding adds another substantial peril to the well-being of the already vulnerable southern resident killer whale community, which is grappling with numerous challenges.
A vast collection of digital photographs, amounting to thousands, has played a pivotal role in this research endeavor.
The project is spearheaded by Joseph K. Gaydos, a wildlife veterinarian and the science director of the SeaDoc Society, a program affiliated with the School of Veterinary Medicine at the University of California, Davis.
Gaydos and a team of collaborators conducted an analysis of over a decade’s worth of digital photographs. These images, acquired by the Center for Whale Research for the purpose of identification, encompassed nearly 20,000 sightings of individual whales in the Salish Sea. This comprehensive photographic dataset provides crucial information for remotely assessing the health of these endangered creatures.
Since 1976, the Center for Whale Research has conducted photographic identification surveys of southern resident killer whales in the Salish Sea, capturing clear images of each distinct individual. During the analysis of these images, biologists discovered sporadic and occasionally persistent abnormal skin changes in the whales. However, these skin alterations had never been systematically characterized or monitored over time for research purposes.
The photographs unveiled the existence of six distinct skin disease syndromes, none of which were linked to mortality. Nevertheless, the unexpected steady increase in the prevalence of the two most common lesions raised concerns.
Gaining an understanding of the occurrence and significance of skin changes in southern resident killer whales is crucial for assessing their overall health and determining their potential impact on population recovery.
This endangered population, consisting of specialized fish-eating salmon experts, roams coastal and inland waters from southeastern Alaska to California. They are socially structured into three pods: J, K, and L.
With fewer than 75 individuals remaining, the population is in a perilous state. Previous studies have primarily focused on identifying causes of mortality and evaluating body condition, leaving limited knowledge about the role of health in the population’s failure to recover.
Gaydos expressed surprise at the substantial increase in the prevalence of these skin lesions, stating, “Before we looked at the data, we had no idea that the prevalence of these skin lesions were increasing so dramatically. It’s worrisome. Now we need to try and isolate the potential infectious agent.”
Providing valuable insights into the well-being of an endangered species, photographic identification serves as a noninvasive method for studying skin disorders and their epidemiology. While it may not pinpoint specific causes, it remains instrumental in assessing the overall health of the animals, especially when capture-release health assessments are impractical.
This research represents a significant stride in comprehending the epidemiology of skin changes observed in southern resident killer whales. The findings underscore the necessity for ongoing monitoring and research endeavors aimed at unraveling the causes and health implications associated with these skin alterations. The ultimate objective is to contribute to the conservation and recovery of this endangered population.
The collaborative effort involved various institutions, including the SeaDoc Society, the Center for Whale Research, British Columbia’s Animal Health Center, NOAA’s Northwest Fisheries Science Center, San Diego Zoo Wildlife Alliance, SeaWorld Parks and Entertainment, the Vancouver Aquarium, Wild Orca, and several others. Together, they have contributed to this important endeavor.
Image Credit: Joe Gaydos, UC Davis