Akin to a regional accent or dialect in human language, highly social naked mole-rats form distinctive and unique colony-specific chirps, which convey information about an individual's social membership, according to a new study. What's more, these dialects are culturally transmitted across generations, supporting the idea that social complexity evolved concurrently with vocal complexity. Naked mole-rats (Heterocephalus glaber) form some of the most cooperative and social groups known in the animal kingdom, living in multigenerational, maze-like subterranean colonies dominated by a single breeding matriarch or "queen." They are also highly xenophobic and are known to attack and kill those from other colonies. However, how these mostly blind creatures maintain their complex and highly organized social structure is mostly a mystery. To investigate the role of vocal communication in mole-rat society, Alison Barker and colleagues applied machine learning techniques to analyze the acoustic features in more than 36,000 individual recordings of "soft chirps" - the most common mole-rat vocalization - from animals housed in separate colonies around the world. The authors found that naked mole-rats have distinctive soft chirps, unique to an animal's group. In a series of experiments, Barker et al. show that this dialect appears to be determined by a colony's queen and is learned by mole-rat pups early in life. However, these dialects are not fixed - they change when a colony's queen dies and is replaced, and young pups fostered in foreign colonies learn the dialect of their adoptive groups. According to the authors, this suggests that individual colony dialects, including their transmission from generation to generation, is cultural rather than genetic. "This is an astonishing feat for a rodent and is in stark contrast to the majority of mammalian vocalizations, which are innate, immutable, and genetically inherited," writes Rochelle Buffenstein in a related Perspective.
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Journal
Science