Fast-moving animals process visual information in shorter time frames

A dragonfly pursuing prey and a starfish slowly making its way across the seafloor inhabit the same planet, yet they experience time very differently.

New research indicates that animals which move quickly process visual information over shorter time periods than slower species. This variation influences how predators pursue food, how prey avoid attack, and even the ways artificial light can affect wildlife.

After examining 237 species of insects, birds, fish and mammals, researchers found that visual speed is strongly associated with lifestyle – showing that evolution adjusts perception to suit the way animals travel through their surroundings.

Visual speed across animals

Dr Clinton Haarlem and colleagues at Trinity College Dublin (TCD) and the University of Galway found that flying species and predators that pursue their prey consistently noticed rapid visual changes that slower-moving or sedentary animals did not.

This trend was evident across widely separated animal groups, connecting rapid visual perception with lifestyles dependent on manoeuvrability and prolonged pursuit, rather than with one particular evolutionary lineage.

By directly relating visual tempo to ecological pace, the results provide a basis for examining how energy constraints, light levels and hunting methods further shape what individual species are able to see.

When flicker becomes sight

To compare how rapidly different eyes process change, scientists use critical flicker fusion (CFF): the highest rate at which a flickering light is still seen as distinct flashes.

Once a light flickers faster than an animal’s CFF, its brain merges the pulses into a continuous glow rather than registering separate flashes.

Certain insects and birds can perceive changes at over 200 flashes per second, whereas slower animals fail to detect much of that movement.

“From a dragonfly tracking prey in mid-air to a starfish grazing slowly across the seabed, animals live in very different perceptual worlds,” said Dr. Haarlem.

Flying requires faster vision

The effect of flight was especially clear. Species capable of flying had CFF values approximately twice those recorded in non-flying animals.

At speed, wings and bodies alter course quickly, meaning the eyes need to detect hazards and prey with almost no lag. A momentary blur may result in either a lost catch or a collision, favouring faster neural updates through natural selection.

Such speed is useful only when muscles can react equally fast, linking high CFF to the performance of the entire body rather than the eyes alone.

Hunters showed a similar relationship. Animals pursuing quick prey had CFF values around 1.5 times higher than species that eat stationary or slowly moving food.

As a target continually changes position, a predator requires rapid visual updates to steer and strike. If food scarcely moves, however, slower visual signals can often suffice, enabling animals to save energy for growth or reproduction.

Taken together, these patterns demonstrate that perceptual speed follows ecological pace – rather than simply an animal’s lineage or body type.

Fast sight drains energy

Fast visual processing has an energetic price. To keep up with rapid change, nerve cells need to fire more often, requiring a continual supply of energy.

Briefer retinal integration windows speed up vision, but they capture fewer photons – the particles of light reaching the eye – in low-light conditions. This compromise is unavoidable in dim habitats.

In brighter settings, on the other hand, eyes can take in scenes in shorter intervals while still collecting sufficient photons to create a sharp image.

This may explain why high CFF values occurred most often in brightly lit environments, while dark habitats and deep water favoured slower processing that gives priority to sensitivity rather than speed.

Body size introduced an additional factor in aquatic environments. Smaller species generally saw more quickly than larger species, particularly when they lived and hunted in bright water.

Because smaller bodies can brake and turn rapidly, delayed visual information may hinder either pursuit or escape. Bigger aquatic animals commonly move with more consistent momentum, while their CFF decreased as body mass rose in high-light conditions.

The findings indicate that energy needs, habitat light, the physics of water and body structure all limit how far evolution can accelerate visual processing.

Electric lights and animal vision

The flicker produced by many electric lights may look like rapid flashing to wildlife, even though people perceive the illumination as steady.

“These findings suggest species with fast visual systems may be especially vulnerable to flickering artificial lights,” said Dr. Haarlem.

Creating outdoor lighting with more consistent output could lessen invisible stressors for animals that rely on rapid visual updates.

Evolution fine-tunes vision

The findings support Autrum’s hypothesis – the proposal that an animal’s senses are moulded by its lifestyle, rather than by chance features of evolution.

Depending on what most effectively promotes survival within a particular animal habitat, natural selection can refine eye cells and brain circuits for either speed or sensitivity.

Animals can occupy the same physical environment while their brains divide movement into strikingly different units of time, affecting how they hunt, evade predators and move through their world.

“Understanding how animals perceive time helps us understand how they behave, evolve, and respond to environmental change,” said Haarlem.

Acknowledging the close connection between perception and lifestyle may also allow scientists to identify which species are most at risk as environments change quickly.

Future studies could include further species and monitor shifts in lighting and habitat conditions – enabling conservation planning to better reflect how animals genuinely see and experience their world.