Life in a Sandwich Board

Imagine living in a sandwich board.  Not one you could remove, like an advertisement people parade at busy intersections, but one that is made of your own bones and will be with you for your entire life.  No bending to touch your toes.  In fact, forget about touching your toes.  Forget about curling up, sitting down, even rolling over.  You can't breathe by expanding your rib cage, instead you have to pump air into your lungs using the muscles in your throat.  Now imagine that you need to swim around in order to survive.

Red-eared slider, Trachemys scripta. Photo: J. A. Gervais

This improbable body plan is actually a pretty ancient idea, because turtles have been using it, without major changes, since the Triassic.  In other words, over 200 million years.  Good ideas simply don't go out of style, and this good idea has endured ice ages, drifting continents, the disappearance of the dinosaurs, the appearance of mammals, and the arrival of the ape with the big brain and opposable thumbs.

The shell is an extraordinary piece of biological architecture.  Formed from the ribs and the spine, it incorporates the the carapace, or top shell, the plastron, or lower shell, and the bridge, the plates that hold the two together. The hips and shoulder blades are encompassed inside the rib cage.  Ultimately, nearly half a turtle's mass is bone.

Red-eared slider, Trachemys scripta.  Photo: J. A. Gervais

Life inside the shell has its advantages, in that you carry your fortress with you.  Although the shell offers some protection, determined otters and other predators have been known to pry legs or the tail free and gnaw them off.  There are no fast getaways, and if the fortress is breached, there isn't much that the turtle can do about it.

There are other drawbacks.  Reproduction is challenging, to say the least, when both participants are dancing in suits of their own unremovable armor.  The distinctly domed carapace of the female makes things more difficult, as does the fact that most female turtles are larger than the males.  The male turtles' plastrons are slightly dished, and their front claws are extra long, to help them hang on to get the deed done.  It's an awkward affair, but one that has worked well enough for a long time.

The shell has to grow with the turtle.  Each bony plate must grow in synchrony to keep the shell in its proper shape.  Turtles lay eggs, and unlike birds, they form a clutch and lay it all at once.  All those eggs have to fit in there somewhere, which is why females have taller, more domed carapaces than males.  Too big a shell wastes energy, both in its growth and in the effort needed to haul it around.  Too small, and turtles cannot gain weight to form their eggs, carry them til laying, or get fat to survive the winter- not to mention draw deep enough inside to be safe from their more nimble, agile enemies.

Turtle shells have worked so well they've not only been around for millions of years but turtles and tortoises also occupy all continents except Antarctica, in habitats ranging from the deep ocean to deserts.  They can survive in some pretty degraded environments, appearing to be much more robust than many other vertebrates to pollution, reduced water quality, and other challenges thrown at them in recent times. 

This pond supported turtles...  Photo: J. A. Gervais

However, the ape with the big brain and opposable thumbs may be too much for them, as wetlands disappear and turtles fall victim to roadways, over harvesting, the pet trade, and other human activities.  With a little care, however, at least a few may survive for another few million years, moving through time in that same cautious, patient manner that has served them so well for so long.

Delphinium

I first noticed that they had all vanished along the creek bed near the road the first day of summer.  Farther up in the shadier parts of the forest, a few still linger, but their wrinkled, faded appearance suggests that they, too, will soon disappear.  Below the last faded flowers, fat pods are forming, swelling with the seeds of a spectacular display in the future.  The Delphinium flowers of the western Oregon woods belong to spring, however, and their season is now over.

I begin watching for Delphinium long before the buds have even formed.  The leaves begin pushing up in February, a welcome sign of spring after a long, dark, wet winter.  By April, the plants are beginning to form their buds, and the first flowers appear at the end of the month. 

Photo: J. A. Gervais

The flowers are a brilliant deep bluish-purple, a color so intense one friend remarked that it makes your teeth hurt.  They seem to glow, and I can only imagine what visual signal they send to bees and other insects that can see in the ultraviolet spectrum.  That incredible blue colors not only some of the petals but also the sepals, which form the star-like form of this flower and the long trailing spur that give this flower its common name, larkspur.  The true petals are small and held tight in the flower’s center.  The topmost petal arcs white in color, a bright flash in a field of midnight blue.

The genus Delphinium is large, with several hundred species currently recognized.  Individual plants growing in different places vary dramatically in size and form, and Delphinium species can hybridize with one another.  Keying them out often involves digging them up and studying their roots.  I’m pretty sure that the larkspurs growing along the shady creek banks in the forest above me are Delphinium trollifolium, but I haven’t dug one up to fully key it out.  I don’t need to know so much that I’m willing to murder a plant that each spring gives me such a marvelous gift.

Photo: J. A. Gervais

Hummingbirds, bees, and butterflies visit Delphinium flowers for their nectar.  The plants however contain an alkaloid compound that is highly toxic; although some insects use it as a host plant for their larvae, Delphinium has frequently been responsible for livestock poisoning.  Presumably, wild grazers learn to leave it alone.  So it grows locally in dense stands of stunning color, heralding in the growing season even when overcast and wet weather in western Oregon continues.  It may be raining, but there is still cause for celebration.

The flowers remind me of dark velvet stars, each with a comet’s tail trailing behind it as it leans out from the stem.  Or they might be little people, arms and legs outstretched in a joyous leap.  Flowers are structures evolved with the sole purpose of ensuring cross-pollination and the production of viable seeds.  Delphinium burst forth each spring to mark the renewal that arises only from the loss of those that came before.

Photo: J. A. Gervais

Bananas in the woods

It is finally getting warm here in western Oregon, but it is still very humid so the banana slugs (Ariolimax columbianus) are still active.  I have a soft spot for banana slugs.  The idea of a six-inch long monster yellow slug that looked like a piece of overripe fruit seemed too far-fetched to believe when I knew them only by reputation.  I was delighted to find them just as large and spectacular in life as legend made them out to be.  My interest in them from a biological point of view began while I was doing research for my Master’s degree, on the seed dispersal dynamics of salmonberry in the Oregon Coast Range.  One rainy afternoon in early June, I looked down and realized there were a dozen massive slugs slowly working their way through the tangled vegetation within the bounds of my one-meter-square quadrat.

Photo: National Park Service

That’s a lot of animal when you look at it from a biomass standpoint, even if the animal possesses a very slow metabolism.  Slugs eat everything, from fungus and fruit to their dead kin and other animals’ feces.  Mostly they are herbivores.  Work in the 1970s demonstrated that slugs can affect plant community composition in the forest understory.  They also act as a host to a number of generalist parasites (another good reason not to eat one, even if the slime didn’t put you off), and they likely disperse the spores of fungi as well.  In other words, slugs do stuff to their environment. 

I found salmonberry seeds in their droppings and asked the obvious question: are they seed dispersers, or seed predators?  I set up ten Tupperware slug houses, raided the nearby forest for volunteers for science, and kept ten slugs going on potato, carrot, and fresh lettuce in addition to the salmonberries and other wild fruits in my living room.  You could actually hear the slugs chewing.  Fortunately, my roommate thought this was intriguing if a bit weird.  After the animals obligingly ate a series of fruits from the local forest, I let them go, perhaps a bit fatter than they were before.

Salmonberry (Rubus spectabilis) and its two color morphs. Photo: J.A. Gervais

I planted the seeds, and discovered that banana slugs do disperse viable seeds, although their gut kills some of them.  Interestingly, red salmonberry seeds were more likely to die during gut passage than orange ones.  All of the other seeds from native plants producing fleshy fruits also were capable of germination.  I tried to use the word “molluschrory” to indicate this novel dispersal agent of seeds, but my co-author on the paper, ecologist Mary Willson, shot that down.  It is hard to have your tongue in your cheek in a scientific paper, apparently, and have others get the joke.

Slugs aren’t the most spectacular seed dispersers, because in the twenty four hours that it takes them to pass a seed, they don’t go very far.  In fact, slugs have fairly small home ranges with a number of shelters that they will return to repeatedly, following their own slime trails around their neighborhood.  The slime they secrete under the muscular foot is astonishing in itself.  Slugs change the chemistry of the slime according to their needs, secreting a more watery version when traveling along the ground, a tough cord they use to rappel down from the heights of a shrub, and thick viscous goo to deter predators.  They can change the composition of the slime to fit the circumstances, and the chemistry can be altered in a matter of minutes.

Predators can track the slugs from their trail of slime, so their trails may work against them.  One slug, the jumping slug (several species in the genus Hemphillia) actually twists off its slime trail, breaking the chain of evidence a predator might use to track it down.  Another slug, the tail-dropper of the genus Prophysaon, drops a bit of its tail to distract a predator while it makes its getaway.  I am not making this up.  The banana slug has no such defense, and must either outrun or hide from its enemies, which include predatory ground beetles, snakes, Pacific giant salamanders, and even other slugs.  You can blink more than once while watching a predatory slug hot on the trail of a fleeing banana, but it is still a race of life and death for the participants.

The magnificent blue-gray tail-dropper (Prophysaon coerleum), photo: USDA Forest Service

Scientific literature is not often very amusing, but one of the best papers in my collection describes how to individually mark slugs by freeze branding them.  The publication included illustrations of miniature brands and instructions on how to use dry ice to do the deed.  The spotted slugs’ markings are unique to the individual, so photographic records work for identifying them.

Getting to know slugs as individuals revealed that banana slugs can reach at least six years of age in the wild.  They aren’t prolific egg layers, relying on their longevity to produce enough young to carry the species.  Simply put, a nice-sized banana slug may be older than the vast majority of mammals on earth.

 The study of banana slugs pretty much petered out 30 years ago, although the Northwest Forest Plan did at least pay them lip service in terms of requiring that forest managers survey for them.  It is good to remember there is a great deal we don’t know about our fellow travelers, even the ones right underfoot.  Step carefully.

Lost in Space?

I was scanning the pages of a scientific journal one evening and fell upon a guest editorial that made me fall out of my chair. Two scientists from a respectable institution suggested, with all apparent sincerity, that the best way to avoid the extinction of humanity would be to colonize outer space. 

This immediately brought to my mind the image of the interstellar community frantically deploying some kind of cosmic germ killer to deal with the infectious blob spinning off from our mortally wounded biosphere.  What have we done here to deserve welcome anywhere out there?  Our record of stewardship is not good.  We have not been kind to any life forms that have had the misfortune to be present when we have colonized new territory- not even members of our own species.  Those of us left behind could only hope that any life forms out there would not have a view of epidemiology that included going after the source of the incipient infection.

Venus bus probes, image from NASA.

 

Humor aside, there are some very troubling aspects to this argument.  I was surprised and disappointed that such a view could be espoused in an ecological journal.  Ecologists, of all people, should appreciate the intricate, invisible bonds that tie us to the biosphere of this planet.  The history of the evolution of this biosphere is inseparably bound within us, from the micro nutrients we need, our bodies' metabolism, and the bacteria that live in our digestive systems to our circadian rhythms, set by the sun as we move around it with our planet Earth.  We have proven we can survive, briefly, out of the context of our world, but do we really have the arrogance and hubris to believe we can recreate everything we need somewhere else, when we have only the shallowest understanding of the interrelationships here that sustain us?  Ecologists should know better.

Home Sweet Home

View of Earth from Apollo 17. Image from NASA

There are even more disturbing aspects to this argument.  Who's going to get to go? There are nearly seven billion people here.  Do we really think there can be a morally justifiable process to pick those few?  What traits would we choose?  There is a saying regarding China- if your talents make you one in a million, there are ten thousand people just like you. That would mean seventy thousand just like you throughout the world. Are we willing to deliberately condemn most people to linger on a dying planet while we pour the last of our scarce resources into flinging those few into space?  How could those few live with that decision?  Even worse, what if they could? What would that say about the values and ethics that we chose to propagate beyond our planet's boundaries?

It would take a tremendous investment of resources, including non-renewable ones, in order to succeed.  Even if we decide that we do not care about the moral implications of allowing billions of individuals of our own species, not to mention all the rest of the life forms, to suffer slow death on a ruined planet, why do we think those condemned masses would allow the chosen few to despoil the remaining resources of the planet in order to make their getaway?  And again, the fact that a few might be willing to ruin the futures of so many also says nothing good about the values and attitudes we would be broadcasting into the cosmos.

Unfortunately, this really isn't a hypothetical situation.  There are a chosen few who are already busy destroying the futures of the many, apparently without a single second ethical thought.  Our goal is not to colonize the final frontier, but simply to espouse a lifestyle that happens to extend far beyond our ecological means.  Ironically, it is a lifestyle that frequently leaves us frenetic, sick, and miserable in addition to creating a tremendous delayed cost that our children will have to bear.  The chemistry of our atmosphere, oceans, and even the soils are changing rapidly.  They are not changing in ways that will enhance our survival.  It is sad indeed that ecologists are not at the forefront of sounding the warning, and leading the way in reinventing our society so that we are not committing an act of genocide whose victims will include all of us and our children.

View of Earth from the moon. Image from NASA.

I can imagine that little space capsule spinning out of the Earth's orbit, carrying the seed of incipient disaster to new worlds blissfully ignorant of the fate that awaits them. Out the little window, a message forms in the clouds over the small planet they leave behind:

Do not enter. Toxic dead zone.

Surely we can do better than that.

Swallows

The violet-green swallows are back, wheeling under lowering clouds threatening more winter rain, even though the pasture grass is greening up and the spring wildflowers are defiantly blooming.  These plants are not pollinated by honeybees, but rather by beetles, bumblebees, and other animals less prone to an unusually cold, late spring.

Violet-green swallow, Tachycineta thalassina. Photo by Tom Munson

The swallows are back.  Their internal drives told them to head north into the teeth of cold wind, rain, and hail.  The day I first saw them this year was hardly in the mid-40s, with a sharp-tongued wind laying bare the fragile promise of my jacket.  I wondered if there were any airborne insects for the birds, between the cold and that wind.

These birds spend the northern hemisphere winter in South America, a long way away. They make their way there and back again on those marvelous, fragile wings, guided by the shared hertitage twisted into the strands of their DNA.  We call it instinct, which means we don’t know how they know.  At leas, it doesn’t appear to be knowledge acquired only through the individual’s own experience.

Animal navigation has been the subject of a great deal of human curiosity and research, and we are slowly making headway in understanding the cues that animals use when traveling over vast differences.  Recent work with loggerhead sea turtle hatchlings suggest that the hatchlings use magnetic forces in the earth to find their way, both with respect to latitude, their north-south position, and longitude, their east-west position.  The magnetic field isn’t consistent particularly on the east-west gradient, but the variation through space may be sufficient for the hatchling turtles to recognize their position and make their huge circuit of the Sargasso Sea. 

Loggerhead sea turtle, Caretta caretta. Photo credit: NOAA

Birds also use magnetic cues to find their way.  However, their ability to navigate is also clearly influenced by their experience.  When a biologist captured and transported south-bound starlings en route from northern Europe in the Netherlands and released them in Switzerland, the adult birds compensated for the sideways shift, but the young birds did not.  Juvenile barn swallows responded to magnetic cues when skies were overcast, but didn't do so otherwise. Different birds use different methods of migration, a result of the behavior having evolved again and again. Landmarks and stars and the sun all are used to some extent.  Migrating birds travel enormous distances and risk death if they arrive in the wrong place.  No wonder they draw their navigational information from many sources.

The feat is perhaps all the more spectacular for braiding together multiple lines of evidence, experience, and instinct in a brain we are more likely to mock than admire.  However they do it, I’m glad the swallows found their way back to our pastures again.  Their astonishing flight seems more an aerial celebration than simply a means of survival.

One Becomes Three

Our old ewe decided to do us a favor and drop her lambs in the middle of a relatively pleasant Sunday afternoon, when we would be easily available to help her out.  She's taken advantage of our assistance during the two previous lambings, even when the lambs are lined up nicely without tangled legs or twisted heads, and ready to go with a good push.  Buttercup doesn't seem to want to push anymore.  Maybe she's decided she's too old for heroics when there is help available.  She's a wise old sheep.

Dan begins the assist, drawing on the front legs of the lamb.

The lamb is almost out.  They are incredibly slippery.

Touchdown!

First wide-eyed look at a new world.

Buttercup does her stuff.

With an assist, the new lamb is soon delivered onto the straw, and the old ewe immediately begins cleaning off the membranes and fluid, rasping steadily with her rough tongue and chuckling away.  Sheep have a special gutteral bleat they use just for their newborn babies.  The lamb soon answers, a high-pitched protest.  What must it be like, to go from tight hot darkess, into cold bright light and too much space in a matter of seconds?  The lamb works to rise, stumbling and flopping forward and sideways.  She soon has mastered tucking her shockingly long legs tight under her body, and within a few minutes of that, she can rise and stand.  At this point, we deliver the second lamb, and while Buttercup begins another round of cleaning and chuckling, the first lamb finds her udder, and after several long minutes of apparent confusion, she takes her first meal of rich milk.  The second lamb soon follows.

Despite thousands of years of domestication and intense selective breeding, they all know what to do.  It is easy to understand the need for a wild lamb to quickly climb to its feet and feed, and be ready to either run or hide within minutes of its birth.  It is harder to imagine the slow steps along that evolutionary journey, the process of encoding these complex behaviors into genes piece by piece.

This morning we only had one sheep, our old ewe with her low-hanging udder and enormous swollen body, standing a bit dejectedly by the fence.  The ewe is now fired up with a new purpose, both protective and nuturing, carrying on the instructions that have carried life through the ages.

So one became three.

Postscript. This morning I rode my bicycle by the pasture at dawn, and saw Buttercup resting in the shed with her two lambs curled up in tight black commas beside her.  It was cold last night, with a light frost.  Imagine your first day, watching an overcast afternoon fade into nightfall and cold moonlight.  You keep warm by pressing one side of yourself into your dam, while the little meal of milk that is all your stomach can hold has to fire up your body heat, something you've never had to do for yourself before.  What is that like for a lamb, or any other newborn animal that is born aware of its surroundings?  The sun was just edging up over the ridge when I saw them this morning, washing the hilltops with the promise of a day without rain.  The lambs looked out from their shelter at their lives opening out before them.

Soundscapes

I bought a small tape recorder recently, and decided to record the chorus of Pacific tree frogs in a nearby wetland next to our road.  I chose a nice warm rainy night and the frogs obligingly sang their hearts out, for love, for mates, for genetic fitness, maybe just for the sheer joy of it.  Whatever the reason, they filled the darkness with their urgent sound.

I couldn't record for more than a minute or so before the performance was interrupted by the sounds of tires on wet pavement, leaving a lower-intensity backwash of sound in the vehicle's wake.  The frogs kept singing through most of the interruptions, which was a good thing or they would have lost much of their stage time even on this relatively quiet dead-end road.  It got me thinking of how all the racket we make affects other organisms.

Pacific Tree Frog, Pseudachris regilla.  Photo: thewakingdragon

We are a visual species, despite using sound extensively for intraspecific communication.  If you sat down and described your favorite place, would you include sounds at all?  Even when we talk about concepts, we use visual imagery: as you can see from the big picture, if we took the long view, we could see the problem through to its logical conclusion.  We don't even have the language for a soundscape.  Do we call it the big audio?  The whole noise?

Bryan Pijanowski and four colleagues explore the ecology of soundscapes in a review article recently published in the journal Bioscience. The basic working idea is captured by the Sender-Propagation-Receiver model, where the sender's biophysical characteristics and intent shape the form of the message.  The message may be further modulated by its passage through the physical environment, and its ultimate effect depends on the perception and interpretation of the recipient.  The male frogs' individual success not only depends on the quality of the competition, but also the ability of their calls to carry successfully to the ears of female frogs who will undersand the message- and respond as the males desperately hope they will.

Pacific tree frog, Pseudachris regilla, singing. Photo: GregTheBusker

You can also break sounds down into three general categories.  Geophony describes the sounds of the natural environment that are from physical processes.  Think of the sound of wind hissing across long grass, the sharp pure crack of rockfall, or the extraordinary sound of moving water.  Biophony are noises made by living organisms, although Pijanowski and Company seem to reserve the term for non-human organisms.  Birdsong is obvious; the sounds of a slug munching vegetation, or the whir of a beetle's wings, a little less so.  Finally, the sounds made by Homo sapiens are classed as anthrophony.  It is probably a relevant distinction, because even though we're very much a part of the biological fabric, the vast majority of the noise associated with us is empty of meaning.  Think lawnmower, or air conditioning, or the sounds of vehicles on wet pavement.  That's not to suggest chewing slugs are communicating, but the noise is relevant to slug predators such as ground beetles or garter snakes.

Do we affect the natural world with our racket?  There is a great deal of concern now about ocean noise pollution interfering with the communication and navigation of marine life.  European robins shift the timing of their song in noisy environments.  Song sparrows shifted the lower-frequency notes upwards in their songs, and great tits use higher pitches when confronted with more ambient noise.  In short, the din of civilization has an impact, one we are just starting to recognize and measure.

Song sparrow, Melospiza melodia.  Photo by Alan Vernon

Our cacophony of meaningless noise may have another undesirable effect, this one on us.  We fill our leisure time with the sounds of music or podcasts or television, which have become so portable we can take them right into the very heart of biophonic and geophonic symphonies in progress.  Hearing loss is so obvious and so well publicized it hardly bears mentioning.  But, if we navigate our world by cultivating the skill of blocking out the sounds surrounding us, how well can we listen and actively hear when confronted with an environment that demands it?

Fortunately, very few of us need worry about the signals of natural sound.  We might miss the sudden snap of a branch broken by the deer, the liquid silver of moving water, or the sex calls of frogs, but our lives don't immediately depend on our hearing those signals.  But, by choosing to venture into natural environments without opening ourselves to one of the major dimensions of experience they offer to us, we do perhaphs further alienate ourselves from our biological roots.  Further losing our sense of place on this small planet may not be a matter of just making meaningless noise.