Biology subjects

Capshaw, G.

Publications and source records attributed to Capshaw, G..

6 recordsLinked to original sources

bioRxiv2026

Bats decouple sonar gaze from steering to resolve sensory conflict

When sensory modalities yield conflicting information, animals must rapidly reassess stimuli to select their actions. We induced auditory-visual conflict in free-flying echolocating Egyptian fruit bats, by fitting animals with prisms that shifted the perceived visual location of a landing perch while echoes returned from its veridical location. Bats that course-corrected within a single goal-directed flight did so by decoupling sonar gaze from steering, to enable rapid reweighting of visual and auditory cues. We designed artificial agents that used Bayesian inference to construct estimates of goal locations in their environment. When competing estimates directed active-sensing behaviors distinctly from steering, agents course-corrected more rapidly. Consistent with this idea, when bats were fit with prisms and earplugs that attenuated auditory localization cues, they were unable to course-correct. Removing prisms produced no systematic after-effects. Our framework suggests that instead of correcting their behavior after failure, animals could efficiently employ active sensing to resolve sensory conflict before failure occurs. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=178 SRC="FIGDIR/small/743555v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@e9374aorg.highwire.dtl.DTLVardef@12d03bforg.highwire.dtl.DTLVardef@5109d2org.highwire.dtl.DTLVardef@5bbb2e_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOCover figure.C_FLOATNO Bat wearing helmet with clear-glasses and tracking markers. Photograph (C) 2026 Nikita M. Finger / Moss Laboratory. C_FIG

neuroscience↗

bioRxiv2026

Bat eye movements resolve a long-standing question in gaze control

Eye movements enable visual information gathering and stabilize gaze via optokinetic (OKR) and vestibulo-ocular reflex (VOR) pathways.1 Echolocating bats, despite their rapid and agile flight maneuvers to land upside down and navigate 3D space, have long been thought not to move their eyes, an assumption originating from Wallss influential assertion over 80 years ago2 but never tested with empirical measurements. Here we present quantitative analysis of eye movements driven by visual and vestibular signals in Sebas short-tailed bat (Carollia perspicillata). Bats generated robust visually driven OKR with an oculomotor range of [~]{+/-}10{degrees}, and displayed strong otolith-mediated responses during off-vertical axis rotation. In contrast, they showed minimal semicircular canal-driven angular VOR (aVOR) for passive head rotations that elicit large, sustained responses in mice. Micro-CT reconstructions revealed that bats and mice have similar semicircular canal geometry, indicating that the weak aVOR does not reflect peripheral anatomical constraints. These findings provide the first empirical demonstration that bats make robust eye movements and exhibit strong visual and otolith-driven components of gaze stabilization. We propose that semicircular canal signals may be more strongly engaged during active flight and modulated by behavioral state-dependent tuning of vestibular pathways to support ecologically specialized behaviors.

physiology↗

bioRxiv2026

Soft tissue morphology of the vomeronasal organ in Lontra canadensis and its osteological correlate: Implications for the evolution of the caniform accessory olfactory system

The olfactory system plays a critical role in mammalian environmental perception, with some clades relying on an expanded accessory olfactory (vomeronasal) system (VNS) to detect larger, non-volatile odorants. Mammals make extensive use of this system for social communication between conspecifics. Recent studies have begun to investigate how the VNS changes in response to or as part of ecological transitions. Several studies have identified trends of VNS-associated gene loss or regression in secondarily aquatic mammals. However, continuing discussion on genotype-phenotype correlation within the VNS means that greater effort should be made to investigate the morphology of the VNS in species where it remains poorly understood. Here, we use skeletal and soft-tissue data to demonstrate that the vomeronasal groove, an established osteological correlate for the VNO in bats and primates, is also a valid indicator for its presence in Caniformia. Additionally, we confirm the presence of the VNO in the secondarily aquatic North American river otter (Lontra canadensis) and compare its morphology with that of two close-related species, the semi-aquatic American mink (Neogale vison) and the terrestrial long-tailed weasel (Neogale frenata). This study expands the valid taxonomic scope of the vomeronasal grooves proxy as an osteological correlate, confirms the presence of the VNO in the previously undescribed system of the North American river otter, and highlights the complexity of the mammalian accessory olfactory system.

evolutionary biology↗

bioRxiv2024

Resistance to age-related hearing loss in the echolocating big brown bat (Eptesicus fuscus)

Hearing mediates many behaviors critical for survival in echolocating bats, including foraging and navigation. Most mammals are susceptible to progressive age-related hearing loss; however, the evolution of biosonar, which requires the ability to hear low-intensity echoes from outgoing sonar signals, may have selected against the development of hearing deficits in echolocating bats. Although many echolocating bats exhibit exceptional longevity and rely on acoustic behaviors for survival to old age, relatively little is known about the aging bat auditory system. In this study, we used DNA methylation to estimate the ages of wild-caught big brown bats (Eptesicus fuscus) and measured hearing sensitivity in young and aging bats using auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). We found no evidence for hearing deficits in aging bats, demonstrated by comparable thresholds and similar ABR wave and DPOAE amplitudes across age groups. We additionally found no significant histological evidence for cochlear aging, with similar hair cell counts, afferent, and efferent innervation patterns in young and aging bats. Here we demonstrate that big brown bats show minimal evidence for age-related loss of peripheral hearing sensitivity and therefore represent informative models for investigating mechanisms that may preserve hearing function over a long lifetime.

neuroscience↗

bioRxiv2023

Experience-Dependent Plasticity in Nucleus Laminaris of the Barn Owl

Barn owls experience increasing interaural time differences (ITDs) during development, because their head width more than doubles in the month after hatching. We therefore hypothesized that their ITD detection circuit might be modified by experience. To test this, we raised owls with unilateral ear inserts that delayed and attenuated the acoustic signal, then measured the ITD representation in the brainstem nucleus laminaris (NL) when they were adult. The ITD circuit is composed of delay line inputs to coincidence detectors, and we predicted that plastic changes would lead to shorter delays in the axons from the manipulated ear, and complementary shifts in ITD representation on the two sides. In owls that received ear inserts starting around P14, the maps of ITD shifted in the predicted direction, but only on the ipsilateral side, and only in those tonotopic regions that had not experienced auditory stimulation prior to insertion. The contralateral map did not change. Experience-dependent plasticity of the ITD circuit occurs in NL, and our data suggest that ipsilateral and contralateral delays are independently regulated. Thus, altered auditory input during development leads to long-lasting changes in the representation of ITD. Significance StatementThe early life of barn owls is marked by increasing sensitivity to sound, and by increasing ITDs. Their prolonged post-hatch development allowed us to examine the role of altered auditory experience on the development of ITD detection circuits. We raised owls with a unilateral ear insert and found that their maps of ITD were altered by experience, but only in those tonotopic regions that had not experienced auditory stimulation prior to insertion. Thus experience-induced plasticity allows the sound localization circuits to be customized to individual characteristics, such as the size of the head, and potentially to compensate for natural conductive hearing losses.

neuroscience↗

bioRxiv2022

A general mechanism of air-borne hearing in Recent and early non-tympanate tetrapods

Tetrapod tympanic hearing probably emerged in the Triassic with independent origins in each of the major groups, more than 120 Myr after the water-land transition. During this long period, any auditory sensitivity must have been based on non-tympanic, bone conduction mechanisms. However, bone conduction is a non-specific term describing several different modes of vibration that can stimulate the inner ear. To understand hearing in a non-tympanic ear, we focus on the simplest model: that sound translates the head, i.e., that the head is pushed and pulled by the sound wave, and that this vibration is transduced by the inner ear. Simple translation is the mode of human low-frequency bone conduction sensitivity and translation by underwater sound is also the mode of auditory stimulation for most fishes. It is therefore a straightforward assumption that this may have been the mechanism of hearing in the early tetrapods. According to acoustic theory, the efficiency of translation of an object by sound is determined by its density and ka, the product of the acoustic wavenumber (k) and the radius (a) of the head. Simple finite-element models of translation by sound show that vibration velocities only depend on ka and density (for objects of the same shape and composition) and are almost constant (between 4 and 5 {micro}m/s/Pa depending on shape) for objects with ka<1. We compare sensitivity to sound and to vibrations of the skull in animals lacking tympanic middle ears (snakes, salamanders, earless frogs, and lungfish) and show that the low-frequency air-borne sound sensitivity in these species is largely consistent with a translation mechanism. How translation of the head or body can stimulate the inner ear is most evident in an inertial system like the otolithic/otoconial ears of fish and early tetrapods, but fluid inertia in the inner ear may also generate hydrodynamic waves that can stimulate hair cells in the tetrapod inner ear, providing a mechanism for this simple mode of sound reception to confer hearing in earless animals.

animal behavior and cognition↗