The Mighty Dragonfly

Of all insects there are few that capture our attention and interest the way dragonflies do.  They have, perhaps, the coolest, most evocative name of any group of insects: Dragonfly.  In English there are a great number of other common categorical names: Devil’s Darning Needle, Snake Doctor, and Ear Cutter among others.  Many of these names come from the mystifying apparent fear of nature that crops up over and over in European views of the world.  Many European cultures viewed dragonflies as sinister creatures, servants of the devil, in league with other evils such as snakes and bats.

Other cultures, often more agrarian ones, had a far more benign view of dragonflies, based, perhaps, on the recognition of their fundamental role in controlling populations of pest insects of all sorts.  An archaic name for the Japanese Islands is Akitsushima (秋津島), the Dragonfly Islands, where dragonflies symbolized courage, strength, and happiness.  For some native American tribes dragonflies symbolized clean, pure water, swiftness, and agility.  In the modern world dragonflies are good indicators of environmental heath, indicating a robustly functioning ecosystem.

Libellula quadrimaculata – Four Spotted Skimmer
The Alaskan State Insect

Dragonflies and their close relatives, Damselflies, come in a dazzling array of colors and patterns, ranging in size from less than  an inch long up to the South American Megaloprepus caerulatus with a wingspan of over 7 inches.  The largest dragonfly we know of is from the 300 million year old fossil Meganeura that had a wingspan of over 2 feet.

Dragonflies are powerful hunters, both in their nymph and adult stages.  Dragonfly nymphs are aquatic and prey on any animal or insect they can grab with their claws or their extendible jaws.  Insects, small fish, tadpoles, and small amphibians are all food for these voracious predators.  The nymphs are large, and, in turn, are prey for a wide range of other animals, insects, birds, and fish.  Elva Paulson has some wonderful watercolors of a dragonfly emerging from its nymph stage.  Humans are included as predators, many Asian cultures eating both dragonfly nymphs and adult dragonflies as delicacies.  One of the most tasty things I’ve eaten (from a long list of foods most people would consider to be unusual) was a plate of deep fried dragonfly larvae.  Absolutely delicious.  In Beijing I would sometimes find adult dragonflies candied in liquid sugar, their wings crispy with the hardened sugar.

Unknown green dragonfly – note the barbs on the forelegs for catching prey

The adult phase of a dragonfly’s life is short, in temperate climates only the length of the summer.  This is their mating stage and it takes them between 2 months and 6 years living under water to reach this stage.  Dragonflies are extremely active during this mating phase and must eat often.  They have enormous eyes giving nearly 360 vision, incredibly swift reactions, fast, powerful flight, and wicked barbs on their legs to assist capturing insects in flight.  The inset above shows these barbs.

Libellula exusta – White Corporal (I think)
eating its prey

The common names of dragonflies often reflect their speed or their abilities as hunters.  Meadow-hawk is one of my favorite names, and watching one dart away to catch an insect and return to its roost to devour it definitely brings hawks to mind.

Libellula quadrimaculata – Four Spotted Skimmer
note the different wing heights

Dragonflies are powerful fliers.  They have been clocked at over 35 miles an hour, fast enough to get a speeding ticket in a school zone, and, like hummingbirds, can fly forwards, backwards, sideways, up and down, and hover.  Their backs are sloped where their wings anchor, placing each pair at different heights, allowing for tremendous wing mobility.  Some species of dragonfly migrate, but the scale of some of those migrations has only recently been realized.  One dragonfly species in particular, the Globe Skimmer (Pantala flavescens) flies from India to Africa and back, island hopping cross the Indian Ocean, making open water crossings of nearly 1000km (620 miles) between island stops.  The only places they can breed are at the Indian and African ends of the migration, many of the islands they use as stopover points do not have sufficient freshwater for dragonflies to breed.  This is a stunning feat of flying for an insect and may be a behavior that evolved as a result of plate tectonics splitting India and Africa apart, eventually thrusting India into Asia.  If so, this migration could have begun 135 millions years ago.  Unfortunately, we have no reliable way of telling if this is the case.

Last year was a good year for dragonflies in Vermont, and this year looks like it is shaping up to be a good one as well.  The ecologist in me cannot help wondering why and one idea is that it may be linked to the calamitous drop in bat populations as a result of white-nose disease, a fungus that infects hibernating bats, weakening and eventually killing them.  It may be that adult dragonflies have more to eat with fewer bats and a greater percentage of them are surviving through the summer.  There is a historical precedent for this sort of boom in insect populations.  During the Great Leap Forward, Chairman Mao promoted a policy of killing off all things he thought were eating grain, birds amongst these.  With the crash in bird populations in China the insect population exploded.

Unidentified dragonfly – maybe a Darner of some sort

I am happy to see the dragonflies here.  Their presence means that the water is clean, we will have fewer mosquitoes, midges, and black-flies, and they are extraordinarily beautiful creatures.

Three-hundred twenty-five millions years old and going strong.  They have it figured out!

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The Short-Tailed Shrew, an evolutionary superstar

He [Raven] looked about and thought there was nothing on the land as lively as the fish in the water, so he made the shrew-mice, for he said, “They will skip about and enliven the ground and prevent it from looking dead and barren, even if they are not good for food.”                                                                                     – from Clara Bayliss’s 1909 collection A Treasury of Eskimo Tales.

Northern Short-Tailed Shrew (Blarina brevicauda) sniffing the air for prey

Creation myths aside, our early mammalian ancestors were little omnivorous insectivores very much like modern shrews.  Mammals evolved some 200 million or so years ago and lived alongside the dinosaurs, but did not grow to large size until millions of years after the dinosaurs went extinct some 65 million years ago.

Today we are a diverse group of flying, swimming, and running creatures ranging in size from the blue whale 120 feet long with a heart the size of a small car down to shrews no more than a few inches long, weighing less than an ounce.  We don’t know much about our early ancestors, small terrestrial creatures rarely leave fossil remains, but from what we can tell it seems that the shrew body design and hunting strategy is extremely successful and has remained a persistent mammalian body plan.

Shrew-like creatures live all over the world and are renowned for their ferocity, appetite, boldness, and their unusual (at least in mammals) venomous bite.  Here in Vermont the shrew you are most likely to encounter is the Northern Short-Tailed Shrew (Blarina brevicauda).  As near as I can make out, Blarina roughly translates to “nose-necked” and brevicauda actually does mean “short-tailed”, making this one of the few animals that has a matching common and scientific name.  Shrews are in the Soricidae family, which just means, “the shrew family.”

Short-Tailed Shrew running over freshly cut grass

Shrews move rapidly, driven by their rapid metabolism and resulting need to eat constantly.  They move with a peculiar blend of short, jerky twitches and weasel-like fluidity.  The shrew in the photos was hunting for insects and earthworms in freshly cut grass.  I followed it for perhaps 200 feet, and during that time it only stopped to sniff out prey, to eat it, and to hide from the dog that wanted to know what I was watching so avidly.

Like many predators, shrews are curious, engaging in high risk, high reward activities.  Their eyesight is poor, but their sense of smell is excellent.  How good their hearing is seems to be uncertain, some people thinking it is good, others poor.  I suspect that it is pretty good and that they are sensitive to vibrations via their whiskers and feet.

Searching for food

Unlike many animals the shrew had no fear of me what-so-ever, not even flinching when I stroked its back as it ate one of the 4 earthworms it caught while I was watching.  Every small animal nearby, on the other hand, was terrified of the shrew.  Insects froze into immobility, antennae twitching and heads slowly tracking as the shrew passed by.  Well should these creatures be wary of the shrew.  If a shrew goes more than a few hours without eating it will starve to death.

Short-Tailed shrews are tiny, massing between 2 and 5 US quarters (about .5 to 1 ounce), but they are perfectly capable of killing and eating prey several times their size.  There is a 3 minute National Geographic TV video of a shrew exploring a garden, then killing and eating a garter snake much larger than itself.  Most of the time shrews will content themselves with insects, worms, and seeds.

The dense fur of a shrew

Shrew fur is thick and dense, like the fur of an otter, but lacking the oily guard hairs.  The fur is so dense that it is waterproof, allowing some species of shrew to hunt underwater.  Shrews need this dense fur to keep warm through the winter.  Their small size means they lose heat quickly, necessitating both a rapid metabolism and good insulation.  In winter they remain beneath the snow as much as possible, eating cached food, keeping activity to a minimum, and burning brown adipose tissue (what we commonly call “brown fat”) to keep warm without resorting to shivering.

They have as many predators as they have prey, but their venom and unpleasant musk helps to keep some mammalian predators at bay.

Shrews are tremendously strong for their size.  I could see the back and neck muscles bulging as this shrew pulled earthworms from the soil.  It pulled a short section of the worm from the ground and ate it, pulled another short bit, ate that, and continued, as though it was eating Twizzlers at the movies.

Pulling an earthworm from the ground

We humans are proud of our accomplishments, but perhaps we should be more humble before the little shrew.  This tiny creature, so easily killed by a careless foot is upholding 200 million years of successful mammalian tradition, wearing a body design that gave rise to all other mammals from humans to whales, bats to elephants, beavers to monkeys.

Porcupines

North American porcupines specifically…  Erethizon dorsatum to be even more specific.

I like porcupines. They are large and slow-moving, meaning that when you find a live one in the woods you can often get a really good look.  Their defense is to turn their back, erect their spines while periodically slapping their tails, and give you dirty looks.  Usually you will encounter them in a rocky den or in a tree, positions from which they will not flee.  On the ground they will scurry to a place where they can present you with their spines while hiding their faces.

They have a very good reason for this strategy, two really.  One is that their back and tail are densely covered in long, loosely held, barbed harpoons that will gradually work their way deeply into any flesh they encounter.  Many a dog owner will unhappily tell you of traumatizing encounters their dogs have had with porcupines, often followed by either a compliment for their dog’s learning ability for avoiding porcupines from that point on, or with a disgusted expression of affection for their dog despite its incredible stupidity for not learning to avoid porcupines after the third or fourth encounter.

To actually catch and kill a porcupine with your teeth and claws is a dangerous, potentially fatal proposition.  This brings us to the second reason porcupines huddle rather than run.  Their primary predator in New England, and in much of northern America, is the fisher (Martes pennanti), a weasel of largish stature, by weasel standards.  Contrary to what the fisher’s name suggests they are primarily forest and tree-dwelling animals and the only non-bipedal North American animal that regularly, and successfully, hunts porcupines.

Weasels are fast.  They are meat eaters.  They are the sports cars of the animal world; energy to burn, but you have to fill them up often with costly fuels.  They do not hibernate.

Porcupines are the electric forklifts of the animals world.  They are slow and they are tough.  They also do not hibernate.

One of the things that amazes me about porcupines is that, despite the low quality, high volume food they eat and the virtual lack of fur under the posterior spines, they remain active all through the winter.  They are large, for a rodent, just a little smaller than a modern American beaver, but they are not all that big.  A porcupine has about the surface area of two basket balls and slightly less volume.  When it’s -20F that’s a bad surface area to volume ratio to have, and a rock crevice, boulder cave, or hollow tree is  poor shelter from the cold.  They are tough creatures.

Unchecked porcupines can reach densities that make foresters tear their hair and reach for their guns.  They are not gregarious animals, neither are they particularly territorial.  Like many animals their willingness to tolerate others is resource dependent, and, in the absence of predators, in an area with sufficient resources such as food and denning sites they will proliferate.

This happened in New England after fishers were hunted to local extinction for their rich fur.  It’s actually more complicated than that, as the spread, species composition, and variation in age of the trees in the New England Forest underwent dramatic changes as the land was converted from Native American land to simple American land.  Fishers were killed and porcupine numbers skyrocketed.

In Vermont the damage to the regrowing forests was so great that fishers were reintroduced to the state in the late 50s.  Vermont, like many New England states had been paying a bounty on porcupines for decades before fisher reintroduction.  The bounties started off at 5 cents an ear (per pair I’d assume) and eventually reached 25 cents an ear.  By the time fishers were reintroduced Vermont Fish & Wildlife reports that around $160,000 had been paid out in bounties.  Think about that… that’s a lot of small change.

In any event, by the 70s fisher reintroduction was considered to be a success and porcupine numbers to be manageable, except for the odd dog owner or two.

So, why do I like porcupines?  Well, they’re an animal you can track easily, get close to, and spend time next to really studying.  How long can you stand next to a rabbit, trout, bear, or deer out in the wild?  I’ve stood watching rabbits 20 feet away for perhaps 30 minutes, but nearly had to hold my breath while each tiny movement of mine made them twitch and prepare to bolt.  Most of the time spent watching rabbits has been spent trying to be invisible and not think of them roasted over an open fire stuffed with potatoes, bacon, and onions basted with a thick rosemary – Dijon mustard – black pepper paste.  Animals can tell when you are thinking of eating them, I am convinced of it.

Porcupines are probably pretty good eating, but they are so easy to catch that many native tribes had taboos about catching them for food.  They were food for hard times, last resort stuff after all the animals you had to work to catch were gone.  Save the easiest for last, good advice in many situations.

You can get up to petting distance of a porcupine and sneeze and it won’t go far.  They’re wary, perhaps even afraid, but they have an effective defense and they know it.  You will eventually go away and they can get back to eating tasty bark, twigs, hemlock needles, and basswood buds.  At least, I hope porcupines think their food is tasty.

Perhaps most importantly, porcupines are part of the environment.  They also live on this planet.  They are part of its ecology.

This is important; they are part of how the environment (the discrete things out there) relates to itself (ecology).  Relationships, as I think we can all agree are complicated, sometimes non-intuitive, and riddled with hidden depths and counter currents.  When I look at a porcupine track I think of bobcats, fishers, trees, geology, land use, history, and everything those touch.

Like everything else, porcupines are a window into a larger world, if you allow them to be.