Short-term Exposure of Environmentally Relevant Concentrations of Nitrate and its Effect on Olfactory Male Attractiveness and Repellent Cues in Pacific Newts

Amphibian decline has quickly become a complex global issue, warranting the attention of behavioral ecologists and conservation biologists alike. A ubiquitous natural compound, nitrate, has greatly increased in environmental concentrations due to anthropogenic sources. Nitrate has been shown to affect amphibian larval development as well as courtship behavior in adults. Species recognition often precedes courtship behavior and thus plays a critical role in the conservation of reproductive isolation between closely related sympatric species. Here, we investigate species recognition and mate preference by female rough-skinned newts, Taricha granulosa via chemical cues alone in the presence of aged water and water treated with nitrate. We found that females preferred the odor source of conspecific males when given the option of heterospecific male species. However, in the presence of nitrate, pond breeding females no longer preferred conspecific males, while creek breeding females maintained their preference for conspecifics. Pond breeding females also avoided heterospecific cues while this trend was not apparent in creek breeding females. Our results suggest that female rough-skinned newts respond to both attractant and repellent.chemical cues and that a repellent cue may act to prevent heterospecific mate pairings. Our findings also support geographic variation in mate preference response in the presence of nitrate.