Our research program explores the sensory, cognitive, and behavioral ecology of marine mammals. The approach we apply to these areas is to study individuals in controlled and natural settings. Experiments conducted in the laboratory allow us to generate hypotheses about the perceptual and cognitive mechanisms that enable animals to acquire, organize, and utilize various types of information. Observations made in the field allow us to see how perception and cognition are translated into behavior. Comparative studies in both settings help us to understand how ecological, evolutionary, and life history factors have influenced different marine mammal species.

The program is based at Long Marine Lab at the University of California Santa Cruz, in Santa Cruz, California. Here, a small group of marine mammals work closely with researchers in behavioral psychophysical studies. The animals are trained using operant conditioning and positive reinforcement to participate in various research procedures that involve active decision-making. The procedures used tend to be either detection or discrimination tasks. For detection tasks, subjects are trained to report the presence of a signal, much like human subjects performing in sensory assessment procedures. We typically use stimuli that vary along a single dimension, such as sounds of a fixed frequency and duration that are varied systematically in level. These signal detection procedures allow us to measure sensory thresholds, or stimulus levels at which subjects can no longer differentiate signals from background noise. Multiple thresholds measured for different stimulus conditions can then be used to depict sensitivity profiles for signals of a given type. Examples of studies we have carried out using detection procedures include investigation of visual dark adaptation, auditory masking, and amphibious hearing capabilities. For the discrimination tasks, subjects learn to differentiate between at least two alternative stimuli. Discrimination tasks can be fairly simple, where subjects choose from one of two alternatives on the basis of preference or previous experience, or they can be conditional, where the correct alternative is controlled by another stimulus known as a sample stimulus. Examples of studies we have completed using discrimination procedures include assessment of sound localization abilities, associative learning within and across sensory modalities, concept formation, and short- and long-term memory.

In the field, our interests focus on how individuals use sensory cues to communicate, forage, navigate, and avoid predation. We combine sensitivity measures obtained in the lab with vocalization and ambient noise measurements obtained in the wild to estimate biologically significant variables such as communicative ranges, zones of masking in natural and anthropogenic noise, and directional propagation of vocal signals. These approaches help us to better understand how marine mammals use sound and other sensory cues in social and ecological contexts. The signals produced in natural environments are generally more complex than those used in experimental situations, and various aspects of these signals-including stereotypy, redundancy, duration, frequency range, amplitude, and context-are oftentimes particularly suited to gain the attention of receivers as well as convey information about the identity, status, location, and/or the motivational state of the of the signaler. On a cognitive level, unraveling relationships between signal form and function reveals how signals acquire meaning and how they may be recognized and remembered by individuals over time.

In terms of ecological policy-making, our work has direct application to the impact of noise pollution on marine habitats. For example, we are interested in how exposure to noise may interfere with an animal's biologically significant activities, such as a female attending her pup or a male defending his territory during the breeding season. We believe that by evaluating the auditory capabilities of marine mammals, sensible regulations can be drafted which will mitigate the impact of noise pollution (from sources including shipping traffics, oceanographic experiments, military sonar, and acoustic harassment devices) and its deleterious effects on the behavior and physiology of these diving mammals.

Finally, our work on learning, memory, concept formation, and artificial language in sea lions and other marine mammals has shown how well these animals can integrate a variety of sensory cues in order to organize perceptual information into meaningful associations and categories. These aspects of cognition are likely to be critical for the evolution of complex problem solving abilities, referential communication, and perhaps even proto-linguistic skills including syntax and semantics. Our evidence for non-verbal thinking in sea lions informs understanding of the development of non-verbal thinking in humans such as infants, children, and language- or cognitively-impaired adults.

The research program was developed by Dr. Ronald J. Schusterman and his collaborators over a period of more than 40 years. The project has been based at UCSC's Long Marine Lab since 1985, and is currently headed by Dr. Colleen Reichmuth.

An aerial view taken over the Monterey Bay of Long Marine Lab and the Seymour Marine Discovery Center.

Our sound attenuating, hemi-anechoic chamber where we conduct in-air acoustic experiments (aka "the chamber").

One of our 22,000 gallon saltwater pools where underwater acoustic experiments are conducted. The chamber is in the background (top right).
How to Get Involved
The Cognition and Sensory Systems Laboratory is supported by a team of hard working individuals, including research staff, graduate students, undergraduate research assistants, and interns. Volunteer research assistantships are typically offered to undergraduate students at UC Santa Cruz who work in the lab part-time year round. Internships last 3-4 months and are full time, unpaid, positions available to college students close to completing their degrees, or to those who have finished their degrees and intend to pursue post-graduate education in some form. For more information about research assistantships or internships, please write to pinnipedlab@gmail.com. Individuals interested in graduate student positions with the laboratory should contact the PI at this address as well. The program seeks motivated individuals with background and/or interest in a variety of fields including biology, psychology, physics, engineering, environmental studies, computer sciences, and veterinary medicine.

More Information
Long Marine Lab is part of the Institute of Marine Sciences at UC Santa Cruz. The Seymour Marine Discovery Center at LML offers tours and additional information about the facility and ongoing research.
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