Hectic lives for the smaller creatures — yet they manage to avoid collisions

Winter ‘murmuration’ season is under way: starlings wheel about in spectacular aerial ballet but don’t collide. This is how they avoid pile-ups...

Thu, 05 Jan, 2023 - 12:05

Richard Collins

Immanuel Kant argued that time and space are part of the furniture of our minds. We structure our perceptions, and our understanding, using them; the world, as it in itself, transcends space-time and is unknowable.

For Albert Einstein, time and space are relative. Each of us functions within a personal time-frame, flowing at its own rate; there can’t be absolute simultaneity. According to relativity theory, this applies to all moving objects, including animals.

Bird-watchers are well aware of an analogous phenomenon — the huge variation in the rates at which time flows for wild creatures. But this has nothing whatever to do with ‘special relativity’. It is down to another great law of nature: adaptation through natural selection.

A murmuration of hundreds of thousands of starlings fly over a field at dusk. That the starlings don’t collide with each other seems miraculous. How do they avoid pile-ups, we ask. Picture: Owen Humphreys/PA Wire

Now that the winter ‘murmuration’ season is underway, starlings congregate in huge flocks at roosting time. The birds wheel about in spectacular aerial ballet, a great natural spectacle. That the starlings don’t collide with each other seems miraculous. How do they avoid pile-ups, we ask?

Heart-rate can serve as a proxy for time flow. A starling’s heart beats several times faster than a person’s. The aerial gyrations of the birds in the sky seem dizzyingly fast to us, but to the starlings, they may be just ‘a walk in the park’.

A whale’s heart beats much more slowly than ours. If an ocean giant could visit an Irish town, it would be astonished that shoppers in the busy streets don’t crash into each other.

That birds live within radically different time frames to ours can be demonstrated experimentally. Starlings, renowned mimics, incorporate the calls of other species in their songs. In North America, the song of a local bird, the poorwill, is incorporated in the starling repertoire.

To our ears, there seem to be three syllables; ‘whip-poor-will’. When a sonogram is taken, however, a short fourth syllable is detected; ‘whip-poor-a-will’. Sonograms of starlings imitating the poorwill’s call include that fourth syllable. The birds’ ‘temporal resolution’, clearly, is far superior to ours.

Look away from a cinema screen and you’ll notice flickering from the succession of images being projected. The sequence on the screen appears continuous because we can’t detect the change from one frame to the next.

A study of 'temporal perception' in more than 100 animal species show that dragonflies have one of the fastest reactions — they can detect up to 300 images changes per second whereas humans manage only 65

Insects are not ‘film-buffs’. They would see each cinema frame individually, not as a continuously moving image. Research by Dr Kevin Healy, of the University of Galway, seems to confirm this. He has studied ‘temporal perception’ in more than 100 animal species.

Creatures exposed to flickering lights had the responses in their optic nerves monitored. Dragonflies and humble blowflies recorded the fastest reactions. They can detect up to 300 image changes per second.

Humans manage only 65 changes, while starfish were able to detect no more than 0.7 changes.

The smaller a creature, the faster its pace of life tends to be, the research shows. Shrews and tiny hummingbirds live what seem to be particularly hectic lives, with heart-rates exceeding 1000Hz. Elephants, the largest land animals, can manage only 30Hz.

Aquatic creatures tend to be faster than land-based ones. This enabled them to alter their trajectories while lunging at prey, an option not available in air.