Taking and Importing Marine Mammals; U.S. Naval Surface Warfare Center Panama City Division Mission Activities, 20156-20199 [E9-9645]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 74, Number 82 (Thursday, April 30, 2009)]
[Proposed Rules]
[Pages 20156-20199]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-9645]



[[Page 20155]]

-----------------------------------------------------------------------

Part IV





Department of Commerce





-----------------------------------------------------------------------



National Oceanic and Atmospheric Administration



-----------------------------------------------------------------------



50 CFR Part 218



Taking and Importing Marine Mammals; U.S. Naval Surface Warfare Center 
Panama City Division Mission Activities; Proposed Rule

Federal Register / Vol. 74, No. 82 / Thursday, April 30, 2009 / 
Proposed Rules

[[Page 20156]]


-----------------------------------------------------------------------

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 218

RIN 0648-AW80


Taking and Importing Marine Mammals; U.S. Naval Surface Warfare 
Center Panama City Division Mission Activities

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: Proposed rule; request for comments.

-----------------------------------------------------------------------

SUMMARY: NMFS has received a request from the U.S. Navy (Navy) for 
authorization to take marine mammals incidental to Naval Surface 
Warfare Center Panama City Division (NSWC PCD) Research, Development, 
Test, and Evaluation (RDT&E) mission activities for the period of July 
2009 through July 2014. Pursuant to the Marine Mammal Protection Act 
(MMPA), NMFS is proposing regulations to govern that take and 
requesting information, suggestions, and comments on these proposed 
regulations.

DATES: Comments and information must be received no later than June 1, 
2009.

ADDRESSES: You may submit comments, identified by 0648-AW80, by any one 
of the following methods:
     Electronic Submissions: Submit all electronic public 
comments via the Federal eRulemaking Portal https://www.regulations.gov
     Hand delivery or mailing of paper, disk, or CD-ROM 
comments should be addressed to Michael Payne, Chief, Permits, 
Conservation and Education Division, Office of Protected Resources, 
National Marine Fisheries Service, 1315 East-West Highway, Silver 
Spring, MD 20910-3225.
    Instructions: All comments received are a part of the public record 
and will generally be posted to https://www.regulations.gov without 
change. All Personal Identifying Information (for example, name, 
address, etc.) voluntarily submitted by the commenter may be publicly 
accessible. Do not submit Confidential Business Information or 
otherwise sensitive or protected information.
    NMFS will accept anonymous comments (enter N/A in the required 
fields if you wish to remain anonymous). Attachments to electronic 
comments will be accepted in Microsoft Word, Excel, WordPerfect, or 
Adobe PDF file formats only.

FOR FURTHER INFORMATION CONTACT: Shane Guan, Office of Protected 
Resources, NMFS, (301) 713-2289, ext. 137.

SUPPLEMENTARY INFORMATION: 

Availability

    A copy of the Navy's application may be obtained by writing to the 
address specified above (See ADDRESSES), telephoning the contact listed 
above (see FOR FURTHER INFORMATION CONTACT), or visiting the internet 
at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm. The Navy's 
Draft Environmental Impact Statement (DEIS) for the NSWC PCD mission 
activities was published on April 4, 2008, and may be viewed at https://nswcpc.navsea.navy.mil/Environment-Documents.htm. NMFS participated in 
the development of the Navy's DEIS as a cooperating agency under the 
National Environmental Policy Act (NEPA).

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce (Secretary) to allow, upon request, 
the incidental, but not intentional taking of marine mammals by U.S. 
citizens who engage in a specified activity (other than commercial 
fishing) during periods of not more than five consecutive years each if 
certain findings are made and regulations are issued or, if the taking 
is limited to harassment, notice of a proposed authorization is 
provided to the public for review.
    Authorization shall be granted if NMFS finds that the taking will 
have a negligible impact on the species or stock(s), will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses, and if the permissible methods of taking 
and requirements pertaining to the mitigation, monitoring and reporting 
of such taking are set forth. NMFS has defined ``negligible impact'' in 
50 CFR 216.103 as:

An impact resulting from the specified activity that cannot be 
reasonably expected to, and is not reasonably likely to, adversely 
affect the species or stock through effects on annual rates of 
recruitment or survival.

    The National Defense Authorization Act of 2004 (NDAA) (Public Law 
108-136) removed the ``small numbers'' and ``specified geographical 
region'' limitations and amended the definition of ``harassment'' as it 
applies to a ``military readiness activity'' to read as follows 
(Section 3(18)(B) of the MMPA):

(i) Any act that injures or has the significant potential to injure 
a marine mammal or marine mammal stock in the wild [Level A 
Harassment]; or (ii) any act that disturbs or is likely to disturb a 
marine mammal or marine mammal stock in the wild by causing 
disruption of natural behavioral patterns, including, but not 
limited to, migration, surfacing, nursing, breeding, feeding, or 
sheltering, to a point where such behavioral patterns are abandoned 
or significantly altered [Level B Harassment].

Summary of Request

    On April 1, 2008, NMFS received an application, which was 
subsequently amended on February 12, 2009 with additional information, 
from the Navy requesting authorization for the take of 10 species of 
cetaceans incidental to the NSWC PCD RDT&E mission activities over the 
course of 5 years. These RDT&E activities are classified as military 
readiness activities. The Navy states that these RDT&E activities may 
cause various impacts to marine mammal species in the proposed action 
area (e.g., mortality, Level A and B harassment). The Navy requests an 
authorization to take individuals of these cetacean species by Level B 
Harassment. Further, the Navy requests authorization to take 2 
bottlenose dolphins, 2 Atlantic spotted dolphins, 1 pantropical spotted 
dolphin, and 1 spinner dolphin per year by Level A harassment (injury), 
as a result of the proposed mission activities. Please refer to Tables 
6-3, 6-4, 6-6, 6-7, 6-8, and 6-9 of the Letter of Authorization (LOA) 
Addendum for detailed information of the potential marine mammal 
exposures from the NSWC PCD mission activities per year. However, due 
to the proposed mitigation and monitoring measures, NMFS estimates that 
the take of marine mammals is likely to be lower than the amount 
requested. Although the Navy requests authorization to take marine 
mammals by mortality, NMFS does not expect any animals to be killed, 
and NMFS is not proposing to authorize any mortality incidental to the 
Navy's NSWC PCD mission activities.

Background of Navy Request

    The purpose of the proposed action is to enhance NSWC PCD's 
capability and capacity to meet littoral and expeditionary warfare 
requirements by providing RDT&E and in service engineering for 
expeditionary maneuver warfare, operations in extreme environments, 
mine warfare, maritime operations, and coastal operations.
    The need for the proposed action is for the Navy to successfully 
meet current and future national and global defense challenges by 
developing a robust capability to research, develop, test, and evaluate 
systems within the NSWC PCD Study Area. This capability allows the Navy 
to meet its statutory

[[Page 20157]]

mission to deploy worldwide naval forces equipped to meet existing and 
emergent threats and to enhance its ability to operate jointly with 
other components of the armed forces. NSWC PCD was established on the 
current site maintained by the Naval Support Activity Panama City (NSA 
PC) after a thorough site selection process in 1942. The Navy 
considered locations along the east coast and in the Gulf of Mexico 
(GOM). NSWC PCD provides:
     Accessibility to deep water
     Tests in clear water
     Conducive sand bottom
     Available land and sheltered areas, and
     Average good weather (year-round testing).
    In addition to these requirements for testing, the area was 
selected based on the moderate cost of living, the availability of 
personnel, and the low level of crowding from industries and 
development. In 1945, the station was re-commissioned as the U.S. Navy 
mine countermeasure station after its turnover as a section base for 
amphibious forces in 1944. The factors identified in 1942 during the 
selection process solidified the decision.
    NSWC PCD provides the greatest number of favorable circumstances 
needed to conduct RDT&E, in particular mine countermeasure exercises. 
Many of the other locations have large amounts of vessel traffic, rough 
waters and windy conditions, and closure of waterways seasonally due to 
water level. NSWC PCD has the established infrastructure, equipment, 
and personnel as well as the conditions required to fulfill the 
Proposed Action.
    The proposed mission activities involving sonar, ordnance and line 
charges, and projectile firing would occur in the NSWC PCD Study Area, 
which includes St. Andrew Bay (SAB) and military warning areas (areas 
within the Gulf of Mexico (GOM) subject to military operations) W-151 
(includes Panama City Operating Area), W-155 (includes Pensacola 
Operating Area), and W-470 (see Figures 2-1 and 2-2 of the LOA 
application). The NSWC PCD Study Area includes a Coastal Test Area, a 
Very Shallow Water Test Area, and Target and Operational Test Fields. 
The NSWC PCD RDT&E activities may be conducted anywhere within the 
existing military operating areas and SAB from the mean high water line 
(average high tide mark) out to 222 km (120 nm) offshore (see Figures 
2-1 and 2-2 of the LOA application). The locations and environments 
include:
     Test area control sites adjacent to NSWC PCD.
     Wide coastal shelf 97 km (52 nm) distance offshore to 183 
m (600 ft), including bays and harbors.
     Water temperature range of 27 [deg]C (80 [deg]F) in summer 
to 10 [deg]C (50[deg]F) in winter.
     Typically sandy bottom and good underwater visibility.
     Seas less than 0.91 m (3 ft) 80 percent of the time 
(summer) and less than 0.91 m (3 ft) 50 percent of the time (winter).

Description of the Specified Activities

    The purpose of the proposed action is to improve NSWC PCD's 
capabilities to conduct new and increased mission operations for the 
Department of the Navy (DON). NSWC PCD provides RDT&E and in-service 
support for expeditionary maneuver warfare, operations in extreme 
environments, mine warfare, maritime (ocean-related) operations, and 
coastal operations. A variety of naval assets, including vessels, 
aircraft, and underwater systems support these mission activities for 
eight primary test operations that occur within or over the water 
environment up to the high water mark. These operations include air, 
surface, and subsurface operations, sonar, electromagnetic energy, 
laser, ordnance, and projectile firing. Among these activities, surface 
operations, sonar, ordnance, and projectile firing may result in the 
incidental take of a marine mammal species or population stock, and are 
the focus of the Navy's LOA application and LOA Addendum. A detailed 
description of these operations is provided below.

Surface Operations

    The proposed NSWC PCD mission activities include up to 7,443 hours 
of surface operations per year in the NSWC PCD Study Area. Four 
subcategories make up surface operations.
    The first subcategory is support activities which are required by 
nearly all of the testing missions within the NSWC PCD Study Area. The 
size of these vessels varies according to test requirements and vessel 
availability. Often multiple surface crafts are required to support a 
single test event. Acting as a support platform for testing, these 
vessels are utilized to carry test equipment and personnel to and from 
the test sites and are also used to secure and monitor the designated 
test area. Normally, these vessels remain on site and return to port 
following the completion of the test; occasionally, however, they 
remain on-station throughout the duration of the test cycle for 
guarding sensitive equipment in the water. Testing associated with 
these operational capabilities may include a single test event or a 
series of test events spread out over consecutive days or as one long 
test operation that requires multiple days to complete.
    The remaining subcategories of additional support include tows, 
deployment and recovery of equipment, and systems development. Tows are 
also conducted from vessels at NSWC PCD to test system functionality. 
Tow tests of this nature involve either transporting the system to the 
designated test area where it is deployed and towed over a pre-
positioned inert minefield or towing the system from NSWC PCD to the 
designated test area. Surface vessels are also utilized as a tow 
platform for systems that are designed to be deployed by helicopters. 
Surface craft are also used to perform the deployment and recovery of 
underwater unmanned vehicles (UUVs), sonobuoys, inert mines, mine-like 
objects, versatile exercise mine systems, and other test systems. 
Surface vessels that are used in this manner normally return to port 
the same day. However, this is test dependent, and under certain 
circumstances (e.g., endurance testing), the vessel may be required to 
remain on site for an extended period of time. Finally, RDT&E 
activities also encompass testing of new, alternative, or upgraded 
hydrodynamics, and propulsion, navigational, and communication software 
and hardware systems.

Sonar Operations

    NSWC PCD sonar operations involve the testing of various sonar 
systems in the ocean and laboratory environment as a means of 
demonstrating the systems' software capability to detect, locate, and 
characterize mine-like objects under various environmental conditions. 
The data collected is used to validate the sonar system's effectiveness 
and capability to meet its mission.
    Based on frequency, the Navy has characterized low, mid, or high 
frequency sound sources as follows:
     Low frequency: Below 1 kHz
     Mid-frequency: From 1 to 10 kHz
     High frequency: Above 10 kHz
    Low frequency sonar is not proposed to be used during NSWC PCD 
operations. The various sonar systems proposed to be tested within the 
NSWC PCD Study Area range in frequencies of 1 kHz to 5 megahertz (MHz) 
(5,000 kHz). The source levels associated with NSWC PCD sonar systems 
that require analysis in this document based on the systems' parameters 
range from between 118 dB to 235 dB re 1 microPa at 1 m. The sonar 
systems tested are typically part of a towed array or hull mounted

[[Page 20158]]

to a vessel. Additionally, subsystems associated with an underwater 
unmanned vehicle (UUV) or surf zone crawler operation are included. A 
detailed description of the frequency class and the reporting metric 
for each sonar system used at NSWC PCD can be found in Table A-1 of 
Appendix A, Supplemental Information for Underwater Noise Analysis, of 
the Navy's LOA application. Tables 1A and 1B present an overview of the 
number of operating hours annually for each of these sonar systems in 
territorial and non-territorial waters, respectively.

    Table 1A--Hours of Sonar Operations by Representative System for
                       Territorial Water Per Year
------------------------------------------------------------------------
                                                               Annual
                          System                              operating
                                                                hours
------------------------------------------------------------------------
AN/SQS-53/56 Kingfisher...................................           3
Sub-bottom profiler (2-9 kHz).............................          21
REMUS SAS-LF..............................................          12
REMUS Modem...............................................          25
Sub-bottom profiler (2-16 kHz)............................          24
AN/SQQ-32.................................................          30
REMUS-SAS-LF..............................................          20
SAS-LF....................................................          35
AN/WLD-1 RMS-ACL..........................................          33.5
BPAUV Sidescan............................................          25
TVSS......................................................          15
F84Y......................................................          15
BPAUV Sidescan............................................          25
REMUS-SAS-HF..............................................          10
SAS-HF....................................................          11.5
AN/AQS-20.................................................         545
AN/WLD-11 RMS Navigation..................................          15
BPAUV Sidescan............................................          30
------------------------------------------------------------------------


  Table 1B--Hours of Sonar Operations by Representative System for Non-
                       territorial Water Per Year
------------------------------------------------------------------------
                                                               Annual
                          System                              operating
                                                                hours
------------------------------------------------------------------------
AN/SQS-53/56 Kingfisher...................................           1
Sub-bottom profiler (2-9 kHz).............................           1
REMUS SAS-LF..............................................           0
REMUS Modem...............................................          12
Sub-bottom profiler (2-16 kHz)............................           1
AN/SQQ-32.................................................           1
REMUS-SAS-LF..............................................           0
SAS-LF....................................................          15
AN/WLD-1 RMS-ACL..........................................           5
BPAUV Sidescan............................................          38
TVSS......................................................          16.5
F84Y......................................................          15
BPAUV Sidescan............................................           0
REMUS-SAS-HF..............................................          25
SAS-HF....................................................          15
AN/AQS-20.................................................          15
AN/WLD-11 RMS Navigation..................................           0
BPAUV Sidescan............................................          25
------------------------------------------------------------------------

    Table 2 provides an overall summary of the total tempos associated 
with the proposed action. The table includes number of hours of 
operation per year for mid-frequency and high-frequency sonar testing 
activities for territorial and non-territorial waters, respectively. 
The ranges for the operations are given in the column, where 
appropriate. For example, sonar operations are divided into mid-
frequency and high-frequency ranges. The three columns to the left of 
the double vertical line contain the amount of operations for each 
subcategory conducted in territorial waters of the NSWC PCD Study Area. 
The values to the right of this demarcation, except those contained in 
the last column of the table, indicate the number of hours and/or 
operations that would occur in the non-territorial waters. The final 
column provides the total number of hours per year and/or operations in 
the NSWC PCD Study Area (or tempo in the territorial waters plus tempo 
in the non-territorial waters).

[[Page 20159]]

[GRAPHIC] [TIFF OMITTED] TP30AP09.000

Ordnance Operations

    Ordnance operations include live testing of ordnance of various net 
explosive weights and line charges. The following subsections provide 
an overview of the events for ordnance and line charges, respectively.
1. Ordnance
    Live testing is only conducted after a system has successfully 
completed inert testing and an adequate amount of data has been 
collected to support the decision for live testing. Testing with live 
targets or ordnance is closely monitored and uses the minimum number of 
live munitions necessary to meet the testing requirement. Depending on 
the test scenario, live testing may occur from the surf zone out to the 
outer perimeter of the NSWC PCD Study Area. The Navy must develop its 
capability to conduct ordnance operations in shallow water to clear 
surf zone areas for sea-based expeditionary operations. The size and 
weight of the explosives used varies from 0.91 to 272 kg (2 to 600 lb) 
trinitrotoluene (TNT) equivalent net explosive weight (NEW) depending 
on the test requirements. For this document, ordnance was analyzed 
based on three ranges of NEW: 0.45 to 4.5 kg (1 to 10 lb), 5 to 34 kg 
(11 to 75 lb), and 34.5 to 272 kg (76 to 600 lb). Detonation of 
ordnance with a NEW less than 34.5 kg (76 lb) is conducted in 
territorial waters (with the exception of line charges and because of 
the need to use higher amounts of NEW to clear surf zone areas) and 
detonation of ordnance with a NEW greater than 34.5 kg (76 lb) is 
conducted in non-territorial waters.
2. Line Charges
    Line charges consist of a 107 m (350 ft) detonation cord with 
explosives lined from one end to the other end in 2 kg (5 lb) 
increments and total 794 kg (1,750 lb) of NEW. The charge is considered 
one explosive source that has multiple increments that detonate at one 
time. The energy released from line charges is comprised of a series of 
small detonations exploding sequentially rather than one simultaneous, 
large explosion. Therefore, they are treated as a series of small 
explosives rather than a large detonation. The Navy proposes to conduct 
up to three line charge events in the surf zone annually. Line charge 
testing would only be conducted in the surf zone along the portion of 
Santa Rosa Island that is part of Eglin Air Force Base (AFB). The Navy 
must develop its capability to safely clear surf zone areas for sea-
based expeditionary operations. To that end, NSWC PCD occasionally 
performs testing on various surf zone clearing systems that use line 
charges to neutralize mine threats. These tests are typically conducted 
from a surface vessel (e.g., Landing Craft Air Cushion [LCAC]) and are 
deployed using either a single or dual rocket launch scenario. This is 
a systems development test and only assesses the in-water components of 
testing.
    Table 2 also provides an overview of ordnance testing at NSWC PCD.

Projectile Firing

    Current projectile firing includes 50 rounds of 30-mm ammunition 
each year within the NSWC PCD Study Area. The ability to utilize 
gunfire during test operations was identified as a future requirement. 
Rounds (individual shots) identified include 5 inch, 20 mm, 25 mm, 30 
mm, 40 mm, 76 mm, and various small arms ammunition (i.e., standard 
target ammo). Projectiles associated with these rounds are mainly 
armor-piercing projectiles. The 5-in round is a high explosive (HE) 
projectile containing approximately 3.63 kg (8 lbs) of explosive 
material. Current projectile firing includes 50 rounds of 30-mm 
ammunition each year within the NSWC PCD Study Area. The preferred 
alternative would provide for increases in the number of 30-mm rounds 
as well as for expansion of projectile firing operations to 5 in, 20 
mm, 40 mm, 76 mm, 25 mm, and small arms ammunition. All projectile 
firing would occur over non-territorial waters.

[[Page 20160]]

Description of Marine Mammals in the Area of the Specified Activities

    There are 30 marine mammal species with possible or confirmed 
occurrence in the NSWC PCD Study Area. As indicated in Table 3, there 
are 29 cetacean species (7 mysticetes and 22 odontocetes) and one 
sirenian species. Table 3 also includes the federal status of these 
marine mammal species. Seven marine mammal species listed as federally 
endangered under the Endangered Species Act (ESA) occur in the study 
area: The humpback whale, North Atlantic right whale, sei whale, fin 
whale, blue whale, sperm whale, and West Indian manatee. Of these 30 
species with occurrence records in the NSWC PCD Study Area, 22 species 
regularly occur here. These 22 species are: Bryde's whale, sperm whale, 
pygmy sperm whale, dwarf sperm whale, Cuvier's beaked whale, Gervais' 
beaked whale, Sowerby's beaked whale, Blainville's beaked whale, killer 
whale, false killer whale, pygmy killer whale, short-finned pilot 
whale, Risso's dolphin, melon-headed whale, rough-toothed dolphin, 
bottlenose dolphin, Atlantic spotted dolphin, pantropical spotted 
dolphin, striped dolphin, spinner dolphin, Clymene dolphin, and 
Fraser's dolphin. The remaining 8 species (i.e., North Atlantic right 
whale, humpback whale, sei whale, fin whale, blue whale, minke whale, 
True's beaked whale, and West Indian manatee) are extralimital and are 
excluded from further consideration of impacts from the NSWC PCD 
testing mission.

     Table 3--Marine Mammal Species Found in the NSWC PCD Study Area
------------------------------------------------------------------------
   Family and scientific name         Common name       Federal status
------------------------------------------------------------------------
Order Cetacea
------------------------------------------------------------------------
Suborder Mysticeti (baleen whales)
------------------------------------------------------------------------
Eubalaena glacialis.............  North Atlantic      Endangered.
                                   right whale.
Megaptera novaeangliae..........  Humpback whale....  Endangered.
Balaenoptera acutorostrata......  Minke whale.......  ..................
B. brydei.......................  Bryde's whale.....  ..................
B. borealis.....................  Sei whale.........  Endangered.
B. physalus.....................  Fin whale.........  Endangered.
B. musculus.....................  Blue whale........  Endangered.
------------------------------------------------------------------------
Suborder Odontoceti (toothed whales)
------------------------------------------------------------------------
Physeter macrocephalus..........  Sperm whale.......  Endangered.
Kogia breviceps.................  Pygmy sperm whale.  ..................
K. sima.........................  Dwarf sperm whale.  ..................
Ziphius cavirostris.............  Cuvier's beaked     ..................
                                   whale.
Mesoplodon europaeus............  Gervais' beaked     ..................
                                   whale.
M. Mirus........................  True's beaked       ..................
                                   whale.
M. bidens.......................  Sowerby's beaked    ..................
                                   whale.
M. densirostris.................  Blainville's        ..................
                                   beaked whale.
Steno bredanensis...............  Rough-toothed       ..................
                                   dolphin.
Tursiops truncatus..............  Bottlenose dolphin  ..................
Stenella attenuata..............  Pantropical         ..................
                                   spotted dolphin.
S. frontalis....................  Atlantic spotted    ..................
                                   dolphin.
S. longirostris.................  Spinner dolphin...  ..................
S. clymene......................  Clymene dolphin...  ..................
S. coeruleoalba.................  Striped dolphin...  ..................
Lagenodephis hosei..............  Fraser's dolphin..  ..................
Grampus griseus.................  Risso's dolphin...  ..................
Peponocephala electra...........  Melon-headed whale  ..................
Feresa attenuata................  Pygmy killer whale  ..................
Pseudorca crassidens............  False killer whale  ..................
Orcinus orca....................  Killer whale......  ..................
Globicephala melas..............  Long-finned pilot   ..................
                                   whale.
G. macrorhynchus................  Short-finned pilot  ..................
                                   whale.
------------------------------------------------------------------------
Order Sirenia
------------------------------------------------------------------------
Trichechus manatus..............  West Indian         Endangered.
                                   manatee.
------------------------------------------------------------------------

    The information contained herein relies heavily on the data 
gathered in the Marine Resource Assessments (MRAs). The Navy MRA 
Program was implemented by the Commander, Fleet Forces Command, to 
initiate collection of data and information concerning the protected 
and commercial marine resources found in the Navy's Operating Areas 
(OPAREAs). Specifically, the goal of the MRA program is to describe and 
document the marine resources present in each of the Navy's OPAREAs. 
The MRA for the NSWC PCD, which includes Pensacola and Panama City 
OPAREAs, was recently updated in 2007 (DoN, 2008).
    The MRA data were used to provide a regional context for each 
species. The MRA represents a compilation and synthesis of available 
scientific literature (for example, journals, periodicals, theses, 
dissertations, project reports, and other technical reports published 
by government agencies, private businesses, or consulting firms), and 
NMFS reports including stock assessment reports (SAR) (Waring et al., 
2007), which can be viewed at: https://www.nmfs.noaa.gov/pr/sars/species.htm.

[[Page 20161]]

    A detailed description of marine mammal density estimates in the 
NSWC PCD Study Area is provided in the Navy's LOA application and LOA 
Addendum.

A Brief Background on Sound

    An understanding of the basic properties of underwater sound is 
necessary to comprehend many of the concepts and analyses presented in 
this document. A summary is included below.
    Sound is a wave of pressure variations propagating through a medium 
(for the sonar considered in this proposed rule, the medium is marine 
water). Pressure variations are created by compressing and relaxing the 
medium. Sound measurements can be expressed in two forms: intensity and 
pressure. Acoustic intensity is the average rate of energy transmitted 
through a unit area in a specified direction and is expressed in watts 
per square meter (W/m\2\). Acoustic intensity is rarely measured 
directly, it is derived from ratios of pressures; the standard 
reference pressure for underwater sound is 1 microPascal (microPa); for 
airborne sound, the standard reference pressure is 20 microPa (Urick, 
1983).
    Acousticians have adopted a logarithmic scale for sound 
intensities, which is denoted in decibels (dB). Decibel measurements 
represent the ratio between a measured pressure value and a reference 
pressure value (in this case 1 microPa or, for airborne sound, 20 
microPa). The logarithmic nature of the scale means that each 10 dB 
increase is a tenfold increase in power (e.g., 20 dB is a 100-fold 
increase, 30 dB is a 1,000-fold increase). Humans perceive a 10-dB 
increase in noise as a doubling of sound level, or a 10 dB decrease in 
noise as a halving of sound level. The term ``sound pressure level'' 
implies a decibel measure and a reference pressure that is used as the 
denominator of the ratio. Throughout this document, NMFS uses 1 microPa 
as a standard reference pressure unless noted otherwise.
    It is important to note that decibels underwater and decibels in 
air are not the same and cannot be directly compared. To estimate a 
comparison between sound in air and underwater, because of the 
different densities of air and water and the different decibel 
standards (i.e., reference pressures) in water and air, a sound with 
the same intensity (i.e., power) in air and in water would be 
approximately 63 dB lower in air. Thus, a sound that is 160 dB loud 
underwater would have the same approximate effective intensity as a 
sound that is 97 dB loud in air.
    Sound frequency is measured in cycles per second, or Hertz 
(abbreviated Hz), and is analogous to musical pitch; high-pitched 
sounds contain high frequencies and low-pitched sounds contain low 
frequencies. Natural sounds in the ocean span a huge range of 
frequencies: from earthquake noise at 5 Hz to harbor porpoise clicks at 
150,000 Hz (150 kHz). These sounds are so low or so high in pitch that 
humans cannot even hear them; acousticians call these infrasonic and 
ultrasonic sounds, respectively. A single sound may be made up of many 
different frequencies together. Sounds made up of only a small range of 
frequencies are called ``narrowband'', and sounds with a broad range of 
frequencies are called ``broadband''; airguns are an example of a 
broadband sound source and tactical sonars are an example of a 
narrowband sound source.
    When considering the influence of various kinds of sound on the 
marine environment, it is necessary to understand that different kinds 
of marine life are sensitive to different frequencies of sound. Based 
on available behavioral data, audiograms derived using auditory evoked 
potential, anatomical modeling, and other data, Southall et al. (2007) 
designate ``functional hearing groups'' and estimate the lower and 
upper frequencies of functional hearing of the groups. Further, the 
frequency range in which each group's hearing is estimated as being 
most sensitive is represented in the flat part of the M-weighting 
functions developed for each group. The functional groups and the 
associated frequencies are indicated below:
     Low frequency cetaceans (13 species of mysticetes): 
Functional hearing is estimated to occur between approximately 7 Hz and 
22 kHz.
     Mid-frequency cetaceans (32 species of dolphins, six 
species of larger toothed whales, and 19 species of beaked and 
bottlenose whales): Functional hearing is estimated to occur between 
approximately 150 Hz and 160 kHz.
     High frequency cetaceans (eight species of true porpoises, 
six species of river dolphins, Kogia, the franciscana, and four species 
of cephalorhynchids): Functional hearing is estimated to occur between 
approximately 200 Hz and 180 kHz.
     Pinnipeds in Water: Functional hearing is estimated to 
occur between approximately 75 Hz and 75 kHz, with the greatest 
sensitivity between approximately 700 Hz and 20 kHz.
     Pinnipeds in Air: Functional hearing is estimated to occur 
between approximately 75 Hz and 30 kHz.
    Because ears adapted to function underwater are physiologically 
different from human ears, comparisons using decibel measurements in 
air would still not be adequate to describe the effects of a sound on a 
whale. When sound travels away from its source, its loudness decreases 
as the distance traveled (propagates) by the sound increases. Thus, the 
loudness of a sound at its source is higher than the loudness of that 
same sound a kilometer distant. Acousticians often refer to the 
loudness of a sound at its source (typically measured one meter from 
the source) as the source level and the loudness of sound elsewhere as 
the received level. For example, a humpback whale three kilometers from 
an airgun that has a source level of 230 dB may only be exposed to 
sound that is 160 dB loud, depending on how the sound propagates. As a 
result, it is important not to confuse source levels and received 
levels when discussing the loudness of sound in the ocean.
    As sound travels from a source, its propagation in water is 
influenced by various physical characteristics, including water 
temperature, depth, salinity, and surface and bottom properties that 
cause refraction, reflection, absorption, and scattering of sound 
waves. Oceans are not homogeneous and the contribution of each of these 
individual factors is extremely complex and interrelated. The physical 
characteristics that determine the sound's speed through the water will 
change with depth, season, geographic location, and with time of day 
(as a result, in actual sonar operations, crews will measure oceanic 
conditions, such as sea water temperature and depth, to calibrate 
models that determine the path the sonar signal will take as it travels 
through the ocean and how strong the sound signal will be at a given 
range along a particular transmission path). As sound travels through 
the ocean, the intensity associated with the wavefront diminishes, or 
attenuates. This decrease in intensity is referred to as propagation 
loss, also commonly called transmission loss.

Metrics Used in This Document

    This section includes a brief explanation of the two sound 
measurements (sound pressure level (SPL) and sound exposure level 
(SEL)) frequently used in the discussions of acoustic effects in this 
document.
SPL
    Sound pressure is the sound force per unit area, and is usually 
measured in microPa, where 1 Pa is the pressure

[[Page 20162]]

resulting from a force of one newton exerted over an area of one square 
meter. SPL is expressed as the ratio of a measured sound pressure and a 
reference level. The commonly used reference pressure level in 
underwater acoustics is 1 microPa, and the units for SPLs are dB re: 1 
microPa.

SPL (in dB) = 20 log (pressure/reference pressure)

    SPL is an instantaneous measurement and can be expressed as the 
peak, the peak-peak, or the root mean square (rms). Root mean square, 
which is the square root of the arithmetic average of the squared 
instantaneous pressure values, is typically used in discussions of the 
effects of sounds on vertebrates and all references to SPL in this 
document refer to the root mean square. SPL does not take the duration 
of a sound into account. SPL is the applicable metric used in the risk 
continuum, which is used to estimate behavioral harassment takes (see 
Level B Harassment Risk Function (Behavioral Harassment) Section).
SEL
    SEL is an energy metric that integrates the squared instantaneous 
sound pressure over a stated time interval. The units for SEL are dB 
re: 1 microPa\2\-s.

SEL = SPL + 10log(duration in seconds)

    As applied to tactical sonar, the SEL includes both the SPL of a 
sonar ping and the total duration. Longer duration pings and/or pings 
with higher SPLs will have a higher SEL. If an animal is exposed to 
multiple pings, the SEL in each individual ping is summed to calculate 
the total SEL. The total SEL depends on the SPL, duration, and number 
of pings received. The thresholds that NMFS uses to indicate at what 
received level the onset of temporary threshold shift (TTS) and 
permanent threshold shift (PTS) in hearing are likely to occur are 
expressed in SEL.

Potential Impacts to Marine Mammal Species

    The Navy considers that the proposed NSWC PCD mission activities 
associated with surface operations, sonar, ordnance, and projectile 
firing operations are the activities with the potential to result in 
Level A or Level B harassment or mortality of marine mammals. The 
following sections discuss the potential for ship strikes to occur from 
surface operations, potential effects from noise related to sonar, 
potential effects from noise related to ordnance, potential effects 
from noise related to projectile firing operations, and direct physical 
impacts from projectile firing.

Surface Operations

    Typical operations occurring at the surface include the deployment 
or towing of mine countermeasures (MCM) equipment, retrieval of 
equipment, and clearing and monitoring for non-participating vessels. 
As such, the potential exists for a ship to strike a marine mammal 
while conducting surface operations. In an effort to reduce the 
likelihood of a vessel strike, the mitigation and monitoring measures 
discussed below would be implemented.
Surface Operations in Territorial Waters
    Collisions with commercial and U.S. Navy vessels can cause major 
wounds and may occasionally cause fatalities to marine mammals. The 
most vulnerable marine mammals are those that spend extended periods of 
time at the surface in order to restore oxygen levels within their 
tissues after deep dives (e.g., the sperm whale). Laist et al. (2001) 
identified 11 species known to be hit by ships worldwide. Of these 
species, fin whales are struck most frequently; followed by right 
whales, humpback whales, sperm whales, and gray whales. More 
specifically, from 1975 through 1996, there were 31 dead whale 
strandings involving four large whales along the GOM coastline. 
Stranded animals included two sei whales, four minke whales, eight 
Bryde's whales, and 17 sperm whales. Only one of the stranded animals, 
a sperm whale with propeller wounds found in Louisiana on 9 March 1990, 
was identified as a result of a possible ship strike (Laist et al., 
2001). In addition, from 1999 through 2003, there was only one 
stranding involving a false killer whale in the northern GOM (Alabama 
1999) (Waring et al., 2006). None of these identified species are 
likely to occur in the territorial waters of the NSWC PCD Study Area. 
This area encompasses waters that are less than 33 m (108 ft) in depth 
and it is unlikely any species, including Bryde's whales are located 
here.
    It is unlikely that activities in territorial waters will result in 
a vessel strike because of the nature of the operations and size of the 
vessels. For example, the hours of surface operations take into 
consideration operation times for multiple vessels during each test 
event. These vessels range in size from small rigid hull inflatable 
boat (RHIB) to surface vessels of approximately 180 ft (55 m). The 
majority of these vessels are small RHIBs and medium-sized vessels. A 
large proportion of the timeframe for NSWC PCD test events include 
periods when vessels remain stationary within the test site. The 
greatest time spent in transit for tests includes navigation to and 
from the sites. At these times, the Navy follows standard operating 
procedures (SOPs). The captain and other crew members keep watch during 
vessel transits to avoid objects in the water. Furthermore, with the 
implementation of the proposed mitigation and monitoring measures 
described below, NMFS believes that it is unlikely vessel strikes would 
occur. Consequently, because of the nature of the surface operations 
and the size of the vessels, the proposed mitigation and monitoring 
measures, and the fact that cetaceans typically more vulnerable to ship 
strikes are not likely to be in the project area, the NMFS concludes 
that ship strikes are unlikely to occur in territorial waters.
Surface Operations in Non-Territorial Waters
    As stated above, there have been two reports of possible 
watercraft-related cetacean deaths in the GOM. These deaths include one 
sperm whale found with propeller wounds in Louisiana in March 1990 and 
one false killer whale in Alabama in 1999 (Laist et al., 2001; Waring 
et al., 2007). According to the 2008 SAR, no other marine mammal that 
is likely to occur in the northern GOM has been reported as either 
seriously or fatally injured from a ship strike between 1999 through 
2003 (Waring et al., 2007). The nature of operations, size of vessels 
and standard operating procedures to minimize the risk of vessel 
collisions will be similar to those expected to occur in territorial 
waters. Moreover, the implementation of additional mitigation and 
monitoring measures will reduce further the probability of a vessel 
strike. Thus, NMFS concludes that the potential effects to marine 
mammals from surface operations in non-territorial waters will be 
similar to those described for territorial waters.

Acoustic Effects: Exposure to Sonar

    For activities involving active tactical sonar, underwater 
detonations, and projectile firing, NMFS's analysis will identify the 
probability of lethal responses, physical trauma, sensory impairment 
(permanent and temporary threshold shifts and acoustic masking), 
physiological responses (particular stress responses), behavioral 
disturbance (that rises to the level of harassment), and social 
responses that would be classified as behavioral harassment or injury 
and/or would be likely to adversely affect the species or

[[Page 20163]]

stock through effects on annual rates of recruitment or survival. In 
this section, we will focus qualitatively on the different ways that 
mid-frequency active sonar (MFAS) and high frequency active sonar 
(HFAS), ordnance, and projectile firing may affect marine mammals (some 
of which NMFS would not classify as harassment). Then, in the Estimated 
Take of Marine Mammals section, NMFS will relate the potential effects 
to marine mammals from HFAS/MFAS, ordnance, and projectile firing to 
the MMPA regulatory definitions of Level A and Level B Harassment and 
attempt to quantify those effects.

Direct Physiological Effects

    Based on the literature, there are two basic ways that HFAS/MFAS 
might directly result in physical trauma or damage: Noise-induced loss 
of hearing sensitivity (more commonly-called ``threshold shift'') and 
acoustically mediated bubble growth. Separately, an animal's behavioral 
reaction to an acoustic exposure might lead to physiological effects 
that might ultimately lead to injury or death, which is discussed later 
in the Stranding section.

Threshold Shift (Noise-Induced Loss of Hearing)

    When animals exhibit reduced hearing sensitivity (i.e., sounds must 
be louder for an animal to recognize them) following exposure to a 
sufficiently intense sound, it is referred to as a noise-induced 
threshold shift (TS). An animal can experience temporary threshold 
shift (TTS) or permanent threshold shift (PTS). TTS can last from 
minutes or hours to days (i.e., there is recovery), occurs in specific 
frequency ranges (i.e., an animal might only have a temporary loss of 
hearing sensitivity between the frequencies of 1 and 10 kHz), and can 
be of varying amounts (for example, an animal's hearing sensitivity 
might be reduced by only 6 dB or reduced by 30 dB). PTS is permanent 
(i.e., there is no recovery), but also occurs in a specific frequency 
range and amount as mentioned in the TTS description.
    The following physiological mechanisms are thought to play a role 
in inducing auditory TSs: Effects to sensory hair cells in the inner 
ear that reduce their sensitivity, modification of the chemical 
environment within the sensory cells, residual muscular activity in the 
middle ear, displacement of certain inner ear membranes, increased 
blood flow, and post-stimulatory reduction in both efferent and sensory 
neural output (Southall et al., 2007). The amplitude, duration, 
frequency, temporal pattern, and energy distribution of sound exposure 
all affect the amount of associated TS and the frequency range in which 
it occurs. As amplitude and duration of sound exposure increase, so, 
generally, does the amount of TS. For continuous sounds, exposures of 
equal energy (the same SEL) will lead to approximately equal effects. 
For intermittent sounds, less TS will occur than from a continuous 
exposure with the same energy (some recovery will occur between 
exposures) (Kryter et al., 1966; Ward, 1997). For example, one short 
but loud (higher SPL) sound exposure may induce the same impairment as 
one longer but softer sound, which in turn may cause more impairment 
than a series of several intermittent softer sounds with the same total 
energy (Ward, 1997). Additionally, though TTS is temporary, very 
prolonged exposure to sound strong enough to elicit TTS, or shorter-
term exposure to sound levels well above the TTS threshold, can cause 
PTS, at least in terrestrial mammals (Kryter, 1985) (although in the 
case of HFAS/MFAS, animals are not expected to be exposed to levels 
high enough or durations long enough to result in PTS).
    PTS is considered auditory injury (Southall et al., 2007). 
Irreparable damage to the inner or outer cochlear hair cells may cause 
PTS, however, other mechanisms are also involved, such as exceeding the 
elastic limits of certain tissues and membranes in the middle and inner 
ears and resultant changes in the chemical composition of the inner ear 
fluids (Southall et al., 2007).
    Although the published body of scientific literature contains 
numerous theoretical studies and discussion papers on hearing 
impairments that can occur with exposure to a loud sound, only a few 
studies provide empirical information on the levels at which noise-
induced loss in hearing sensitivity occurs in nonhuman animals. For 
cetaceans, published data are limited to the captive bottlenose dolphin 
and beluga whale (Finneran et al., 2000, 2002b, 2005a; Schlundt et al., 
2000; Nachtigall et al., 2003, 2004).
    Marine mammal hearing plays a critical role in communication with 
conspecifics, and interpreting environmental cues for purposes such as 
predator avoidance and prey capture. Depending on the frequency range 
of TTS degree (dB), duration, and frequency range of TTS, and the 
context in which it is experienced, TTS can have effects on marine 
mammals ranging from discountable to serious (similar to those 
discussed in auditory masking, below). For example, a marine mammal may 
be able to readily compensate for a brief, relatively small amount of 
TTS in a non-critical frequency range that takes place during a time 
when the animal is traveling through the open ocean, where ambient 
noise is lower and there are not as many competing sounds present.
    Alternatively, a larger amount and longer duration of TTS sustained 
during time when communication is critical for successful mother/calf 
interactions could have more serious impacts. Also, depending on the 
degree and frequency range, the effects of PTS on an animal could range 
in severity, although it is considered generally more serious because 
it is a long term condition. Of note, reduced hearing sensitivity as a 
simple function of development and aging has been observed in marine 
mammals, as well as humans and other taxa (Southall et al., 2007), so 
we can infer that strategies exist for coping with this condition to 
some degree, though likely not without cost. There is no empirical 
evidence that exposure to HFAS/MFAS can cause PTS in any marine 
mammals; instead the probability of PTS has been inferred from studies 
of TTS (see Richardson et al., 1995).

Acoustically Mediated Bubble Growth

    One theoretical cause of injury to marine mammals is rectified 
diffusion (Crum and Mao, 1996), the process of increasing the size of a 
bubble by exposing it to a sound field. This process could be 
facilitated if the environment in which the ensonified bubbles exist is 
supersaturated with gas. Repetitive diving by marine mammals can cause 
the blood and some tissues to accumulate gas to a greater degree than 
is supported by the surrounding environmental pressure (Ridgway and 
Howard, 1979). The deeper and longer dives of some marine mammals (for 
example, beaked whales) are theoretically predicted to induce greater 
supersaturation (Houser et al., 2001b). If rectified diffusion were 
possible in marine mammals exposed to high-level sound, conditions of 
tissue supersaturation could theoretically speed the rate and increase 
the size of bubble growth. Subsequent effects due to tissue trauma and 
emboli would presumably mirror those observed in humans suffering from 
decompression sickness.
    It is unlikely that the short duration of sonar pings would be long 
enough to drive bubble growth to any substantial size, if such a 
phenomenon occurs. Recent work conducted by Crum et al. (2005) 
demonstrated the possibility of rectified diffusion for short duration

[[Page 20164]]

signals, but at sound exposure levels and tissue saturation levels that 
are improbable to occur in a diving marine mammal. However, an 
alternative but related hypothesis has also been suggested: Stable 
bubbles could be destabilized by high-level sound exposures such that 
bubble growth then occurs through static diffusion of gas out of the 
tissues. In such a scenario the marine mammal would need to be in a 
gas-supersaturated state for a long enough period of time for bubbles 
to become of a problematic size. Yet another hypothesis (decompression 
sickness) has speculated that rapid ascent to the surface following 
exposure to a startling sound might produce tissue gas saturation 
sufficient for the evolution of nitrogen bubbles (Jepson et al., 2003; 
Fernandez et al., 2005). In this scenario, the rate of ascent would 
need to be sufficiently rapid to compromise behavioral or physiological 
protections against nitrogen bubble formation. Collectively, these 
hypotheses can be referred to as ``hypotheses of acoustically mediated 
bubble growth.''
    Although theoretical predictions suggest the possibility for 
acoustically mediated bubble growth, there is considerable disagreement 
among scientists as to its likelihood (Piantadosi and Thalmann, 2004; 
Evans and Miller, 2003). Crum and Mao (1996) hypothesized that received 
levels would have to exceed 190 dB in order for there to be the 
possibility of significant bubble growth due to supersaturation of 
gases in the blood (i.e., rectified diffusion). More recent work 
conducted by Crum et al. (2005) demonstrated the possibility of 
rectified diffusion for short duration signals, but at SELs and tissue 
saturation levels that are highly improbable to occur in diving marine 
mammals. To date, Energy Levels (ELs) predicted to cause in vivo bubble 
formation within diving cetaceans have not been evaluated (NOAA, 
2002b). Although it has been argued that traumas from some recent 
beaked whale strandings are consistent with gas emboli and bubble-
induced tissue separations (Jepson et al., 2003), there is no 
conclusive evidence of this. However, Jepson et al. (2003, 2005) and 
Fernandez et al. (2004, 2005) concluded that in vivo bubble formation, 
which may be exacerbated by deep, long duration, repetitive dives may 
explain why beaked whales appear to be particularly vulnerable to sonar 
exposures. Further investigation is needed to further assess the 
potential validity of these hypotheses. More information regarding 
hypotheses that attempt to explain how behavioral responses to HFAS/
MFAS can lead to strandings is included in the Behaviorally Mediated 
Bubble Growth section, after the summary of strandings.
Acoustic Masking
    Marine mammals use acoustic signals for a variety of purposes, 
which differ among species, but include communication between 
individuals, navigation, foraging, reproduction, and learning about 
their environment (Erbe and Farmer, 2000; Tyack, 2000). Masking, or 
auditory interference, generally occurs when sounds in the environment 
are louder than and of a similar frequency to, auditory signals an 
animal is trying to receive. Masking is a phenomenon that affects 
animals that are trying to receive acoustic information about their 
environment, including sounds from other members of their species, 
predators, prey, and sounds that allow them to orient in their 
environment. Masking these acoustic signals can disturb the behavior of 
individual animals, groups of animals, or entire populations.
    The extent of the masking interference depends on the spectral, 
temporal, and spatial relationships between the signals an animal is 
trying to receive and the masking noise, in addition to other factors. 
In humans, significant masking of tonal signals occurs as a result of 
exposure to noise in a narrow band of similar frequencies. As the sound 
level increases, though, the detection of frequencies above those of 
the masking stimulus decreases also. This principle is expected to 
apply to marine mammals as well because of common biomechanical 
cochlear properties across taxa.
    Richardson et al. (1995) argued that the maximum radius of 
influence of an industrial noise (including broadband low frequency 
sound transmission) on a marine mammal is the distance from the source 
to the point at which the noise can barely be heard. This range is 
determined by either the hearing sensitivity of the animal or the 
background noise level present. Industrial masking is most likely to 
affect some species' ability to detect communication calls and natural 
sounds (i.e., surf noise, prey noise, etc.; Richardson et al., 1995).
    The echolocation calls of odontocetes (toothed whales) are subject 
to masking by high frequency sound. Human data indicate low frequency 
sound can mask high frequency sounds (i.e., upward masking). Studies on 
captive odontocetes by Au et al. (1974, 1985, 1993) indicate that some 
species may use various processes to reduce masking effects (e.g., 
adjustments in echolocation call intensity or frequency as a function 
of background noise conditions). There is also evidence that the 
directional hearing abilities of odontocetes are useful in reducing 
masking at the high frequencies these cetaceans use to echolocate, but 
not at the low-to moderate frequencies they use to communicate 
(Zaitseva et al., 1980).
    As mentioned previously, the functional hearing ranges of 
mysticetes (baleen whales) and odontocetes (toothed whales) all 
encompass the frequencies of the sonar sources used in the Navy's RDT&E 
activities. Additionally, almost all species' vocal repertoires span 
across the frequencies of the sonar sources used by the Navy. The 
closer the characteristics of the masking signal to the signal of 
interest, the more likely masking is to occur. However, because the 
pulse length and duty cycle of the HFAS/MFAS signal are of short 
duration and would not be continuous, masking is unlikely to occur as a 
result of exposure to HFAS/MFAS during the mission activities in the 
NSWC PCD Study Area.
Impaired Communication
    In addition to making it more difficult for animals to perceive 
acoustic cues in their environment, anthropogenic sound presents 
separate challenges for animals that are vocalizing. When they 
vocalize, animals are aware of environmental conditions that affect the 
``active space'' of their vocalizations, which is the maximum area 
within which their vocalizations can be detected before it drops to the 
level of ambient noise (Brenowitz, 2004; Brumm et al., 2004; Lohr et 
al., 2003). Animals are also aware of environmental conditions that 
affect whether listeners can discriminate and recognize their 
vocalizations from other sounds, which are more important than 
detecting a vocalization (Brenowitz, 1982; Brumm et al., 2004; Dooling, 
2004; Marten and Marler, 1977; Patricelli et al., 2006). Most animals 
that vocalize have evolved an ability to make vocal adjustments to 
their vocalizations to increase the signal-to-noise ratio, active 
space, and recognizability of their vocalizations in the face of 
temporary changes in background noise (Brumm et al., 2004; Patricelli 
et al., 2006). Vocalizing animals will make one or more of the 
following adjustments to their vocalizations: Adjust the frequency 
structure; adjust the amplitude; adjust temporal structure; or adjust 
temporal delivery.
    Many animals will combine several of these strategies to compensate 
for high levels of background noise. Anthropogenic sounds that reduce 
the signal-to-noise ratio of animal

[[Page 20165]]

vocalizations, increase the masked auditory thresholds of animals 
listening for such vocalizations, or reduce the active space of an 
animal's vocalizations impair communication between animals. Most 
animals that vocalize have evolved strategies to compensate for the 
effects of short-term or temporary increases in background or ambient 
noise on their songs or calls. Although the fitness consequences of 
these vocal adjustments remain unknown, like most other trade-offs 
animals must make, some of these strategies probably come at a cost 
(Patricelli et al., 2006). For example, vocalizing more loudly in noisy 
environments may have energetic costs that decrease the net benefits of 
vocal adjustment and alter a bird's energy budget (Brumm, 2004; Wood 
and Yezerinac, 2006). Shifting songs and calls to higher frequencies 
may also impose energetic costs (Lambrechts, 1996).
Stress Responses
    Classic stress responses begin when an animal's central nervous 
system perceives a potential threat to its homeostasis. That perception 
triggers stress responses regardless of whether a stimulus actually 
threatens the animal; the mere perception of a threat is sufficient to 
trigger a stress response (Moberg, 2000; Sapolsky et al., 2005; Seyle, 
1950). Once an animal's central nervous system perceives a threat, it 
mounts a biological response or defense that consists of a combination 
of the four general biological defense responses: Behavioral responses, 
autonomic nervous system responses, neuroendocrine responses, or immune 
response.
    In the case of many stressors, an animal's first and most 
economical (in terms of biotic costs) response is behavioral avoidance 
of the potential stressor or avoidance of continued exposure to a 
stressor. An animal's second line of defense to stressors involves the 
autonomic nervous system and the classical ``fight or flight'' response 
which includes the cardiovascular system, the gastrointestinal system, 
the exocrine glands, and the adrenal medulla to produce changes in 
heart rate, blood pressure, and gastrointestinal activity that humans 
commonly associate with ``stress.'' These responses have a relatively 
short duration and may or may not have significant long-term effects on 
an animal's welfare.
    An animal's third line of defense to stressors involves its 
neuroendocrine or sympathetic nervous systems; the system that has 
received the most study has been the hypothalamus-pituitary-adrenal 
system (also known as the HPA axis in mammals or the hypothalamus-
pituitary-interrenal axis in fish and some reptiles). Unlike stress 
responses associated with the autonomic nervous system, virtually all 
neuro-endocrine functions that are affected by stress--including immune 
competence, reproduction, metabolism, and behavior--are regulated by 
pituitary hormones. Stress-induced changes in the secretion of 
pituitary hormones have been implicated in failed reproduction (Moberg, 
1987; Rivier, 1995) and altered metabolism (Elasser et al., 2000), 
reduced immune competence (Blecha, 2000) and behavioral disturbance. 
Increases in the circulation of glucocorticosteroids (cortisol, 
corticosterone, and aldosterone in marine mammals; Romano et al., 2004) 
have been equated with stress for many years.
    The primary distinction between stress (which is adaptive and does 
not normally place an animal at risk) and distress is the biotic cost 
of the response. During a stress response, an animal uses glycogen 
stores that can be quickly replenished once the stress is alleviated. 
In such circumstances, the cost of the stress response would not pose a 
risk to the animal's welfare. However, when an animal does not have 
sufficient energy reserves to satisfy the energetic costs of a stress 
response, energy resources must be diverted from other biotic 
functions, which impair those functions that experience the diversion. 
For example, when mounting a stress response diverts energy away from 
growth in young animals, those animals may experience stunted growth. 
When mounting a stress response diverts energy from a fetus, an 
animal's reproductive success and its fitness will suffer. In these 
cases, the animals will have entered a pre-pathological or pathological 
state which is called ``distress'' (sensu Seyle, 1950