Virginia Tech
1075 Life Science Cir
Blacksburg, VA 24061

Popular version of paper 2pAB1
Presented Tuesday afternoon, November 6, 2018
176th ASA Meeting, Victoria, BC, Canada

Ultrasound plays a pivotal role in the life of bats, since the animals rely on echoes triggered by their ultrasonic biosonar pulses as their primary source of information on their environments.

However, air is far from an ideal medium for sound propagation since it subjects the waves to severe absorption that dissipates sound energy into heat. Because absorption gets a lot worse with increasing frequency, the ultrasonic frequencies of bats are particularly effected by this and the operation range of bat biosonar is just a few meters for typical sensing tasks.

Absorption limits the highest ultrasonic frequencies that the bats can operate on. This has consequences for the ability of the animals to concentrate the acoustic energy they emit or receive in narrow beams. Forming a narrow beam requires a sonar emitter/receiver that is much larger than the wavelength. Being small mammals, bat have not been able to evolve ears that are much larger (i.e., 2 or 3 orders of magnitude) than the ultrasonic wavelengths of their biosonar systems and hence have fairly wide beams (e.g., 60 degrees or wider).

Figure 1. Ultrasonic pulses followed by their echo trains that where created by a robot that mimics the biosonar system of horseshoe in a forest.

For bat species that navigate and hunt in dense vegetation, a broad sonar beam means that the animals receive a lot of “clutter” echoes from the surrounding vegetation. These clutter echoes are likely to drown out informative echoes related to important the presence of prey or passage ways.

Figure 2. Biomimetic robot mimicking the biosonar system of horseshoe bats.

Given these basic acoustical conditions, it appears that bat biosonar should be a complete disaster, but in reality the opposite is the case. Bats are the second most species-rich group of mammals (after rodents) and have successfully conquered a diverse set of habitats and food sources based on a combination of active biosonar and flapping flight. Hence, a narrow focus on standard sonar parameters like beamwidth, signal-to-noise ratio, resolution, etc. may not be the right direction to understand the biosonar skills of bats. To remedy this situation, we have created a robot that mimics the biosonar system of horseshoe bats. The robot is currently being used to collect large numbers of echoes from natural environments to create a data basis to identify non-standard informative echo features using machine learning methods.

Youenn Jézéquel¹, Julien Bonnel², Jennifer Coston-Guarini¹, Jean Marc Guarini¹, Laurent Chauvaud¹

¹Laboratoire des Sciences de l’Environnement Marin, UBO, CNRS, IRD, Ifremer, LIA BeBEST, UMR 6539, rue Dumont D’Urville, 29280 Plouzané, France
²Woods Hole Oceanographic Institution, Woods Hole, MA 02543 USA

Session 1 pAB, Fish and Marine Invertebrate Bioacoustics II
Buzzing sounds as a mean of intra species-specific communication during agonistic encounters in male European lobsters (Homarus gammarus)?

An important application of marine ecological knowledge today is designing new indicators of marine ecosystems’ health. Passive acoustics, which simply consists on listening to sounds, is promising because it is non invasive and non destructive. However to develop passive acoustics as a tool for monitoring, we need to identify sound-emitting species with high potential for this type of application. Then, the sounds need to be analysed and and understood within their ecological context. In the coastal waters of Brittany (France), crustaceans would seem to be good study model, because they emit a wide range of sounds and also have a high commercial and cultural importance.

Figure 1: The European lobster (Homarus gammarus). Photographer: E. Amice (CNRS)

My PhD research, is focussed on the European lobster (Homarus gammarus, Figure 1). In our first study, we have shown that when stressed, the European lobster produces a species-specific sound that we call a “buzz” (Jézéquel et al. 2018, insert link for sound file). These sounds are characteristic low frequency and continuous sounds. We have shown that they are similar to those produced by the American lobster, but we .

While no studies have described the behaviours of the European lobster with ethograms (sequences of observed behaviours during behavioural experiments), there is a large literature on behaviours of American lobsters. Researchers have found that male American lobsters use agonistic encounters through aggressive behaviours to establish dominance between individuals (Figure 2A).

2A

2B

Figure 2: Agonsitic encounters between male American lobsters (A) (Atema and Voigt 1995) and male European lobsters (B) (Photographer: Y. Jézéquel, Université de Bretagne Occidentale)

This allows them to gain access more easily to shelters and suitable mates during reproduction periods. These researchers have also shown that visual and chemical signals are used, but no studies have reported the use of sounds during these events to communicate. In our study, we have done agonistic encounters with male European lobsters to understand if they use sounds as a mean of intra species-specific communication  (Figure2B).

Our results show that male European lobsters use a highly complex panel of behaviours, from physical display to aggressive claw contact, in order to establish dominance. Once the dominant and submissive individuals are determined, they each adopt different behaviours:  the “winners” (dominants) continue physical and aggressive displays toward the submissive individuals that attempt to escape from their opponent’s presence.

During these experiments, we did not record buzzing sounds, probably because of the poor propagation of low frequencies (like those of the buzzing sounds) in the experimental tanks.  We concluded that this could explain the non detection of these sounds by the hydrophones installed for the experiments (Jézéquel et al. 2018).

The mechanism of sound production in both American and European lobsters is known: they contract rapidly internal muscles located at the base of their antennas to vibrate their carapace which produces the buzzing sound. We completed a new series of agonistic encounters with male European lobsters, but this time adding high frequency sampling accelerometers on their carapace. The accelerometery data clearly showed that European lobsters vibrated their carapace during agonistic encounters (with up to 90 vibration episodes per 15 minutes of experiment per individual), but their associated buzzing sounds were not recorded with hydrophones. Carapace vibrations were emitted by both dominant and submissive individuals, even if submissive individuals produced significantly more vibration episodes than dominant ones. These vibrations were associated to particular behaviours such as physical display and fleeing.

We have shown for the first time that male European lobsters exhibit complex, rapid patterns of movements during agonistic encounters that include carapace vibration episodes. However  during these events, the reactions of the receivers toward these signals remain unclear. We remain uncertain if the lobsters “sense” the carapace vibrations or their associated buzzing sounds in the experimental tanks.

Even if it is too soon yet to talk about a new type of communication in crustaceans, we have shown that buzzing sounds might have a role in the intra species-specific interactions displayed during agonistic encounters between male European lobsters. Field  experiments with better sound propagation conditions are in progress to determine if these sounds are indeed used as a mean of communication (Figure 3).

Figure 3:Bioacoustic experiments conducted in cages in coastal waters with European lobsters. Photographer: E. Amice (CNRS)

Marla Holt – marla.holt@noaa.gov, NOAA NMFS Northwest Fisheries Science Center
Brad Hanson – brad.hanson@noaa.gov, NOAA NMFS Northwest Fisheries Science Center
Candice Emmons – candice.emmons@noaa.gov, NOAA NMFS Northwest Fisheries Science Center
Jennifer Tennessen – jennifer.tennessen@noaa.gov, Lynker Technologies
Deborah Giles – dagiles7@gmail.com, University of Washington Friday Harbor Labs
Jeffery Hogan – jeff@killerwhaletales.org, Cascadia Research Collective

Popular version of paper 4aAB8, “Effects of vessels and noise on the subsurface behavior of endangered killer whales (Orcinus orca)”
Presented Thursday morning, November 8, 2018, 10:00-10:15 AM, Shaughnessy (FE)
176th ASA Meeting, Victoria, BC

Southern Resident killer whales are unique and iconic to the Pacific Northwest. They are also among the most endangered marine mammals in the world.

Researchers have identified three main threats to the recovery of Southern Residents: 1.) availability of prey, 2.) vessel noise and traffic, and 3.) chemical pollutants.  Unlike transient killer whales that prey on marine mammals such as seals, Southern Residents prey on fish.

Like all killer whales, Southern Residents use echolocation, a process of producing short sound pulses that bounce off objects to detect and identify things in the water, including their preferred prey, Chinook salmon.  But vessel traffic can disrupt the whales’ behavior and radiated noise from vessels can mask echolocation signals the whales use for hunting. This crowded and noisy environment can make it more difficult for hungry whales to find and catch their prey.

For the past several years, we have been working to better understand the effect that vessel traffic and underwater noise is having on individual whales. We have done this by placing suction-cup tags on several members of the Southern Resident population.  These digital acoustic recording tags, or DTAGs, contain two underwater microphones to record sound along with pressure, accelerometer and magnetometer sensors that allow us to re-create whale movement [1], much like an activity tracker in your watch or smart phone.

When whales were tagged, we collected GPS data on all nearby vessels and took observations of the whale’s feeding behavior. When possible we also collected any scraps left behind after a feeding event to better understand how the whales make their catch and what they are eating.

Over the past four years, we have deployed 28 DTAGs, yielding a rich set of acoustic and movement data.  So far, we have found:

• Unsurprisingly, the DTAGs measured higher noise levels when there are more vessels around and when the vessels are moving fast [2].
• The frequencies of sounds emitted by vessels overlapped with the echolocation frequencies that the whales use to hunt fish.
• Additionally, we could differentiate different foraging activities from the acoustic and movement record, including when the whales used echolocation signals to search and pursue fish, fast rolls and jerks during fish chases, and the detection of crunching sounds from eating after fish kills.

Figure 1. A Southern Resident killer whale with a suction-cup attached DTAG.  Photo taken by Candice Emmons under NOAA NMFS issued Research Permit No. 781-1824.

These results allowed us to identify different phases of foraging and determine how vessels and/or noise affect  the whales’ behavior and their ability to catch fish. This work, along with a comparative investigation involving DTAG data from Northern Resident killer whales, a fisheating population that is growing steadily, is improving our understanding of these killer whale populations.

This improved understanding is informing killer whale conservation and management measures, including assessing the effectiveness of vessel regulations for killer whales in the U.S. [3].  Additionally, the Pacific Whale Watch Association’s updated guidelines include a slow zone around killer whales because recent research showed that speed is the biggest factor in how much noise reaches the whales. Science is informing real change for the benefit of the whales.

Fig 2 Video:  Legend can read, “An animation of the track of a tagged whale and all of the boats around it during an entire tag deployment.  The whale track is shown by the thicker pale yellow line and each vessel track is connected by a thin line.” Animation prepared by Damon Holzer of NOAA Northwest Fisheries Science Center.

[1] M. P. Johnson and P. L. Tyack, “A digital acoustic recording tag for measuring the response of wild marine mammals to sound,” IEEE Journal of Ocean Engineering, vol 28, pp. 3-12, 2003.

[2] M. M. Holt, M. B Hanson, D. A. Giles, C. K. Emmons, and J.  T. Hogan “Noise levels received by endangered killer whales Orcinus orca before and after implementation of vessel regulations” Endangered Species Research, vol. 34, pp. 15-26, 2017.

[3] G. A. Ferrara, T. M. Mongillo, and L. M. Barre “Reducing disturbance from vessels to Southern Resident killer whales:  Assessing the effectiveness of the 2011 federal regulations in advancing recovery goals.” NOAA Technical Memorandum NMFS-OPR-58, 76 pp. 2017.

William D. Halliday
Stephen J. Insley
Xavier Mouy

Presented at the 176th ASA Meeting

Climate change is causing rapid changes to the Arctic marine environment through a combination of sea ice loss and increased human activity. It is imperative that we monitor marine species in order to determine how they are reacting to these changes, but to do this, we must monitor these species over long periods of time, and must have a baseline for comparison. In this presentation, I examine underwater acoustic data that our team collected at two sites in the western Canadian Arctic (Sachs Harbour and Ulukhaktok), and use these data to assess when four species of marine mammals in the region (beluga and bowhead whales, bearded and ringed seals) were vocalizing. For the whales, the timing of vocalization serves as an estimate of migration timing, and for the seals, vocalization timing is more representative of the timing of the mating season. Our data show that both whale species migrated into the region in April, and that beluga whales migrated out of the region in the early autumn, whereas bowhead whales migrated in the late autumn. Both whale species at Ulukhaktok were recorded later into the year than at Sachs Harbour. Patterns in seal species vocalizations were quite different between the two sites. Bearded seals vocalized constantly during the winter and spring at Sachs Harbour, vocalizing 24 hours a day between April and June, whereas at Ulukhaktok, vocalizations began around the same time as at Sachs Harbour, but were much more sporadic and appeared to taper off before the mating season began in the spring. Ringed seals were generally quiet at Sachs Harbour, whereas their vocalizations were abundant throughout the winter at Ulukhaktok. These data serve as a baseline record for all four of these species, and will allow for useful comparisons as we continue to monitor these species at both sites into the future as climate continues to change. These data will also allow us to examine the influence of human-induced stressors, such as increased underwater noise, on these animals. We will also expand our monitoring network throughout the region in order to more fully understand these species in this region.