Kristi Larkin, Jessica Lancaster, and Stephanie Trimble

In general, communication is thought of mainly as contact through vocalization. However, communication among pinnipeds also includes "learned language" through human interaction, dominance within a population, body contact, and mother/pup relationships.

Studies performed in 1981 by Schusterman summarized several aspects of conditioning and learning in pinnipeds through habituation. The rate of habituation to a particular stimulus varies among species, populations, and individuals, and the occurrence of the fright/startle response varies with respect to sex, age, season, time of day, and location (Bekoff 1972). California sea lions, for example, show signs of being afraid of humans, yet sea lions in the Galapagos Islands do not display fear. Two important aspects of the ontogeny, or course of development, of social behavior include: (1) the development of control of agonistic behavior and the formation of dominance relationships and (2) the development of non-agonistic social interactions (Bekoff 1972). Behavioral observations made about most species must be performed in the laboratory because the natural habitat of the animal may be an unsuitable locale for making detailed observations, social interactions may be hard to control, particular individuals may be difficult to identify, and younger individuals may not emerge from the den until well after the critical period of social development has passed (Bekoff 1972). The ability to distinguish between playful and threatening interactions must be acquired early in development. Most messages concerning a species’ mood are conveyed through vocalizations, facial expressions, and bodily gestures (Bekoff 1972). Schusterman demonstrated that sea lions have the ability to comprehend an artificial language that includes words and signals that correspond to objects and actions. They are also able to carry out complex commands (Riedman 1990). The sea lions, during the study, were capable of combining such learning and cognitive skills as higher-order conditioning or paired-associate learning (relationship between A and B), categorizing of objects and events into classes and relational concepts (class = square versus round, relational = large versus larger), and discriminating the temporal order of paired associates (A-B association precedes C-D association) (Bekoff 1972). Studies conducted on "Rocky," a female California sea lion, were performed to determine whether adjectives for size had an absolute meaning (small versus large) or a comparative meaning (smaller versus larger) (Schusterman 1986). "Rocky" was able to follow trainers’ gestures when designating properties of size, brightness, location, object types, and actions. During a study of object permanence, "Rocky" was given signs for objects that were hidden or absent from the other objects; these trials resulted in prolonged searches before she would return. The sea lion had the most difficulty in distinguishing between smaller or larger objects during the searches; when "Rocky" was told to retrieve the smaller ball, for example, her search time would increase (Schusterman 1986). Sea lions are considered to be "prelinguistic," because they appear to have many of the basic cognitive skills necessary for language, but they do not have the language itself (Schusterman 1986).

Vocalization for breeding activities occurs particularly among males that are protecting their territories or competing for mates. These breeding males produce a distinctive call or song that is associated with dominance or territorial maintenance. Sounds are referred to as songs if they are repetitive, directional, and produced seasonally (Riedman 1990). Males "rear and trumpet," throw their heads back, and emit a series of distinct drum-like pulses of sound (Riedman 1990). Most disputes are resolved by these ceremonial threats and not by fighting (Gentry 1987). Occasional fighting includes chest to chest pushing, lunging, and slashing, and it typically subsides after boundaries are established. Male California sea lions have a strong directional bark that serves to threaten other males and advertise dominance. These barks are often repetitive with a frequency range greater than 4kHz (Schusterman 1969). While the sea lion’s nose and mouth are in the air, its bark is transmitted into the water by the vibration of the submerged throat area (Schusterman 1969). Dominant male elephant seals participate in the majority of mating and fights among the males can be intense. A dominant male will produce a loud trumpeting sound that is characterized by a low frequency (Reist 1998). Bearded seal songs consist of oscillating sounds with changing frequencies that are punctuated by a brief low frequency moan (Riedman 1990). Walruses are among the most vocal of all pinnipeds. They produce growls, grunts, and soft whistles. Males position themselves around the females and engage in continuous acoustical and visual displays (Sea World 1994). Underwater sounds are produced using pharyngeal pouches. By striking their inflated throats with their foreflippers, walruses are able to produce sound (Sea World 1994).

Vocalization and body contact appear to have a larger role in pinniped communication than visual recognition. Female otariids produce a warbling call after returning from a foraging trip. Any pup in the vicinity will rush toward the female, but she responds only to the call of her own pup (Riedman 1990). California sea lions, for example, breed in rookeries, or established breeding grounds, in Baja and Southern California from May to July. Several days after birth, the mother leaves the pup and begins foraging for food. When she returns, the mother produces a trumpeting sound to attract her pup, and they continue to emit vocalized responses until they are reunited (Sea World 1996). Northern Fur Seal mothers will not nurture their pups without a vocalization to distinguish the pup. A mother will bite or toss a pup for venturing too close, whether it is her own or not, if it does not vocalize to her (Riedman 1990). During foraging trips, female phocids (true seals) leave their pups alone for shorter periods than do otariids. Adult phocids will maintain constant contact with pups and will attack pups that wander away from their mothers (Riedman 1990). Odobenids (walruses), rely more on body contact for communication. Mothers with calves that are more than two days old gather in "nursery herds" to keep calves separate from males and other females (Sea World 1994). A pregnant walrus that is near-term usually separates from her calf from the previous pregnancy just before her new calf is born. The mother and calf remain together for two years or more if the mother doesn’t produce another calf (Sea World 1994). Calves are protected in the water by riding on their mothers’ backs and are sheltered between their mothers’ foreflippers under the chest (Riedman 1990). Based on these examples, visual recognition is not believed to be as important in pinniped communication as are vocalization and body contact.

 Bekoff, M. "The development of social interaction, play, and metacommunication in mammals: An ethological perspective". The Quarterly Review of Biology, 47: 412-428. 1972.

Gentry, R.L. "Seals and their kin." National Geographic, 4: 475-501. 1987.

Reidman, M. The Pinnipeds: Seals, Sea Lions, and Walruses. University of California Press: Los Angeles. 1990.

Reist, N. "Sounds of Science: Sound and Male Dominance". 1998. www.anonuevo.org/elephant.html

Schusterman, R.J. "Underwater Barking by Male Sea Lions". Nature, 222: 1179-1181. 1969.

Schusterman, R.J. and K. Krieger. Artificial Language Comprehension and Size Transposition by a California Sea Lion. 100, (4):348-356. 1986.

Sea World. " Walrus Communication and Birth and Care of Young". 1994. www.seaworld.org/walrus/communwal.html

Sea World. "California Sea Lion Fast Facts". 1996. www.seaworld.org/animal_bytes/sea_lionab.html

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