| Summary: | The degree of sexual dimorphism in species is indicative of the communication process in sexual selection. This signaling of males to attract females, functions as an advertisement for good genes, specifically their resistance to parasites and hence ability to produce healthy progeny. The sexual signals are subject to influence by parasites due to the dynamic co-evolutionary nature of parasites and hosts. This co-evolutionary mechanism is examined with respect to the Hamilton-Zuk hypothesis- that of showiness correlating to parasitic load. There are many intra-specific studies showing preferences for males with strong sexual signals correlating strongly with reduced parasitic load. However, inter-specific research illustrating that the species exhibiting the strongest sexual signals are those carrying the largest parasitic load, is much limited, and raises issues of taxonomy as well as other confounding variables. Using the behaviour of eavesdropping and manipulation of host sexual signals by parasites, an alternative hypothesis where such manipulation could possibly create a symbiotic relationship between montane vole Microtus montanus and parasite Toxoplasma gondii, is explored. If experimentally tested, this could further support the Hamilton-Zuk hypothesis of how sexual selection can be driven by resistance to parasites.
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