Biology subjects

Chaverri, G.

Publications and source records attributed to Chaverri, G..

10 recordsLinked to original sources

bioRxiv2024

The role of vocalizations in agonistic interactions during competition for roosts in a solitary bat

Inter- and intraspecific competition for resources is common among individuals which share ecological niches. To avoid physical confrontations, individuals can use various types of signals to demonstrate their dominance, including vocalizations. Kerivoula hardwickii is a solitary bat species that lives in highly ephemeral plant structures, which are therefore a limited resource. So far, it is unknown if individuals of K. hardwickii use vocalizations during competitive encounters for roosts, and if the intention of these vocalizations can be deduced by potential rivals. We hypothesized that the calls emitted during roost competition contain information that influences the ability of an individual to defend its roost. We conducted roost competition experiments in a flight cage, where there was an individual roost owner and an intruder who would attempt to evict the owner from the roost. All the vocalizations emitted during these encounters were recorded and analyzed to determine which acoustic parameters, if any, had an influence on the successful defense of the roost. We found that the calls emitted by males can influence their ability to defend the roost, and that entropy is the parameter that most strongly explains a successful defense. High entropy suggests that encounters between individuals of K. hardwickii escalate to high levels of aggressiveness and explain whether calls influence an individuals capacity to defend a roost. We suggest that bat vocalizations contain important information about individual characteristics, which in turn help bats make decisions during resource competition.

animal behavior and cognition↗

bioRxiv2024

Food-associated calls in disc-winged bats

Animals that engage in social foraging can produce food-associated calls that elicit two main responses in receivers: the recruitment of other individuals to a foraging site, and an increase in feeding-related behaviors in conspecifics. Spixs disc-winged bat, Thyroptera tricolor, is a highly gregarious species that lives in stable social groups and relies on group call-and-response vocalizations to find ephemeral roosting sites. Because this bat also is known to feed on resources that are abundant but ephemeral - for example insect swarms - we hypothesized that it likewise emits vocalizations that serve to recruit conspecifics to a foraging site and elicit food consumption. We found that indeed, feeding bats emitted distinct vocalizations exclusively while consuming an abundant prey item, a call type that has not been previously described in the acoustic repertoire of any bat to date. We also observed that these "food calls" prompted responses typically associated with food-calling: they increased both feeding-related behaviors and social recruitment. Specifically, we observed that the onset of the consumption of novel prey items was strongly associated with the emission of food calls but not with other types of sounds. In addition, individuals approached a speaker broadcasting food calls, especially when food calls had not been broadcast before, while other types of sounds did not consistently prompt inspection. Taken together, these results suggest that T. tricolor coordinates foraging behavior through the emission of food-associated communication calls. SUMMARY STATEMENTThis study provides evidence of food-associated calling in Spixs disc-winged bats (Thyroptera tricolor), revealing its association with feeding contexts and its potential role in prompting social recruitment and feeding-related behaviors.

animal behavior and cognition↗

bioRxiv2023

Variation in echolocation call emission of Neotropical insect-eating bats in response to shifting ambient temperatures

The sensory systems of animals are essential for them to respond to environmental cues and signals. However, their functionality might be altered by climate change. Most bats, for example, rely on acoustic signal emission for acquiring food, but their high-frequency echolocation calls are strongly attenuated in the air. Attenuation in air changes with changing weather conditions, which can lead to shifts in echo-based prey detection distance. However, bats adjust call parameters to the task and environment, and this behavioural plasticity may also help them to counteract potential increases in sound attenuation to keep echo detectability constant. We explored this ability in a community of insectivorous bats in a montane forest of Costa Rica. We recorded bat echolocation calls in response to experimentally increased temperatures, simulating intermediate and arguably realistic projected climate change scenarios. We calculated atmospheric attenuation and detection distance for each temperature and echolocation call. We found some changes in source level and call duration, yet not in peak frequency, and responses were not consistent across species with increasing atmospheric attenuation. This might be explained by several non-mutually exclusive reasons, including that the experimental increase in temperature and change of atmospheric attenuation were not sufficient to affect close-range prey detection. Ultimately, this study contributes to our understanding of sensory system adaptation under the pressure imposed by climate change. SUMMARY STATEMENTStudying adjustments in bats call parameters can reveal responses to the pressure imposed by climate change.

ecology↗

bioRxiv2023

Effects of habitat and fruit scent on the interactions between short-tailed fruit bats and Piper plants

Piper is a mega-diverse genus of pioneer plants that contributes to the maintenance and regeneration of tropical forests. With deforestation and climate change threatening forest ecosystems, understanding the mutualism between Piper and its seed dispersers becomes especially important. In the Neotropics, Carollia bats use olfaction to forage for Piper fruit and are a main disperser of Piper seeds via consumption and subsequent defecation during flight. In return, Piper fruits provide essential nutrients for Carollia year-round. There is evidence that the types and diversity of Piper frugivores are influenced by the primary habitat of different Piper species (forest, gap), with forest Piper depending more on bats for seed dispersal; however, this pattern has not been tested broadly. We aimed to characterize and compare the interactions between Carollia and Piper across forested and gap habitats, and further investigate whether differences in fruit traits relevant to bat foraging (i.e., scent) could underlie differences in Carollia-Piper interactions. We collected nightly acoustic ultrasonic recordings and 24h camera trap data in La Selva, Costa Rica across 12 species of Piper (6 forest, 6 gap) and integrated this information with data on Carollia diet and Piper fruit scent. Merging biomonitoring modalities allowed us to characterize ecological interactions in a hierarchical manner: from general activity and presence of bats, to visitations and inspections of plants, to acquisition and consumption of fruits. We found significant differences in Carollia-Piper interactions between forested and gap habitats; however, the type of biomonitoring modality (camera trap, acoustics, diet) influenced our ability to detect these differences. Forest Piper were exclusively visited by bats, whereas gap Piper had a more diverse suite of frugivores; the annual diet of Carollia, however, is dominated by gap Piper since these plants produce fruit year-round. We found evidence that fruit scent composition significantly differs between forest and gap Piper, which highlights the possibility that bats could be using chemical cues to differentially forage for gap versus forest Piper. By integrating studies of Piper fruit scent, plant visitation patterns, and Carollia diet composition, we paint a clearer picture of the ecological interactions between Piper and Carollia, and plant-animal mutualisms more generally.

ecology↗

bioRxiv2022

ohun: an R package for diagnosing and optimizing automatic sound event detection

Animal acoustic signals are widely used in diverse research areas due to the relative ease with which sounds can be registered across a wide range of taxonomic groups and research settings. However, bioacoustics research can quickly generate large data sets, which might prove challenging to analyze promptly. Although many tools are available for the automated detection of sounds, choosing the right approach can be difficult only a few tools provide a framework for evaluating detection performance. Here we present ohun, an R package intended to facilitate automated sound detection. ohun provides functions to diagnose and optimize detection routines and compare performance among different detection approaches. The package uses reference annotations containing the time position of target sounds in a training data set to evaluate detection routines performance using common signal detection theory indices. This can be done both with routine outputs imported from other software and detections run within the package. The package also provides functions to organize acoustic data sets in a format amenable to detection analyses. ohun also includes energy-based and template-based detection methods, two commonly used automatic approaches in bioacoustic research. We show how ohun automatically can be used to detect vocal signals with case studies of adult male zebra finch (Taenopygia gutata) songs and Spixs disc-winged bat (Thyroptera tricolor) ultrasonic social calls. We also include examples of how to evaluate the detection performance of ohun and external software. Finally, we provide some general suggestions to improve detection performance.

ecology↗

bioRxiv2022

Consistent individual positions within roosts in Spix's disc-winged bats

Individuals within both moving and stationary groups arrange themselves in a predictable manner; for example, some individuals are consistently found at the front of the group or in the periphery and others in the center. Each position may be associated with various costs, such as greater exposure to predators, and benefits, such as preferential access to food. In social bats, we would expect a similar consistent arrangement for groups at roost-sites, which is where these mammals spend the largest portion of their lives. Here we study the relative position of individuals within a roost-site and establish if sex, age, and vocal behavior are associated with a given position. We focus on the highly cohesive and mobile social groups found in Spixs disc-winged bats (Thyroptera tricolor) given this species use of a tubular roosting structure that forces individuals to be arranged linearly within its internal space. We obtained high scores for linearity measures, particularly for the top and bottom positions, indicating that bats position themselves in a predictable way despite constant roost-switching. We also found that sex and age were associated with the use of certain positions within the roost; for example, males and subadults tend to occupy the top part (near the roosts entrance) more often than expected by chance. Our results demonstrate, for the first time, that bats are capable of maintaining a consistent and predictable position within their roosts despite having to relocate daily, and that there is a link between individual traits and position preferences.

ecology↗

bioRxiv2022

Landing manoeuvres predict roost-site preferences in bats

Roosts are vital for the survival of many species, and how individuals choose one site over another is affected by various ecological factors. Biomechanical constraints could also affect roost selection, particularly in volant taxa that require sites with easy access, thereby reducing costs (i.e., predation, accidents). To date, no studies have established an association between landing performance and roost-site selection, as predicted by biomechanical constraints associated with flight. We aim to determine roost-site selection in disc-winged bats (Thyroptera tricolor), a species known to roost within developing tubular leaves. This study is coupled with various experiments that measure how a conspicuous apex affects landing tactics and performance. We show that T. tricolor prefers leaves with a longer apex, the space typically used for landing. Bats also approach and enter these leaves more consistently, increasing task performance while reducing the risk of injuries. Summary statementSpixs disc-winged bats prefer to roost in some types of leaves, which we show may be related to costly maneuvers during the approach and landing phases.

ecology↗

bioRxiv2021

Comparing the efficiency of monofilament and traditional nets for capturing bats

Traditional mist nets used for capturing bats have several drawbacks, particularly that they are inefficient at sampling many insectivorous species. One possible alternative is to use monofilament nets, whose netting is made of single strands of yarn instead of several as regular nets, making them less detectable. To date, no study has quantified the capture efficiency of monofilament nets compared to regular mist nets for the study of bats. Here we compare capture efficiency of monofilament and regular mist nets, focusing on bat abundance and species diversity at a lowland tropical forest in southwestern Costa Rica. During our sampling period, we captured 90 individuals and 14 species in regular nets and 125 individuals and 20 species in monofilament nets. The use of monofilament nets increased overall capture rates, but most notably for insectivorous species. Species accumulation curves indicate that samples based on regular nets are significantly underestimating species diversity, most notably as these nets fail at sampling rare species. We show that incorporating monofilament nets into bat studies offers an opportunity to expand records of different guilds and rare bat species and to improve our understanding of poorly-known bat assemblages while using a popular, relatively cheap and portable sampling method.

zoology↗

bioRxiv2020

The energetics of social signaling during roost location in Spix's disc-winged bats

Long-term social aggregations are maintained by multiple mechanisms, including the use of acoustic signals, which may nonetheless entail significant energetic costs. To date, however, no studies have gauged whether there are significant energetic costs to social call production in bats, which heavily rely on acoustic communication for a diversity of social tasks. We measure energetic expenditure during acoustic signaling in Spixs disc-winged bats (Thyroptera tricolor), a species that commonly uses contact calls to locate the ephemeral furled leaves that they use for roosting. To determine the cost of sound production, we measured oxygen consumption using intermittent-flow respirometry methods, with and without social signaling. Our results show that the emission of contact calls significantly increases oxygen consumption; vocal individuals spent, on average, 12.42 kJ more during social signaling trials than they spent during silent trials. Furthermore, production of contact calls during longer periods increased oxygen consumption for males but not for females. We also found that as resting metabolic rates increased in males, there was a decreasing probability that they would emit response calls. These results provide support to the "allocation model", which predicts that only individuals with lower self-maintenance costs can afford to spend energy in additional activities. Our results provide a step forward in our understanding of how physiology modulates behavior, specifically how the costs of call production and resting metabolic rates may explain the differences in vocal behavior among individuals. Summary StatementSpixs disc-winged bats constantly produce contact calls while searching for roosts, which we show significantly increases an individuals metabolic rate.

physiology↗

bioRxiv2019

A missing link in mutualistic networks: symbiotic fungi in plant-animal interactions

We explored the hypothesis of an indirect mutualistic relationship (i.e., when the association between two species is modified by a third one) within a plant-animal seed dispersal network. Bats are important long-distance dispersers of many tropical plants, yet, by consuming fruits they may disperse not only the plants seeds, but also the endosymbiotic fungi within those fruits. We characterized fungal communities in fruits of Ficus colubrinae and in feces of Ectophylla alba to determine if passage through the digestive tract of the bats affected the total mycobiome. Results show a significant reduction, after passage through the gut, of fungi known to be plant pathogenic, while abundance of species known to have beneficial properties significantly increased. These findings suggest that the role of frugivores in plant-animal mutualistic networks may extend beyond seed dispersal: they also promote the dispersal of potentially beneficial microbial symbionts while hindering those that can cause plant disease.

ecology↗