Female Iberian wall lizards prefer male scents that signal a better cell-mediated immune response.

In spite of the importance of chemoreception in sexual selection of lizards, only a few studies have examined the composition of chemical signals, and it is unknown whether and how chemicals provide honest information. Chemical signals might be honest if there were a trade-off between sexual advertisement and the immune system. Here, we show that proportions of cholesta-5,7-dien-3-ol in femoral secretions of male Iberian wall lizards (Podarcis hispanica) were related to their T-cell-mediated immune response. Thus, only males with a good immune system may allocate higher amounts of this chemical to signalling. Furthermore, females selected scents of males with higher proportions of cholesta-5,7-dien-3-ol and lower proportions of cholesterol. Thus, females might base their mate choice on the males' quality as indicated by the composition of their chemical signals.