Biology / Wildlife

Die young, live fast?

Ground squirrel or chipmunk running

Photo credit: Kevin Saff

Whatever you do, don’t take your pigeon to the cinema. I’m not sure why you’d consider it, but your movie-going experience would be considerably different, as your poor pigeon companion would be observing a rather slow, boring slideshow, whilst you’re on the edge of your seat watching Bruce Willis save the world. Again.

Imagine looking out from the eyes of a golden-mantled ground squirrel, with every second containing twice as much information. Suddenly you’re looking through a microscope at time, with every second containing much more action than you previously perceived. Maybe you’d be able to dodge bullets, Matrix-style.

A team of scientists from Trinity College Dublin, including researchers from the University of Edinburgh and the University of St Andrews, have recently published a study in the journal Animal Behaviour that investigates the links between animals’ pace of life and how they perceive time. They found that smaller animals, with high metabolic rates, had the fastest critical flicker fusion frequency (CFF), which is the lowest frequency of flashing at which a flickering light source (like a television in the above example) is perceived as constant.

Understandably, the power of perceiving more information per second comes with high energetic costs, for both the eyes and the brain processing the images. But for some animals, like swordfish, the skill of being able to closely track agile prey’s swift movements is a price worth paying. These speedy aquatic predators actually invest extra energy into warming their eyes and brain 10-15ᵒC above the water temperature to keep their vision sharp and quick.

The study compared the resting metabolic rates, body mass and environment light level of thirty four species of mammals, reptiles, amphibians, birds and fish. Their results showed that animals living in lower light levels (eg. Nocturnal) invested less in their CFF, whereas animals living in higher light levels have more need of it. A good example of this is comparing the small short-eared owl (CFF 70), which often hunts voles during the day, with the large great horned owl (CFF 45), which hunts small mammals under the cover of night. Those with a smaller mass, good manoeuvrability and high metabolic rates observe the world on the finest timescales. These are often prey animals that rely on being able to spot predators approaching and react quickly. But these impressive skills don’t compare to that of invertebrates- flies can observe light flickering at four times faster than we can, which explains their amazing ability to escape just before a hand manages to swat it.

Dr Luke McNally from the University of Edinburgh described how this might be advantageous, “Animals may also use variation in time perception to send covert signals, for example, many species using flashing lights as signals, such as fireflies and many deep-sea animals. Larger and slower predator species may not be able to decode these signals if their visual system isn’t fast enough, giving the signallers a secret channel of communication.”

The speed of the human eye was less than dogs, chickens and pigeons, but faster than domestic cats, rats and most reptiles investigated. But other investigations into human light perception shed some interesting facts on our limits. A 2010 study called ‘Bending It Like Beckham: How to Visually Fool the Goalkeeper’ described how human sight struggles to track spin-induced acceleration, explaining why curved free kicks in football are the best way to fool the goalie.

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