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Free-ranging bats combine three different cognitive processes for roost localization.

ABSTRACT: Animals have evolved different cognitive processes to localize crucial resources that are difficult to find. Relevant cognitive processes such as associative learning and spatial memory have commonly been studied in a foraging related context under controlled laboratory conditions. However, in natural environments, animals can use multiple cognitive processes to localize resources. In this field study, we used a pairwise choice experiment and automatic roost monitoring to assess how individually marked, free-ranging Bechstein's bats belonging to two different colonies use associative learning, spatial memory and social information when localizing suitable day roosts. To our knowledge, this study tests for the first time how associative learning, spatial memory and social information are used in the process of roost localization in bats under the natural conditions. We show that, when searching for new roosts, bats used associative learning to discriminate between suitable and unsuitable roosts. For re-localizing previously occupied roosts, bats used spatial memory rather than associative learning. Moreover, bats significantly improved the localization of suitable unfamiliar roosts and tended to increase their accuracy to re-localize previously occupied day roosts using social information. Our field experiments suggest that Bechstein's bats make hierarchical use of different cognitive processes when localizing day roosts. More generally, our study underlines that evaluating different cues under natural conditions is fundamental to understanding how natural selection has shaped the cognitive processes used for localizing resources.

SUBMITTER: Hernandez-Montero JR

PROVIDER: S-EPMC7165157 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Free-ranging bats combine three different cognitive processes for roost localization.

Hernández-Montero Jesús R JR Reusch Christine C Simon Ralph R Schöner Caroline Regina CR Kerth Gerald G

Oecologia 20200331 4

Animals have evolved different cognitive processes to localize crucial resources that are difficult to find. Relevant cognitive processes such as associative learning and spatial memory have commonly been studied in a foraging related context under controlled laboratory conditions. However, in natural environments, animals can use multiple cognitive processes to localize resources. In this field study, we used a pairwise choice experiment and automatic roost monitoring to assess how individually ...[more]

PMID: 32236689

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Project description:BackgroundMixed-species groups in animals have been shown to confer antipredator, foraging and other benefits to their members that may provide selective advantages. In most cases, however, it is unclear whether functional benefits are a principal driver of heterospecific groups, or whether groups simply result from simultaneous exploitation of common resources. Mixed-species groups that form independently of environmental conditions may, however, evidence direct benefits of species associations. Bats are among the most gregarious mammals, with sometimes thousands of individuals of various species roosting communally. Despite numerous potential functional benefits of such mixed-species roosting groups, interspecific attraction has never been shown. To explore alternative explanations for mixed-species roosting, we studied roost selection in a speciose neotropical understory bat community in lowland rainforest in Costa Rica. Long term roost data were recorded over 10 years in a total of 133 roosts comprising both natural roosts and structurally uniform artificial roosts. We modelled bat roost occupancy and abundance in each roost type and in forest and pasture habitats to quantify the effects of roost- and environmental variability.ResultsWe found that bat species presence in natural roosts is predictable from habitat and structural roost parameters, but that the presence and abundance of other bat species further modifies roost choice. One third of the 12 study species were found to actively associate with selected other bat species in roosts (e.g. Glossophaga commissarisi with Carollia sowelli). Other species did not engage in communal roosting, which in some cases indicates a role for negative interspecific interactions, such as roost competition.ConclusionsMixed-species roosting may provide thermoregulatory benefits, reduce intraspecific competition and promote interspecific information transfer, and hence some heterospecific associations may be selected for in bats. Overall, our study contributes to an improved understanding of the array of factors that shape diverse tropical bat communities and drive the dynamics of heterospecific grouping in mammals more generally.

Project description:Understanding microhabitat preferences of animals is critical for effective conservation, especially for temperate-zone bats, which receive fitness benefits from selecting optimal roost microhabitats. Artificial roost structures are increasingly being used in conservation efforts for at-risk bat species. To evaluate microhabitat differences in common artificial roost structures and determine if roost selection occurs based on structure type, we installed artificial roosts of three different styles (bat box, rocket box, and bark mimic) in six clusters. We compared size and measured temperature parameters (12 points/roost) while bats were excluded from one cluster. We simultaneously conducted census counts during the active season at five more clusters open to bats for 1-2 years. The rocket box style provided larger entrance area, surface area, and volume versus other roost types. Microclimate varied with roost design. More positions inside the bat box and rocket box stayed within critical temperature limits for bats (0-45°C)-i.e., were usable. The bark-mimic provided less usable space than the rocket box and, often, large proportions of the roost were > 45°C. The rocket box provided the widest temperature availability in a given hour (max range available 7°C) and was more stable than the bark mimic. A maternity colony of Indiana bats (Myotis sodalis) selected the rocket box style; four of five available rocket boxes became primary maternity roosts, with 2-210 bats emerging per night. Future work should aim to manipulate roost size, temperature availability, and temperature stability in isolation to identify which features drive roost microhabitat selection by bats. Comparative studies of artificial roosts account for some inherent irregularity in natural systems, allowing us to study the dynamics of roost microhabitats. We recommend season-long monitoring of microhabitat in novel artificial refuges and comparative studies of artificial and natural roosts, and urge managers to consider potential positive and negative effects when substituting artificial roosts for natural habitat.

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Project description:Background and aimsTree diameter, tree height and canopy closure have been described by previous meta-analyses as being important characteristics in roost selection by cavity-roosting bats. However, size and direction of effects for these characteristics varied greatly among studies, also referred to as heterogeneity. Potential sources of heterogeneity have not been investigated in previous meta-analyses, which are explored by correlating additional covariates (moderator variables). We tested whether effect sizes from 34 studies were consistent enough to reject the null hypothesis that trees selected by bats did not significantly differ in their characteristics from randomly selected trees. We also examined whether heterogeneity in tree diameter effect sizes was correlated to moderator variables such as sex, bat species, habitat type, elevation and mean summer temperature.MethodsWe used Hedges' g standardized mean difference as the effect size for the most common characteristics that were encountered in the literature. We estimated heterogeneity indices, potential publication bias, and spatial autocorrelation of our meta-data. We relied upon meta-regression and multi-model inference approaches to evaluate the effects of moderator variables on heterogeneity in tree diameter effect sizes.ResultsTree diameter, tree height, snag density, elevation, and canopy closure were significant characteristics of roost selection by cavity-roosting bats. Size and direction of effects varied greatly among studies with respect to distance to water, tree density, slope, and bark remaining on trunks. Inclusion of mean summer temperature and sex in meta-regressions further explained heterogeneity in tree diameter effect sizes.ConclusionsRegional differences in roost selection for tree diameter were related to mean summer temperature. Large diameter trees play a central role in roost selection by bats, especially in colder regions, where they are likely to provide a warm and stable microclimate for reproductive females. Records of summer temperature fluctuations inside and outside tree cavities that are used by bats should be included in future research.

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Free-ranging bats combine three different cognitive processes for roost localization.

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Free-ranging bats combine three different cognitive processes for roost localization.

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