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Christian C. Voigt - One of the best experts on this subject based on the ideXlab platform.
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how bats escape the competitive exclusion principle seasonal shift from intraspecific to Interspecific Competition drives space use in a bat ensemble
Frontiers in Ecology and Evolution, 2018Co-Authors: Manuel Roeleke, Lilith Johannsen, Christian C. VoigtAbstract:Finding prey is crucial for predators that hunt on patchily distributed prey aggregations. At prey-rich patches, intraspecific and Interspecific Competition should be high. While the competitive exclusion principle suggests that species can only coexist if their ecological niches show considerable differences, newer theory suggests stabilizing and equalizing mechanisms besides classical niche differences that facilitate local coexistence. To identify such mechanisms, the understanding of the strength and nature (i.e. interference or exploitation) of Competition in a species ensemble is a prerequisite. Here, we investigated intra- and Interspecific Competition between aerial-hawking insectivores, using the interactions between two open-space foraging bats as a model. In particular, we tested for shifts in space use of the common noctule bat Nyctalus noctula in response to simulated aggregations of conspecific and heterospecific competitors at foraging patches. When confronted with playbacks of heterospecific Pipistrellus nathusii, N. noctula increased their activity in the experimental area in early summer, but decreased activity in late summer. When confronted with playbacks of conspecifics, activity of N. noctula remained the same, irrespective of season. This pattern was accompanied by a decrease in the proportion of large insects during late summer. Our results suggest that intraspecific Competition is more severe than Interspecific Competition for aerial insectivores in early summer. Probably, conspecifics engage in interference Competition for flight space, and in the case of echolocating bats, may interfere with each other’s echolocation calls. Interspecific Competition may be mediated by fine scale vertical partitioning and the use of different, non-interfering echolocation frequencies during insect rich times. In contrast, during late summer, bats may rather compete for the exploitation of relatively scarce large prey items. We speculate that N. noctula decreased activity in response to P. nathusii playbacks due to its inferior manoeuvrability and thus probably inferior hunting success in the presence of smaller, more agile bat species. However, N. noctula’s specialization on fast and efficient flight may enable them to use farther away and possibly less rich foraging patches, thus equalizing for a lower fitness compared to superior hunters.
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Data_Sheet_2_How Bats Escape the Competitive Exclusion Principle—Seasonal Shift From Intraspecific to Interspecific Competition Drives Space Use in a Bat Ensemble.DOCX
2018Co-Authors: Manuel Roeleke, Lilith Johannsen, Christian C. VoigtAbstract:Predators that depend on patchily distributed prey face the problem of finding food patches where they can successfully compete for prey. While the competitive exclusion principle suggests that species can only coexist if their ecological niches show considerable differences, newer theory proposes that local coexistence can be facilitated by so-called stabilizing and equalizing mechanisms. A prerequisite to identify such mechanisms is the understanding of the strength and the nature of Competition (i.e., interference or exploitation). We studied the interaction between two open-space foraging bats by testing if common noctule bats Nyctalus noctula shift their space use in response to simulated aggregations of conspecifics or heterospecific Pipistrellus nathusii. When confronted with playbacks of heterospecifics, N. noctula increased their activity in early summer, but decreased activity in late summer. This pattern was accompanied by a decrease in the proportion of large insects in late summer, suggesting a more intense Competition for food in late compared to early summer. When confronted with playbacks of conspecifics, N. noctula did not change their activity, irrespective of season. Our results indicate that in early summer, intraspecific Competition is more severe than Interspecific Competition for insectivorous bats. Likely, conspecifics engage in interference Competition for flight space, and may suffer from reduced prey detectability as echolocation calls of conspecifics interfere with each other. During insect rich times, Interspecific Competition on the other hand may be mediated by fine scale vertical partitioning and the use non-interfering echolocation frequencies. In contrast, when food is scarce in late summer, bats may engage in exploitation Competition. Our data suggests that N. noctula avoid aggregations of more agile bats like P. nathusii, probably due to impeded hunting success. Yet, as fast and efficient fliers, N. noctula may be able to escape this disadvantage by exploiting more distant foraging patches.
Manuel Roeleke - One of the best experts on this subject based on the ideXlab platform.
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how bats escape the competitive exclusion principle seasonal shift from intraspecific to Interspecific Competition drives space use in a bat ensemble
Frontiers in Ecology and Evolution, 2018Co-Authors: Manuel Roeleke, Lilith Johannsen, Christian C. VoigtAbstract:Finding prey is crucial for predators that hunt on patchily distributed prey aggregations. At prey-rich patches, intraspecific and Interspecific Competition should be high. While the competitive exclusion principle suggests that species can only coexist if their ecological niches show considerable differences, newer theory suggests stabilizing and equalizing mechanisms besides classical niche differences that facilitate local coexistence. To identify such mechanisms, the understanding of the strength and nature (i.e. interference or exploitation) of Competition in a species ensemble is a prerequisite. Here, we investigated intra- and Interspecific Competition between aerial-hawking insectivores, using the interactions between two open-space foraging bats as a model. In particular, we tested for shifts in space use of the common noctule bat Nyctalus noctula in response to simulated aggregations of conspecific and heterospecific competitors at foraging patches. When confronted with playbacks of heterospecific Pipistrellus nathusii, N. noctula increased their activity in the experimental area in early summer, but decreased activity in late summer. When confronted with playbacks of conspecifics, activity of N. noctula remained the same, irrespective of season. This pattern was accompanied by a decrease in the proportion of large insects during late summer. Our results suggest that intraspecific Competition is more severe than Interspecific Competition for aerial insectivores in early summer. Probably, conspecifics engage in interference Competition for flight space, and in the case of echolocating bats, may interfere with each other’s echolocation calls. Interspecific Competition may be mediated by fine scale vertical partitioning and the use of different, non-interfering echolocation frequencies during insect rich times. In contrast, during late summer, bats may rather compete for the exploitation of relatively scarce large prey items. We speculate that N. noctula decreased activity in response to P. nathusii playbacks due to its inferior manoeuvrability and thus probably inferior hunting success in the presence of smaller, more agile bat species. However, N. noctula’s specialization on fast and efficient flight may enable them to use farther away and possibly less rich foraging patches, thus equalizing for a lower fitness compared to superior hunters.
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Data_Sheet_2_How Bats Escape the Competitive Exclusion Principle—Seasonal Shift From Intraspecific to Interspecific Competition Drives Space Use in a Bat Ensemble.DOCX
2018Co-Authors: Manuel Roeleke, Lilith Johannsen, Christian C. VoigtAbstract:Predators that depend on patchily distributed prey face the problem of finding food patches where they can successfully compete for prey. While the competitive exclusion principle suggests that species can only coexist if their ecological niches show considerable differences, newer theory proposes that local coexistence can be facilitated by so-called stabilizing and equalizing mechanisms. A prerequisite to identify such mechanisms is the understanding of the strength and the nature of Competition (i.e., interference or exploitation). We studied the interaction between two open-space foraging bats by testing if common noctule bats Nyctalus noctula shift their space use in response to simulated aggregations of conspecifics or heterospecific Pipistrellus nathusii. When confronted with playbacks of heterospecifics, N. noctula increased their activity in early summer, but decreased activity in late summer. This pattern was accompanied by a decrease in the proportion of large insects in late summer, suggesting a more intense Competition for food in late compared to early summer. When confronted with playbacks of conspecifics, N. noctula did not change their activity, irrespective of season. Our results indicate that in early summer, intraspecific Competition is more severe than Interspecific Competition for insectivorous bats. Likely, conspecifics engage in interference Competition for flight space, and may suffer from reduced prey detectability as echolocation calls of conspecifics interfere with each other. During insect rich times, Interspecific Competition on the other hand may be mediated by fine scale vertical partitioning and the use non-interfering echolocation frequencies. In contrast, when food is scarce in late summer, bats may engage in exploitation Competition. Our data suggests that N. noctula avoid aggregations of more agile bats like P. nathusii, probably due to impeded hunting success. Yet, as fast and efficient fliers, N. noctula may be able to escape this disadvantage by exploiting more distant foraging patches.
Lilith Johannsen - One of the best experts on this subject based on the ideXlab platform.
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how bats escape the competitive exclusion principle seasonal shift from intraspecific to Interspecific Competition drives space use in a bat ensemble
Frontiers in Ecology and Evolution, 2018Co-Authors: Manuel Roeleke, Lilith Johannsen, Christian C. VoigtAbstract:Finding prey is crucial for predators that hunt on patchily distributed prey aggregations. At prey-rich patches, intraspecific and Interspecific Competition should be high. While the competitive exclusion principle suggests that species can only coexist if their ecological niches show considerable differences, newer theory suggests stabilizing and equalizing mechanisms besides classical niche differences that facilitate local coexistence. To identify such mechanisms, the understanding of the strength and nature (i.e. interference or exploitation) of Competition in a species ensemble is a prerequisite. Here, we investigated intra- and Interspecific Competition between aerial-hawking insectivores, using the interactions between two open-space foraging bats as a model. In particular, we tested for shifts in space use of the common noctule bat Nyctalus noctula in response to simulated aggregations of conspecific and heterospecific competitors at foraging patches. When confronted with playbacks of heterospecific Pipistrellus nathusii, N. noctula increased their activity in the experimental area in early summer, but decreased activity in late summer. When confronted with playbacks of conspecifics, activity of N. noctula remained the same, irrespective of season. This pattern was accompanied by a decrease in the proportion of large insects during late summer. Our results suggest that intraspecific Competition is more severe than Interspecific Competition for aerial insectivores in early summer. Probably, conspecifics engage in interference Competition for flight space, and in the case of echolocating bats, may interfere with each other’s echolocation calls. Interspecific Competition may be mediated by fine scale vertical partitioning and the use of different, non-interfering echolocation frequencies during insect rich times. In contrast, during late summer, bats may rather compete for the exploitation of relatively scarce large prey items. We speculate that N. noctula decreased activity in response to P. nathusii playbacks due to its inferior manoeuvrability and thus probably inferior hunting success in the presence of smaller, more agile bat species. However, N. noctula’s specialization on fast and efficient flight may enable them to use farther away and possibly less rich foraging patches, thus equalizing for a lower fitness compared to superior hunters.
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Data_Sheet_2_How Bats Escape the Competitive Exclusion Principle—Seasonal Shift From Intraspecific to Interspecific Competition Drives Space Use in a Bat Ensemble.DOCX
2018Co-Authors: Manuel Roeleke, Lilith Johannsen, Christian C. VoigtAbstract:Predators that depend on patchily distributed prey face the problem of finding food patches where they can successfully compete for prey. While the competitive exclusion principle suggests that species can only coexist if their ecological niches show considerable differences, newer theory proposes that local coexistence can be facilitated by so-called stabilizing and equalizing mechanisms. A prerequisite to identify such mechanisms is the understanding of the strength and the nature of Competition (i.e., interference or exploitation). We studied the interaction between two open-space foraging bats by testing if common noctule bats Nyctalus noctula shift their space use in response to simulated aggregations of conspecifics or heterospecific Pipistrellus nathusii. When confronted with playbacks of heterospecifics, N. noctula increased their activity in early summer, but decreased activity in late summer. This pattern was accompanied by a decrease in the proportion of large insects in late summer, suggesting a more intense Competition for food in late compared to early summer. When confronted with playbacks of conspecifics, N. noctula did not change their activity, irrespective of season. Our results indicate that in early summer, intraspecific Competition is more severe than Interspecific Competition for insectivorous bats. Likely, conspecifics engage in interference Competition for flight space, and may suffer from reduced prey detectability as echolocation calls of conspecifics interfere with each other. During insect rich times, Interspecific Competition on the other hand may be mediated by fine scale vertical partitioning and the use non-interfering echolocation frequencies. In contrast, when food is scarce in late summer, bats may engage in exploitation Competition. Our data suggests that N. noctula avoid aggregations of more agile bats like P. nathusii, probably due to impeded hunting success. Yet, as fast and efficient fliers, N. noctula may be able to escape this disadvantage by exploiting more distant foraging patches.
Jon Olav Vik - One of the best experts on this subject based on the ideXlab platform.
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the arctic fox alopex lagopus in fennoscandia a victim of human induced changes in Interspecific Competition and predation
Biodiversity and Conservation, 2007Co-Authors: Vidar Selas, Jon Olav VikAbstract:After a marked decline at the beginning of the 1900s, the arctic fox Alopex lagopus population in Fennoscandia has remained at a very low level. We suggest that the main cause for the population crash was winter starvation caused by (1) over-hunting of reindeer Rangifer tarandus populations, and thus reduced carcass availability in the mountains, and (2) increased Interspecific Competition for these carcasses because of increased invasion of red foxes Vulpes vulpes from lower altitudes. The failure of arctic fox populations to recover, despite increasing reindeer populations in the mid 1900s, can be explained by a concurrent strong increase in red fox numbers. Analyses of countywide hunting statistics from Norway 1891–1920 suggest that there actually was an increase in red fox numbers in the period of arctic fox decline, and that the increase in reindeer populations from the 1920s to the 1950s was accompanied by a new increase in red fox numbers. We conclude that restoring arctic fox populations most likely will require a substantial and lasting reduction of red fox populations.
Raleigh J. Robertson - One of the best experts on this subject based on the ideXlab platform.
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Interspecific Competition for nestboxes affects mate guarding in eastern bluebirds, Sialia sialis
Animal Behaviour, 1994Co-Authors: Susan Meek, Raleigh J. RobertsonAbstract:Abstract Abstract. Eastern bluebirds, Sialia sialis and tree swallows, Tachycineta bicolor , compete aggressively for nest cavities, and Competition for cavities may force a trade-off between mate guarding and territory defence in eastern bluebirds. Behaviour of eastern bluebird pairs was examined to test (1) whether male eastern bluebirds guard their mates, and (2) whether males reduce mate guarding on territories containing multiple nestboxes, where greater Interspecific Competition for nest sites was found. Non-resident male bluebirds intruded onto both single-box and multi-box territories, and resident males on both territory types spent significantly more time near their mates and followed them significantly more often during the fertile period than during the non-fertile periods, supporting the hypothesis that males guard their mates to protect their paternity. Tree swallows usurped nestboxes from bluebirds on 22% of their territories during spring nesting attempts, indicating that tree swallow Competition can result in displacement of bluebird pairs. Bluebirds on multi-box territories had shorter intervals between broods than bluebirds on territories with only one nestbox, but Competition between eastern bluebirds and tree swallows was more intense at multi-box sites. When female bluebirds were fertile, there were significantly more intrusions by tree swallows (requiring nest-site defence by bluebirds) at multi-box territories than at single-box territories. Consequently, male eastern bluebirds on multi-box territories guarded their mates significantly less than males on single-box territories, and there was a significant correlation between the amount of time male bluebirds spent on the territory and the level of tree swallow intrusions. This study shows that there are trade-offs between mate guarding and territory defence, and that individuals within a population may adjust their mate guarding with regard to varying environmental conditions.
