Abstract
Advanced cognitive abilities have long been hypothesized to be important in mating. Yet, most work on sexual selection has focused on morphological traits and its relevance for cognitive evolution is poorly understood. We studied the spatial memory of lekking long-billed hermits (Phaethornis longirostris) and evaluated its role in lek territory ownership, the magnitude of its effect compared to phenotypic traits expected to influence sexual selection, and whether its variation is indicated in the structure of mating vocal signal. Spatial memory (the ability to recall the position of a rewarding feeder) was compared between “territorial” and “floater” males. Interestingly, although spatial memory and body size both positively affected the probability of lek territory ownership, our results suggest a stronger effect of spatial memory. Bill tip length (used as weapon in agonistic interactions) also showed a positive but smaller effect. Load lifting during vertical flight, a measure of physical performance relevant to agonistic interactions, had no effect on territory ownership. Finally, both body size and spatial memory were indicated in the structure of male song: body size negatively correlated with song lowest frequency, while spatial memory positively predicted song consistency. Together, our findings lend support for cognition as a sexual selection target.
Highlights
Elucidating the forces that have favored the evolution of advanced cognitive abilities remains central to understand some of the most elaborate behaviors found in nature, including ones that characterize our own species[1]
Primate species with stronger male-male competition have more developed brain structures involved in sensory motor skills and aggression[21], which indirectly suggests that intra-sexual selection shapes cognitive traits
We studied the link between a cognitive ability, spatial memory, and a critical element for mating success in lekking species: the ability to acquire and defend a lek territory
Summary
Elucidating the forces that have favored the evolution of advanced cognitive abilities remains central to understand some of the most elaborate behaviors found in nature, including ones that characterize our own species[1]. Hummingbirds offer a compelling group to examine the link between cognition and mating behavior[31] They are among the smallest of vertebrates while employing some of the most energetically costly forms of locomotion[32,33], and face extreme challenges in maintaining energy balance[34,35]. They maintain their high-energy lifestyle largely with constant access to nectar[36], a resource that varies in quality over space and time[37] In response they have evolved advanced cognitive abilities including fine-tuned discrimination[38,39,40,41,42], detailed spatial memory, and episodic-like memory, all of which allows them to maximize foraging efficiency[31,37,43]. Males are well known for their active vocal signaling[47], which involves advanced vocal learning skills[48,49], providing a potential link between cognition and mating signals
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