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Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations
although such encounters would be rare due to the limited distribution of walruses in the Beaufort Sea. These encounters may occur within certain cohorts of the population, such as calves or animals under stress. In 2004, a suspected orphaned calf hauled-out on the armor of Northstar Island numerous times over a 48-hour period, causing Industry to cease certain activities and alter work patterns before the walrus disappeared in stormy seas.
Additionally, a walrus calf was observed for 15 minutes during an exploration program 60 ft from the dock at Cape Simpson in 2006. From 2009
through 2020, Industry reported no similar interactions with walruses.
In the nearshore areas of the Beaufort Sea, stationary offshore facilities could produce high levels of noise that have the potential to disturb walruses. These include Endicott, Hilcorps Saltwater Treatment Plant located on the West Dock Causeway, Oooguruk, and Northstar facilities. The Liberty project will also have this potential when it commences operations. From 2009
through 2020, there were no reports of walruses hauling out at Industry facilities in the Beaufort Sea ITR region.
Previous observations have been reported of walruses hauled out on Northstar Island and swimming near the Saltwater Treatment Plant. In 2007, a female and a subadult walrus were observed hauled-out on the Endicott Causeway. The response of walruses to disturbance stimuli is highly variable.
Anecdotal observations by walrus hunters and researchers suggest that males tend to be more tolerant of disturbances than females and individuals tend to be more tolerant than groups. Females with dependent calves are considered least tolerant of disturbances. In the Chukchi Sea, disturbance events are known to cause walrus groups to abandon land or ice haulouts and occasionally result in trampling injuries or cow-calf separations, both of which are potentially fatal. Calves and young animals at terrestrial haulouts are particularly vulnerable to trampling injuries. However, due to the scarcity of walrus haulouts in the ITR area, the most likely potential impacts of Industry activities include displacement from preferred foraging areas, increased stress, energy expenditure, interference with feeding, and masking of communications. Any impact of Industry presence on walruses is likely to be limited to a few individuals due to their geographic range and seasonal distribution.
The reaction of walruses to vessel traffic is dependent upon vessel type,
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distance, speed, and previous exposure to disturbances. Walruses in the water appear to be less readily disturbed by vessels than walruses hauled out on land or ice. Furthermore, barges and vessels associated with Industry activities travel in open water and avoid large ice floes or land where walruses are likely to be found. In addition, walruses can use a vessel as a haulout platform. In 2009, during Industry activities in the Chukchi Sea, an adult walrus was observed hauled out on the stern of a vessel.
Walrus: Effects of In-Water Activities Walruses hear sounds both in air and in water. They have been shown to hear from 60 hertz Hz to 23 kilohertz kHz in air Reichmuth et al. 2020. Tests of underwater hearing have shown their range to be between 1 kHz and 12 kHz with greatest sensitivity at 12 kHz Kastelein et al. 2002. The underwater hearing abilities of the Pacific walrus have not been studied sufficiently to develop species-specific criteria for preventing harmful exposure. However, sound pressure level thresholds have been developed for members of the other carnivore group of marine mammals Table 1.
When walruses are present, underwater noise from vessel traffic in the Beaufort Sea may prevent ordinary communication between individuals by preventing them from locating one another. It may also prevent walruses from using potential habitats in the Beaufort Sea and may have the potential to impede movement. Vessel traffic will likely increase if offshore Industry expands and may increase if warming waters and seasonally reduced sea-ice cover alter northern shipping lanes.
The most likely response of walruses to acoustic disturbances in open water will be for animals to move away from the source of the disturbance.
Displacement from a preferred feeding area may reduce foraging success, increase stress levels, and increase energy expenditures.
Walrus: Effects of Aircraft Overflights Aircraft overflights may disturb walruses. Reactions to aircraft vary with range, aircraft type, and flight pattern as well as walrus age, sex, and group size.
Adult females, calves, and immature walruses tend to be more sensitive to aircraft disturbance. Walruses are particularly sensitive to changes in engine noise and are more likely to stampede when planes turn or fly low overhead. Researchers conducting aerial surveys for walruses in sea-ice habitats have observed little reaction to fixedwinged aircraft above 457 m 1,500 ft
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USFWS unpubl. data. Although the intensity of the reaction to noise is variable, walruses are probably most susceptible to disturbance by fastmoving and low-flying aircraft 100 m 328 ft above ground level or aircraft that change or alter speed or direction.
In the Chukchi Sea, there are recent examples of walruses being disturbed by aircraft flying in the vicinity of haulouts. It appears that walruses are more sensitive to disturbance when hauled out on land versus sea-ice.
Effects to Prey Species Industry activity has the potential to impact walrus prey, which are primarily benthic invertebrates including bivalves, snails, worms, and crustaceans Sheffield and Grebmeier 2009. The effects of Industry activities on benthic invertebrates would most likely result from disturbance of seafloor substrate from activities such as dredging or screeding, and if oil was illegally discharged into the environment.
Substrate-borne vibrations associated with vessel noise and Industry activities, such as pile driving and drilling, can trigger behavioral and physiological responses in bivalves and crustaceans Roberts et al. 2016, Tidau and Briffa 2016. In the case of an oil spill, oil has the potential to impact benthic invertebrate species in a variety of ways including, but not limited to, mortality due to smothering or toxicity, perturbations in the composition of the benthic community, as well as altered metabolic and growth rates.
Additionally, bivalves and crustaceans can bioaccumulate hydrocarbons, which could increase walrus exposure to these compounds Engelhardt 1983.
Disturbance from Industry activity and effects from oil exposure may alter the availability and distribution of benthic invertebrate species. An increasing number of studies are examining benthic invertebrate communities and food web structure within the Beaufort Sea Rand and Logerwell 2011, Divine et al. 2015. The low likelihood of an oil spill large enough to affect walrus prey populations see the section titled Risk Assessment of Potential Effects Upon Polar Bears from a Large Oil Spill in the Beaufort Sea combined with the low density of walruses that feed on benthic invertebrates in this region during openwater season indicates that Industry activities will likely have limited effects on walruses through impacted prey species.
The effects of Industry activity upon polar bear prey, primarily ringed seals and bearded seals, will be similar to that of effects upon walruses and primarily through noise disturbance or exposure
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