Cognition-mediated evolution of low-quality floral nectars.

Plants pollinated by hummingbirds or bats produce dilute nectars even though these animals prefer more concentrated sugar solutions. This mismatch is an unsolved evolutionary paradox. Here we show that lower quality, or more dilute, nectars evolve when the strength of preferring larger quantities or higher qualities of nectar diminishes as magnitudes of the physical stimuli increase.

Weber's law, the magnitude effect and discrimination of sugar concentrations in nectar-feeding animals.

Weber's law quantifies the perception of difference between stimuli. For instance, it can explain why we are less likely to detect the removal of three nuts from a bowl if the bowl is full than if it is nearly empty. This is an example of the magnitude effect - the phenomenon that the subjective perception of a linear difference between a pair of stimuli progressively diminishes when the average magnitude of the stimuli increases.

Lack of generalization of object discrimination between spatial contexts by a bat.

Discrimination and generalization are important elements of cognition in the daily lives of animals. Nectar-feeding bats detect flowers by olfaction and probably vision, but also use echolocation and echo-perception of flowers in immediate target surroundings. The echo received from an interference-rich flower corolla is a function of a bat's own relative position in space.

Foraging in a complex naturalistic environment: capacity of spatial working memory in flower bats.

Memory systems have evolved under selection pressures, such as the need to remember the locations of resources or past events within spatiotemporally dynamic natural environments. The full repertoire of complex behaviours exhibited by animals in dynamic surroundings are, however, difficult to elicit within simply structured laboratory environments. We have developed a computer-controlled naturalistic environment with 64 feeders for simulating dynamic patterns of water or food resource availability (depletion and replenishment) within the laboratory.