Reproductive success in whale species due to sonar interference

Alison LynchUID: 111677979

BSCI338B: Marine BiologyDue: December 2nd, 2015

Reproductive success in whale species due to sonar interference

Marine mammals are a vital part of the marine ecosystem. Whales, dolphins, seals, and

sea lions are some of the most beloved creatures in the sea, which is part of why so many

organizations have been fighting to protect them for years. As a general characteristic between

them, they all “use sound for activities essential to survival and reproduction” (Holt, 2009).

Communication and echolocation are both key behaviors and when these are disrupted, it could

mean devastation for some species. Recently various human actions, mainly the Navy’s use of

sonar noise, have impacted the reproductive success of whales in the Atlantic Ocean. Sonar

interferes with not only diving patterns, but also as a result foraging and mate selection in many

species. It is vitally important that people are aware of the implications these types of activities

have on the lifestyles of cetacean species such as the endangered right whale (Eubalaena

glacialis) pictured in figure one below.

The oceanic atmosphere has been changing in recent years and this change is mainly

attributed to the navy’s use of sonar systems in their training. A recent study estimated that ocean

noise is rising at a rate of approximately 3–5 dB per decade at some frequencies in some

locations” (Reeder, 2006). At first glance, this does not seem like a significant increase, but for

whales, this is enough to cause problems. This rise has specifically been attributed to

“anthropogenic sources such as Navy sonar systems” because this is a clear change that has

happened in the time range that would directly increase the noise levels (Reeder, 2006). The

Marine Mammal Protection Act is already in place and have placed restrictions on what the

military can do in marine waters; it “establish[es] marine mammal mitigation zones around each



vessel using sonar [and] ensure[s] that explosives are not detonated when animals are detected

within a certain distance” (www.noaanews.noaa.gov). While these precautions are in place, this

still does not address the fact that the oceanic noise level is increasing. Sound carries

significantly through water and therefore better changes need to be made because of its impacts

on marine mammals, such as whales.

One such behavior that these oceanic noises affect is the whales’ diving patterns which

are important not only for foraging, but also reproduction. In one study, diving behavior was

monitored in killer whales (Orcinus orca), pilot whales (Globicephala melas), and sperm whales

(Physeter macrocephalus) “during controlled exposures to naval sonar [low frequency active

sonar (LFAS): 1–2 kHz and mid frequency active sonar (MFAS): 6–7kHz] during three field

seasons (2006–2009)” (Sivle, 2012). In the study they found that the changes in diving behavior

significantly decreased efficiency in foraging in the animals because they were forced out of

paths that they normally took to get food. Many whales have specific dietary needs and therefore

disrupting the depth with which they are foraging at could lead to different prey items. As a

result, individuals may not be able to survive as well and so this is a very important consideration

for those using sonar. Another factor that goes along with foraging is the importance of blubber

build up in whales. For whales, blubber “serves a number of functions, including maintaining the

hydrodynamic shape of the body insulating the body core adjusting buoyancy and storing energy

reserves” so proper build up of these reserves is critical to the survival of these whales (Miller,

2011). If whales are forced out of their normal feeding spots, then they may not be able to build

up the necessary blubber to swim properly, as well as have the energy to reproduce. This is

mainly important for females as reproduction is so much more energetically costly to them than

http://www.noaanews.noaa.gov/



males. It is a known fact that “adult females measured prior to the start of pregnancy had the

thickest blubber of all life history classes” of the species (Miller, 2011). This is unsurprising

given knowledge of mammalian reproduction and the investment in egg production. In a study

done in 2005, “12% of adult females were reproductively inactive [in their study] which may be

a consequence of females not attaining adequate body fat reserves necessary for successful

reproduction” based on their overall findings. (Miller, 2011). Realistically, if these female

whales are not able to dive to the feeding grounds they are used to, then they will not have the

blubber reserves in order to reach their maximum fecundity and therefore in a species such as the

right whales which are endangered, they need every opportunity to have successful reproductions

as possible. These sound deterrents also affect sexual selection in whales.

Sound communication is used by many cetacean species and is a primary form of sexual

selection for the majority of species. One such example is seen in humpback whales (Megaptera

novaeangliae). Mature, male humpback whales have been known to “start singing while still on

their feeding grounds to gain access to more females” (Magnusdottir, 2014). Going back to the

previous argument about feeding grounds, if males have to move their feeding grounds to avoid

sonar, then it is possible that both foraging and reproductive success would suffer. These songs

can be viewed as “similar to both leks and to male dominance polygyny, in which males display

(sing) or directly compete (perhaps sometimes in coalitions) for access to females” (Clapham,

1996). This means that the songs determine mating success in the males. Therefore it is very

important that these songs are actually carried through the water so that the females can hear

them unobstructed. If sonar noise were to be happening on breeding grounds, then reproduction

across the board may deplete. Male whales would have to “compensate for background noise by



changing their signal’s amplitude, duration, repetition rate, and/or frequency” which could have

various consequences (Holt, 2009). For one, the females may not like the changes to the songs

and therefore not allow copulation with those males. Also this compensation most likely has

“energetic costs, [that] lead to increased stress levels” which is also detrimental to the survival of

those males (Holt, 2009). If they have to expend more energy on producing their songs, then they

are going to need more food resources, but if the noise obstructs their diving patterns, then they

will not receive proper nutrition and so their survival rates will decrease. In a species such as the

right whales, this is not going to help bring them out of their endangered status. One study done

in 2000, suggested “that humpbacks sang longer songs during sonar transmissions to compensate

for acoustic interference” (Miller, 2000). Increasing song length intuitively would correlate with

using more energy and therefore these sonar trainings are detrimental to these whale species. The

noises cause individuals to waste energy which should be put towards their survival. For species

such as the right whale, energy should not be wasted because of human interaction.

The endangered right whale (Eubalaena glacialis) normally forms surface active groups.

These groups’ primary function is to “encompass both reproductive and non-reproductive

behaviors,” and the composition of these groups are described as “fluid, with individuals leaving

and joining the group through time” (Parks, 2007). Communication is important not only within

the groups, but between them also. As stated previously, sexual selection happens in whale

species and this is no different for the right whales. Once in these groups males sing in order to

gain reproduction opportunities. If sonar testing is taking place in nearby waters this will put

strain on these groups and reproductive success could easily plummet. Also if a whale is trying

to find a new group, the sonar interferences may cause the individual to not hear other groups or



just not encounter them because they have not swum in the correct direction due to the noise.

Part of the reason they have formed these groups in the first place is to “to increase the likelihood

for success during the actual mating event, or if males are establishing dominance relations that

affect later mate acquisition” (Parks, 2007). Because this species in particular is nearing

extinction, it is ever more important that humans not interfere with behaviors that have evolved

to help them thrive. Better regulations must be made in order to save the species. Many

researchers are hopeful and believe that “through a continued and expanded monitoring program

and the restriction of potentially harmful activities in right whale habitats, perhaps the North

Atlantic right whale population will not just survive, but steadily grow” (Knowlton, 1994). Their

habitat, as their full name suggests in the entire north Atlantic as shown in figure two. This area

of the ocean is a prime route for not only military training but also transatlantic ships that are

transporting goods, etc. These companies and organizations need to be made more aware of the

impacts they have on such a species.

Figure 1: North Atlantic Right Whale (IUCNredlist.org)

Figure 2: Geographic Distribution of Right Whales (IUCNredlist.org)



Recently the Navy’s use of sonar noise in addition to other human actions has impacted

the reproductive success of whales in the Atlantic Ocean. Sonar noise interferes with cetacean

diving patterns, foraging, and mate selection in many species. People need to be aware of the

implications these types of activities have on the lifestyles of marine mammals such as the

endangered right whale (Eubalaena glacialis) because their status depends on it. If these

situations get bad enough, even more marine mammals will become endangered and ultimately

extinct. As they are such an important creature in the marine ecosystem, more regulations must

be made specifically in the military training but also oceanic travel in general.

Works Cited:

Barclay, Connie. "Noaa Announces Regulations to Protect Marine Mammals During Navy Training and Testing in Atlantic and Gulf of Mexico." National Oceanic and Atmospheric Administration 2013. Web. November 25 2014.

Clapham, PJ. "The Social and Reproductive Biology of Humpback Whales: An Ecological Perspective." Mammal Review 26.1 (1996): 27-49. Print.

Holt, MM, et al. "Speaking Up: Killer Whales (Orcinus Orca) Increase Their Call Amplitude in Response to Vessel Noise." Journal of the Acoustical Society of America 125.1 (2009): EL27-EL32. Print.

KNOWLTON, AR, SD KRAUS, and RD KENNEY. "Reproduction in North-Atlantic Right Whales (Eubalaena-Glacialis)." Canadian Journal of Zoology-Revue Canadienne De Zoologie 72.7 (1994): 1297-305. Print.

Magnusdottir, EE, et al. "Humpback Whale Songs During Winter in Subarctic Waters." Polar Biology 37.3 (2014): 427-33. Print.

Miller, CA, et al. "Blubber Thickness in Right Whales Eubalaena Glacialis and Eubalaena Australis Related with Reproduction, Life History Status and Prey Abundance." Marine Ecology Progress Series 438 (2011): 267-83. Print.



Miller, PJO, et al. "Whale Songs Lengthen in Response to Sonar." Nature 405.6789 (2000): 903-03. Print.

Parks, SE, et al. "Occurrence, Composition, and Potential Functions of North Atlantic Right Whale (Eubalaena Glacialis) Surface Active Groups." Marine Mammal Science 23.4 (2007): 868-87. Print.

Reeder, Benjamin D, Rommel Pucan, and Curtis A Collins. "Long-Tern Trends in Ocean Noise." The Journal of the Acoustical Society of America, 2006. 3382. Vol. 120. Print.

Sivle, L.D., et al. "N Dive Behavior During Naval Sonar Exposure in Killer Whales, Long-Finned Pilot Whales, and Sperm Whales." Frontiers in Physiology, 2012. Print.

Documents

Reproductive success in whale species due to sonar interference