Banded mongooses discriminate relatedness and MHC diversity in unfamiliar conspecifics

Abstract

Olfactory cues are critical in mammalian social communication, conveying fitness-relevant information such as relatedness, genetic quality, and compatibility. Recognizing kin through scent can help avoid inbreeding depression and guide nepotistic behaviors, enhancing both direct and indirect fitness. While many species use familiarity to identify relatives, others rely on phenotype matching, where animals assess genetic similarity by comparing their own genetically determined odor with that of others. In banded mongooses, synchronized breeding disrupts familiarity cues, increasing reliance on alternative mechanisms for kin discrimination and mate selection. 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 that reflect genetic diversity and relatedness. We found that individuals respond differently to odors from unfamiliar individuals based on MHC diversity and genetic relatedness. Specifically, individuals show more interest in less MHC diverse and less related unfamiliar conspecifics, suggesting odor cues are used to evaluate threat level of intruders or competitors. Genetic diversity had no impact on responses to odors and was not significantly associated with MHC diversity, implying that responses to MHC diversity did not result from an underlying correlation with over-all genetic diversity. We also found no effect of MHC similarity, which might be caused by the limited sample size for this analysis. Our findings show that MHC diversity might signal the genetic quality of individuals, but regions of the genome other than MHC may be used to assess relatedness. These findings provide the basis for future research on the involvement of the MHC and other genes in social communication in species where phenotype matching is likely to be advantageous.