Oregon State study finds new way to monitor whales' hormone health

The physiology of baleen whales is not well understood, but a new research project is changing what marine biologists know about the health and environmental stress of these large aquatic animals. 

Baleen whales are named for the material that hangs from their upper jaw and helps them filter small krill, fish and other food from the water.

A team of scientists working with the Marine Mammal Institute at Oregon State University devised an innovative and noninvasive method to study the hormones of Northern Pacific gray whales. They used drones to identify, track and record whales in the summer feeding grounds, within 10 kilometers (6.2 miles) of the Oregon coast during 2016-2018. 

From an inflatable boat, the researchers sent drones to identify particular whales. The drones' observations helped the researchers find whale "defecation events" and the researchers also were close enough to spot events with their eyes. They collected fecal samples from the whales in nylon mesh nets. This fecal material was then analyzed for its hormone quantification.

In this way the research team was able to establish a hormonal baseline for the whales along with their nutritional states. They recorded fluctuations that could be correlated with age, sex, stressful events and reproductive or nutritional states . The team's assessment of fecal steroid and hormone metabolites was published in Conservation Physiology, Dec. 7, 2020.

Current Science Daily interviewed lead author Leila Lemos, who is now a postdoctoral associate at Florida International University. We asked her about the project and its importance for understanding how environmental stressors affec the Northern Pacific gray whale.

"This was the first effort to try identifying baseline vs. abnormal hormone concentrations in gray whales, as nobody has done that before in this species," Lemos said. "It is important to first understand the range of common levels to later identify what is out of this range and why."

She added, "We were able to determine the range of four hormone metabolite concentrations [progestin, androgen, thyroid, and glucocorticoid] for the species and to also present a few case studies that helped us determine what are baseline and abnormal hormone concentrations."

Lemos spelled out some specific findings of the project:

1) Post-weaning and pregnant females displayed the highest progestin metabolite concentrations.

2) Mature males displayed the highest androgen, glucocorticoid and thyroid metabolite concentrations.

3) All hormone metabolites, with the exception of androgens, significantly varied by year.

There were also two case studies of abnormal concentrations, Lemos said. "In the first one, an injured whale displayed higher glucocorticoid metabolite concentrations after an injury, possibly a vessel strike, when compared to previous fecal samples of the same individual."

"In the second case," she said, "we observed that a male displaying reproductive competitive behavior with another male towards a female, displayed higher androgen concentrations."  

Tracking and sample collection

How were the fecal samples collected and how were individual whales tracked? 

Lemos described the process: "There were usually three to four people in the boat looking for gray whales. Whenever a gray whale was spotted, we would start taking photos for photo identification and we flew overhead with drones for photogrammetry analyses to determine their body condition/nutritional state."

"Then we would just wait for any defecation event," she continued. "Gray whales would come to the surface and breathe three to five times before heading down for longer periods of time, so we would just wait for that final breath and the dive. That's when they would defecate."

Lemos explained that the researchers noted the time and photo of each defecation event so that they could match it to the individual whale that produced the sample.

The samples were collected using two fine mesh nets, Lemos said. "We would scoop the feces out of the sea surface multiple times--and as fast as possible, as they tend to sink within 30 seconds--and then combine the material collected from both nets into a single jar by using a squeeze bottle containing seawater." 

Stressors

The project aimed to look at hormone concentrations over time, Lemos said, adding, "to determine possible variations that might be linked to stressors, such as vessel traffic, noise, pollution, lack of food. Once these stressors are identified, we can inform population management and conservation efforts regarding minimizing the impact of these stressors on whales and work closely with the government and stakeholders."

Lemos described some of the project's case studies that linked stressors or reproductive states linked to abnormal hormone concentrations. 

"The first case study was an injured whale named `Equal' that we have fortunately collected samples from before and after the injury event" Lemos said. "We found increased glucocorticoid levels --stress-related hormone metabolites, e.g. cortisol--in the feces collected about 24 hours or less after the injury event, which we believe to be a vessel strike. This fact also tells us about the gut transit time of a gray whale: from the time that the stress response began to the moment when the hormone metabolite came out in the feces, which is still unknown in baleen whales."

Lemos also reported on a second case study of a whale named "Harry." 

"We know Harry is a mature male, according to photo-identification efforts and information collected --based on genetics--from the long-term catalog held by the Cascadia Group, up in Olympia, Washington," she said.

After Harry was seen in a competitive behavior with another male toward a female, Lemos said, we were able to collect a fecal sample that displayed elevated androgen levels, e.g., testosterone, when compared to other males," she noted.

"We also found that known pregnant females, seen in the following year with a calf, also displayed elevated concentrations of progestin levels (e.g., progesterone), when compared to other females," Lemos said.

The next steps

"The study must continue to be able to determine the causes and effects of varied stressors in  these individuals, and at a larger scale, in this population," Lemos said. "Are these stressors affecting their communication, their body condition, their ability to find food? Are these stressors affecting their immune system, their reproduction? These are all good questions that we are trying to answer with studies like this."

She noted that other ongoing studies are looking at the link of stress-related hormones to nutritional state and to ambient noise.

"I think these are the next steps, in addition to continuing the monitoring and collecting samples," Lemos said. "Stay tuned."

The research was conducted under the NOAA/NMFS permits #16011 and #21678 issued to John Calambokidis, and the fecal samples were analyzed at the Seattle Acquarium.