Acoustics and Behavior
Listening To Right Whales
A relatively new approach to right whale monitoring is the use of passive acoustics to record right whale vocalizations. Passive acoustic monitoring involves deploying stand-alone devices in the marine environment, which listen and record whale vocalizations remotely. Over the past 10 years researchers at the Cornell Laboratory of Ornithology’s Bioacoustic Research Program (BRP) have been developing Autonomous Recording Units (ARUs) to record marine mammal sounds. In collaboration with Dr. Christopher Clark from BRP, CCS researchers have deployed such units in Cape Cod Bay since 2001 to record the vocal presence of right whales in the Bay. These recordings in correlation with information gathered through aerial surveys and habitat studies are important in understanding how right whales use Cape Cod Bay as one of their primary habitats.
Focal Follow Research
Relatively little is known about how often right whales produce sounds, as well as the behavioral significance of most call types. Are the whales acoustically active during certain types of behaviors (e.g. feeding, resting)? Do they change their acoustic behavior in different behavioral stages? Do they change their acoustic behavior when in groups as compared to when they are on their own? This is important knowledge when trying to use passive acoustic monitoring in order to determine the presence of whales in a particular area. It is crucial to determine whether certain sounds are associated with behavioral stages in which the whales are particularly vulnerable (e.g. near-surface feeding, social groups).
In 2006, researchers at CCS started a project to examine the vocalizations, vocalization rates and behavior of right whales in Cape Cod Bay. Using a hydrophone to record vocalizations, researchers hope to determine the amount of time that right whales spend vocalizing in correlation to group size and behavior. This information will assist researchers in determining the percentage of time that right whales vocalize and can therefore be detected by passive acoustics.
This project will also undertake focal follows, which involve following individual whales for extended periods of time. Focal follows will help to provide further information on the amount of time that whales spend at the surface (and are therefore vulnerable to ship strike), small-scale movements within the Bay and behavior. Individual whales that are subject to focal follows will also be photographed and matched to the North Atlantic right whale catalog to determine their identity. All of this data will help scientists to better understand the behavior of right whales and thus improve their ability to protect them.
Right Whale Vocal Behavior
Like many other marine mammals, right whales produce a variety of different sounds for communication. While so-called contact calls seem to help individuals to stay in contact, right whales also emit various calls while engaged in social behavior. In good conditions some of these calls might be detected up to 13 miles from their source. The different calls that may be recorded from Northern right whales fall broadly into three main categories. Below you will find sound samples of some commonly recorded Northern right whale calls.
Stereotyped tonal calls (i.e. upcalls, downcalls, constant calls)
The upcall is a commonly heard vocalization and referred to as contact call. Its behavioral function seems to be the announcement of the caller’s presence to other whales in its vicinity.
Variable tonal calls (i.e.screams, warbles, hybrid calls, pulsive calls)
Right whales produce a variety of variable calls in different social contexts (e.g. in reproductive groups, mother-calf groups).
Gunshot calls are brief, intense, broadband sounds, mainly produced by males, often in a reproductive context.