U.S. Navy - Living Marine Resources Program - Hearing and estimated noise impacts in three species of Auk: Implications for the marbled murrelet

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Marbled murrelets (Brachyramphus marmoratus) are long-lived seabirds that spend most of their life in the marine environment. While old-growth forests are used for nesting, many vital biological activities such as courtship, foraging, molting, and preening occur in near-shore marine waters. Unfortunately for this bird its amount of suitable habitat has declined over many years and all population modeling efforts to date predict a long-term downward trend for marbled murrelet populations. Consequently, the species is listed as threatened under the Federal Endangered Species Act in Washington, Oregon and California, and State-listed as endangered in California.

This poses a problem for the U.S. Navy. Many areas that are natural habitat of the endangered marbled murrelet also overlap with interests of the U.S. Navy. For example the Hood Canal, WA is site designated for Navy construction of a second explosives handling wharf to support the Trident D-5 Missile program. Concerns for noise impacts on the marbled murrelet are influencing and slowing some construction and training/operations plans. According to the U.S. Navy’s final Environmental Assessment of proposed action to remove and replace fender piles at Naval Base (NAVBASE) Kitsap Bremerton, both “underwater and airborne sound from impact and vibratory pile driving at this and other sites have the potential to harass marbled murrelets foraging and resting in the project area. Exposure to underwater sounds from pile replacement could cause behavioral disturbance” (Navy 2013; Navy 2015). Underwater acoustics are a particular concern because sound travels relatively efficiently underwater, and high-intensity, low-frequency and mid-frequency sounds such as pile-driving and sonar may convey acoustic energy long distances away from the source (Brandt et al. 2011). The final report from the Marbled Murrelet Underwater Noise Injury Threshold Panel (convened by the US Fish and Wildlife and NAVFAC Northwest) suggested that pile driving and other impulse activities have the potential to cause auditory injuries including temporary and permanent hearing threshold shifts (NAVFAC Northwest and USFWS 2011). Yet, there are no data on temporary and permanent hearing threshold shifts. Nor are there even basic data on the hearing of marbled murrelets or any other Auk family limiting any predictions of the frequencies or sound levels which would actually induce impacts. Thus, the U.S. Navy is unable to predict with any certainty the appropriate criterion for evaluating the onset of hearing loss injury in the marbled murrelet.

The goal of this work is to define the hearing of three Auk species providing clear data to predict the hearing of the marbled murrelet. Secondly, we plan to carry out a feasibility study addressing temporary threshold shifts (TTS) in Auks, in order to lay the framework of the levels and methods to induce and measure auditory noise-impacts in this taxon. The final products will include underwater behavioral audiograms; additionally, comparative in-air physiological and behavioral tests will be conducted first to outline the frequencies and sound levels used in the underwater tests, as well as help groundtruth the underwater data and address potential Auk underwater auditory adaptations. The audiograms will then provide the data and training foundation for the TTS response feasibility study.

Because of its protected status, the marbled murrelet itself will not be used, yet the incorporation of three closely related species greatly supports the power of this endpoint: underwater Auk audiograms.
The specific objectives of this study include:

1) Conduct field-based, in-air evoked potential audiograms to address the initial sensitivity, and potential species differences of three Auk species.
2) Establish the in-air psychophysical (behavioral) audiograms of 1-3 Auk species.
3) Establish the underwater psychophysical (behavioral) audiograms of 1-3 Auk species.
4) Compare physiological and behavioral methods, and underwater vs. air results to evaluate the best means to quantify Auk hearing, setting the foundation for future noise-exposure studies.
5) Determine the levels at which Auks show TTS responses to sonar (1 species).
StatusAfsluttet
Effektiv start/slut dato01/09/201731/08/2019