Jean-François Motsch

Bio: Jean-François Motsch is an academic researcher from University of Paris. The author has contributed to research in topics: Whale & Sperm whale. The author has an hindex of 10, co-authored 23 publications receiving 291 citations.

Source level estimation of two blue whale subspecies in southwestern Indian Ocean

Abstract: Blue whales produce intense, stereotypic low frequency calls that are particularly well suited for transmission over long distances. Because these calls vary geographically, they can be used to gain insight into subspecies distribution. In the Southwestern Indian Ocean, acoustic data from a triad of calibrated hydrophones maintained by the International Monitoring System provided data on blue whale calls from two subspecies: Antarctic and pygmy blue whales. Using time difference of arrival and least-squares hyperbolic methods, the range and location of calling whales were determined. By using received level of calls and propagation modeling, call source levels of both subspecies were estimated. The average call source level was estimated to 179±5 dB re 1 μParms at 1 m over the 17–30 Hz band for Antarctic blue whale and 174±1 dB re 1 μParms at 1 m over the 17–50 Hz band for pygmy blue whale. According to previous estimates, slight variations in the source level could be due to inter-individual differences,...

Male sperm whale acoustic behavior observed from multipaths at a single hydrophone

Abstract: Sperm whales generate transient sounds (clicks) when foraging. These clicks have been described as echolocation sounds, a result of having measured the source level and the directionality of these signals and having extrapolated results from biosonar tests made on some small odontocetes. The authors propose a passive acoustic technique requiring only one hydrophone to investigate the acoustic behavior of free-ranging sperm whales. They estimate whale pitch angles from the multipath distribution of click energy. They emphasize the close bond between the sperm whale’s physical and acoustic activity, leading to the hypothesis that sperm whales might, like some small odontocetes, control click level and rhythm. An echolocation model estimating the range of the sperm whale’s targets from the interclick interval is computed and tested during different stages of the whale’s dive. Such a hypothesis on the echolocation process would indicate that sperm whales echolocate their prey layer when initiating their dives and follow a methodic technique when foraging.

Definition of the Antarctic and Pygmy blue whale call templates. Application to fast automatic detection

Abstract: This paper deals with the automatic detection of low-frequency Antarctic (Balaenptera musculus intermedia) and Pygmy (B. m. brevicauda) blue whale sounds produced in the Southwestern Indian Ocean. A new detection method based on a matched filter is introduced. Four original match templates are presented and tested against original blue whale subspecies calls. The mathematical formulas of these templates, defined by Gaussian curve models, are provided. The detection threshold is based on the correlation coefficients. The threshold was set to reduce false detections obtained on simulated signals at various signal-to-noise ratios. We focus our work on the true detections of whale calls. Moreover, to obtain a real-time system, we decrease the computational time by decimating the recorded signal (Fs=250Hz). We show that this new method enables us to effectively detect both subspecies in various ambient noises, in the Southern Ocean.

Social Emergence: Societies As Complex Systems

Abstract: Can we understand important social issues by studying individual personalities and decisions? Or are societies somehow more than the people in them? Sociologists have long believed that psychology can't explain what happens when people work together in complex modern societies. In contrast, most psychologists and economists believe that if we have an accurate theory of how individuals make choices and act on them, we can explain pretty much everything about social life. Social Emergence takes a new approach to these longstanding questions. Sawyer argues that societies are complex dynamical systems, and that the best way to resolve these debates is by developing the concept of emergence, focusing on multiple levels of analysis - individuals, interactions, and groups - and with a dynamic focus on how social group phenomena emerge from communication processes among individual members. This book makes a unique contribution not only to complex systems research but also to social theory.

Passive Acoustic Monitoring of Cetaceans

Abstract: Acknowledgements Introduction Part I. Underwater Acoustics (The Basics): 1. Principles of underwater sound 2. Cetacean sounds 3. Sonar equation Part II. Signal Processing (Designing the Tools): 4. Detection methods 5. Classification methods 6. Localisation and tracking Part III. Passive Acoustic Monitoring (Putting It All Together): 7. Applications of PAM 8. Detection functions 9. Simulating sampling strategies 10. PAM systems 11. References and literature Index.

Recording and quantification of ultrasonic echolocation clicks from free-ranging toothed whales

Abstract: Toothed whales produce short, ultrasonic clicks of high directionality and source level to probe their environment acoustically. This process, termed echolocation, is to a large part governed by the properties of the emitted clicks. Therefore derivation of click source parameters from free-ranging animals is of increasing importance to understand both how toothed whales use echolocation in the wild and how they may be monitored acoustically. This paper addresses how source parameters can be derived from free-ranging toothed whales in the wild using calibrated multi-hydrophone arrays and digital recorders. We outline the properties required of hydrophones, amplifiers and analog to digital converters, and discuss the problems of recording echolocation clicks on the axis of a directional sound beam. For accurate localization the hydrophone array apertures must be adapted and scaled to the behavior of, and the range to, the clicking animal, and precise information on hydrophone locations is critical. We provide examples of localization routines and outline sources of error that lead to uncertainties in localizing clicking animals in time and space. Furthermore we explore approaches to time series analysis of discrete versions of toothed whale clicks that are meaningful in a biosonar context.