Underwater volcanoes, earthquakes, rain and wind make our oceans a continuously changing dynamic ecosystem. This underwater world is not as silent as it seems. Sound travels farther and is four times faster in water than in air. International shipping, naval activity and seismic surveys are all anthropogenic sources of sound pollution. Understanding how sound impacts marine species and how different species use sound to communicate has been an increasingly important field as we work to address climate change and human-level impacts on our oceans.
Nat Hab Expedition Leader Kristina Disney and Bioacoustician Niki Diogou dive into an informative and engaging discussion of acoustic ecology and how the research is helping us understand how human activities and climate change impact vital marine species like the bowhead whale and the sperm whale.
Often referred to as “ambassadors” of the health of ocean ecosystems, whales are top predators. Like many marine species, they make loud and complex noises that are necessary for reproduction, feeding and communication. Acoustic ecology is integral to preserving whale populations in the coming decades, and the field is growing.
Acoustic Ecology Technology and Whale Songs
Acoustic ecology is the study of how sounds are involved in the interactions of living organisms and their environment. All marine animals have evolved to create very sophisticated instruments and tools for producing and recognizing sound. Every marine mammal has a unique frequency in which they emit sounds, and they do so for reproduction, feeding and communication.
Humans can only sense sounds at frequencies between 20 and 20,000 cycles per second, or hertz (Hz). Frequency can be understood simply as pitch, and loudness is the amount of energy that goes into that frequency. No matter how loud something might be, if it is outside the frequency range we can sense, we won’t be able to hear it. For marine animals, the larger the species, the lower the frequency, and vice versa. Each species will produce sounds at a unique frequency. Blue whales make sounds at around 15 hertz. Before we, as humans, can hear audio recordings of marine life like whales, audio samples need to be sped up to a frequency that human ears can recognize. When recording and analyzing the sounds of marine animals, we can tell the specific species recorded, their behavior and gender.
Humpback whales are known as singers, especially males, as they use songs as reproduction displays. Beluga whales are called the “canary of the oceans” as they use their flexible rounded forehead, called a “melon,” to make noises such as chirps, clicks, whistles and squeals.
Marine mammals make sounds that we can use to detect presence, behavior and gender. Some animals, like sperm whales, produce a pattern of clicks depending on their behavior. For instance, when a sperm whale is surveying deep ocean waters along the Gulf Shore or in the Mediterranean, looking for squid, sharks, skates or fish, they will use a series of regular clicks as an eco-location tool to feed. When close to their prey, they produce what scientists call a creek (male sperm whales also produce a slow creek as a reproduction display). Females have geographically distinct sound patterns called coda to communicate with each other. Science shows us that even underwater, marine species use sounds, which vary like human dialects, to communicate and survive.
While sperm whales are found in all deep oceans, species like the bowhead whale reside almost exclusively in the Arctic and subarctic waters experiencing seasonal sea ice coverage. Surviving the icy cold waters of the Arctic required sperm whales to develop an insulating layer of blubber that can be up to 1.6 feet thick. Bowhead whales make calls, which can be upstream or downstream frequency signals, to communicate. The animals also produce moans and tonal signals that scientists believe are used to navigate through ice fields. During reproduction displays, males sing bi-phonated songs, complex signals that support mating and communication.
Why Should We Care About Ocean Sounds?
Sound is a vital feature of marine habitats, so understanding how marine animals use sound and how man-made noise impacts the underwater environment is crucial. Anthropogenic sounds interfere with many aquatic species’ ability to perform vital behaviors and functions. Sound pollution from the fishing industry, naval activities, shipping, oil drilling and seismic surveys can overlap with the sound frequencies of blue and bowhead whales. Drilling for oil doesn’t just harm the environment when we are left with an excess of carbon dioxide in the atmosphere; surveying our ocean beds for oil drilling can disrupt aquatic environments and affect marine creatures’ habitats and behaviors.
Noise can affect whale behaviors and activities in different ways depending on how loud and close it is. Anthropogenic sounds can mask other vital sounds animals need to navigate their environment. Noise disruptions can cause stress, hearing loss and death. When whales are faced with excessive foreign sounds, it can alter behavioral responses, changing how a species dives, feeds and mates. Many species end up abandoning areas where they are subject to sound pollution.
The Great Gray Whales of Baja
Hearing is the most crucial sense a whale possesses–especially for the gray whale. It is believed that these whales can hear very low frequencies, and their superior hearing is suited for dark ocean habitats, making up for their poorer vision. Gray whales make the longest mammal migration on Earth. They travel 6,000 miles from Alaska’s Bering Sea to their traditional breeding and birthing grounds along the Pacific coast of Mexico’s Baja Peninsula. With Natural Habitat Adventures, you can explore San Ignacio Lagoon and observe Pacific gray whales while learning about their behaviors, migration patterns and conservation from expert guides. In small groups, travelers frequently interact with gray whales breaching, spy-hopping and even mating. Accommodations include an overnight stay in solitude in private “whale cabanas” at our eco-camp on the shore of San Ignacio Lagoon. Many whale-watching tours—off Boston or Maui, for example—take place on large commercial boats where you have to strain to see around guests crowding the rail, and if you do spot a whale, it’s likely you’ll glimpse only a tail or a spout of spray on the horizon. Our Baja whale experience couldn’t be more different! We foray into the whales’ world at close range, with frequent, intimate encounters the norm.