Why do cats have vertical pupils? - Emma Bryce

Translator: Penny Martínez Reviewer: Xusto Rodriguez

Peering into the eyes of different animals,

Se te fixas nos ollos de diferentes animais,

you’ll see some extraordinarily shaped pupils.

verás algunhas pupilas con formas extraordinarias.

But why?

Pero, por que?

It turns out that pupil shape is a powerful indicator

Pois porque a forma da pupila é un poderoso indicador

of what role an animal plays in its ecosystem.

do papel que un animal ten no seu ecosistema.

Pupils mark the hollow opening in the iris,

As pupilas marcan a abertura do iris, esa zona pigmentada do ollo.

the eye’s band of pigmented muscle.

They’re the portholes through which light enters the eye,

Son os ocos polos que a luz entra no ollo,

where it then strikes the retina and activates light-sensitive cells,

para despois incidir na retina e activar as células fotosensibles,

setting the process of vision in motion.

poñendo en marcha o proceso da visión.

Pupils are black because most of the light that enters them is absorbed.

As pupilas son negras porque absorben a maior parte da luz que entra nelas.

Their size changes in response to brightness,

O seu tamaño varía segundo a claridade,

as well as certain drugs and emotional and mental states—

así como ante certas drogas e estados emocionais e mentais,

but their basic form varies greatly among species.

pero a súa forma básica varía moito entre especies.

House cats, for one, are twilight hunters with vertically elongated pupils.

Así, os gatos domésticos son cazadores nocturnos con pupilas verticais,

In the dark, these structures expand dramatically,

que se dilatan moito na escuridade, para aproveitar a luz dispoñible,

taking in the available light.

When it’s bright, they shrink into slits.

e que se converten en fendas cando hai moita luz.

In fact, cat pupils are so flexible that their maximum area is 135 times greater

As súas pupilas son tan flexibles, que a súa área máxima

é 135 veces maior ca a área mínima,

than their minimum area—

whereas our pupils only shrink and expand 15-fold.

mentres que as nosas só se contraen e se dilatan 15 veces o seu tamaño.

And because of how the slit pupil takes in light,

E debido á forma en que a pupila vertical recibe a luz

it creates sharp, vertical contours.

crea contornos nítidos e verticais.

When the cat’s brain processes the visuals from each eye,

Cando o cerebro do gato procesa as imaxes de cada ollo,

the small but sharp differences between them

as diferenzas entre elas, pequenas pero nítidas

help the cat judge the precise distance of its target.

axúdanlle a calcular a distancia exacta ao seu obxectivo.

In fact, many other ambush hunters also have vertically elongated pupils—

De feito, moitos depredadores de emboscada tamén teñen pupilas verticais,

but mainly those whose eyes are located closer to the ground.

pero sobre todo aqueles que teñen os ollos máis preto do chan.

This may be because these pupils are especially useful in perceiving objects

Iso pode deberse a que esas pupilas son especialmente útiles

para percibir obxectos nas distancias relativamente curtas en que soen cazar.

at the relative short distances these animals tend to hunt.

The world looks very different from behind the horizontally elongated pupils

O mundo vese moi diferente tras das pupilas horizontais

of many grazing and browsing animals, like goats.

de moitos animais que pastan e remoen, como as cabras.

These pupils, situated on either side of the head,

Esas pupilas, situadas a ambos os lados da cabeza,

let horizontal bands of light in that give the goat a near-360-degree view

deixan entrar bandas de luz horizontais, que lle dan á cabra

unha visión de case 360 graos e unhas imaxes nítidas e horizontais.

and provide it with sharp, horizontal images.

This helps goats detect any disruption to the horizon—

Isto axúdalle a detectar calquera cambio no horizonte,

alerting them to potential predators— while still enabling them to see ahead

alértaa de posibles depredadores, permítelle ver diante dela

and detect obstacles as they make their escape.

e detectar obstáculos mentres foxe.

In fact, goats always keep their pupils aligned with the horizon,

De feito, as cabras manteñen sempre as pupilas aliñadas co horizonte,

rotating their eyeballs in their sockets as they move their heads up and down.

xirando os ollos nas súas órbitas mentres moven a cabeza arriba e abaixo.

Meanwhile, nocturnal geckos have pupils that shrink into slits

Pola súa parte, os geckos nocturnos teñen pupilas que se contraen

studded with pinholes in higher light conditions.

en fendas con buratos se hai moita luz.

Each pinhole projects a separate, sharp image onto the geckos retina.

Cada burato proxecta unha imaxe separada e nítida na súa retina.

Scientists think that comparing these different inputs

Os científicos cren que comparar esa información diferente

might help the gecko judge distance without having to move.

pódelle axudar ao gecko a calcular a distancia sen ter que moverse.

And while they might have fooled you,

E aínda que se cadra enganáronte,

mantises and other insects and crustaceans have “pseudopupils.”

as barbantesas e outros insectos e crustáceos teñen “pseudopupilas”,

These aren’t optical structures;

que non son estruturas ópticas, senón ilusións ópticas do observador.

they’re optical illusions experienced by the observer.

Mantises have compound eyes composed of thousands of light-sensing units.

As barbantesas teñen ollos compostos por miles de unidades detectoras de luz.

When some are aimed at you, they appear black

Cando te ollan parecen ser negros,

because they’re absorbing most wavelengths of incoming light—

porque absorben a maioría das lonxitudes de onda da luz entrante,

but there’s no actual opening.

pero non hai ningunha abertura real.

So, why do we have round pupils?

E por que nós temos pupilas redondas?

Elongated pupils help sharpen certain dimensions of an animal's vision.

As pupilas alongadas axudan a afinar certas dimensións da visión dun animal.

But scientists think that, for animals like us with circular pupils,

Pero os científicos cren que, para animais coma nós, de pupilas circulares,

this is a lower priority.

esa é unha prioridade menor.

Instead of seeing some elements of a scene in extreme focus,

No canto de ver algúns elementos da escena moi enfocados,

we see a larger picture in relative detail,

vemos unha imaxe máis grande en relativo detalle,

which enables more general skills of observation.

o que permite mellores capacidades xerais de observación.

This may be especially helpful for foragers looking for food,

Isto pode ser especialmente útil para os buscadores de comida,

hunters eyeballing and chasing their prey,

os cazadores que xiran os ollos perseguindo as súas presas,

and social animals recognizing other faces.

e os animais sociais que recoñecen outras caras.

As we peer at different pupils, patterns emerge.

A medida que observamos as distintas pupilas, aparecen patróns.

And yet there are exceptions.

E aínda así hai excepcións.

For example, Pallas’s cats and mongooses are both small ambush predators,

Por exemplo, os gatos de Pallas e as mangostas son pequenos depredadores,

but the Pallas’s cat has round pupils and mongooses have goat-like pupils.

pero o gato de Pallas ten pupilas redondas e as mangostas téñenas coma as das cabras.

And we’ve only explored a few pupil shapes.

E iso que só exploramos unhas poucas pupilas.

Other animals have crescent- or heart-shaped pupils.

Outros animais teñen pupilas en forma de media lúa ou de corazón.

And the cuttlefish has perhaps some of the most bizarre:

E o choco ten se cadra unha das máis estrañas:

their pupils are circular in the dark, but W-shaped in the light.

as súas pupilas son circulares na escuridade, pero en forma de W á luz.

So, what’s going on here?

Por que?

Well, wouldn’t we all like to know?

Ben, a todos nos gustaría sabelo.