The smallest sprouts show there is really no death


Within Walt Whitman’s poem “Song of Myself” is a section known as “A child said, what is the grass?”  The narrator has been asked the question, and, after admitting that he does not know himself, attempts to answer anyway.

“I guess it must be the flag of my disposition, out of hopeful
          green stuff woven.
Or I guess it is the handkerchief of the Lord,
A scented gift and remembrance designedly dropped,
Bearing the owner’s name somewhere in the corners, that we
          may see and remark and say Whose?
Or I guess the grass is itself a child…the produced babe 
          of the vegetation.
Or I guess it is a uniform heiroglyphic, 
And it means, Sprouting alike in broad zones and narrow
Growing among black folks as among white,
Kanuck, Tuckahoe, Congressmen, Cuff, I give them the 
same, I receive them the same.
And now it seems to me the beautiful uncut hair of graves.”

It’s as if, through presenting these guesses, the narrator is working through his thoughts out loud until arriving at the final line, the assertion that grass seems to be “the uncut hair of graves.”  He is no longer guessing; and this confident decision leads into the second half of this section, in which the link between the living and the dead is examined.

But let us go back and examine the original question for ourselves: what is grass?  What is so special about it that it is cultivated and pampered for our lawns and landscaping, and yes, our graveyards?

This nearly ubiquitous plant belongs to the Gramineae family, which contains more than 9,000 species that are the dominant vegetation in many habitats, from grassland to saltmarsh, reedswamp and steppe.  In addition, grasses have adapted to thrive in rain forests, deserts, mountains, and intertidal zones.  Humans depend on grasses for an incredible number of things: for clothes, food, beer and whiskey, paper, sugar, plastics, and food for our livestock.

The grass plant itself can be annual (living only one year), biennial (two years), or perennial (comes back every year).  Most varieties are herbaceous, with a soft stem, though some are woody, possessing a permanent hard stem.  Leaves are always basal, which means they grow directly from the bottom of the stem, which is why the grass of your lawn grows back so efficiently after being cut.  See below for a diagram of the parts of a grass plant:

Diagram of grass parts.  (

Diagram of grass parts. (

So what’s so great about grasses?  For one thing, they’re a main part of many people’s diet worldwide.  Grasses provide our cereal crops as well as sugar, rice, corn, and feed for both wild and domestic animals (which we eat!)  Grass also cleans the air and conserves water.  Due to its sheer volume, grass traps more than 12 million tons of dust and dirt and to absorbs hundreds of pounds of sulfur dioxide each year.  This plant also traps water in its roots and prevents soil erosion; the average grassy yard can absorb more than 6,000 gallons of rainwater.  As an added bonus, the grass in your yard helps to keep you cool: according to Oregon State University, yards with grass lower the surface temperature of the ground 30-40 degrees when compared with bare soil.

So now we can think about the function of grass, and about its parts and its uses, but do these answer Whitman’s question?  After his initial musings, Whitman decides he knows what the grass is.  The poem changes at this point to be a tender meditation on the people who have gone before us, those unknown who have left only their names on a slab, or perhaps nothing at all but the uncut hair of their graves.

“What do you think has become of the young and old men?
What do you think has become of the women and
They are alive and well somewhere;
The smallest sprouts show there is really no death,
And if ever there was it led forward life, and does not wait
          at the end to arrest it,
And ceased the moment life appeared.
All goes onward and outward…and nothing collapses,
And to die is different from what any one supposed, and

 In this poem the existence of the grass gives Whitman hope about what happens at the end of our lives.  The people we loved are alive and well somewhere, maybe not as something we would recognize, maybe transformed by the magic of biology into something else, but not gone forever.  What I take from this poem is a reminder that life goes on, that though one’s physical body may decay, nature allows beautiful life to go on all around us every day, drawing strength and sustenance from those who have gone before.  And so birds keep singing, flowers bloom, and grass sprouts anew from a fresh-dug grave.


“Family Poaceae: Grass Family.”  Link.

Harris, Tom. 2002.   “How Grass Works.”  Link.

Henderson, Desiree.  2008.  “”What is the Grass?” The roots of Walt Whitman’s cemetary meditation.”  Walt Whitman Quarterly Review 25(3): 89-107.  Link.

Whitman, Walt.  “A child said, what is the grass?”  Read it here.

Each bolt a burning river


The oaks shone
gaunt gold
on the lip
of the storm before
the wind rose, 
the shapeless mouth 
opened and began
its five-hour howl;
the lights
went out fast, branches
sidled over 
the pitch of the roof, bounced
into the yard
that grew black
within minutes, except 
for the lightning–the landscape
bulging forth like a quick
lesson in creating, then
thudding away.

The opening lines of Mary Oliver’s poem “Lightning” are rapid-fire and breathless as the author describes the onset of a storm.  Summer is the time of year for thunderstorms, and in New England, we have been beset by one after another for days on end.  Do you remember being a child in a thunderstorm?  Perhaps you were afraid or enchanted or awed as the sky seemed to rip apart and you could imagine the earth itself trembling.  As adults, we have learned to stifle our most primal urges, yet a thunderstorm still gives us pause.  Step onto your porch or front step on a muggy afternoon just as those distant growls begin, smell the ozone and electricity in the air, and for just a moment, you can allow that same fear or enchantment or awe to take you over.

In order for a thunderstorm to form, there must be moisture and rapidly-rising warm air.  Since both moisture and warmth are required, thunderstorms occur most often in the spring and summer.  Once a thundercloud is formed, a charge separation develops within the cloud.  The inside of a cloud contains turbulent winds, water droplets, and suspended ice particles.  Drops of water in the bottom part of the cloud are lifted by updrafts to the colder top of the cloud, where they freeze.  At the same time, downdrafts within the cloud push the frozen ice and hail down from the top of the cloud.  As the falling ice meets the rising water, electrons are stripped off, creating a charge separation in the cloud.  The lost electrons accumulate at the bottom of the cloud, giving it a negative charge, while the newly positive unfrozen droplets continue rising, giving the top of the cloud a positive charge.

Charge distribution inside  a storm cloud.  (

Charge distribution inside a storm cloud. (

The cloud now has an electric field associated with it, one whose strength depends on the amount of charge in the cloud.  When the negative charges at the bottom of the cloud become strong enough, they actually repel electrons on the Earth’s surface, causing  a strong positive charge, which moves up to the top of the tallest objects. When the strength of the cloud’s negative charge overcomes the insulating properties of the surrounding atmosphere, lightning results.

The strong electric field in the cloud now creates a channel called a “stepped leader” which descends from the cloud seeking a path to the ground  (this happens faster than the human eye can see).  As it nears the ground, the negative charge is met by what’s called a “streamer” of positive charge that reaches upwards from the tallest object.  When the leader meets the streamer, a powerful electrical current begins to flow, and we see what we call “lightning” as  a return stroke barrels back up to the cloud at around 60,000 miles per second.  A lightning flash can contain as many as 20 return strokes.

as always, 
it was hard to tell
fear from excitement:
how sensual 
the lightning’s 
poured stroke!  and still,
what a fire and a risk!
Slow motion lightning.  Note the stepped leader prior to the strike!

Slow motion lightning. Note the stepped leader prior to the strike!

Thunder is caused by the creation of lightning.  In a fraction of a second, the lightning channel heats the surrounding air to temperatures around 18,000 degrees Fahrenheit.  The heated air expands rapidly, and causes a sound wave called thunder.  The different sounds we hear in a thunderstorm correspond to the different stages of the lightning strike: the initial tearing sound is caused by the stepped leader, the ground streamer causes the click heard at close range, and the main crash of thunder is caused by the connection between the two and the enormous amount of energy generated in a lightning “bolt”.  The reason why our perception is that thunder occurs after lightning is because light travels so much faster than sound.

So what explains the way we react to a thunderstorm?  What is it about electricity, noise, and light that results in such a visceral response in many people?  It is possible that thunderstorms are merely the most common way many people come in contact with nature on an epic scale; natural events like tornadoes and hurricanes, while terrifying, are much more rare.  There is a name for a fear of thunderstorms: astraphobia.  It occurs in adults as well as children, and is listed among the top phobias in the US.  Sufferers experience symptoms of anxiety, as well as increased interest in weather forecasts.  So in some cases, people never feel entirely safe with this weather phenomenon.  Some never escape that childhood feeling of powerlessness.

Mary Oliver’s poem swiftly and beautifully leads the reader from the rapid buildup of a storm through to its violent height.  The speaker is both terrified and excited–electrified, one might say–by the power all around.  Once again, I am amazed at how much science can be divined by the pure emotion of a natural event.  Oliver’s sensitivity to this storm allows her the ability to describe both the internal and external chaos:

As always the body
wants to hide,
wants to flow toward it–strives
to balance while
fear shouts,
excitement shouts, back
and forth–each 
bolt a burning river
tearing like escape through the dark
field of the other. 


“Lightning,” by Mary Oliver.  Read it here.  

“Lightning Basics.” National Severe Storms Laboratory: NOAA.  Link.

“Thunderstorm Basics.” National Severe Storms Laboratory: NOAA.  Link.

“What Causes Lightning and Thunder?” SciJinks: NASA.  Link. 

There are wonderful holes in my brain


One of the more terrifying diseases to appear in the last few decades is mad cow disease, scientifically known as bovine spongiform encephalopathy (BSE).  Unlike some other diseases in which the more you understand, the better able you are to cope with the concept, the more you understand about mad cow disease, the more terrifying it becomes.  This disease is a fatal brain disorder that is neurodegenerative, meaning it causes degeneration in the brain and spinal cord.  The incubation period for BSE ranges anywhere from 30 months to 8 years, and it is transmissable to humans, though the form of the disease humans contract is called “variant Creutzfeldt-Jacob disease” (vCJD).

This subject may seem an unlikely one for poetry, but then again, what is poetry if not a medium for discussing your deepest fears or exploring something from a new angle?  In her poem, “The Mad Cow Talks Back,” Jo Shapcott writes from the point of view of the mad cow herself, relating what Shapcott imagines the disease might be like:

I’m not mad.  It just seems that way
because I stagger and get a bit irritable.
There are wonderful holes in my brain
through which ideas from outside can travel
at top speed and through which voices,
sometimes whole people, speak to me
about the universe.  Most brains are too 
compressed.  You need this spongy 
generosity to let the others in.

This first stanza describes the main effect of the disease: an infected brain is so filled with holes that it resembles a sponge.

A section of brain from a BSE-infected cow shows the many sponge-like holes.  Photo by Dr. Al Jenny of the USDA.

A section of brain from a BSE-infected cow shows the many sponge-like holes.
Photo by Dr. Al Jenny of the USDA.

But what causes this disease, with its bizarre manifestation and fatal diagnosis?  Why is it transmissible to humans at all?  What can we do to prevent it?

Unlike most other illnesses we are familiar with, this one is not caused by a bacterium or a virus, or even a parasite.  Rather, the cause of mad cow disease and all other diseases of this type (called transmissible spongiform encephalopathies, or TSEs) is a prion.  A prion is, believe it or not, a misfolded protein that causes other prions to fold incorrectly.  That’s right: an infectious protein.  The strangest thing about a prion is that, unlike all other known infectious agents, it does not contain any nucleic acids (DNA or RNA).

Infection occurs when a prion enters a healthy organism and there induces normal proteins to fold into prion form.  The resulting structure is extremely stable and resistant to denaturation, a term used to describe a protein unfolding and losing structure as a result of chemical or physical agents.  Misfolded proteins aggregate into plaques, which cause the infected cell to die (leaving a hole).  The prions are then released to infect surrounding cells.

Since they don’t have any genetic material, prions are not alive, and so cannot be killed.  Measures to sterilize contaminated meat are extreme: incineration at 1000 degrees C (1832 degrees F!), autoclaving at 134 degrees C, boiling in lye for 15 minutes, or exposure to concentrated bleach for over an hour.  Since you can’t “kill” or inactivate prions by cooking or freezing, the best prevention is to completely avoid potentially contaminated meat.  To this end, the USDA has tightened restrictions on tissues known to carry mad cow disease (brain and spinal cord tissues) and bans “non-ambulatory” cows (those that can’t walk) from being processed for human consumption.

So, the progression of disease: a cow becomes infected by a prion, most likely through its feed.  Prions get into the bloodstream and cross into the nervous system.  Once in the nevous system, clumped prions kill the nerve cell, and the prions are released to infect surrounding cells.  Numerous nerve cell deaths lead to loss of voluntary muscle movement and abnormal behavior, including increased aggression and excessive reaction to noise or touch. Eventually, the cow can no longer walk, and dies.  Perhaps, as Jo Shapcott envisions in her poem, the brain goes so quickly that the cow doesn’t realize the horror of its situation.  Maybe the infected cow simply experiences things in a different way.  Though hard to imagine, we can allow this poem to give us hope that these unfortunate animals don’t go so harshly.  The cow tells us in no uncertain terms:

I love the staggers.  Suddenly the surface
of the world is ice and I’m a magnificent
skater turning and spinning across whole hard 
Pacifics and Atlantics.  It’s risky when
you’re good, so of course the legs go before,
behind, and to the side of the body from time
to time, and then there’s the general embarassing
collapse, but when that happens it’s glorious
because it’s always when you’re travelling
most furiously in your mind.  My brain’s like
the hive: constant little murmurs from its cells
saying this is the way, this is the way to go.  


“The Basics of Mad Cow Disease.”  WebMD.  2013.  Link.

“The Brain Eater.”  NOVA Online.  1998.  Link.

Freudenrich, Craig.  “How mad cow disease works.”  Link.

“The Mad Cow Talks Back.” by Jo Shapcott.  Read it here.

Max, D.T.  2007.  The Family That Couldn’t Sleep: A Medical Mystery.  Random House.  Buy it here.

Tenenbaum, David.  2004.  “Mad cow comin’ home.”  Link.

Weeds where woods once were.


“Between forest and field, a threshold
like stepping from a cathedral into the street–
the quality of air alters, an eclipse lifts,
boundlessness opens, earth itself retextured
into weeds where woods once were.”

Ravi Shankar’s poem “Crossings” describes something quite familiar to us all: the edge of the forest.  The speaker is struck by the clear division between a forest and a field, by how different it feels, even, to step from one to the other, from the cathedral-like hush of the forest under the canopy to the wide-open world of a field.  What Shankar is describing here is, in fact, an ecological phenomenon, one called an ecotone.

An ecotone is a transition between two biomes and can be regional (such as between an entire forest and grassland ecosystems) or local (such as the line between a forest and a field).  The name comes from the Greek  words oikos, meaning household or place to live (“ecology” is the study of the place you live!) and tonos, or tension.  So an ecotone is a place where two environments are in tension.

The most interesting part of an ecotone is how it allows for blending of the different organismal communities.  On either side of the boundary, species in competition extend as far as they can before succumbing to other species.  The influence of these two communities on each other is called the edge effect.  Some species actually specialize in ecotonal regions, using this transitional area for foraging, courtship, or nesting.

Terrestrial environments are not the only ones in which we can experience Shankar’s “threshold” between biomes.  There are also land-to-water ecotones, such as marshes or wetlands, and strictly aquatic ecotones, such as estuaries, where a river meets the sea.  Perhaps in these more dramatic transitions it is easier to see how some species can thrive in this unique habitat.

Even without knowing the biology behind ecotones, it is possible to sense the tension inherent in this boundary.  When hiking on a hot summer day, when the trail leads into a forest it’s like an exhalation.  We, as animals, sense the natural world much more acutely than society would like us to believe.  Ravi Shankar, using the skills of the poet to express what the rest of us cannot verbalize, notes this feeling, writing:

Even planes of motion shift from vertical
navigation to horizontal quiescence:
there’s a standing invitation to lie back
as sky’s unpredictable theater proceeds.
Suspended in this ephemeral moment
after leaving a forest, before entering
a field, the nature of reality is revealed.  


“Crossings,” by Ravi Shankar.  Read it here.

“Ecotone.”  Wikipedia.  Link.

Senft, Amanda.  2009.  Species diversity patterns at ecotones.  (Master’s thesis). University of North Carolina.  Link.

Darkness thickens our feathers


One of the greatest dangers to wild birds worldwide is predation by the domestic cat, Felis catus.  This issue has gained more attention recently with the proposed ban on cats in New Zealand.  In response to data that New Zealand cats had succeeded in killing off nine native species and endangering 33, economist and environmentalist Gareth Morgan suggested that cats should eventually be eliminated from his country.  New Zealand isn’t the only country with a problem, however: in a study of cat predation in the United States, kill rates were found to be two to four times higher than previously thought, with a median estimate of 2.4 billion birds killed each year.

Caleb Parkin’s poem “The Angry Birds,” addresses the threat of the housecat and the willful ignorance of its human owners.  Written from the point of view of a bird observing a hunting cat, a sense of dark foreboding hangs over each word:

Dusk.  The swish of the tear
in the door.  Silence.  The sky a cage
of black-blue branches.  Breathing.
A darkness thickens our feathers,
sticks to the points of our beaks.  
We petrify.  By the table of bait, 
it waits.  A first screech flickers
life into the street-lights.  Then–
reflected on narrow green eyes–
a manicured lawn of limbs.
The baby ape takes in tiger cubs.  
We watch you through the glass,
face alight, twiddling your thumbs.
Playing games in the night,
with our heads.
From up here, we look down on
the pastel television-picture within:
Kitty returns, is named, tickled under the chin:
delicately purrs at an opening tin.
And you, unwitting napkin,
with blood all over
your hunter’s hands.

In this poem, the human is “the baby ape” who has taken in “tiger cubs.”  This language emphasizes the ferocity of the cat, and the human’s position as unwitting ally.

The numbers involved from the previously-mentioned study suggest that cats are very likely causing population declines in some species of birds.  So why are we surprised that so many birds are being killed?  Most likely, this is because cat owners only see a small fraction of their cat’s prey.  A recent study by the University of Georgia with National Geographic obtained estimates of domestic cat predation by attaching video cameras to cats in order to investigate the cats’ activities.  They found that 44% of the cats they studied killed wildlife.  Of these predators, only 23% brought captured prey home, while 49%  left prey at the site of capture, and 28% consumed what they caught.  These results support that previous studies (and owners!) have been significantly underestimating the effect of cats on native wildlife.

So if even well-fed domestic cats are indicated in the decline of local bird populations, what’s a cat owner to do?  Obviously, keeping a cat indoors is the best solution to the problem.  If, for whatever reason, you need to allow your cat outdoor access, there are still steps to curb bird predation.  Never praise a cat that has caught a bird, since positive reinforcement will only enhance this behavior.  Keeping claws trimmed will hinder a cat trying to climb trees or catch wild birds, and a bell on the cat’s collar may warn birds of its approach.  Finally, never feed feral or stray cats.  The instinct to hunt is independent of hunger, and, simply, a well-fed cat has more energy to catch birds.  Report stray cats to a no-kill shelter or humane society.  Remember that, technically, cats are an invasive species, and it is within our grasp to control their effect on the environment.


Angier, Natalie.  2013.  “That Cuddly Kitty is Deadlier Than You Think.”  New York Times.  Link.

“The Angry Birds.”  by Caleb Parkin.  Read it here.

Loyd et al.  2013.  Quantifying free-roaming domestic cat predation using animal-borne video cameras.  Biological conservation 160: 183-189.  Link.

Morelle, Rebecca.  2013.  “Cats Killing Billions of Animals in the US.”  BBC News.  Link.

Mullany, Gerry.  2013.  “A Plan to Save New Zealand’s birds: Get Rid of Cats.”  International Herald Tribune.  Link.


Special thanks to Caleb Parkin for permission to use his work.  Please check out his blog, Skylab Stories, for weekly science poems, as well as various other creative writings.

Alive beyond compare.


“…the heart, exposed exactly for what it is: homelier
than we’d like to imagine.  And alive beyond compare.  
Here, the heart is the heart, and isn’t
a fist or a flower or a smooth-running engine
and especially not one of those ragged valentines
someone’s cut out, initialed, shot full of cartoon arrows:
the adolescent voodoo of desire.  Here, nothing’s colored
that impossibly red.”  

In honor of the holiday, I’d like to consider the human heart.  No, not the one usually found in poetry, but the one actually inside of you; the one functioning to carry blood throughout your body, the one transporting oxygen and nutrients and chemicals to every extremity.  David Clewell’s poem “Not to Mention Love: A Heart for Patricia,” is, as the title implies, a love poem written (almost) without the word “love”.  Clewell has tried to

“keep the heart in its proper place for once.  It’s not
in my mouth or on my sleeve  or winging its way lightheartedly 
in circles over my head.  It’s more or less right
where it belongs inside of me, no small thing.”  

So, dispensing with hyperbole and flowery romantic language, what we have left is the heart itself.  Put most simply, the heart is just a muscular pump.  But what is its function?  And how does it work?

Inside your heart are four chambers (fun fact: while mammals have four chambers, reptiles and amphibians have three, and fishes, without the need to breathe air, have only two).  The top two are the left atrium and right atrium (plural: atria), and the lower two are the left and right ventricles.  (The “left” and “right” designation always refers to the animal/person whose heart it is: so if a surgeon was looking down a patient, the left ventricle would be on the patient’s left).  Each chamber bears a one-way valve so that when the chamber is contracting, blood can come in, but when the muscles relax, the valve is shut.

The heart works with a two-stage contraction (the contraction phase is called “systole”).  In the first stage, the right and left atria contract simultaneously, pumping blood through their associated valves into the right and left ventricles.  In the second stage of contraction, the right and left ventricles contract simultaneously to push blood out of the heart.  This two-stage process is why you hear a heartbeat as two sounds “lub-DUB”–that’s the sound of your heart valves closing.  After the contraction, the heart muscle relaxes, a phase called “diastole.”  As Clewell writes,

“There’s nothing cute about it.  The heart 
is the heart, chamber after chamber.  Ventricular.  Uncooked.  
In all its sanguine glory.  I couldn’t make up a thing
like that.  The heart’s perfected its daily making do, the sucking
and pumping, its mindless work: sustaining a blood supply
that’s got to go around a lifetime.”  

(This last point is not exactly true.  Blood is, in fact, produced in the bone marrow).  In their contractions, the right and left sides of the heart fulfill different functions.  Blood returning from the body is oxygen-poor and enters the right side of the heart (atrium to ventricle).  The right ventricle sends this blood out to the lungs to be oxygenated (and to release carbon dioxide).  This blood then returns to the left side of the heart (atrium to ventricle again) where the much-larger left ventricle pumps oxygenated blood out to the entire body.

But it’s Valentine’s Day!  What about love?

What we call “love” is a combination of emotional attachment and brain chemicals.  Though we may seem to feel things in our “heart”, the heart really has only one thing to do with love: it acts to circulate the aforementioned brain chemicals (dopamine, serotonin, and oxytocin) in the blood out to the body and all the rest of the organs, where they can have the physiological effects that make us feel love.  Does this mean love is all in our heads?  Not at all.  It’s everywhere inside of us, thanks to our powerful hearts.

“Sure, there’s a brain somewhere, another planet,
just seconds or light-years away, and maybe some far-flung
intelligence madly signalling for all it’s worth–
but the heart wouldn’t know about that.  It has its own
evidence to go on.  What’s convincing to the heart
is only the heart.  It doesn’t have the luxury of stopping
to weigh, to reconsider, to fold and unfold the raw data of the world
until it’s creased beyond recognition.  Some days it can’t distinguish 
a single sad note from a chorus of exhilaration, but still
the heart has its one answer down to a science: yes.  Over
and over, the iambic uh-huh.  Whatever it takes, some kind of nerve
or unlikely grace: the heart never knows what to think.”


Bianco, Carl.  1999.  “How Your Heart Works.”  Link.

“Biological basis of love,” Wikipedia.  Link.

Boston Scientific.  2009.  “Heart Valves.”  Link.  (Check out the cool animations on this site as well!)

“Not to Mention Love: A Heart for Patricia,” by David Clewell.  Read it here.

Wilson, Sue.  2002.  “Red Gold: the Epic Story of Blood.”  Link.

The dead float back toward them.

Sockeye salmon photo by Phillip Colla.

Sockeye salmon photo by Phillip Colla.

Kim Addonizio is probably my favorite contemporary poet.  She can infuse such sadness, such wistful longing into her works, with a talent for such human description that is never too overwhelmingly emotional.  In her poem “Salmon,” she describes the experience of seeing adult salmon at the end of their long journey, laying eggs and then dying:

In this shallow creek
they flop back and forth and writhe forward as the dead
float back toward them.  Oh, I know
what I should say: fierce burning in the body
as her eggs burst free, milky cloud
of sperm as he quickens them.  I should stand
on the bridge with my camera,
frame the white froth of rapids where one
arcs up for an instant in its final grace.”  

The life of a salmon is unique among fish.  All Pacific salmon species are anadromous, which means that they are born in freshwater and spend their adult lives in saltwater, returning to breed in natal rivers.  After a 2-3 month incubation period, eggs in freshwater hatch into what are called alevin.  The alevin are still connected to the yolk sac, and continue to feed on it for the first few months while the mouth and digestive system develop.  See below for a great image of a freshly hatched alevin, complete with vascularized yolk sac:


Once the alevin consumes the yolk sac, it is called a fry.  Fry emerge from the gravel nest in the stream bed in order to feed (some species take off for the ocean at this point; others remain in freshwater for a longer period of time).  The salmon fry will begin to develop vertical stripes, at which point it is called a parr.  The vertical stripes are thought to act as camouflage, allowing the parr to blend in among the rocks and stream  vegetation.  Again, depending on species, the salmon parr stay in freshwater from six months to three years, feeding and growing larger in preparation for the journey out to sea.  When it is time, the parr lose their markings and turn a silvery color, at which point they are called smolts.  Smolts begin to school in large groups and gradually allow their bodies to become accustomed to salt water, often spending time in brackish water before finally achieving the ocean.  After a few years, the smolts have become adult salmon, and live entirely in a saltwater environment for 1-5 years.

One thing that I find incredibly interesting about the salmon is its anadromous lifestyle; the ability to move from freshwater to saltwater and then back without major trauma.  From a biology standpoint, this ability is simply amazing.  Saltwater contains about 1000 times more ions than freshwater (salt, sodium chloride, is broken down into its most stable form in water: sodium ions and chloride ions).  This is a problem for an animal living in either environment.  The internal environment of a fish, for instance, is optimized to be at an intermediate salinity.  The fish must have what is called an osmoregulatory system in order to maintain the balance of water and ion in its aquatic environment.

So, in freshwater, the fish is in an environment where its body is ‘saltier’ (contains more ions) than its surroundings.  To deal with it, its kidneys work to dump water; in other words, it urinates frequently.  At the same time, the fish takes in ions (there are a few, even in freshwater!) through its gills.

In saltwater, on the other hand, it is the opposite.  The surrounding water is much saltier (more ions!) than its body, and has the effect of being dehydrating to the fish.  To deal with this, a fish drinks a lot of water, but does not urinate.  Salt is stripped away from the water it drinks and is secreted by the gills.

Possessing the capacity to osmoregulate in either environment is a physiological miracle in itself.  Being anadromous means that a salmon can actually switch from one mode to another and back.  The first transition, from fresh to saltwater, is arguably the most incredible since during this period the smolts actually restructure their entire physiology prior to changing environments.

The return journey, back to freshwater, is no less amazing than the journey out.  Salmon return to the same rivers they hatched in to spawn.  A salmon is considered mature when it begins to change to a deeper color.  Male salmon prepare for combat by developing other striking features: a distinct hump, canine teeth, and a kype, or pronounced curvature of the jaws.  These mature salmon spend anywhere from a day to a week at the mouth of the river  and then begin to travel upriver, using the same route taken as a smolt.  This homing ability is thought to be facilitated in large part by the salmon’s sense of smell; they can actually smell where they were born and navigate towards it.

Salmon can travel hundreds of miles upstream to reach a spawning ground.  Very few survive the journey, and those that do manage to lay or fertilize eggs are beset by accelerated aging.  Their bodies begin to rapidly deteriorate right after spawning as a result of the release of massive amounts of corticosteroid hormones.  It is at this point that Addonizio observes the salmon, having fought hundreds of miles upstream to lay eggs and pass on their genes to the next generation, their bodies wasted and spent, rotting in the sunshine.  She refuses to shy away from this aspect of their lives, writing,

“I have to study the small holes
gouged into their skin, their useless gills, 
their gowns of black flies.  I can’t
make them sing.  I want to,
but all they do is open
their mouths a little wider
so the water pours in
until I feel like I’m drowning.  
On the bridge the tour bus waits
and someone waves, and calls down
it’s time, and the current keeps lifting
dirt from the bottom to cover the eggs.”


“About Pacific Salmon.” Pacific Salmon Commission.  Link.

“Salmon,” by Kim Addonizio.  Read it here.

“Salmon Biology”.  2010.  Salmon Fishing Now.  Link.

“Salmon”.  Wikipedia.  Link.


Jon Velotta was instrumental in writing an understandable explanation of osmoregulation.  Please go check out his research on osmoregulation in the alewife (a river herring).  His webpage is here.