Eric Warrant

• BSc (Hons) PhD
• Professor at Lund University

In celebration of the excellence of articles published in the Journal of Comparative Physiology A, Editors’ and Readers’ Choice Awards are annually conferred to the top papers in the categories Original Research Paper and Review/Review-History Article. The recipients of the 2025 Editors’ Choice Awards were selected based on votes cast by the Editor...

Moving in straight lines is a behaviour that enables organisms to search for food, move away from threats, and ultimately seek suitable environments in which to survive and reproduce. This study explores a vision-based technique for detecting a change in heading direction using the Milky Way (MW), one of the navigational cues that are known to be u...

Vespula germanica and Vespula vulgaris are two common European wasps that have ecological and economic importance due to their artificial introduction to many different countries and environments. Their success has undoubtedly been aided by their capacity for visually guided hunting, foraging, learning, and using visual cues in the context of homin...

Many species rely on celestial cues as a reliable guide for maintaining heading while navigating. In this paper, we propose a method that extracts the Milky Way (MW) shape as an orientation cue in low-light scenarios. We also tested the method on both real and synthetic images and demonstrate that the performance of the method appears to be accurat...

Each spring, billions of Bogong moths escape hot conditions across southeast Australia by migrating up to 1000 km to a place they have never previously visited – a limited number of cool caves in the Australian Alps, historically used for aestivating over summer1,2. At the beginning of autumn the same individuals make a return migration to their br...

The Editors’ and Readers’ Choice Awards were established in 2022 to celebrate some of the outstanding articles published every year in the Journal of Comparative Physiology A. The recipients of the 2024 Editors’ Choice Awards were selected based on votes cast by the Editorial Board on articles published in 2023. In the category Original Paper, this...

The Journal of Comparative Physiology A is the premier peer-reviewed scientific journal in comparative physiology, in particular sensory physiology, neurophysiology, and neuroethology. Founded in 1924 by Karl von Frisch and Alfred Kühn, it celebrates its 100th anniversary in 2024. During these 100 years, many of the landmark achievements in these d...

The seasonal migrations of insects involve a substantial displacement of biomass with significant ecological and economic consequences for regions of departure and arrival. Remote sensors have played a pivotal role in revealing the magnitude and general direction of bioflows above 150 m. Nevertheless, the take-off and descent activity of insects be...

A fateful decision as a 15-year-old high school student, and good advice from a distinguished professor of zoology, were the catalysts that not only decided my entire career but also led me to the Journal of Comparative Physiology A, and to the myriad biological wonders that were held within its covers. In my celebration of JCPA, I look back on the...

Many species of insects undertake long-range, seasonally reversed migrations, displaying sophisticated orientation behaviors to optimize their migratory trajectories. However, when invasive insects arrive in new biogeographical regions, it is unclear if migrants retain (or how quickly they regain) ancestral migratory traits, such as seasonally pref...

Introduction The Bogong moth Agrotis infusa is well known for its remarkable annual round-trip migration from its breeding grounds across eastern and southern Australia to its aestivation sites in the Australian Alps, to which it provides an important annual influx of nutrients. Over recent years, we have benefited from a growing understanding of t...

The ability to measure flying insect activity and abundance is important for ecologists, conservationists and agronomists alike. However, existing methods are laborious and produce data with low temporal resolution (e.g. trapping and direct observation), or are expensive, technically complex, and require vehicle access to field sites (e.g. radar an...

In this special issue of articles from leading neuroethologists-all of whom gave outstanding presentations within the Presidential Symposium of the 2022 International Congress of Neuroethology held in Lisbon, Portugal-we learn about the role of cryptochrome molecules in the magnetic sense of animals, how honeybees construct their honeycombs, why fi...

Eyes in low-light environments typically must balance sensitivity and spatial resolution. Vertebrate eyes with large "pixels" (e.g., retinal ganglion cells with inputs from many photoreceptors) will be sensitive but provide coarse vision. Small pixels can render finer detail, but each pixel will gather less light, and thus have poor signal relative...

We discovered nocturnal colour vision in the Asian giant honeybee Apis dorsata—a facultatively nocturnal species—at mesopic light intensities, down to half-moon light levels (approx. 10⁻² cd m⁻²). The visual threshold of nocturnality aligns with their reported nocturnal activity down to the same light levels. Nocturnal colour vision in A. dorsata i...

The Milky Way is used by nocturnal flying and walking insects for maintaining heading while navigating. In this study, we have explored the feasibility of the method for machine vision systems on autonomous vehicles by measuring the visual features and characteristics of the Milky Way. We also consider the conditions under which the Milky Way is us...

Spatial orientation is a prerequisite for most behaviors. In insects, the underlying neural computations take place in the central complex (CX), the brain’s navigational center. In this region different streams of sensory information converge to enable context-dependent navigational decisions. Accordingly, a variety of CX input neurons deliver info...

All bats possess eyes that are of adaptive value. Echolocating bats have retinae dominated by rod photoreceptors and use dim light vision for navigation, and in rare cases for hunting. However, the visual detection threshold of insectivorous echolocating bats remains unknown. Here we determine this threshold for the vespertilionid bat Myotis dauben...

During the 99 years of its history, the Journal of Comparative Physiology A has published many of the most influential papers in comparative physiology and related disciplines. To celebrate this achievement of the journal’s authors, annual Editors’ Choice Awards and Readers’ Choice Awards are presented. The winners of the 2023 Editors’ Choice Award...

Spatial orientation is a prerequisite for most behaviors. In insects, the underlying neural computations take place in the central complex (CX), the brain's navigational center. In this region different streams of sensory information converge to enable context-dependent navigational decisions. Accordingly, a variety of CX input neurons deliver info...

The ability to see colour at night is known only from a handful of animals. First discovered in the elephant hawk moth Deilephila elpenor , nocturnal colour vision is now known from two other species of hawk moths, a single species of carpenter bee, a nocturnal gecko and two species of anurans. The reason for this rarity—particularly in vertebrates...

Giant honeybees, including the open-nesting Asian giant honeybee Apis dorsata, display a spectacular collective defence behaviour – known as “shimmering” – against predators, which is characterised by travelling waves generated by individual bees flipping their abdomens in a coordinated and sequential manner across the bee curtain. We examined if s...

There are hundreds of thousands of moth species with crucial ecological roles that are often obscured by their nocturnal lifestyles. The pigmentation and appearance of moths are dominated by cryptic diffuse shades of brown. In this study, 82 specimens representing 26 moth species were analysed using infrared polarimetric hyperspectral imaging in th...

One of the most interesting macroscopic phenomena in the animal world is seasonal migration. A central goal of research into animal migration is to better understand the mechanisms that evolved to solve the complex challenges which a migratory life history presents. Each year, and with a high degree of species-level site fidelity, the Australian Bo...

During their period of summer dormancy, Australian Bogong moths Agrotis infusa undertake seemingly random evening flights, filling the air with densities in the dozens per cubic metre. The purpose of these flights is unknown, but they may serve an important role in Bogong moth navigation, which remarkably enables them to return to the same exact su...

The Bogong moth Agrotis infusa is well known for its remarkable annual round-trip migration from its breeding grounds across eastern Australia to its aestivation sites in the Australian Alps, to which it provides an important annual influx of nutrients. Over recent years, we have benefited from a growing understanding of the navigational abilities...

Due to the absence of physical barriers, the open-nesting giant honeybee Apis dorsata has evolved a spectacular collective defence behaviour – known as “shimmering” – against predators, which is characterised by travelling waves generated by individual bees flipping their abdomens in a coordinated and sequential manner across the bee curtain. We ex...

This year marks the inauguration of the annual Editors' Choice Award and the Readers' Choice Award, each presented for outstanding original papers and review articles published in the Journal of Comparative Physiology A. The winners of the 2022 Editors' Choice Award were determined by vote of the Editorial Board for the most highly recommended pape...

For navigation, animals use a robust internal compass. Compass navigation is crucial for long-distance migrating animals like monarch butterflies, which use the sun to navigate over 4,000 km to their overwintering sites every fall. Sun-compass neurons of the central complex have only been recorded in immobile butterflies, and experimental evidence...

Recent interest in applying novel imaging techniques to infer optical resolution in compound eyes underscores the difficulty of obtaining direct measures of acuity. A widely used technique exploits the principal pseudopupil, a dark spot on the eye surface representing the ommatidial gaze direction and the number of detector units (ommatidia) viewin...

1. The ability to measure flying insect activity and abundance is important for ecologists, conservationists and agronomists alike. However, existing methods are laborious and produce data with low temporal resolution (e.g. trapping and direct observation), or are expensive, technically complex, and require vehicle access to field sites (e.g. radar...

Insect neuroscience generates vast amounts of highly diverse data, of which only a small fraction are findable, accessible and reusable. To promote an open data culture, we have therefore developed the InsectBrainDatabase ( IBdb ), a free online platform for insect neuroanatomical and functional data. The IBdb facilitates biological insight by enab...

Studying the routes flown by long-distance migratory insects comes with the obvious challenge that the animal’s body size and weight is comparably low. This makes it difficult to attach relatively heavy transmitters to these insects in order to monitor their migratory routes (as has been done for instance in several species of migratory birds. Howe...

Bees, ants, and wasps are well known to visually navigate when traveling between their nests and foraging sites. When leaving their nest, landmarks in the vicinity are memorized and used upon return to locate the nest entrance.¹,² The Neotropical nocturnal sweat bee Megalopta genalis navigates under the forest canopy at light intensities ten times...

How animals sense Earth’s magnetic field is an enduring mystery. The protein cryptochrome ErCRY4, found in the eyes of migratory European robins, has the right physical properties to be the elusive magnetosensor. Cryptochrome protein has the properties needed to be a magnetosensor.

Bees are typically diurnal but around 1% of described species have nocturnal activity. Nocturnal bees are still poorly studied due to bias towards studying diurnal insects. However, knowledge concerning their biology and role as crop pollinators has increased. We review the literature on nocturnal bees’ traits and their host plants, and assess the...

Vertical-beam entomological radars provide precise measurements of the body alignment of individual overflying insects but are unable to distinguish which of the two axial directions the insect is heading towards. Insects migrating at altitude typically show common alignment, although with a broad spread. We show here that when observations from mu...

Head direction can be represented in a self-centered egocentric or a viewpoint-invariant allocentric reference frame. Using the most efficient representation is especially crucial for migrating animals, like monarch butterflies ( Danaus plexippus ) that use the sun for orientation. With tetrode recordings from the brain of tethered flying monarch b...

1. We carried out three choice experiments with 6116 nocturnal lepidopteran individuals (95 species, 7 families, 32075 counts), each replicated 105 times during the seasons of two years. Moths were released indoors at the centre of a 10 x 10 m area with different lamps placed at each corner. 2. In experiment 1, lamps emitted UV (peak at 365 nm), bl...

Wing integrity is crucial to the many insect species that spend distinct portions of their life in flight. How insects cope with the consequences of wing damage is therefore a central question when studying how robust flight performance is possible with such fragile chitinous wings. It has been shown in a variety of insect species that the loss in...

Distant and predictable features in the environment make ideal compass cues to allow movement along a straight path. Ball-rolling dung beetles use a wide range of different signals in the day or night sky to steer themselves along a fixed bearing. These include the sun, the Milky Way, and the polarization pattern generated by the moon. Almost two d...

The Bogong moth Agrotis infusa is well known for its remarkable long‐distance migration – a return journey from the plains of southeast Australia to the Australian Alps – as well as for its cultural significance for Indigenous Australians. Each Spring, as many as four billion moths are estimated to arrive in the Australian Alps to aestivate in cool...

Insect neuroscience generates vast amounts of highly diverse data, of which only a small fraction are findable, accessible and reusable, despite open data mandates by funding bodies. We have therefore developed the InsectBrainDatabase (IBdb), an open platform for depositing, sharing and managing a wide range of insect neuroanatomical and functional...

Insect neuroscience generates vast amounts of highly diverse data, of which only a small fraction are findable, accessible and reusable, despite open data mandates by funding bodies. We have therefore developed the InsectBrainDatabase (IBdb), an open platform for depositing, sharing and managing a wide range of insect neuroanatomical and functional...

Diverse organisms use Earth's magnetic field as a cue in orientation and navigation. Nevertheless, eliciting magnetic orientation responses reliably, either in laboratory or natural settings, is often difficult. Many species appear to preferentially exploit non-magnetic cues if they are available, suggesting that the magnetic sense often serves as...

The foraging activity of diurnal bees often relies on flower availability, light intensity and temperature. We do not know how nocturnal bees, which fly at night and twilight, cope with these factors, especially as light levels vary considerably from night to day and from night to night due to moon phase and cloud cover. Given that bee apposition c...

Bats are nocturnal mammals known for their ability to echolocate, yet all bats can see, and most bats of the family Pteropodidae (fruit bats) do not echolocate – instead they rely mainly on vision and olfaction to forage. We investigated whether echolocating bats, given their limited reliance on vision, have poorer spatial resolving power (SRP) tha...

The integrity of their wings is crucial to the many insect species that spend distinct portions of their life in flight. How insects cope with the consequences of wing damage is therefore a central question when studying how robust flight performance is possible with such fragile chitinous wings. It has been shown in a variety of insect species tha...

The cover image is based on the Original Article The brain of a nocturnal migratory insect, the Australian Bogong moth by Andrea Adden, Keram Pfeiffer, Eric J. Warrant et al., https://doi.org/10.1002/cne.24866.

Monarch butterflies (Danaus plexippus) are prominent for their annual long-distance migration from North America to their overwintering area in Central Mexico. To find their way on this long journey, they use a sun compass as their main orientation reference but will also adjust their migratory direction with respect to mountain ranges. This indica...

How neural form and function are connected is a central question of neuroscience. One prominent functional hypothesis, from the beginnings of neuroanatomical study, states that laterally extending dendrites of insect lamina monopolar cells (LMCs) spatially integrate visual information. We provide the first direct functional evidence for this hypoth...

Entomological radars employing the ‘ZLC’ (zenith-pointing linear-polarized narrow-angle conical scan) configuration detect individual insects flying overhead and can retrieve information about a target’s trajectory (its direction and speed), the insect’s body alignment and four parameters that characterize the target itself: its radar cross section...

Monarch butterflies ( Danaus plexippus ) are prominent for their annual long-distance migration from North America to its overwintering area in Central Mexico. To find their way on this long journey, they use a sun compass as their main orientation reference but will also adjust their migratory direction with respect to mountain ranges. This indica...

Moth wings are densely covered by wing scales that are assumed to specifically function to camouflage nocturnally active species during day time. Generally, moth wing scales are built according to the basic lepidopteran Bauplan, where the upper lamina consists of an array of parallel ridges and the lower lamina is a thin plane. The lower lamina hen...

Every year, millions of Australian Bogong moths (Agrotis infusa) complete an astonishing journey: in spring, they migrate over 1000 km from their breeding grounds to the alpine regions of the Snowy Mountains, where they endure the hot summer in the cool climate of alpine caves. In autumn, the moths return to their breeding grounds, where they mate,...

Synopsis This review explores the physical properties of natural light, both celestial and bioluminescent, and its distribution in terrestrial and aquatic habitats. A description of the natural sources of light is followed by a discussion of the spatial, temporal, spectral and polarization properties of visual scenes, and how the predictable struct...

Synopsis This review explores the physical properties of natural light, both celestial and bioluminescent, and its distribution in terrestrial and aquatic habitats. A description of the natural sources of light is followed by a discussion of the spatial, temporal, spectral and polarization properties of visual scenes, and how the predictable struct...

The retina has a very high energy demand but lacks an internal blood supply in most vertebrates. Here we explore the hypothesis that oxygen diffusion limited the evolution of retinal morphology by reconstructing the evolution of retinal thickness and the various mechanisms for retinal oxygen supply, including capillarization and acid-induced haemog...

Every year, millions of Australian Bogong moths ( Agrotis infusa ) complete an astonishing journey: in spring, they migrate over 1000 km from their breeding grounds to the alpine regions of the Snowy Mountains, where they endure the hot summer in the cool climate of alpine caves. In autumn, the moths return to their breeding grounds, where they mat...

The use of highly visible body colours as signals during courtship is well known from animals active in brighter light. Now a sexually dimorphic colouration signal has been discovered in a nocturnal moth, suggesting that visual courtship rituals might even occur at night.

Insect migrations are spectacular natural events and resemble a remarkable relocation of biomass between two locations in space. Unlike the well-known migrations of daytime flying butterflies, such as the painted lady (Vanessa cardui) or the monarch butterfly (Danaus plexippus), much less widely known are the migrations of nocturnal moths. These mi...

Despite their tiny brains, insects show impressive abilities when navigating over short distances during path integration or during migration over thousands of kilometers across entire continents. Celestial compass cues often play an important role as references during navigation. In contrast to many other insects, South African dung beetles rely e...

Like many birds [1], numerous species of nocturnal moths undertake spectacular long-distance migra- tions at night [2]. Each spring, billions of Bogong moths (Agrotis infusa) escape hot conditions in different regions of southeast Australia by making a highly directed migration of over 1,000 km to a limited number of cool caves in the Australian Al...

For over half a century, the multitudinous mirror eyes of the lowly scallop have continuously amazed us with their visual eccentricities. The latest surprise is the mirror itself, which turns out to be an extraordinary optical wonder.

Substantial evidence now supports the hypothesis that the common ancestor of bats was nocturnal and capable of both powered flight and laryngeal echolocation. This scenario entails a parallel sensory and biomechanical transition from a nonvolant, vision-reliant mammal to one capable of sonar and flight. Here we consider anatomical constraints and o...

The extraordinary adaptability of invertebrates is in no small part due to their sense organs, and particularly their eyes, which help them to find food, locate mates, escape predators and migrate to new habitats. Even though most invertebrates do not see as sharply as we do, many see much better in dim light, can experience many more colours, can...

A Quick guide to oilbirds: nocturnal birds found only in Neotropical rainforests that, rather like many bat species, live in caves where they use echolocation for orientation.

Path integration is a widespread navigational strat- egy in which directional changes and distance covered are continuously integrated on an outward journey, enabling a straight-line return to home. Bees use vision for this task—a celestial-cue-based visual compass and an optic-flow-based visual odometer—but the underlying neural integration mechan...

Brain structure and function are tightly correlated across all animals. While these relations are ultimately manifestations of differently wired neurons, many changes in neural circuit architecture lead to larger-scale alterations visible already at the level of brain regions. Locating such differences has served as a beacon for identifying brain a...

[This corrects the article on p. 77 in vol. 10, PMID: 27147998.].

The visual systems of many animals, particularly those active during the day, are optimized for high spatial acuity. However, at night, when photons are sparse and the visual signal competes with increased noise levels, fine spatial resolution cannot be sustained and is traded-off for the greater sensitivity required to see in dim light. High spati...

To sample information optimally, sensory systems must adapt to the ecological demands of each animal species. These adaptations can occur peripherally, in the anatomical structures of sensory organs and their receptors; and centrally, as higher-order neural processing in the brain. While a rich body of investigations has focused on peripheral adapt...

Nocturnal insects have evolved remarkable visual capacities, despite small eyes and tiny brains. They can see colour, control flight and land, react to faint movements in their environment, navigate using dim celestial cues and find their way home after a long and tortuous foraging trip using learned visual landmarks. These impressive visual abilit...

Flying insect predators intercept their aerial prey with deadly precision. New research reveals that a tiny robber fly, with a brain smaller than a pinhead, achieves this using the same visual mechanism that we ourselves employ to catch a passing ball.

Sexual dimorphism in eye structure is attributed to sexual selection in animals that employ vision for locating mates. In many male insects, large eyes and eye regions of higher acuity are believed to facilitate the location of females. Here, we compare various features of male and female eyes in three sympatric carpenter bee species, which include...

Field experiments estimating the reaction of perching male X. tenuiscapa to stones thrown of known sizes. (XLSX)

Mate location behaviour and associated morphological adaptations reported in male carpenter bees. (DOCX)

Light represents one of the most reliable environmental cues in the biological world. In this review we focus on the evolutionary consequences to changes in organismal photic environments, with a specific focus on the class Insecta. Particular emphasis is placed on transitional forms that can be used to track the evolution from (1) diurnal to noctu...

Visual sensory demands vary substantially across vertebrates. Different visual sensory components have evolved to meet these sensory demands and enhance visual behavioral performance. One of these components is the retinal specialization, which is a portion of the retina with generally high ganglion cell densities, which increase spatial resolving...