Efficient coding in dolphin surface behavioral patterns

We show that the law of brevity, i.e. the tendency of words to shorten as their frequency increases, is also found in dolphin surface behavioral patterns. As far as we know, this is the first evidence of the law in another species, suggesting that coding efficiency is not unique to humans.Peer ReviewedPostprint (author's final draft

The law of brevity in macaque vocal communication is not an artifact of analyzing mean call durations

Words follow the law of brevity, i.e. more frequent words tend to be shorter. From a statistical point of view, this qualitative definition of the law states that word length and word frequency are negatively correlated. Here the recent finding of patterning consistent with the law of brevity in Formosan macaque vocal communication (Semple et al., 2010) is revisited. It is shown that the negative correlation between mean duration and frequency of use in the vocalizations of Formosan macaques is not an artifact of the use of a mean duration for each call type instead of the customary 'word' length of studies of the law in human language. The key point demonstrated is that the total duration of calls of a particular type increases with the number of calls of that type. The finding of the law of brevity in the vocalizations of these macaques therefore defies a trivial explanation.Comment: Little improvements of the statistical argument

Compression as a universal principle of animal behavior

A key aim in biology and psychology is to identify fundamental principles underpinning the behavior of animals, including humans. Analyses of human language and the behavior of a range of non-human animal species have provided evidence for a common pattern underlying diverse behavioral phenomena: words follow Zipf's law of brevity (the tendency of more frequently used words to be shorter), and conformity to this general pattern has been seen in the behavior of a number of other animals. It has been argued that the presence of this law is a sign of efficient coding in the information theoretic sense. However, no strong direct connection has been demonstrated between the law and compression, the information theoretic principle of minimizing the expected length of a code. Here we show that minimizing the expected code length implies that the length of a word cannot increase as its frequency increases. Furthermore, we show that the mean code length or duration is significantly small in human language, and also in the behavior of other species in all cases where agreement with the law of brevity has been found. We argue that compression is a general principle of animal behavior, that reflects selection for efficiency of coding.Comment: This is the pre-proofed version. The published version will be available at http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291551-670

Parallels of human language in the behavior of bottlenose dolphins

A short review of similarities between dolphins and humans with the help of quantitative linguistics and information theory

Cetacean Exhalation: An Examination of Bottlenose Dolphin (\u3ci\u3eTursiops truncatus\u3c/i\u3e) Use of Three Bubble Production Types through Associated Behaviors

Bubble production through exhalation is unique to marine mammals due to the combination of their air-breathing physiology and aquatic environment. Multiple types of bubble production are reported in the literature, including bubble netting, trails, bursts, and rings. Unfortunately, apart from bubbles produced to facilitate hunting or play, current understanding of the function of bubble production in cetaceans is limited to anecdotal accounts and author interpretations. This study aims to identify the function of three bubble types though observations of behaviors present before, during, and after bubble production. Instances of bubble trails, bubble bursts, and scant bubbles were selected from underwater video observation of bottlenose dolphins in human care. Rates of behaviors before, during, and after bubble production were recorded for each individual present during a bubble event, along with the individual’s age, sex, and role as bubbler or bystander. Suites of observed behaviors were grouped by function for analyses. Logistic regressions were used to determine which behavioral factors and demographics predicted bubble production across time periods for different bubble types. Predicting behaviors for bubble trail production showed use in multiple social situations. Behaviors predicting bubble burst production indicated use in avoidance, sexual behavior, object engagement, and as early exhalation during surfacing. Scant bubble production predictive behaviors demonstrated use in close proximity social behavior and non-social interest. These results provide a better understanding of how bubble production types fit into the behavioral repertoire, which supports some previously suggested behavioral uses of bubble production, and provides future research on bubble production directions to explore. By identifying these differences in behavioral patterns, we can better identify the function of bubble behaviors and how they fit into the bottlenose dolphin behavioral repertoire. Ultimately, this will enable us to better interpret bubble behaviors, benefiting future experimental and observational studies interested in behavioral responses of bottlenose dolphins

Exploring Temperament in Beluga Whale Calves (\u3ci\u3eDelphinapterus leucas\u3c/i\u3e)

Studies of personality and temperament in humans span many disciplines, although animal research is still relatively undeveloped. Research investigating stable individual differences in marine mammals has been limited, and to date there have not been any studies with beluga whales. As an ongoing longitudinal study, seven beluga calves, housed at SeaWorld San Antonio, were videotaped throughout their first two years of life. Four videos were selected from archived video recordings for each calf from the following nine phases: newborn phase (month 1), Q1 (month 2-3), Q2 (month 4-6), Q3 (month 7-9), Q4 (month 10-12), Q5 (month 13-15), Q6 (month 16-18), Q7 (month 19-21), Q8 (month 22-24). Videos were coded for 40 behaviors: three behavioral states, including durations, and 37 behaviors for frequency. These behaviors were later consolidated to 23 behaviors for analysis. A Principal Components Analysis (PCA) of these 23 behaviors across all seven whales yielded a five-factor model for beluga calf temperament. Factors included mother-calf bond, sociability, independence, exploration-vigilance, curiosity-playfulness. A PCA for year one and a PCA from year two were compared and did not yield the same five factors. A paired-samples t-test revealed that five of 26 behaviors were significantly different between year one and year two, and 21 behaviors were significantly different between the newborn phase and year one. While there was only one behavior, orient at researcher, that was not observed in the newborn phase, the calves’ behavior was significantly different during their first month of life. The orient at researcher behavior was observed for the first time around quarter three in all seven whales, signifying a potential milestone. The time the calves spent swimming with their mothers decreased with age, while the time spent swimming socially and swimming alone increased with age. Based on the five-factor model, beluga calves each had their own distinct temperament. While temperament appears to not have stabilized by year two, distinct patterns of behavior were observable in year one and year two. Based on the behavioral patterns of the whales in the first two years of life, it can be argued that beluga calves have distinct temperaments

A law of word meaning in dolphin whistle types

We show that dolphin whistle types tend to be used in specific behavioral contexts, which is consistent with the hypothesis that dolphin whistle have some sort of “meaning”. Besides, in some cases, it can be shown that the behavioral context in which a whistle tends to occur or not occur is shared by different individuals, which is consistent with the hypothesis that dolphins are communicating through whistles. Furthermore, we show that the number of behavioral contexts significantly associated with a certain whistle type tends to grow with the frequency of the whistle type, a pattern that is reminiscent of a law of word meanings stating, as a tendency, that the higher the frequency of a word, the higher its number of meanings. Our findings indicate that the presence of Zipf's law in dolphin whistle types cannot be explained with enough detail by a simplistic die rolling experiment.Peer ReviewedPostprint (published version