Our senses are constantly bombarded with so many different signals that it can be hard to know what to pay attention to. If you're a male moth, the answer is simple: sex. Moths only live for two weeks, so it's unsurprising that males are preoccupied with sniffing out the fairer sex. But you can't mate if you're dead, so males should not ignore the sound of lurking danger. How male moths handle the trade-off between the sweet smell of their mate and the sound of impending doom depends on the relative intensity of these two sensory cues. Niels Skals and his colleagues have discovered that a whiff of female scent overpowers a male moth's sense of hearing, making the hapless male deaf to the sound of an approaching bat(p. 595).

To see how male moths cope with conflicting sensory information, Skals set up an air stream wafting a female moth's attractive scent across an open arena. He placed male moths at the downwind end of the arena and watched the males excitedly zigzag towards the odour source. When the male was halfway towards the object of his affections, Skals played bat ultrasound attack calls through a loudspeaker. Male moths sniffing synthetic pheromones froze when they heard bat calls, a typical predator evasion response. But as Skals increased pheromone quality and concentration, males became more reckless at the prospect of sex. When Skals used natural female pheromone gland extracts,the love-struck males completely ignored the bat calls and hurried on in hot pursuit of their female. Skals concludes that male moths have to weigh up the relative importance of smells and sounds; a high concentration of female scent could indicate that a potential mate is nearby and the male can't afford to lose his lady, even if that means an increased risk of becoming a bat's dinner.

Skals, N., Anderson, P., Kanneworff, M., Löfstedt, C. and Surlykke, A. (
). Her odours make him deaf: crossmodal modulation of olfaction and hearing in a male moth.
J. Exp. Biol.