Variation in whale stress hormone levels in response to COVID19-related decreases in ocean noise and vessel traffic
Hearing is the primary sensory modality that marine mammals use to communicate, develop social bonds, and forage. Underwater noises from human disturbances, including the presence of marine traffic, can significantly affect their behavior, physiology, and ultimately survivorship. Increased anthropogenic noise can disrupt social interactions, breeding and offspring rearing, increase energy expenditure to vocalize above increased background noise, decrease foraging efficiency through changes in patterns of feeding or habitat abandonment. Further, noise impacts can be manifest physiologically as increased levels of stress-related hormones. Persistence and interactions among behavioral and physiological effects of disturbance can have cumulative effects that are just starting to be understood involving decreases in individual animal survivorship and fecundity leading to population declines. Quantifying these impacts in the absence of disturbance is often challenging, but recent events related to how human activities have been affected by the COVID19 pandemic offer a unique opportunity to conduct a natural experiment that is otherwise impossible.
Monterey Bay, Cape Cod, and Puget Sound are critical feeding ground for several whale species, and also have real-time, calibrated, wide bandwidth passive acoustic monitoring systems (e.g. Monterey Accelerated Research System: MARS, MBARI) in place, and offer easy access to sample whales. We propose a unique study to collect biopsy samples from humpback whales, both as a rapid response to the current COVID19-related slow-down now and in a comparable period when activity and disturbance is more typical. Tissue samples will be evaluated for stress hormone levels and compared with concurrent noise levels and vessel activity (derived from available tracking information and passive acoustic detections of vessels) in each region to monitor how changes in anthropogenic noise and disturbance affect these whales in different conditions. The current conditions for vessel noise in the region associated with changes in human activity related to the COVID-19 pandemic provides a truly unique opportunity for this comparative study. This will help us not only understand the magnitude of physiological stress associated with different levels of disturbance, but inform ongoing efforts to set science-based goals to strategically quiet large vessels once industrial activity returns to more typical conditions.
Our research will:
- Document baseline glucocorticoid levels of humpback whales of different ages/reproductive states around Monterey Bay, CA, Stellwagen Bank, MA, and Puget Sound, WA
- Describe natural variation in glucocorticoid levels over time within individuals and across populations
- Determine whether we can detect an increase in glucocorticoids in blubber samples that can be related to increased anthropogenic activity and sound in different regions
- Compare blubber glucocorticoid concentration between animals exposed to low anthropogenic activity and then to high anthropogenic activity in the same region at the same time of year as well as across regions
Check out additional COVID related research happening at UC Santa Cruz here.
Other collaborators and partners include: Ms. Carley Lowe (PhD Candidate, Northern Arizona University), Mr. Logan Pallin (PhD Candidate, UC Santa Cruz), Dr. Jim Johnson (NPS), and Dr. Sophie Van Parijs (NEFSC)