Seeing the world through the eyes of a butterfly: visual ecology of the territorial males of Pararge aegeria (Lepidoptera: Nymphalidae).

Combining studies of animal visual systems with exact imaging of their visual environment can get us a step closer to understand how animals see their "Umwelt". Here, we have combined both methods to better understand how males of the speckled wood butterfly, Pararge aegeria, see the surroundings of their perches. These males are well known to sit and wait for a chance to mate with a passing females, in sunspot territories in European forests.

Light pollution forces a change in dung beetle orientation behavior.

Increasing global light pollution threatens the night-time darkness to which most animals are adapted. Light pollution can have detrimental effects on behavior, including by disrupting the journeys of migratory birds, sand hoppers, and moths. This is particularly concerning, since many night-active species rely on compass information in the sky, including the moon, the skylight polarization pattern, and the stars, to hold their course.

Quantifying biologically essential aspects of environmental light.

Quantifying and comparing light environments are crucial for interior lighting, architecture and visual ergonomics. Yet, current methods only catch a small subset of the parameters that constitute a light environment, and rarely account for the light that reaches the eye. Here, we describe a new method, the environmental light field (ELF) method, which quantifies all essential features that characterize a light environment, including important aspects that have previously been overlooked.

Orienting to polarized light at night - matching lunar skylight to performance in a nocturnal beetle.

For polarized light to inform behaviour, the typical range of degrees of polarization observable in the animal's natural environment must be above the threshold for detection and interpretation. Here, we present the first investigation of the degree of linear polarization threshold for orientation behaviour in a nocturnal species, with specific reference to the range of degrees of polarization measured in the night sky. An effect of lunar phase on the degree of polarization of skylight was found, with smaller illuminated fractions of the moon's surface corresponding to lower degrees of polarization in the night sky.

The sea urchin uses low resolution vision to find shelter and deter enemies.

Many sea urchins can detect light on their body surface and some species are reported to possess image-resolving vision. Here, we measure the spatial resolution of vision in the long-spined sea urchin , using two different visual responses: a taxis towards dark objects and an alarm response of spine-pointing towards looming stimuli. For the taxis response we used visual stimuli, which were isoluminant to the background, to discriminate spatial vision from phototaxis.

Low--resolution vision in a velvet worm (Onychophora).

Onychophorans, also known as velvet worms, possess a pair of simple lateral eyes, and are a key lineage with regard to the evolution of vision. They resemble ancient Cambrian forms, and are closely related to arthropods, which boast an unrivalled diversity of eye designs. Nonetheless, the visual capabilities of onychophorans have not been well explored.

How animals follow the stars.

Throughout history, the stars have provided humans with ever more information about our world, enabling increasingly accurate systems of navigation in addition to fuelling some of the greatest scientific controversies. What information animals have evolved to extract from a starry sky and how they do so, is a topic of study that combines the practical and theoretical challenges faced by both astronomers and field biologists. While a number of animal species have been demonstrated to use the stars as a source of directional information, the strategies that these animals use to convert this complex and variable pattern of dim-light points into a reliable 'stellar orientation' cue have been more difficult to ascertain.

Resolving the Trade-off Between Visual Sensitivity and Spatial Acuity-Lessons from Hawkmoths.

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 spatial acuity demands detectors and successive visual processing units whose receptive fields each cover only a small area of visual space, in order to reassemble a finely sampled and well resolved image.

Stellar performance: mechanisms underlying Milky Way orientation in dung beetles.

Nocturnal dung beetles () are currently the only animals that have been demonstrated to use the Milky Way for reliable orientation. In this study, we tested the capacity of to orient under a range of artificial celestial cues, and compared the properties of these cues with images of the Milky Way simulated for a beetle's visual system. We find that the mechanism that permits accurate stellar orientation under the Milky Way is based on an intensity comparison between different regions of the Milky Way.

Neural coding underlying the cue preference for celestial orientation.

Diurnal and nocturnal African dung beetles use celestial cues, such as the sun, the moon, and the polarization pattern, to roll dung balls along straight paths across the savanna. Although nocturnal beetles move in the same manner through the same environment as their diurnal relatives, they do so when light conditions are at least 1 million-fold dimmer. Here, we show, for the first time to our knowledge, that the celestial cue preference differs between nocturnal and diurnal beetles in a manner that reflects their contrasting visual ecologies.

Diurnal dung beetles use the intensity gradient and the polarization pattern of the sky for orientation.

To escape competition at the dung pile, a ball-rolling dung beetle forms a piece of dung into a ball and rolls it away. To ensure their efficient escape from the dung pile, beetles rely on a 'celestial compass' to move along a straight path. Here, we analyzed the reliability of different skylight cues for this compass and found that dung beetles rely not only on the sun but also on the skylight polarization pattern.

The role of the sun in the celestial compass of dung beetles.

Recent research has focused on the different types of compass cues available to ball-rolling beetles for orientation, but little is known about the relative precision of each of these cues and how they interact. In this study, we find that the absolute orientation error of the celestial compass of the day-active dung beetle Scarabaeus lamarcki doubles from 16° at solar elevations below 60° to an error of 29° at solar elevations above 75°. As ball-rolling dung beetles rely solely on celestial compass cues for their orientation, these insects experience a large decrease in orientation precision towards the middle of the day.

A new galloping gait in an insect.

An estimated three million insect species all walk using variations of the alternating tripod gait [1]. At any one time, these animals hold one stable triangle of legs steady while swinging the opposite triangle forward. Here, we report the discovery that three different flightless desert dung beetles use an additional gallop-like gait, which has never been described in any insect before.

Flicker is part of a multi-cue response criterion in fiddler crab predator avoidance.

Predator avoidance behaviour costs time, energy and opportunities, and prey animals need to balance these costs with the risk of predation. The decisions necessary to strike this balance are often based on information that is inherently imperfect and incomplete because of the limited sensory capabilities of prey animals. Our knowledge, however, about how prey animals solve the challenging task of restricting their responses to the most dangerous stimuli in their environment is very limited.

Dung beetles use their dung ball as a mobile thermal refuge.

At midday, surface temperatures in the desert often exceed 60°C. To be active at this time, animals need extraordinary behavioural or physiological adaptations. Desert ants, for instance, spend up to 75% of their foraging time cooling down on elevated thermal refuges such as grass stalks.

Dung beetles ignore landmarks for straight-line orientation.

Upon locating a suitable dung pile, ball-rolling dung beetles shape a piece of dung into a ball and roll it away in a straight line. This guarantees that they will not return to the dung pile, where they risk having their ball stolen by other beetles. Dung beetles are known to use celestial compass cues such as the sun, the moon and the pattern of polarised light formed around these light sources to roll their balls of dung along straight paths.

The dung beetle dance: an orientation behaviour?

An interesting feature of dung beetle behaviour is that once they have formed a piece of dung into a ball, they roll it along a straight path away from the dung pile. This straight-line orientation ensures that the beetles depart along the most direct route, guaranteeing that they will not return to the intense competition (from other beetles) that occurs near the dung pile. Before rolling a new ball away from the dung pile, dung beetles perform a characteristic "dance," in which they climb on top of the ball and rotate about their vertical axis.

Natural visual cues eliciting predator avoidance in fiddler crabs.

To efficiently provide an animal with relevant information, the design of its visual system should reflect the distribution of natural signals and the animal's tasks. In many behavioural contexts, however, we know comparatively little about the moment-to-moment information-processing challenges animals face in their daily lives. In predator avoidance, for instance, we lack an accurate description of the natural signal stream and its value for risk assessment throughout the prey's defensive behaviour.

Topography of vision and behaviour.

Given the great range of visual systems, tasks and habitats, there is surprisingly little experimental evidence of how visual limitations affect behavioural strategies under natural conditions. Analysing this relationship will require an experimental system that allows for the synchronous measurement of visual cues and visually guided behaviour. The first step in quantifying visual cues from an animal's perspective is to understand the filter properties of its visual system.