Counterillumination reduces bites by Great White sharks.

In the open ocean, achieving camouflage is complicated by the fact that the downwelling light is generally much brighter than the upwelling light, which means that any object, even if its ventral surface is white due to countershading, will appear as a dark silhouette when viewed from below. To overcome this, many marine species employ counterillumination, whereby light is emitted from photophores on their ventral surface to replace the downwelling light blocked by their body. However, only a single behavioral study has tested the efficacy of counterillumination as an anti-predation strategy.

Personal electric deterrents can reduce shark bites from the three species responsible for the most fatal interactions.

The frequency of unprovoked shark bites is increasing worldwide, leading to a growing pressure for mitigation measures to reduce shark-bite risk while maintaining conservation objectives. Personal shark deterrents are a promising and non-lethal strategy that can protect ocean users, but few have been independently and scientifically tested. In Australia, bull (Carcharhinus leucas), tiger (Galeocerdo cuvier), and white sharks (Carcharodon carcharias) are responsible for the highest number of bites and fatalities.

Physiological properties of the visual system in the Green Weaver ant, Oecophylla smaragdina.

The Green Weaver ants, Oecophylla smaragdina are iconic animals known for their extreme cooperative behaviour where they bridge gaps by linking to each other to build living chains. They are visually oriented animals, build chains towards closer targets, use celestial compass cues for navigation and are visual predators. Here, we describe their visual sensory capacity.

A shark's eye view: testing the 'mistaken identity theory' behind shark bites on humans.

Shark bites on humans are rare but are sufficiently frequent to generate substantial public concern, which typically leads to measures to reduce their frequency. Unfortunately, we understand little about why sharks bite humans. One theory for bites occurring at the surface, e.

Ocellar spatial vision in Myrmecia ants.

In addition to compound eyes, insects possess simple eyes known as ocelli. Input from the ocelli modulates optomotor responses, flight-time initiation, and phototactic responses - behaviours that are mediated predominantly by the compound eyes. In this study, using pattern electroretinography (pERG), we investigated the contribution of the compound eyes to ocellar spatial vision in the diurnal Australian bull ant Myrmecia tarsata by measuring the contrast sensitivity and spatial resolving power of the ocellar second-order neurons under various occlusion conditions.

The buzz around spatial resolving power and contrast sensitivity in the honeybee, Apis mellifera.

Most animals rely on vision to perform a range of behavioural tasks and variations in the anatomy and physiology of the eye likely reflect differences in habitat and life history. Moreover, eye design represents a balance between often conflicting requirements for gathering different forms of visual information. The trade-off between spatial resolving power and contrast sensitivity is common to all visual systems, and European honeybees (Apis mellifera) present an important opportunity to better understand this trade-off.

Miniaturisation reduces contrast sensitivity and spatial resolving power in ants.

Vision is crucial for animals to find prey, locate conspecifics and navigate within cluttered landscapes. Animals need to discriminate objects against a visually noisy background. However, the ability to detect spatial information is limited by eye size.

The effect of underwater sounds on shark behaviour.

The effect of sound on the behaviour of sharks has not been investigated since the 1970s. Sound is, however, an important sensory stimulus underwater, as it can spread in all directions quickly and propagate further than any other sensory cue. We used a baited underwater camera rig to record the behavioural responses of eight species of sharks (seven reef and coastal shark species and the white shark, Carcharodon carcharias) to the playback of two distinct sound stimuli in the wild: an orca call sequence and an artificially generated sound.

Electrophysiological measures of temporal resolution, contrast sensitivity and spatial resolving power in sharks.

In most animals, vision plays an important role in detecting prey, predators and conspecifics. The effectiveness of vision in assessing cues such as motion and shape is influenced by the ability of the visual system to detect changes in contrast in both space and time. Understanding the role vision plays in shark behaviour has been limited by a lack of knowledge about their temporal resolution, contrast sensitivity and spatial resolution.

Visual resolution and contrast sensitivity in two benthic sharks.

Sharks have long been described as having 'poor' vision. They are cone monochromats and anatomical estimates suggest they have low spatial resolution. However, there are no direct behavioural measurements of spatial resolution or contrast sensitivity.