Seeing What Animals See... Kind of

The contemporary author Andrew Parker writes:  "Today we live in a visual world."  It certainly sounds as if he's describing our contemporary urban societies.  Signs (mostly advertisements) sprout from every surface, all the way down to the tops of gasoline pumps.  Television (especially its commercials) uses more images per minute, trying to hold our attention .  Even our portable phones now use a visual screen.

stick insect
on end of a tree trunk

Andrew Parker was not, however, writing about modern technological societies.  Nor was the "today" he referred to even the past half-century.  Instead, his topic was what resulted from a development in biological evolution that began 500 million years ago -- the sense of sight. Parker's very next sentence describing some of this "visual world" also reveals that he is referring to the world of animals:  "There would be no such animals as stick insects, chameleons, or birds of paradise... if we did not [live in a visual world]." We have a clue as to what Parker means in that two of the animals he lists are familiar examples of camouflage:  A stick insect is hidden from predators because its body so closely resembles a stick.  A chameleon's skin changes colors to match that of its surroundings.

I enjoy watching shows such as PBS's Nature, whose cameras give me a peak into the world of such animals. On TV nature documentaries, however, the narrator usually talks about the evolution of the features of the stick insect, chameleon, or other camouflaged creature.  Andrew Parker points to the other side of the coin, which is equally important.  Namely, the evolution of vision in the predator who sees (or does not see) that camouflaged prey.

Those two sides of one coin thus demonstrate one type of what evolutionary biologists call co-evolution, which means that features of two species evolve in conjunction with each other. The two sides, camouflaged prey and seeing predator, evolved together -- each driving the evolution of the other. Camouflage is an example of one of the paradoxical forms of co-evolution. Part of the paradox is that predators have improved the evolution of their camouflaged prey, making what they want to catch harder to catch.  The paradox also extends to the other side of the coin: The increased camouflage of the prey improves the evolution of the predator species' eyes, making the prey easier to catch.  A sneeky, unconscious cooperation between what seem to be enemies.

This also means that as we look at Nature, a great deal of the diversity of appearances we see has resulted from the evolution of the eyes and power of vision in animals.  We see a world shaped by sight.  It also means that as I delight in looking at the almost amusing stick insect, I am also getting a glimpse into the vision and mind of whatever preys upon that insect.  Thus, in a way, I see some of what animals see... but only up to a point.  Through contemporary scientific research, we also know that some animals eyes can see things our human eyes cannot, such as the ultraviolet end of the spectrum.  To some degree, the worlds of other animals must remain their own, not meant for our eyes.

~~~

Do you remember every seeing an insect, lizard, or other animal whose color especially interested you?  Do you know why that species had evolved that way?

(The quotation by Parker is from Seven Deadly Colours, by Andrew Parker, © 2005.  p.265.)
(The photo of the stick insect is used under a under a
 Creative Commons Attribution-Share Alike 3.0 Unported license [no name given].)

Of Slugs and Slime and Snails

The 20th-century naturalist Gerald Durrell wrote that one of his earliest recollections as a child was of when he and his caretaker were walking along a dirt road in India.  The earthen road was wet from rain.  As he explains, he saw "two huge khaki-colored slugs brought out by the rain.... I remember squatting down and watching them, enraptured, seeing them slide over the earth without any legs to propel them.... To me, they were not only fascinating but, in their own way, as pretty as [an Indian woman] in her beautiful sari."

Durrell's adult caretaker was alarmed, pulling Durrell away from the "filthy" things. Understandably, even though it aids their locomotion, the sliminess of slugs and snails can be a turnoff to us.  But if we are self-reflective, I think we might conclude that such a repugnance comes from a natural concern about mucous discharged from our own bodies.  We should not blame the little animals for that.

Although both slugs and snail are in the same class of gastropods (having a single foot-pad beneath them for locomotion), snails have an edge on engaging practically-minded adults.  Snails, besides being candidates as food (which we delicately call "escargot"), have aesthetically pleasing spiral shells, sometimes used for jewelry.

sea slugs ("nudibranches")

Meanwhile, as we humans eat our escargot and make jewelry, in the deep ocean, cousins of the land-species live their own ocean lives.  The parallel to our land slugs are called either sea slugs or nudibranches, some of which are highly colorful.  Those marine slugs and snails speak of the ancestry of gastropods going back half a billion years.

Although in our everyday life we usually encounter a lone garden snail or garden slug here or there, some species can live in great concentrations in their usually hidden world.  I remember a biology teacher on a field trip probing into the continually damp ground on a river embankment. He wanted to show us what he thought might be the greatest concentration of snail's possible -- tiny ones, less than 1/4-inch in diameter, crowded "shoulder to shoulder," if it could be said that snails have shoulders.

Am I the only child who, when first seeing a slug, thought that it must be a snail that had somehow lost its shell? Am I the only child who felt a concern for the slug, which looked terribly vulnerable without a protective "house" on its back into which it could retreat for safety?  I cannot believe I am the only child who had such thoughts.

Placing that childhood recollection of mine beside Durrell's childhood recollection, I see similarities in the caring about something and in the finding something to be wondrous.  My caring, and Durrell's wonder.  Both having an element of child-fullness.  Maybe wonder, like caring, comes more from the heart than from the head.

~~~

Do you have any childhood or adult recollections of slugs or snails?  What are they?

(The Durrell quote is from The Amateur Naturalist by Gerald Durrell, © 1982.  p. 9.)

(Photo of blue nudibranches is by Alexander R. Jenner; that of the brown slug by Guttorm Flatabø [user:dittaeva].

Both are used under Creative Commons Attribution-Share Alike licenses.)

A Dog Named Polly

Neither Charles Darwin nor his dog Polly made it to the cemetery of the St. Mary's churchyard, which was where Darwin had wanted to be buried.  St. Mary's was a centuries-old flint-stone church in the village where he had lived most of his life.  But Charles Darwin did not get his way because people outside his family intervened, convincing his family that his scientific legacy called for his being buried in Westminster Abbey, where scientists such as Sir Isaac Newton, and poets such as Geoffrey Chaucer had been laid to rest centuries before.

With Darwin's burial at Westminster, it was not just a scientist who was laid to rest, but also a veteran dog-lover.  When Charles's future wife Emma was being courted by Charles, one thing that attracted her was the kindness he demonstrated toward dogs and other animals.  During the course of his lifetime, Charles had a dozen different dogs.

Charles's daughter
 Henrietta
with Polly

The last of those dogs, and Charles's favorite, was Polly, a terrier.  She had originally been given to one of Darwin's daughters, Henrietta, but when Henrietta married and moved away, her dog remained behind with the family. Polly would usually accompany Charles on his daily walks on a sandy path around the grounds of the home.  And when he spent hours in his study doing scientific research or recuperating from illness, Polly would often be found nearby, resting on her dog-bed.  Charles's son Francis recalled that his father "was delightfully tender to Polly, and never showed any impatience at the attention she required."

drawing of Polly from
"The Expression of the Emotions"

As with other animals Charles encountered, Polly also became an object for Darwin's scientific observation. (Even Charles and Emma's children could not escape his scientific interest in human and animal behavior.) Darwin's aim was to find similarities between not only the anatomy of humans and animals but also between their bodily behavior and facial expressions -- similarities that would be additional evidence of common ancestry. That decades-long project of Darwin reached its apex in one of the later books of his career, The Expression of the Emotions in Man and Animals.  That book contained a drawing of Polly, poised, pointing, with one front paw in the air.  The engraving was titled, "Small dog watching a cat on a table."

Polly, the pet who had become most deeply engraved in the affections of Charles Darwin's heart, died less than a month after he passed away.  Polly was buried under the apple tree near the Darwin home.  Being a dog, she would not really have been a candidate for burial in the graveyard of St. Mary's church, the place where Darwin also did not manage to be buried. And yet, then as now, pets were free of the complexities regarding cemetery plots, burial permissions, death certificates, and wills that can make human life complicated.  Nevertheless, Polly, being a pet, had helped Darwin make the case for his theory of evolution.  By including examples of the behavior of dogs, he had taken advantage of the similarities many readers had already observed between themselves and their pets -- animals with which they also had an emotional kinship.

~~~

Do you have a fond recollection of a particular dog?  What was the dog like?

(The quote by Charles Darwin's son Francis is from his "Reminiscences" in

 Selected Letters and Evolution of Origin of Species, ed. Francis Darwin, © 1892, 1958.  p. 74.)

(The drawing of Polly is in the public domain because its copyright has expired.)