BackgroundUrbanization is one of the most influential processes on our globe, putting a great num... more BackgroundUrbanization is one of the most influential processes on our globe, putting a great number of species under threat. Some species learn to cope with urbanization, and a few even benefit from it, but we are only starting to understand how they do so. In this study, we GPS tracked Egyptian fruit bats from urban and rural populations to compare their movement and foraging in urban and rural environments. Because fruit trees are distributed differently in these two environments, with a higher diversity in urban environments, we hypothesized that foraging strategies will differ too.ResultsWhen foraging in urban environments, bats were much more exploratory than when foraging in rural environments, visiting more sites per hour and switching foraging sites more often on consecutive nights. By doing so, bats foraging in settlements diversified their diet in comparison to rural bats, as was also evident from their choice to often switch fruit species. Interestingly, the location of ...
Additional File 4: Figure S3. Urban bats diversify their diets. The Simpsons index as a function ... more Additional File 4: Figure S3. Urban bats diversify their diets. The Simpsons index as a function of the percent of time they spent in urban areas. Each point represents a bat.
Additional File 6: Figure S5. Urban bats visit a larger variety of fruit types. The accumulated p... more Additional File 6: Figure S5. Urban bats visit a larger variety of fruit types. The accumulated percentage of the feeding according to the number of fruit species in urban and rural bats (based on Additional file 1: Table S1).
Additional File 1: Figure S1. Urban bats visit more sites per night. The number of sites visited ... more Additional File 1: Figure S1. Urban bats visit more sites per night. The number of sites visited by bats that were tracked for at least 5 nights as a function of the percent of time they spent in urban areas. Each point represents one night. Each point represents a bat, black for bats from urban colonies and grey for bats from rural 241 colonies.
Additional File 5: Figure S4. Urban bats select the tree-types they visit. The graph shows the di... more Additional File 5: Figure S4. Urban bats select the tree-types they visit. The graph shows the distribution of fruit trees in the city (blue line) with the trees ordered from the most to the least common species (left-right); while in red we present the actual visitation rate for each species. It is very clear that the visitation does not follow the distribution (we highlight a few of the most popular species).
Additional File 3: Figure S2. Fruit trees available in urban environments. We color-coded all tre... more Additional File 3: Figure S2. Fruit trees available in urban environments. We color-coded all trees around the Herzelia cave where most of our urban bats came from (vegetation that was not color-coded is mostly comprised of fields). The great majority of these trees offer fruit that is consumed by fruit bats. Trees were identified using a green-color filter while validating our classification several patches with high-resolution images. We attempted to underestimate the identified trees in the image.
Additional File 7: Figure S6. Fruit bats select ripe fruit. A fruit bat feeding on a Ficus rubigi... more Additional File 7: Figure S6. Fruit bats select ripe fruit. A fruit bat feeding on a Ficus rubiginosa tree. Only red fruit (like the one in the bat's mouth) was marked as ripe when estimating the amount of fruit.
SummaryThe evolution of powered flight involved major morphological changes in Chiroptera. Nevert... more SummaryThe evolution of powered flight involved major morphological changes in Chiroptera. Nevertheless, all bats are also capable of crawling on the ground and some are even skilled sprinters. We asked if a highly derived morphology adapted for flapping flight imposes high metabolic requirements on bats when moving on the ground. We measured the metabolic rate during terrestrial locomotion in mastiff bats, Molossus currentium; a species that is both, a fast-flying aerial-hawking bat and an agile crawler on the ground. Metabolic rates of bats averaged 8.0 ± 4.0 ml CO2 min-1 during a one minute period of sprinting at 1.3 ± 0.6 km h-1. With rising average speed, mean metabolic rates increased, reaching peak values that were similar to those of flying conspecifics. Metabolic rates of M. currentium were higher than those of similar-sized rodents under steady-state conditions that sprinted at similar velocities. When M. currentium sprinted at peak velocities its aerobic metabolic rate wa...
Changes in dietary preferences in animal species play a pivotal role in niche specialization. Her... more Changes in dietary preferences in animal species play a pivotal role in niche specialization. Here, we investigate how divergence of foraging behaviour affects the trophic position of animals and thereby their role for ecosystem processes. As a model, we used two closely related bat species, Myotis myotis and M. blythii oxygnathus, that are morphologically very similar and share the same roosts, but show clear behavioural divergence in habitat selection and foraging. Based on previous dietary studies on synanthropic populations in Central Europe, we hypothesised that M. myotis would mainly prey on predatory arthropods (i.e., secondary consumers) while M. blythii oxygnathus would eat herbivorous insects (i.e., primary consumers). We thus expected that the sibling bats would be at different trophic levels. We first conducted a validation experiment with captive bats in the laboratory and measured isotopic discrimination, i.e., the stepwise enrichment of heavy in relation to light isotopes between consumer and diet, in insectivorous bats for the first time. We then tested our trophic level hypothesis in the field at an ancient site of natural coexistence for the two species (Bulgaria, south-eastern Europe) using stable isotope analyses. As predicted, secondary consumer arthropods (carabid beetles; Coleoptera) were more enriched in (15)N than primary consumer arthropods (tettigoniids; Orthoptera), and accordingly wing tissue of M. myotis was more enriched in (15)N than tissue of M. blythii oxygnathus. According to a Bayesian mixing model, M. blythii oxygnathus indeed fed almost exclusively on primary consumers (98%), while M. myotis ate a mix of secondary (50%), but also, and to a considerable extent, primary consumers (50%). Our study highlights that morphologically almost identical, sympatric sibling species may forage at divergent trophic levels, and, thus may have different effects on ecosystem processes.
Dataset including all traditional morphometric measures and ratios used for methods 1-3. The four... more Dataset including all traditional morphometric measures and ratios used for methods 1-3. The four residuals were used for method 3. The length measures were obtained from two wing pictures of the same individual and therefore the averaged measures are shown in the dataset. Similarly for calculating the ratios averaged length and area measures (not included in the dataset) were taken from two wing pictures per individual. Because the measurement error was low we only took measurements from one wing picture for individuals from 2014
External morphology is commonly used to identify bats as well as to investigate flight and foragi... more External morphology is commonly used to identify bats as well as to investigate flight and foraging behavior, typically relying on simple length and area measures or ratios. However, geometric morphometrics is increasingly used in the biological sciences to analyse variation in shape and discriminate among species and populations. Here we compare the ability of traditional versus geometric morphometric methods in discriminating between closely related bat species – in this case European horseshoe bats (Rhinolophidae, Chiroptera) – based on morphology of the wing, body and tail. In addition to comparing morphometric methods, we used geometric morphometrics to detect interspecies differences as shape changes. Geometric morphometrics yielded improved species discrimination relative to traditional methods. The predicted shape for the variation along the between group principal components revealed that the largest differences between species lay in the extent to which the wing reaches in the direction of the head. This strong trend in interspecific shape variation is associated with size, which we interpret as an evolutionary allometry pattern
BackgroundUrbanization is one of the most influential processes on our globe, putting a great num... more BackgroundUrbanization is one of the most influential processes on our globe, putting a great number of species under threat. Some species learn to cope with urbanization, and a few even benefit from it, but we are only starting to understand how they do so. In this study, we GPS tracked Egyptian fruit bats from urban and rural populations to compare their movement and foraging in urban and rural environments. Because fruit trees are distributed differently in these two environments, with a higher diversity in urban environments, we hypothesized that foraging strategies will differ too.ResultsWhen foraging in urban environments, bats were much more exploratory than when foraging in rural environments, visiting more sites per hour and switching foraging sites more often on consecutive nights. By doing so, bats foraging in settlements diversified their diet in comparison to rural bats, as was also evident from their choice to often switch fruit species. Interestingly, the location of ...
Additional File 4: Figure S3. Urban bats diversify their diets. The Simpsons index as a function ... more Additional File 4: Figure S3. Urban bats diversify their diets. The Simpsons index as a function of the percent of time they spent in urban areas. Each point represents a bat.
Additional File 6: Figure S5. Urban bats visit a larger variety of fruit types. The accumulated p... more Additional File 6: Figure S5. Urban bats visit a larger variety of fruit types. The accumulated percentage of the feeding according to the number of fruit species in urban and rural bats (based on Additional file 1: Table S1).
Additional File 1: Figure S1. Urban bats visit more sites per night. The number of sites visited ... more Additional File 1: Figure S1. Urban bats visit more sites per night. The number of sites visited by bats that were tracked for at least 5 nights as a function of the percent of time they spent in urban areas. Each point represents one night. Each point represents a bat, black for bats from urban colonies and grey for bats from rural 241 colonies.
Additional File 5: Figure S4. Urban bats select the tree-types they visit. The graph shows the di... more Additional File 5: Figure S4. Urban bats select the tree-types they visit. The graph shows the distribution of fruit trees in the city (blue line) with the trees ordered from the most to the least common species (left-right); while in red we present the actual visitation rate for each species. It is very clear that the visitation does not follow the distribution (we highlight a few of the most popular species).
Additional File 3: Figure S2. Fruit trees available in urban environments. We color-coded all tre... more Additional File 3: Figure S2. Fruit trees available in urban environments. We color-coded all trees around the Herzelia cave where most of our urban bats came from (vegetation that was not color-coded is mostly comprised of fields). The great majority of these trees offer fruit that is consumed by fruit bats. Trees were identified using a green-color filter while validating our classification several patches with high-resolution images. We attempted to underestimate the identified trees in the image.
Additional File 7: Figure S6. Fruit bats select ripe fruit. A fruit bat feeding on a Ficus rubigi... more Additional File 7: Figure S6. Fruit bats select ripe fruit. A fruit bat feeding on a Ficus rubiginosa tree. Only red fruit (like the one in the bat's mouth) was marked as ripe when estimating the amount of fruit.
SummaryThe evolution of powered flight involved major morphological changes in Chiroptera. Nevert... more SummaryThe evolution of powered flight involved major morphological changes in Chiroptera. Nevertheless, all bats are also capable of crawling on the ground and some are even skilled sprinters. We asked if a highly derived morphology adapted for flapping flight imposes high metabolic requirements on bats when moving on the ground. We measured the metabolic rate during terrestrial locomotion in mastiff bats, Molossus currentium; a species that is both, a fast-flying aerial-hawking bat and an agile crawler on the ground. Metabolic rates of bats averaged 8.0 ± 4.0 ml CO2 min-1 during a one minute period of sprinting at 1.3 ± 0.6 km h-1. With rising average speed, mean metabolic rates increased, reaching peak values that were similar to those of flying conspecifics. Metabolic rates of M. currentium were higher than those of similar-sized rodents under steady-state conditions that sprinted at similar velocities. When M. currentium sprinted at peak velocities its aerobic metabolic rate wa...
Changes in dietary preferences in animal species play a pivotal role in niche specialization. Her... more Changes in dietary preferences in animal species play a pivotal role in niche specialization. Here, we investigate how divergence of foraging behaviour affects the trophic position of animals and thereby their role for ecosystem processes. As a model, we used two closely related bat species, Myotis myotis and M. blythii oxygnathus, that are morphologically very similar and share the same roosts, but show clear behavioural divergence in habitat selection and foraging. Based on previous dietary studies on synanthropic populations in Central Europe, we hypothesised that M. myotis would mainly prey on predatory arthropods (i.e., secondary consumers) while M. blythii oxygnathus would eat herbivorous insects (i.e., primary consumers). We thus expected that the sibling bats would be at different trophic levels. We first conducted a validation experiment with captive bats in the laboratory and measured isotopic discrimination, i.e., the stepwise enrichment of heavy in relation to light isotopes between consumer and diet, in insectivorous bats for the first time. We then tested our trophic level hypothesis in the field at an ancient site of natural coexistence for the two species (Bulgaria, south-eastern Europe) using stable isotope analyses. As predicted, secondary consumer arthropods (carabid beetles; Coleoptera) were more enriched in (15)N than primary consumer arthropods (tettigoniids; Orthoptera), and accordingly wing tissue of M. myotis was more enriched in (15)N than tissue of M. blythii oxygnathus. According to a Bayesian mixing model, M. blythii oxygnathus indeed fed almost exclusively on primary consumers (98%), while M. myotis ate a mix of secondary (50%), but also, and to a considerable extent, primary consumers (50%). Our study highlights that morphologically almost identical, sympatric sibling species may forage at divergent trophic levels, and, thus may have different effects on ecosystem processes.
Dataset including all traditional morphometric measures and ratios used for methods 1-3. The four... more Dataset including all traditional morphometric measures and ratios used for methods 1-3. The four residuals were used for method 3. The length measures were obtained from two wing pictures of the same individual and therefore the averaged measures are shown in the dataset. Similarly for calculating the ratios averaged length and area measures (not included in the dataset) were taken from two wing pictures per individual. Because the measurement error was low we only took measurements from one wing picture for individuals from 2014
External morphology is commonly used to identify bats as well as to investigate flight and foragi... more External morphology is commonly used to identify bats as well as to investigate flight and foraging behavior, typically relying on simple length and area measures or ratios. However, geometric morphometrics is increasingly used in the biological sciences to analyse variation in shape and discriminate among species and populations. Here we compare the ability of traditional versus geometric morphometric methods in discriminating between closely related bat species – in this case European horseshoe bats (Rhinolophidae, Chiroptera) – based on morphology of the wing, body and tail. In addition to comparing morphometric methods, we used geometric morphometrics to detect interspecies differences as shape changes. Geometric morphometrics yielded improved species discrimination relative to traditional methods. The predicted shape for the variation along the between group principal components revealed that the largest differences between species lay in the extent to which the wing reaches in the direction of the head. This strong trend in interspecific shape variation is associated with size, which we interpret as an evolutionary allometry pattern
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Papers by Ivailo M . Borissov