These ripple cues are an unintentional by-product of calling, but have become part of the sexual display, as their presence modulates receiver responses to their acoustic signal components ( Halfwerk et al., 2014a). Similarly, floating frogs produce water ripples when calling from the water. A famous example in humans is the McGurk effect which shows lip movement (the by-product of pronunciation) affects speech perception ( McGurk and MacDonald, 1976).
Human and many animals often generate by-product cues during signaling that can influence the perception of the dominant part of the signal. An important question remains whether and when multimodal signals evolve de novo, or evolve through a process of co-option, by incorporating additional cues into a unimodal display ( Halfwerk et al., 2019). Contra to why, we know far less how multimodal signals evolve from unimodal ones. The production and reception of multimodal signals is often more costly in terms of energy loss or predation and parasitism risk when compared to unimodal signals ( Bro-Jørgensen, 2010), and their evolution is therefore often explained through functional benefits, such as cross-modal perception by receivers, which can improve signal detection and discrimination, or enhance attention and memory time ( Halfwerk et al., 2019 Hebets and Papaj, 2004 Halfwerk et al., 2014b). Such multimodal signaling can be highly complex, often involving multiple underlying neuronal motor programs that need to be synchronized in order to perform well ( Partan and Marler, 1999 Ryan et al., 2019 Halfwerk et al., 2019 Higham and Hebets, 2013). Many animals can increase their communication efficiency by enhancing the complexity in a single sensory modality or by evolving displays that target multiple sensory modalities ( Cui et al., 2016 Partan and Marler, 1999). Our results thus help to understand the relationship between natural and sexual selection pressure operating on signalers and how in turn this may influence multimodal signal evolution. Females may play an important role in incorporating these multiple components because they prefer signals which combine multiple modalities. Our data suggest that midge-induced movements may be incorporated into a sexual display, targeting both hearing and vision in the intended receiver. Through mate choice tests we show that some of these midge-evoked movements influence female preference for acoustic signals. Calling males of this species often display limb movements in order to defend against blood-sucking parasites such as frog-biting midges that eavesdrop on their acoustic signal.
#ALPHA PROTOCOL TORRENT TORRENT#
Here, we assess whether the physical movements of parasite defense behavior increase the complexity and attractiveness of an acoustic sexual signal in the little torrent frog ( Amolops torrentis). Despite being taxonomically widespread, we often lack insight into how multimodal signals evolve from unimodal signals and in particular what roles unintended eavesdroppers play.
#ALPHA PROTOCOL TORRENT DRIVER#
These multimodal displays can however also attract unintended receivers, which can be an important driver of signal complexity. Many animals rely on complex signals that target multiple senses to attract mates and repel rivals.
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