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 computercontrolled naturalistic environment with 64 feeders for simulating dynamic patterns of water or food resource availability (depletion and replenishment) within the laboratory. The combination of feeder and cage remote control permits the automated transfer of animals between cage and test arena and, therefore, high experimental throughput and minimal disturbance to the animals (bats and mice). In the present study, we investigated spatial working memory in nectar-feeding bats (Glossophaga soricina, Phyllostomidae) collecting food from a 64-feeder array. Feeders gave only single rewards within trials so that efficient foraging required bats to avoid depleted locations. Initially, bats tended to revisit feeders (win-stay), but within three trials changed towards a win-shift strategy. The significant avoidance of revisits could not be explained by algorithmic search guiding movement through the array nor by scent cues left by the bats themselves and, thus, the data suggest that bats remembered spatial locations depleted of food. An examination of the recency effect on spatial working memory after bats shifted to a win-shift strategy indicated that bats held more than 40 behaviour actions (feeder visits) in working memory without indication of decay. This result surpasses previous findings for other taxa.Supplementary material available online at
Online biomonitors register biological effects of toxic discharges on selected indicator species and allow for fast, continuous, and ecological relevant water quality control. This paper presents a new online biomonitor based on a quadropole impedance conversion technique that records simultaneously several behavioral parameters of Gammarus pulex, a new biomonitoring test species. The behavior of two different populations of G. pulex was compared; one population originated from an anthropogenically unpolluted stream, and the other population lived at the copper-polluted study site, where the biomonitor was placed. Responses to simulated copper pollution peaks of 70 μg of Cu2+/L were registered in the biomonitor and compared to the natural drift. G. pulex was the most abundant species in the natural drift. A nocturnal drift maximum was found in the natural drift and for both popula tions in the biomonitor. Mortality was high in the biomonitor; the local population survived slightly better than the reference population. The reference population showed significantly less activity than the local population measured as number of active organisms per day and time spent on locomotion and ventilation. Copper pollution pulses provoked increases in number of active organisms and time spent on locomotion in the biomonitor; however, no significant changes in the natural drift were registered.
SUMMARY 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. This raises the question how easily a free-flying bat will generalize an echo stimulus from a learning situation to a new spatial context where differences in relative flight approach trajectories may lead to an unfamiliar spectral composition of the self-generated echoes. We trained free-flying Glossophaga soricina in echoacoustic discrimination in a two-alternative forced-choice (2-AFC) paradigm at location A. We then tested at location B for spontaneous transfer of discrimination ability. Bats did not spontaneously transfer the discrimination ability acquired at A to location B. This lack of spontaneous generalization may have been caused by factors of the underlying learning mechanisms. 2-AFC tasks may not be representative of the natural foraging behaviour of flower-visiting bats. In contrast to insect-eating bats that constantly evaluate the environment to detect unpredictable prey, the spatial stability of flowers may allow flower visitors to rely on spatial memory to guide foraging. The 2-AFC task requires the disregard (learned irrelevance) of salient spatial location cues that are different at each new location. In Glossophaga, a conjunction between spatial context and 2-AFC discrimination learning may have inhibited the transfer of learned irrelevance of spatial location in the 2-AFC task to new spatial locations. Alternatively, the bats may have learnt the second discrimination task completely anew, and were faster only because of an acquired learning set. We suggest a dissociation between 2-AFC task acquisition and novel object discrimination learning to resolve the issue.
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. Although discrimination performances of both human and animal subjects in various sensory modalities exhibit the magnitude effect, results sometimes systematically deviate from the quantitative predictions based on Weber’s law. An attempt to reformulate the law to better fit data from acoustic discrimination tasks has been dubbed the “near-miss to Weber’s law”. Here, we tested the gustatory discrimination performance of nectar-feeding bats (Glossophaga soricina), in order to investigate whether the original version of Weber’s law accurately predicts choice behavior in a two-alternative forced choice task. As expected, bats either preferred the sweeter of the two options or showed no preference. In 4 out of 6 bats the near-miss to Weber’s law provided a better fit and Weber’s law underestimated the magnitude effect. In order to test the generality of this observation in nectar-feeders, we reviewed previously published data on bats, hummingbirds, honeybees, and bumblebees. In all groups of animals the near-miss to Weber’s law provided better fits than Weber’s law. Furthermore, whereas the magnitude effect was stronger than predicted by Weber’s law in vertebrates, it was weaker than predicted in insects. Thus nectar-feeding vertebrates and insects seem to differ in how their choice behavior changes as sugar concentration is increased. We discuss the ecological and evolutionary implications of the observed patterns of sugar concentration discrimination.
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. In a virtual evolution experiment conducted in the tropical rainforest, bats visited computer-automated flowers with simulated genomes that evolved relatively dilute nectars. Simulations replicated this evolution only when value functions, which relate the physical stimuli to subjective sensations, were nonlinear. Selection also depended on the supply/demand ratio; bats selected for more dilute nectar when competition for food was higher. We predict such a pattern to generally occur when decision-makers consider multiple value dimensions simultaneously, and increases of psychological value are not fully proportional to increases in physical magnitude.W hen presented with a choice, hummingbirds and nectar-feeding bats prefer concentrated solutions of up to 60% sugar (1-3). Plants that are specialized for vertebrate pollination, however, generally offer relatively dilute nectars of 18 to 23% sugar (4, 5). Nectar value depends on both quality and quantity. Quality is primarily determined by sugar concentration, which is genetically controlled and relatively consistent for individual flowers (6-9). However, multiple foragers normally visit the same flowers, which causes nectar quantity to be highly variable and dependent on the elapsed time since the previous visit. Consumer behavior thus determines availability, introducing a complex dynamic into the decision-making process. To study the factors contributing to the evolution of dilute nectars, we incorporated consumer behavior into a virtual evolution experiment by having free-range bats visit artificial flowers.Field experiments were conducted with freerange adult Glossophaga commissarisi bats that had been outfitted with radio-frequency ID tags in the rainforest at La Selva Biological Station, Costa Rica. We presented bats with a computercontrolled array of 23 artificial flowers (Fig. 1A). Each flower was equipped with an ID sensor and a photogate (a device that recorded the duration of a bat visit) and connected to a nectarpump system capable of delivering nectar of defined sugar concentration and volume (10). The density of the array approximated the distribution of a local bat-pollinated bromeliad (Werauhia gladioliflora) that provides nectar with sugar concentrations between 14 and 16% (11). Visiting bats were rewarded with nectar, and the amount of nectar was determined by the secretion rate and the elapsed time since the previous bat visit.We assumed individual plants in our population to have equal rates of photosynthesis and invest equal amounts of photosynthate, as sugar, into nectar (9). However, the sugar concentration of the nectar was determined by a flower's virtual gen...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.