Banded mongooses discriminate relatedness and MHC diversity in unfamiliar conspecifics

Olfactory cues play a vital role in mammalian social communication, conveying fitness-relevant information such as genetic quality and relatedness. Kin recognition through scent can help avoid inbreeding and guide nepotistic behaviors, enhancing fitness. In banded mongooses, synchronized breeding disrupts familiarity-based kin recognition, potentially increasing reliance on phenotype matching, where individuals compare genetically determined odors to assess similarity. We tested whether banded mongooses use odors to assess genetic diversity and relatedness based on (1) major histocompatibility complex (MHC) genotypes and (2) neutral microsatellite loci. Results showed individuals responded differently to odors from unfamiliar conspecifics based on MHC diversity and relatedness. Specifically, less MHC-diverse and less related individuals attracted more interest, suggesting odor cues are used to evaluate intruder or competitor threat levels. Neutral genetic diversity did not affect odor responses and was not correlated with MHC diversity, indicating responses to MHC diversity are independent of overall genetic diversity. No effect of MHC similarity was observed, possibly due to sample size limitations. Our findings suggest MHC diversity may signal genetic quality, while other genomic regions might contribute to assessing relatedness. These results provide a foundation for further research into the role of MHC and other genes in social communication in species where phenotype matching offers adaptive benefits.