title: Consumption of grass endophytes alters the ultraviolet spectrum of vole urine.
abstract: Fungal endophytes of grasses are known to benefit their hosts directly by increasing resistance to herbivores through mycotoxins. We propose and test assumptions of a novel hypothesis according to which fungal endophytes of grasses may benefit their hosts also indirectly by increasing the conspicuousness of a mammalian herbivore, the field vole (Microtus agrestis), to its avian predators by enhancing the ultraviolet visibility of vole urine. We found that field voles feeding on endophyte-infected meadow ryegrass (Lolium pratense) lost body mass, while voles feeding on non-infected meadow ryegrass gained mass. More interestingly, the maximum peak intensity of ultraviolet fluorescence in the urine of voles feeding on endophyte-infected grass shifted from over 380 nm to circa 370 nm, which is the suggested maximum sensitivity of the ultraviolet pigments in the eyes of vole-eating raptors. Therefore, grazing on endophyte-infected grass alters the ultraviolet spectrum of vole urine, thus potentially enhancing its visibility to avian predators.
authors.affiliation: Suonenjoki Research Unit, Finnish Forest Research Institute, Juntintie 154, 77600 Suonenjoki, Finland. otso.huitu@metla.fi
authors.forename: Otso
authors.initials: O
authors.lastname: Huitu
authors.forename: Marjo
authors.initials: M
authors.lastname: Helander
authors.forename: Päivi
authors.initials: P
authors.lastname: Lehtonen
authors.forename: Kari
authors.initials: K
authors.lastname: Saikkonen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D003411:Arvicolinae / Q000502:physiology* / Q000652:urine; D005247:Feeding Behavior / Q000502:physiology*; D005387:Finland; D005658:Fungi / Q000737:chemistry*; D008129:Lolium / Q000382:microbiology*; D013050:Spectrometry, Fluorescence; D014466:Ultraviolet Rays; D014556:Urine / Q000737:chemistry