Current projects

Understanding cetacean communication and cognition

Bottlenose dolphin communication and cognition

Bottlenose dolphins are found in oceans and coastal areas around the world and are arguably the best known and most well-studied species of cetaceans. We conduct a variety of research projects with lab and field dolphins around the world to investigate the form, function and evolution of communication in these animals. 

One of our main study populations is in Sarasota, Florida, where we conduct recurring field experiments in collaboration with the Sarasota Dolphin Research Program. This field site is truly unique – 6 generations of dolphins have been documented and followed in the area since research started in 1970, providing an unparalleled range of demographic and life-history information on the local population of dolphins that we in turn can use to inform experiments. Likewise, we have been conducting acoustic research with these animals from ~1985, and have collected a wealth of data on animals in this population. We use a variety of techniques to learn more about how these animals function in their natural environments, and the role that communication plays in their daily lives. Click on each to learn more:

The unique setting in Sarasota allows us to use suction cup hydrophones to record whistles from individual, well-known animals, and this ensures that we know which individual is producing the sound. Over time, this allows us to build a detailed, longitudinal understanding of the whistles used by individuals. We structure these recordings into the Sarasota dolphin whistle database and use them to learn more about the structure of signals such as individually distinctive signature whistles, how individual signals and repertoires differ from one another, and how they develop with age.

Health assessments allow us to instrument animals with small electronic sound and movement recording tags attached to animals using 4 small suction cups. These tags stay on dolphins for up to 24 hours after each health assessment, while they forage through their natural habitat and encounter and socialize with other dolphins. Tags help us investigate a range of questions from how often dolphins eat and what factors determine this, to how communication signals are used in natural contexts. Importantly, they also help us investigate how dolphins cope with underwater noise and disturbances from human activities such as the many recreational vessels that use the dolphins’ natural habitat, or noise from construction events in the area.

We design and implement playback experiments where underwater speakers are used to transmit short sound sequences to dolphins during the health assessments, and to unrestrained wearing tags or monitored with drones. These carefully designed experiments allow us to probe the cognition of these animals and test aspects from how different signals are perceived and differentiated, to what function different signals serve.

Two dolphins instrumented with sound and movement recording DTAGs

Communication in other cetaceans

While much of our work centers around bottlenose dolphins, we investigate communication in a wide range of toothed whale and baleen whale species, from small porpoises to blue whales. These comparative studies help us understand the evolution of communication across cetaceans, and also facilitate species-specific acoustic monitoring used in conservation and management.

Small pod of pilot whales underwater

Pilot whales are highly social and very curious delphinids that live in matrilineal social groups organized about adult females and their offspring. To find food, they dive to depths of up to 1000m in pursuit of squid. In collaboration with partners at CIRCE and Alnilam, we have studied several populations of pilot whales in the Western Mediterranean and in the Strait of Gibraltar to investigate how they communicate, how they coordinate movement and activities, and how they cope with extreme amounts of anthropogenic noise.

Blue whale mother-calf pair seen from drone

Blue whales are the largest animal species on the planet and remain highly endangered despite improvements after the International Whaling Moratorium. We have conducted studies of endangered blue whales off the coast of Chile in collaboration with Centro Fundacion MERI. During these studies, we have deployed DTAGs on whales to study their ecology, behavior, and communication and ultimately improve conservation and management efforts.

Quantifying and mitigating impacts of marine noise

Noise from human activities is nearly ubiquitous underwater, reaching even the deepest parts of the ocean. The last several decades have revealed that marine soundscapes are fundamentally different than in pre-industrial times, and that manmade noise affects life functions in a wide range of marine animals (Duarte et al. 2021, Science). We seek to understand and quantify how noise affects different species of cetaceans, and how we can modify activities to alleviate such effects. We use a wide range of tools and techniques to address effects of noise, from suction cup attached DTAGs that reveal how animals change movement or acoustic behavior in response to noise, to controlled playback experiments with trained or wild animals (using drones or tags to track responses) that allow us to carefully control the sounds that animals are exposed to and quantify how animals modify their movement and behavior as a consequence. Our Board of Directors is also engaged in international efforts to understand, monitor and ultimately mitigate anthropogenic noise in oceans worldwide, most notably through the International Quiet Ocean Experiment (IQOE).

Researcher tagging a long-finned pilot whale

Improving acoustic monitoring and conservation

Acoustic detection of mass strandings

We maintain a long-term acoustic monitoring project off Wellfleet, Massachusetts, where self-contained acoustic recorders are deployed throughout the year to record dolphins and other animals. In collaboration with the Marine Mammal Rescue and Research Team at the International Fund for Animal Welfare (IFAW), we analyze recordings made prior to dolphin mass stranding events to determine whether there are consistent acoustic cues that could help us predict these events. Our ultimate goal is to give stranding response teams advance warning and increase the number of dolphins that survive such events.

Counting dolphins by their whistles

We develop new methods for acoustic monitoring and management of dolphin populations worldwide. Our work establishing and maintain the world’s only large-scale, systematic database of known bottlenose dolphin signature whistles is essential for validation these new methods. In collaboration with the Allen Institute for AI, we use this database to develop algorithms that automatically detect bottlenose dolphin whistles, and that recognize signature whistles from the database, thus allowing us to track individual dolphins acoustically through their signature whistles. In Sarasota, this happens through a network of passive acoustic listening stations maintained by our partners at the Sarasota Dolphin Research Project. Ultimately, we aim to identify novel signature whistles in-situ, and to be able to combine AI-based recognition of dolphin signature whistles with mark-recapture analysis to estimate population size acoustically.

Pod of dolphins

The Sarasota dolphin whistle database

We build and maintain a unique, large-scale database of curated bottlenose dolphin whistles from known individual bottlenose dolphins in Sarasota, FL. This database includes the signature whistles of many of the individuals in the resident Sarasota dolphin community (some 269 individual signature whistles have been recorded and identified so far). Around 60% of recorded individuals have also been recorded multiple times, allowing us to understand how stable signature whistles are, as well as when and why they change. Throughout these studies, we have found that signature whistles are the dolphin equivalent of a “name” – our work has shown that signature whistles are individually distinctive to each animal, generally remain stable across decades, and are used during natural encounters in the wild. Other studies have also shown that dolphins recognize signature whistles of familiar dolphins even after many years of separation, and that signature whistles are important for mediating complex cooperative relationships.

Our ongoing work seeks to integrate all these recordings into an organized database with hundreds of signature whistle examples from all recorded individuals, as well as examples of non-signature whistles and signature whistle copies. This work is integral to understanding the natural variation in signature whistles and whistle repertoires and to understand how both individual identity as well as potentially more subtle information is encoded in the structure of whistles. We also hope to find support to keep adding new data collected in future years to continually expand this database to reflect changes in the Sarasota dolphin community and include more and more individuals from the area. 

Signature whistles from bottlenose dolphins in Sarasota
Overview of the time-frequency structure (spectrogram display) of 269 different bottlenose dolphin signature whistles recorded from a single population of bottlenose dolphins in Sarasota, FL, over the course of 35 years of acoustic studies (Data by L. Sayigh, Visualization by F. Jensen).