Biology subjects

Dornhaus, A.

Publications and source records attributed to Dornhaus, A..

7 recordsLinked to original sources

bioRxiv2025

A comparison of turn identification methods on high-frequency movement trajectories reveals potential comparability issues between studies of movement ecology

High-frequency animal tracks must often be subsampled to allow a simple analysis of the movement on the most meaningful scale for the respective study. One way of achieving this is to identify biologically significant turns, compared to heading changings caused by noise. Many turn identification methods have been developed, but the accuracy and consistency of such methods have rarely been validated against ground truth trajectories with known true turns and noise. We analyze simulated tracks with known parameters as well as two empirical tracks and identify turns with 10 different frequently used resampling methods. We assess the specificity and sensitivity of identifying the location of turns and compare the known mean step length and turn angle of the paths with the resampled trajectories. We found great accuracy differences between, and sometimes within, methods, even on simulated tracks of the same characteristics. Results of some methods were also highly sensitive to the user-set threshold the method requires (e.g. max angle). Overall, the best-performing methods in this study were DP and MRPA, methods used in human mobility research, and TPA, which is mostly used in primate research. We thus advise caution when comparing results of studies using different resampling methods and recommend justifying the use of the resampling method in addition to quantifying the sensitivity of results to the threshold value. This study is also an appeal to authors of novel turn identification methods to consider thorough comparisons in different scenarios with a wide range of previous methods, including those developed outside the movement ecology discipline.

ecology↗

bioRxiv2024

Optimal competitors: the balance of attraction and choices of mutualists, like pollinators, drives facilitation and may promote crop pollination

When two species use the same resource, this typically leads to competition, such as when different plants aim to attract the same mutualist pollinators. However, more flowers may also attract more pollinators to an area, such that one or both competitors actually benefit from the others presence. For example, it has been argued that strips of wildflowers planted next to crops may attract pollinators who spill over into the crop. Here we mathematically examine facilitation and competition in consumer attraction. Contrary to previous claims, no accelerating benefits of density per se are necessary for facilitation. Instead, under very general assumptions, facilitation can be generated by an imbalance between local competition and joint long-distance attraction of consumers; for example, a low presence of highly attractive wildflowers should lead to benefits to a crop. In this mechanism, how pollinator attraction to a patch increases with density of plants is a key factor. Our results generalize to many contexts where local competition may trade off with joint long-distance attraction of consumers, and we show that the exact relationship between competitor density and attraction of consumers can qualitatively shape outcomes, including facilitation or competition.

ecology↗

bioRxiv2024

Inexperienced bumble bees are poor at securely landing regardless of flower orientation or presence of labellum

The mutualism between bees and flowers creates strong selection on both the structure of the flower and behavior of the bee to maximize pollination and foraging success, respectively. Previous research has primarily assessed the costs of foraging by quantifying the time and accuracy of search, and handling time of the flower. However, there is little attention given to the actual success of landing, and it is often not explicitly stated whether failed landing attempts are taken into consideration. We show here that landing attempts often are unsuccessful, especially in inexperienced bees. Orientation of artificial flowers in our experiment neither influenced the preference nor landing success of a naive bumble bee forager. The presence of a labellum, often considered to serve as a landing platform, also did not influence landing success, indicating that it may mostly play a role in flower recognition or act as a nectar guide. Failed landing attempts may thus play an under-recognized role in the foraging efficiency and behavior of bees, and learning may be key in individual bee landing efficiency, not just flower recognition. Further research should aim to quantify the costs of landing failures and consider the role of experience in individual bee landing success.

animal behavior and cognition↗

bioRxiv2024

Stop and go: exploring alternative mechanisms for task allocation in social insects - response and satisfaction thresholds trade off cost, accuracy, and speed differently

Division of labor, a key feature of many complex systems, requires a mechanism that allows individuals to choose tasks. The popular response threshold hypothesis posits that some workers start engaging in particular tasks at a lower level of need than others. However, individuals may only have access to information about need after they actually engage in a task. We therefore introduce two novel interpretations of this task-allocation mechanism. While the response threshold mechanism determines when individuals start working, the satisfaction threshold mechanism drives when individuals stop working. We also model a composite threshold mechanism where workers consider task need both to start and end working. Second, we model the possibility that the stimulus perceived by workers is a completion cue instead of a demand cue. While these may seem like subtle variations, we show here that they can yield dramatically different collective dynamics. In simulations with biologically relevant parameter ranges, response thresholds produced the quickest reaction to increases in task demand, satisfaction thresholds yielded the lowest task-switching rate, and composite thresholds most closely matched the number of workers allocated to the number needed. Different threshold types thus differentially trade off speed, cost, and accuracy. We did not model benefits of specialization; purely in terms of allocating workers to tasks, we also found that response thresholds usually perform worse than a null random choice model in terms of cost and efficiency, and variation among workers does not improve task allocation. Colonies utilizing task demand cues also tend to perform better than those using task completion cues. Our results ultimately suggest that different threshold mechanisms may be suited for different situations or types of tasks. Author SummaryDivision of labor is a phenomenon where workers in a community consistently differ in the tasks they work on. Many scientists believe division of labor arises in social insects (i.e. ants and bees) as a result of difference in workers responsiveness to cues that correspond to the demand for work in a task. For example, some ants in a colony start feeding brood much sooner than others, possibly because of a higher sensitivity, or lower response threshold, to brood pheromone. We show that instead of using such a cue to decide when to start on a task, theoretically workers may instead use it only to decide when to stop working; similarly, workers may use a cue that tells them how much work is needed in a task, or they may use one that corresponds to how much work has already been done. These seemingly subtle differences affect how much a colony invests in work and how quickly stability is reached when the balance of work needed in different tasks changes. Therefore, these different mechanisms may evolve to solve different problems.

animal behavior and cognition↗

bioRxiv2023

The discovery of mixed colonies in Temnothorax ants supports the territoriality hypothesis of dulotic social parasite evolution in myrmicine ants

Social parasitism, where one social species parasitically depends on the other for survival and reproduction, is a highly successful life history strategy, especially in the eusocial Hymenoptera. In ants alone, more 400 species of socially parasitic species exist and multiple forms of social parasitism evolved independently and convergently. Yet disentangling the evolutionary history of obligate social parasitism is challenging. Identifying species that inform the transition from eusocial toward socially parasitic behavior is crucial for understanding the underlying co-evolutionary processes. Here, we report the first case of mixed colonies involving four predominantly free-living Temnothorax ant species from the western United States. Three Temnothorax species supplement their worker force with brood from the nests of their four congeners. We suggest, based on these observations and other published evidence, that this facultative dulotic behavior may have resulted from territorial contests due to limited nest sites. Socially parasitic behavior is not present in all populations across the species distribution ranges, however in populations where this behavior was observed, it is also associated with significant increases in interspecific aggression. These four species of Western US Temnothorax ants represent a particularly interesting case of social parasitism, because the presence of between-population behavioral variation provides a powerful system to test hypotheses about the ecological and behavioral conditions underlying the evolutionary transition from eusocial to socially parasitic behavior.

animal behavior and cognition↗

bioRxiv2022

Temnothorax rugatulus ants do not change their nest walls in response to environmental humidity

Animal architectures are interesting biological phenomena that can greatly increase the fitness of the builder and exist in a variety of forms and functions across taxa. Among the most intricate architectures are social insect nests, which may have several functions, one of which is the control of internal microclimate. In social insects, the regulation particularly of humidity in the nest can be crucial for the survival and growth of the brood. Though much is known on how nest excavating social insects respond to environmental humidity, little is known about how ants that build on to pre-existing cavities respond. Here we use the rock ant Temnothorax rugatulus to determine whether and how colonies respond to environmental humidity by building and changing their nest architectures in pre-existing nest spaces. We specifically test the hypothesis that T. rugatulus colonies build different nest walls, e.g. wider or denser ones, in response to lower environmental humidity. We allowed T. rugatulus colonies to build nest walls with two substrates across a 0-100% relative humidity gradient. We further compare the porosity - empty volume in built nest walls - of natural T. rugatulus nest walls with these artificial building substrates and the substrate compositions of built walls from our experiment. We found that humidity did not influence the nest walls T. rugatulus colonies built in our experiment, concluding that regulating humidity is likely not a key function of T. rugatulus nest wall architecture. We also found that the porosities of the artificial substrate that was predominantly used by the ants in our experiment were like the porosity of natural T. rugatulus nest walls, indicating that ants had constant preferences for particular substrates. Physical nest wall features, including porosity, are therefore unlikely to be flexibly regulated in response to external humidity, but may be adaptations in other ways.

animal behavior and cognition↗

bioRxiv2022

Nest shape influences colony organization in ants: spatial distribution and connectedness of colony members differs from that predicted by random movement and is affected by nest space

Many animals inhabit nests that protect them from adverse environments. However, the effects of living in a built or found structure are not limited to protection: the physical space can shape and organize behavior, particularly in self-organized collective systems. In addition, the geometry of nest space may not be under the animals control, raising the question whether animals can compensate for the effects that unexpected or suboptimal geometries may have. Here we examine how the shape of a nest cavity affects spatial organization of colonies in the ant Temnothorax rugatulus, a species that adapted to nest cavities of unmodifiable internal dimensions, since they inhabit rock crevices with rigid walls. We show that the emerging spatial relationships of workers, brood, queens, and young alates, as well as their relationships and distances to significant points in the nest, are all significantly influenced by nest shape, with the brood distributions most affected. However, we also found that the size of worker spatial fidelity zones, i.e. the areas in the nest that individual workers occupy and that may be key regulators of division of labor, are overall not affected by nest shape. These findings indicate that ants may actively regulate which areas of a nest they occupy, and that they may compensate for effects of nest architecture constraints. Physical properties of nests can thus influence the organization of ant colonies, highlighting the need to explore spatial constraints as a direct influence on the organization, movement, and communication of evolved or engineered self-organized systems.

animal behavior and cognition↗