02835nas a2200169 4500008004100000245012700041210006900168520220200237653003502439653001702474653001902491653003102510100002102541700002002562700002102582856006202603 2020 eng d00aIndividuality in the vocalizations of infant and adult coppery titi monkeys ( Plecturocebus cupreus )0 aIndividuality in the vocalizations of infant and adult coppery t3 a

As social animals, many primates use acoustic communication to maintain relationships. Vocal individuality has been documented in a diverse range of primate species and call types, many of which have presumably different functions. Auditory recognition of one's neighbors may confer a selective advantage if identifying conspecifics decreases the need to participate in costly territorial behaviors. Alternatively, vocal individuality may be nonadaptive and the result of a unique combination of genetics and environment. Pair‐bonded primates, in particular, often participate in coordinated vocal duets that can be heard over long distances by neighboring conspecifics. In contrast to adult calls, infant vocalizations are short‐range and used for intragroup communication. Here, we provide two separate but complementary analyses of vocal individuality in distinct call types of coppery titi monkeys (Plecturocebus cupreus) to test whether individuality occurs in call types from animals of different age classes with presumably different functions. We analyzed 600 trill vocalizations from 30 infants and 169 pulse‐chirp duet vocalizations from 30 adult titi monkeys. We predicted that duet contributions would exhibit a higher degree of individuality than infant trills, given their assumed function for long‐distance, intergroup communication. We estimated 7 features from infant trills and 16 features from spectrograms of adult pulse‐chirps, then used discriminant function analysis with leave‐one‐out cross‐validation to classify individuals. We correctly classified infants with 48% accuracy and adults with 83% accuracy. To further investigate variance in call features, we used a multivariate variance components model to estimate variance partitioning in features across two levels: within‐ and between‐individuals. Between‐individual variance was the most important source of variance for all features in adults, and three of four features in infants. We show that pulse‐chirps of adult titi monkey duets are individually distinct, and infant trills are less individually distinct, which may be due to the different functions of the vocalizations.

10adiscriminant function analysis10apair bonding10avocal duetting10avocalization individuality1 aLau, Allison, R.1 aClink, Dena, J.1 aBales, Karen, L. uhttps://onlinelibrary.wiley.com/doi/abs/10.1002/ajp.2313402062nas a2200181 4500008004100000245014000041210006900181520139100250653001601641653001401657653002201671653002801693653003301721100002001754700002401774700001901798856006301817 2020 eng d00aBrevity is not a universal in animal communication: evidence for compression depends on the unit of analysis in small ape vocalizations0 aBrevity is not a universal in animal communication evidence for 3 a

Evidence for compression, or minimization of code length, has been found across biological systems from genomes to human language and music. Two linguistic laws—Menzerath’s Law (which states that longer sequences consist of shorter constituents) and Zipf’s Law of abbreviation (a negative relationship between signal length and frequency of use)— are predictions of compression. It has been proposed that compression is a universal in animal communication, but there have been mixed results, particularly in reference to Zipf’s Law of abbreviation. Like songbirds, male gibbons (Hylobates muelleri) engage in long solo bouts with unique combinations of notes which combine into phrases. We found strong support for Menzerath’s Law as the longer a phrase, the shorter the notes. To identify phrase types, we used state-of-the-art affinity propagation clustering, and were able to predict phrase types using support vector machines with a mean accuracy of 74%. Based on unsupervised phrase type classification, we did not find support for Zipf’s Law of abbreviation. Our results indicate that adherence to linguistic laws in male gibbon solos depends on the unit of analysis. We conclude that principles of compression are applicable outside of human language, but may act differently across levels of organization in biological systems.

10acompression10aHylobates10aMenzerath’s Law10aunsupervised clustering10aZipf’s Law of abbreviation1 aClink, Dena, J.1 aAhmad, Abdul, Hamid1 aKlinck, Holger uhttps://royalsocietypublishing.org/doi/10.1098/rsos.200151