Integrative Organismal Biology

Locomotor performance often determines the outcome of interactions with competitors, predators, and prey. In flying animals, the asymptotic load-lifting assay measures maximal muscle power output in vertical flight. Previous studies of small birds have shown that load-lifting performance is linked to flight maneuverability and the outcome of competitive species interactions. Here, we quantify sources of performance variation within a species, namely repeatability, and determine the number of trials that accurately capture individual differences. We conducted 124 load-lifting trials on 13 wild-caught male ruby-throated hummingbirds (Archilochus colubris), testing each individual repeatedly over a 3-day period. We report large individual differences in peak performance, with 70% of the total variation in lifted mass attributed to differences among males. Notably, these differences in muscle performance are independent of body mass and size. An additional 23% of the variation in lifted mass was due to short-term fluctuations, wherein a given males performance varied across trials and days. We find no systematic effects of experience or time on load-lifting performance. Using simulation, we test the effect of different sampling protocols for measuring individual performance, and show that single-trial protocols yield the highest repeatabilities, but are less suitable for capturing the true underlying differences among individuals. We discuss recommendations for future studies that aim to measure maximum performance. Overall, our results show that the asymptotic load-lifting assay reveals large individual differences and can closely reflect individuals true maximum capacity. Summary statementMale ruby-throated hummingbirds exhibit large, consistent differences in load-lifting performance, highlighting peak flight performance as a potential driver of differences in competitive abilities between conspecifics.

The energetic demands of courtship are central to sexual selection, but their magnitude and temporal variation remain poorly quantified in many signalling systems. We used closed-chamber respirometry and low-light video analysis to estimate courtship-associated metabolic rates in males of the bioluminescent ostracod Photeros sp. EGD. Low-activity metabolic rate varied strongly across the diel cycle: in small vessels that constrained movement, individually measured males consumed significantly more oxygen at night than during the day. We then compared oxygen consumption across vessels that differed in opportunities for movement and courtship. Metabolic rates were highest in large vessels that permitted bioluminescent courtship displays, intermediate in medium vessels that allowed swimming but not full displays, and lowest in small vessels that constrained movement. Oxygen consumption in large vessels at night was approximately 500% of small-vessel daytime rates, 280% of small-vessel nighttime rates, and 160% of medium-vessel nighttime rates. Because measurements integrated oxygen use over multi-hour intervals, these values represent time-averaged metabolic demand rather than instantaneous costs of individual light pulses or display trains. Video analyses suggested a positive association between signalling rate and oxygen consumption, although this relationship was not statistically supported in our large-vessel dataset, which had low statistical power. Together, these results show that male Photeros undergo strong diel shifts in metabolic state and that the whole-animal performance required to construct bioluminescent courtship displays may often impose substantial energetic demands.

The diversity of body shapes is one of the most prominent features of phenotypic variation in mammals. Yet, mammalian body shapes are poorly quantified and the underlying components contributing to its diversity as well as its relationship to other components of the skeleton are rarely tested. Here, we use lagomorphs (hares, rabbits and pikas) as a model system to (1) investigate which components of the skeleton contributed the most to body shape diversity, (2) examine the relationships between body shape and relative limb lengths, and (3) test how body size, ecotype, burrowing behavior, and locomotor mode influenced variation in lagomorph body shape and appendicular morphology. We quantified the body shape and functional proxies of the appendicular skeleton in 40 lagomorph species from osteological specimens held at museum collections. Using phylogenetic comparative methods, we found the relative length of the ribs and elongation or shortening of the thoracic and lumbar regions contributed the most to body shape evolution across lagomorphs. Second, we found that only leporids (hares and rabbits) exhibited a significant relationship between limb length and body shape, where more elongate species exhibit relatively shorter forelimbs and hindlimbs. Lastly, we found that models incorporating body size were the best predictors of lagomorph body shape and the majority of the appendicular traits, whereas models incorporating burrowing behavior and locomotor mode were largely poor fits. Broadly, these results indicate that larger lagomorphs tend to exhibit more robust body shapes with longer, more gracile forelimbs, whereas smaller lagomorphs tend to exhibit more elongate body shapes with shorter, more robust forelimbs. Overall, this work contributes to the growing understanding of mammalian body shape evolution and demonstrates the importance of not omitting body size in ecomorphological analyses.

Flight feather vanes are the primary aerodynamic surface of the avian wing. Because loading varies across the wing, vane macrostructure should co-vary with local mechanical demands, yet comparative data on how barb and barbule traits change among remiges and between vane surfaces remain scarce. We quantified barb density, barbule density, barb angle, barb length, and vane width on both vanes at three measurement positions along the rachis of all remiges in four species with contrasting flight modes (white stork, common buzzard, house sparrow, pygmy cormorant), generating over 40,000 measurements across 15 response variables from 992 feathers of 41 individuals. Two complementary generalised additive models characterised variation along the spanwise, inter-vane, and longitudinal axes, and compared outer primaries, inner primaries, and secondaries as functional wing regions. Feather macrostructure varied along all three axes and outer primaries represent the most distinctive region, with lower leading-vane barb density, reduced barb angles, and vane width asymmetry two to three times higher than in inner primaries or secondaries. House sparrow exhibited the densest vane architecture and the highest vane width asymmetry, whereas the low wing-beat frequency species showed complex nonlinear spanwise patterns undetectable by single-feather sampling. Pygmy cormorant barbule density was 39-53% lower than in all other species, matching its wettable plumage strategy. Longitudinal gradients in barb density and barb angle (22-31% decline) were conserved across species. The avian wing is thus functionally regionalised at the macrostructural level, with vane architecture reflecting both aerodynamic and ecological pressures. Summary statementFine-scale vane measurements across all remiges in four species show macrostructural regionalisation of the avian wing, with outer primaries showing the most distinctive vane architecture.

Animal weapons are ecologically important traits that mediate contests over limiting resources and can strongly influence survival and reproduction. Weapon traits often exhibit substantial intraspecific morphological diversity, raising questions about the ecological drivers of this variation. Acrorhagi are weapons produced by sea anemones that are used in intraspecific territorial encounters. Although acrorhagial morphology varies widely within species, patterns of intraspecific variation remain poorly characterized, and the extent to which such variation reflects differences in local intraspecific competition is unclear. Here, we conduct morphometric analyses to characterize within-population variation and allometry in acrorhagial traits of the solitary anemone Anthopleura sola. We show that these traits covary with habitats differing in conspecific density. The number of acrorhagi scaled positively with body size, and individuals occupying a high-density habitat tended to possess more acrorhagi than did similar sized individuals from a low-density habitat. In addition, anemones from high-density habitats exhibited longer acrorhagial cnidae, a pattern that was not explained by differences in body size or acrorhagial density. Together, these results suggest that competitive context influences weapon-related traits at multiple levels of biological organization, potentially via phenotypic plasticity or selective processes. More broadly, our findings highlight how fine-scale ecological variation may contribute to the maintenance of trait diversity within and across species.

Multimodal communication plays a central role in animal behavior, particularly when individuals must integrate information from different sensory channels to make rapid decisions. In aquatic environments, chemical and visual cues differ markedly in their spatial and temporal properties, such that chemical signals may be constrained by limited spatial resolution and temporal instability, potentially requiring visual information to reliably guide social decisions. In decapod crustaceans, both cue types are known to mediate reproduction, yet their relative contribution to mate-location behavior remains unclear. Here, we tested how visual and chemical cues from males influence mate-location behavior in females of the prawn Macrobrachium rosenbergii. Females were placed in a central arena and exposed to four stimulus configurations combining visual cues (a life-size photograph of a male or a control background) and chemical cues (water from an aquarium with or without a male). Attraction was quantified as the time spent in each half of the arena. Females showed no directional preference when exposed to chemical cues alone or when visual and chemical cues were spatially incongruent. In contrast, females spent significantly more time near male-associated stimuli only when visual and chemical cues were spatially congruent. These results indicate that mate-location behavior in this species depends on multimodal integration with a strong contextual dependence on visual information, which appears to gate the effectiveness of chemical cues. Spatially congruent multimodal signals are therefore necessary to guide orientation during mate search, suggesting that disruption of visual or chemical information in aquaculture systems may impair mating efficiency.

Factors varying along elevational gradients impose strong aerodynamic and physiological constraints on powered flight, yet the internal anatomical correlates of flight performance in animals under such conditions remain poorly understood. In hummingbirds, sustained hovering requires extreme muscular power output, making the pectoralis muscle a key interface between environmental constraint and performance. We tested whether elevation is associated with variation in pectoralis microanatomy across three hummingbird assemblages spanning a [~]1500 m gradient in the Colombian Andes. Using tissue morphometry of trichrome-stained transverse sections of the pectoralis, we measured interstitial collagen fraction as a proxy for extracellular matrix investment and quantified fiber cross-sectional area, packing density, and size heterogeneity. Collagen investment varied across elevational bands, peaking at mid elevation ([~]1750 m) and declining toward high elevation ([~]2600 m). In contrast, muscle fibers were smaller and more densely packed at higher elevations. Variation among species was small relative to differences among elevational assemblages. Formal model comparisons provided limited support for non-linear responses to elevation, indicating that patterns across traits are better explained by interacting constraints than by a single monotonic response to factors varying along elevational gradients. These results show that hummingbird flight muscle microanatomy varies with elevation in a trait-specific manner, with the strongest evidence in fiber geometry. More broadly, our findings highlight that multiple components of muscle microarchitecture, including the extracellular matrix, vary in a context-dependent manner across elevational gradients in an extreme volant system.

Exaggerated insect traits often show positive allometry, yet nonlinear scaling can reflect either continuous curvature or discrete morphs. Distinguishing between these alternatives is important because they imply different developmental and evolutionary scenarios. Using cross-sectional data from 1,000 adult Oryctes rhinoceros, we analyzed the static allometry of nine traits with pronotum width as the primary body-size proxy and body length for sensitivity analyses. Cross-validated comparisons among linear, continuous nonlinear, and two-component mixture models showed that continuous nonlinear models improved predictive performance over linear models for horn length and pronotal depression width in both sexes. By contrast, mixture regression did not outperform the best continuous model in either sex, providing no positive support for discrete within-sex dimorphism under the tested model set. After accounting for body size, horn length remained positively associated with pronotal depression width, indicating size-independent covariation. These associations were retained when body length was used instead of pronotum width, supporting robustness to body-size proxy choice. Together, these results support continuous nonlinear adult scaling of the horn and pronotal depression in O. rhinoceros and indicate covariation not attributable solely to body size under the tested model set.

Argentine ants (Linepithema humile) utilize adhesive pads (arolia) to climb smooth surfaces. Previous research found that ants can adjust their individual arolium engagement according to their locomotion mode. However, it remains unclear how they distribute arolium engagement across multiple limbs to climb effectively, and how arolium engagement varies within a climbing step. As the arolium is a well-known adhesive organ, we hypothesized that engagement across different legs is distributed according to the normal forces required for balancing the body during climbing. To test this, we measured Argentine ants' arolium engagement on a vertical glass surface using a Frustrated Total Internal Reflection (FTIR) sensor and compared it to the required normal forces from a quasi-static model. Contrary to the required normal force, the measured arolium engagement was asymmetric between upward and downward climbing, and changed over time. Our results indicated that the quasi-static force requirements are not sufficient to explain arolium engagement in climbing Argentine ants, and suggested that other factors, such as body dynamics, ants' anatomy and behavioral preferences, should be included.

The shift to terrestrial environments in ancestrally aquatic animals is often associated with key physiological and physical changes, including shifts in respiratory physiology and in some cases, even the evolution of completely novel respiratory structures. Examining how respiration operates across a gradient of submersion states in ancestrally aquatic terrestrial animals may shed light on how complex biological traits shift under different selective regimes. In this work, we begin exploring respiration in terrestrially-adapted land crabs that still use their gills to respire while underwater. We tested the relationship between aquatic respiratory rates, body size, and sex in red devil vampire crabs (Geosesarma hagen) at two ecologically-relevant temperatures. We found small females respire more than small males at 28{degrees}C, while large females respire more than large males at 21{degrees}C. Additionally, body size is a significant factor affecting respiratory rates of both sexes at 21{degrees}C and warmer temperatures significantly increase respiration in small crabs of both sexes. Interactions between these factors also led to emerging trends that can be explained by both physiological rules, such as reproductive investment and surface-to-volume ratios and heat transfer. We also report a temperature coefficient (Q10) of 1.52 for this species, showing an expected 52% change in respiratory and metabolic rate for every 10{degrees}C increase. This work also demonstrates the importance of understanding how and to what extent biological variables like sex and body size interact with abiotic environmental factors when measuring physiological traits in ectothermic invertebrate animals.

How morphology forms during development and changes during evolution remain major questions in biology. In vertebrates, teeth have long served as model systems to address these questions. In threespine stickleback fish (Gasterosteus aculeatus), repeated and convergent increases in pharyngeal tooth number in derived freshwater sticklebacks occur, suggesting increased tooth number is adaptive in freshwater environments, likely due to a diet of larger prey in freshwater. Whether changes in oral tooth patterning also occur in freshwater sticklebacks was unknown. Here we describe oral tooth number and patterning in a dense developmental time course of lab-reared ancestral marine and derived freshwater fish. We address three major questions. First, is the spatial sequence of early oral tooth formation invariant as we previously described for the pharyngeal dentition? Second, is oral tooth patterning in the upper and lower jaw sexually dimorphic, and if so, when during development does this dimorphism arise? Third, have freshwater fish evolved increases in oral tooth number? We find that (1) unlike the pharyngeal dentition, the oral jaw early spatial sequence is variable, especially in the lower jaw (2) sexual dimorphism in both oral jaws arises at the late juvenile stage with males having more teeth and (3) freshwater fish have evolved more oral teeth similar to the evolved tooth gain in the pharyngeal jaw. Together our morphological descriptions advance the stickleback oral jaw as a model system to study how morphology forms during development and evolves in nature.

Understanding how biological shape and movement interact with surrounding fluids represents a fundamental challenge at the intersection of biology, physics, and engineering. Fish locomotion exemplifies this challenge: body morphology and swimming kinematics together determine the hydrodynamic forces and flow structures that enable efficient propulsion and maneuverability. Whereas biologists have long sought to connect morphological variation to swimming performance, traditional morphometric approaches provide limited insight into the fluid mechanical consequences of shape differences. Similarly, although computational fluid dynamics can reveal detailed flow physics, simulating hydrodynamics across diverse and dynamic morphologies remains prohibitively expensive for systematic investigation. To bridge this gap, we introduce a data-driven framework that connects fish body shape dynamics to hydro-dynamic performance through compact morphospace parameterization and reduced-order modeling. Using CFD simulations of 15 fish species from the Digital Life Project database (www.digitallife3d.org/3d-model), we generate hydrodynamic datasets capturing the shape-flow relationship. Principal Component Analysis (PCA) extracts four dominant shape parameters from dorsal body profiles, which are then integrated into an Inverse-Design with Dynamic Mode Decomposition (ID-DMD) framework to model the resulting fluid dynamics. The resulting modal analysis suggests that locomotion strategies emerge from specific shape-flow interactions. We further demonstrate the frameworks utility through single- and multi-objective shape optimization, showing how it enables efficient exploration of the morphology-hydrodynamics relationship. This approach offers a novel analysis and design tool for understanding how biological form and motion interact with fluid mechanics, with applications ranging from bio-inspired vehicle development to evolutionary biomechanics.

Acoustic communication is fundamental to social interactions in many animal species, allowing individuals to transmit information about identity, reproductive status, and competitive ability. Because call production incurs inherent costs, individuals are expected to modify their vocalizations depending on the social context. However, while context-dependent call variation has been documented in several taxa, including anurans (frogs and toads), glass frogs (Centrolenidae) remain among those for which the acoustic repertoire across social contexts is poorly characterized. Here, we investigated context-dependent call modification in males of the Emerald glass frog, Espadarana prosoblepon, comparing calls produced across four social contexts: advertisement in isolation, advertisement in a group, courtship interactions with females, and agonistic interactions with other males. By integrating detailed behavioral field observations with a robust analytical framework, we present evidence that males modify multiple acoustic properties in response to the social context. Specifically, males produced longer, louder advertisement calls when calling in a group than when calling in isolation. Courtship calls contained more notes and were louder than other call types, whereas aggressive interactions were characterized by pulseless, low-frequency, soft calls. Our findings demonstrate that the distinct call types of E. prosoblepon are consistently associated with specific social contexts and can be reliably distinguished based on their acoustic structure, providing a framework for future studies investigating the functional significance of context-dependent acoustic signals in anurans.

Understanding how anatomical structures evolve requires disentangling the roles of integration and modularity in shaping morphological variation. The vertebral column, a serially repeated and regionally differentiated structure, provides a powerful system for investigating these processes. Here, we examine how vertebral morphology evolves in relation to whole-body elongation across the adaptive radiation of Lake Malawi cichlid fishes. We tested for evolutionary integration between the precaudal and caudal domains, as well as assessed the contributions of vertebral count, centrum shape, and intervertebral spacing on body elongation. We find strong evolutionary integration between precaudal and caudal vertebral shape, with both vertebral shapes varying along shared axes of multivariate shape change. Despite this, precaudal and caudal vertebral counts evolve independently, indicating a decoupling between the evolution of identity and morphology. Whole-body elongation is significantly associated with coordinated changes in vertebral and rib morphology, including proportional increases in centrum size, posterior displacement of neural and haemal spines, and increased rib curvature. In contrast, centrum elongation and intervertebral spacing do not independently explain body elongation beyond vertebral counts. These results demonstrate that body elongation in cichlids necessitates integrated, multivariate changes in axial morphology. Our findings highlight the importance of morphological integration in facilitating coordinated evolutionary responses in anatomical systems.

BackgroundMaximum running speed is a central performance trait, linking morphology, physiology and behaviour to fitness. It is shaped by physical capacity and ecological selection but may also be constrained by ancestry. To examine how these forces interact across macroevolutionary timescales, we conducted an allometric study in a hyper-diverse arthropod taxon--spiders (Araneae). ResultsDrawing on running performance data for 258 species from 64 of the 139 extant spider families, we integrated phylogenetic comparative methods and biomechanical modelling to disentangle the effects of body size, ancestry, leg morphology, ecological guild and preferred locomotor orientation. Maximum running speed varied substantially, both across body mass and among species of similar body mass. By accounting for body mass with a recent biomechanical model, we show that size-specific performance carries a strong phylogenetic signal, and that high-performing runners first evolved within the derived infraorder Araneomorphae.Strong running performance, after accounting for both body size and shared ancestry, was associated with relatively longer legs and, to a lesser extent, ecological guild, but not with leg slenderness or a preference for inverted versus upright locomotion. ConclusionsMacroevolutionary patterns of running performance thus reflect not only variation in body size, but also size-specific leg morphology, ecological differentiation and phylogenetic history. We hope this study contributes to the development of formal evolutionary biomechanics--one that seeks to explain patterns of diversity through the explicit integration of large-scale comparative data, natural history and quantitative models derived from first principles.

ObjectiveRobotic-assisted needle insertions lack haptic feedback, a key sensory cue for detecting tissue transitions and regulating puncture force. Modeling this feedback requires an understanding of soft-tissue biomechanics during insertion. Vibroacoustic signals generated by needle-tissue interactions may provide an additional sensing modality, but their interpretation requires validation against anatomical ground truth. MethodsA multimodal framework was developed to correlate vibroacoustic signals with high-resolution post-puncture microCT ({micro}CT) imaging in Manduca sexta, an insect model containing interconnected soft-tissue layers. A custom clip-on prototype recorded vibroacoustic signals during manual needle insertions. Three trajectory-marking strategies were evaluated to determine 3D coordinates of soft-tissue layer crossings and to assess correlations between acoustic events and anatomical transitions. Distances between layer crossings and needle displacement were used for spatiotemporal alignment of vibroacoustic and {micro}CT data. ResultsA {micro}CT-compatible nylon string preserved puncture trajectories without artifacts and enabled high-resolution 3D reconstruction of anatomy and needle paths. Fusion of vibroacoustic and imaging data allowed identification of acoustic events associated with tissue entry, exit, and transitions. ConclusionBy integrating high-resolution {micro}CT imaging with vibroacoustic sensing, this study establishes a biologically grounded framework for validating the relationship between vibroacoustic signals and anatomical tissue transitions during needle insertion, providing a basis for future quantitative analyses. SignificanceThis work provides initial evidence for correlating vibroacoustic signals recorded during needle insertion with corresponding {micro}CT-identified tissue barriers. Because vibroacoustics offers substantially higher temporal and spatial resolution than most imaging modalities, it has the potential to improve tissue sensing and procedural accuracy in future needle-based interventions.

Animals continuously evaluate environmental cues to guide approach-avoidance decisions, with internal states like hunger dynamically shaping how stimuli are acted upon. While most studies examine the valence-switching of stimuli from appetitive to aversive using simplified or ambiguous stimuli, we leveraged a system in which a single prey contains both appetitive and aversive features. The nudibranch Berghia stephanieae, is a specialist predator of the sea anemone, Exaiptasia diaphana. These nudibranchs must resolve conflicting signals where chemical cues signal food, while contact can result in injury or death. The danger posed by Exaiptasia was described and quantified through direct counts of nematocysts fired into Berghia and multiple instances where the Berghia was captured and consumed by its prey. To test how internal state influenced the perception of stimuli from prey we recorded predatory behavior of Berghia after different periods of food deprivation. We found that the olfactory cues from prey were attractive to Berghia, even when animals were sated, and usually led to a contact-mediated investigation of prey. Hunger independently modulated olfactory and contact cue valence at different internal states and time scales of food deprivation. Hunger specifically altered the threshold for avoidance following contact with prey, indicating that somatosensory and chemotactile cues are modulated by hunger unlike olfactory cues. Our results highlight how internal state and sensory modality interact to shape decision making in a biologically relevant, high-risk predation context.

Take-off is a fast and energy-efficient strategy for bipedal animals, such as birds, to achieve rapid movement; however, how muscle physiology scales to govern this universal behavior remains unresolved. Research in other species physiologies is not readily applicable. As a result, important questions, whether theropod dinosaurs such as Tyrannosaurus rex were capable of jumping, remain unanswered. In this article, we coupled Lagrangian dynamics with Hills muscle equations and developed new experimental methods to quantify joint rotational stiffness and damping, thereby enabling a systematic description of lower-limb mechanics. The approach establishes a novel kinetic framework that links muscle contractile properties to lower-limb performance without invoking control optimization. Animal observations and tabletop mechanisms validate the framework. The mechanics model reveals that the take-off time of about 0.1 s across body masses of 0.003 to 90 kg is achievable, as heavier birds generate proportionally higher reaction forces. Additionally, Tyrannosaurus rex should be capable of jumping, based on the available physiology data. Beyond evolutionary insights, our framework provides a new methodology for analyzing the mechanical properties of biological joints and informing the design of scalable bio-inspired robots.

Encounter rate models are important tools for evaluating and estimating trophic interactions between species. While encounter rate parameters have been measured for many freshwater pelagic fishes, most benthic fishes remain mostly unstudied. Those few efforts to generate encounter rate models for benthic fishes often hold mathematical assumptions based on visual foraging, despite the many cases in which benthic fishes employ the lateral line to forage. Furthermore, encounter rate models are rarely compared, despite the many cases in which prey animals face predation risk from multiple types of predators. For example, the macroinvertebrate Mysis is exposed to both benthic and pelagic predation risk during diel vertical migration (DVM). Comparing the risks between habitats could help evaluate predation risk as an ultimate cause of their DVM behavior. We created a novel encounter rate model based on lateral line ("tactile") foraging by sculpins (Cottidae) given the saltatory (stop-and-go) nature of their movement. The tactile model demonstrated variation in behavior and peak encounter rate with detection distance, movement velocity, and rest durations. We then directly compared predation risk for Mysis by parameterizing both our tactile benthic (2D) encounter rate model for sculpin and a visual pelagic (3D) for rainbow smelt (Osmerus mordax). Tactile encounter rates were generally lower than visual rates for individual predators. However, population level encounter rates at night were greater in the benthic habitat than the pelagic habitat. Overall, our model estimates of encounter rates were consistent with the long-standing hypothesis that predation is an ultimate driver of DVM behavior.

Locating, tracking, and intercepting objects is a fundamental behavior for many organisms. For instance, predators must track and capture erratically moving prey for their survival. Using the echolocating bat as a model species, we investigate how short-term changes in target motion predictability affect longer-term motor plans when tracking a prey item. We used a paradigm where prey motion is under experimental control, and then applied computational methods to characterize how target motion predictability influences short- and long-term behavioral control. We find that target motion predictability during the tracking phase of insect capture influences both short-term changes in sonar call control, as well as longer-term behavioral control for transitioning between hunting phases. For changes in immediate behavioral control, bats produce more bursts of calls at a higher rate when tracking unpredictable moving prey, an indication that the bat is collecting more information about the targets motion for unpredictable than predictable trials. In terms of longer-term behavioral control, target motion unpredictability delays the transition from tracking to capture phase behaviors. We suggest that the bat does this to collect more information about target motion to time the transition from tracking to capture behaviors for hunting success. Additionally, we find the effects of target motion unpredictability are first seen as changes in the vocal motor plan and then the auditory motor plan (ear motion), hinting at a sequencing of motor changes that warrant further investigation. SummaryWhen presented with a more challenging hunting task, bats will increase their production of bursts of calls at a higher rate and delay their transition into capture behaviors.