Love in the cemetery

Happy Valentine’s Day!

I live near Brompton Cemetery, a grand Victorian green oasis near Chelsea FC.

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The story behind this extraordinary gravestone is one of the more remarkable ones: https://en.wikipedia.org/wiki/Reginald_Warneford

But this week, the sun was shining, and everyone decided it was spring. The trees:

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The birds:

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You can hear this European Robin, Erithacus rubecula, song here:

And the squirrels, doing their Cirque du Soleil trapeze act imitations:

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After playing hard to get in a “mating chase”:

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She selected one from a trio of suitors, and there they enjoyed a precarious tryst high, high in the treetops. The tail says it all:

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She will have a litter of 3-4, after a gestation of 44 days. Females can breed at 10-12 months, and often have two litters per year. They may live to the age of 5, so at up to 8 young per year for four years, that is 32 young per female. There are about 2.5 million grey squirrels in the UK, and you can see why their introduction from the US has overwhelmed the more sedate British reds.

Their Chinese name is sōngshû, or ‘pine tree mouse’, 松鼠. The second character looks very mouselike!

PS My computer refuses to put the right accent on the ‘u’ in sōngshû. Sorry to those of you who know it should be a ‘v’ shape, not a little hat. 

 

 

Mirrors of the Soul

Most mammals (including the great apes) and many species of birds have dark brown eyes.

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We forget that humans are unusual in having a wide variety of eye colors: brown, blue, grey or hazel/green.

And in fact elsewhere in the animal kingdom, we find the same eye colors recurring. This Ugandan Grey-necked Crowned Crane, Balearica regulorum, has pale grayish-blue eyes.

Grey Crowned Crane

This Common Cormorant in Central London has eyes greener than those of any human outside Scifi movies:

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And this dragonfly goes one step further:

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But we also find eye colors that in humans would need contact lenses:

Look at this White-eyed Buzzard in India:White-eyed Buzzard

Or the lemon yellow eyes of the Indian Jungle Owlet:

Jungle Owlet

or the tawny eyes of the lion:

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and the tangerine eyes: of the Namibian Southern White-faced Scops Owl, Ptilopsis granti

Southern White-faced Scops OwlMaddest of all, the cherry-red eyes of the loon (aka Great Northern Diver):

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The dragonfly aside, the mechanism for all these eye colors lies in the outer layer of the iris, called the stroma. Dark brown eyes result from the presence of melanin in the stroma.  Blue eyes happen when the stroma contains no pigment and is translucent. This layer scatters the white light, and it scatters the shorter blue wavelengths the most, giving rise to the perception of blue eyes. If the layer has a little more collagen, the blueness is dampened and the eyes look grayish. Green eyes result from the presence of a little melanin only, mixing with the reflected blue to create green.

There are actually two types of melanin, and the full range of colors found in my photos above depends mainly on which type of melanin is found. Here is a great chart, if you’d like to know more.

Melanin Content and Eye Color

Eye color Melanin Presence on Front Layer of Iris Melanin Presence on Back Layer of Iris Dominant Pigment Type
Brown Heavy Normal Eumelanin
Blue Light Normal Eumelanin
Gray Even less than blue Normal Eumelanin
Green More than blue eyes, less than brown Normal Pheomelanin
Hazel More than green, less than brown Normal Pheomelanin and Eumelanin
Amber Heavy Normal Pheomelanin
Red or Violet (in humans) None or extremely little None or extremely little n/a

 

PS Humans are also unusual in having the colored iris surrounded by a large white area, the sclera. This makes it easy to notice the direction of other people’s gaze, a useful trait when cooperating with others.

Natural eye makeup

Many animals and birds have striking markings around their eyes, made of fur, feathers or just plain skin. Why?

Pale circles round the eye may help gather extra light for animals that feed in reduced light. Dark circles around the eyes may reduce glare for animals that feed in bright light. Often, though, these markings have no precise function. They either disguise the eye, or break up and confuse the head contours, or aid in species recognition. Here are some examples.

The American red squirrel has elegant white semi-circles above and below its eye, probably helpful in noticing predators when feeding in dappled light:

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Raccoons famously sport dark highwayman’s masks, but it seems unlikely that reducing glare is their main function, since raccoons are largely nocturnal:

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Wood frogs too have dark masks, and they live mainly in thick woodland, where the light is not bright. (Though the dark lines in front of the eye may help in accurately targeting prey.)

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But the Southern Masked Weaver’s dark mask may indeed be an adaptation to reducing the glare of the Namibian desert:

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And the Egyptian Goose, although this one now lives in Hyde Park in London, originates from Africa and so its dark eye circles may not just be the result of a late night out, but may have given it an edge in that bright light:

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My last few examples are almost certainly not aids to vision of any kind. Just like our eye makeup, they may serve to attract a mate. Whatever works for you…

In Maine, the wood doves have pale blue eye-liner: a look I am considering for next summer.

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In Ecuador, both the male Masked Trogon  (first photo) and the female (second photo) wear red-rimmed spectacles:

Male masked trogon.

Male masked trogon.

As does the Zambian Three-banded Plover:

Three-banded Plover

Here in the UK, the common blackbird has sharp yellow circles:

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But these are outdone by the Ecuadorian the Cock-of-the-Rock’s astonishing yellow goggles:

Cock-of-the Rock, orange variant on Eastern slope of Andes

Finally, by popular demand, the Plate-Billed Toucan: not exactly an eye ‘ring’, but the most flamboyant choice of eye shadow shades that I know:Plate-billed Toucan

Humans need more help:

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[James Charles is sponsored by Covergirl. He is the beauty blogger phenomenon who stopped traffic in Birmingham last week. ].

If you’d like to know more about natural eye makeup, read this:

Ficken, Robert W., Paul E. Matthiae, and Robert Horwich. “Eye marks in vertebrates: aids to vision.” Science 173.4000 (1971): 936-939.

PS There is a separate story about the color of the eyes themselves. Maybe I’ll look at that next.