For a moment, nothing happened. Then, after a second or so, nothing continued to happen.
~ Douglas Adams
Of Moose and Men
The sun is setting. I carry my cup of tea, the last of the day, out onto the back porch. Reclining in a chair, I take in my surroundings. Mountain skies are spellbinding. As dusk approaches, azure blue turns to a breath-taking blend of burnt umber, rouge, lilac, and crimson. Only Turner has come close to capturing the color of nature, in all its subtlety, in all its striking beauty. By six o’clock, the sun’s rays are sepia-toned and fractured as they pass through a tangle of tree branches. Long shadows cross the lawn, on which several deer are sat. They have all made sure to pick spots that will remain illuminated until the last possible moment. Bathing in the gentle warmth of the evening air, their fur glistens and their eyelids droop. They appear as content as I. At last, the sun finally disappears below the horizon. There is a guitar leaning against the side of the house, but in my captivated state it remains unplayed; another time perhaps. It can wait. Everything can wait.
Many Rivers to Cross
Life in the slow lane is a gamble. Species will only refrain from operating at breakneck pace if the rewards are great enough. Species that dare to take their foot off the gas live long enough to experience the vagaries of the seasons; they are forced to endure great change. The longer you live, the more likely it is you will experience lean times, and to deal with such hardship is not a trivial task. What’s more, animals with a protracted life-cycle run the risk of producing no offspring if they die before reaching sexual maturity. Experiments on guppies have shown that when predators are introduced to the streams they inhabit, the fish will mature earlier. “Get some offspring out quick!” is the overarching message of selection. In many amphibians, high predation pressures experienced during the larval stage can trigger early metamorphosis; the elevated risk of the aquatic habitat acts to speed up the transition to land. Similarly, individuals can recognize when the pond they are in is about to dry up, and the possibility of imminent death will translate to rapid development of the tadpoles. Frogs that emerge prematurely are often small, not having as much time as they otherwise would have to gorge themselves on the pond’s bountiful algae supply, but they are alive, and that is what counts. An individual’s pace of life therefore, is not a choice per se, but a consequence of the environment it finds itself in.
If an animal exists in a relatively safe, bountiful environment, the animal will grow big and live a long time. When predators were removed from the experimental guppy populations, females deferred maturation in favor of a prolonged growing period. Bigger females produced more eggs, and thus the benefits of delaying outweighed the risks. This idyllic, predator-free environment is altogether unlikely in a natural setting however; it is after all, a jungle out there. In most instances, the need to find food forces animals into risky situations, and the different ways species’ balance this risk-reward trade-off is what generates much of the diversity that we see in the natural world. Creatures that spend most of their time hiding from the elements and/or would-be predators will not grow very big. Plethodontid salamanders in the Eastern US spend 99% of their lives safe underground, only emerging on a handful of days each year when the risk of foraging is minimal. These salamanders weigh only five grams but can live for three decades. At the opposite end of the spectrum, creatures that are willing to venture into dangerous places to exploit more plentiful resources grow much bigger but will typically not live as long. The exception would come if somehow you can grow so fast and to such a size that you outgrow your natural predators. Big things live longer because fewer things can eat them, but getting there is the challenge. The offspring of big animals must throw caution to the wind and eat like there’s no tomorrow if they are to ever attain the size of their parents. Typically for this risky strategy to succeed, big animals either lay huge clutches of eggs, with the assumption that most will not make it to adulthood, or invest in substantial parental care to improve the survival odds of their young. Only once you are grown can you afford to take your foot off the gas.
Food for Thought
With estimates pushing 400 years, the Greenland shark is by far the longest-lived vertebrate, providing some insight into life in the slow lane. Although not the largest shark species, these geriatric giants are just shy of five meters long and can weigh up to half a ton. As their name suggests, they are found at high latitudes in the northern hemisphere, and live at depths of 7,000 feet. Something about this environment allows Greenland sharks to take their foot off the gas and live a long healthy life, but what? Well firstly, in contrast to the Trinidadian streams occupied by guppies, or the breeding wetlands of frogs and salamanders, the ocean is relatively stable. When one can predict future conditions with relative confidence, a slower pace of life is less risky. Another potential feature of the Greenland shark’s environment that facilitates long lifespans is the lack of UV exposure. Ultraviolet radiation causes genetic mutations, any one of which could develop into a life threatening cancer, but the creatures of the deep do not have to worry about melanomas as we do. Lastly, and perhaps most importantly, the lack of sunlight means that the water at the bottom of the ocean is very cold. Temperature controls the rate of fundamental biological processes operating in every cell, and thus temperature exerts a powerful influence on the pace of life. Metabolic processes are slower at lower temperatures, and more efficient (think about fuel economy at 30mph vs 70mph). Hence in the frigid polar waters of the northern hemisphere, Greenland sharks are converting every drop of food into usable energy. Every morsel they ingest can be directed toward growth, cell maintenance and prolonging life. As they cruise through the gloom not a single calorie is wasted, and every calorie is used to its full potential.
On land you also tend to find older animals in colder climates. Polar bears, moose, and walruses all live longer than their cousins at lower latitudes. But none of these animals live as long as Greenland sharks, and the reason once again relates to temperature and metabolism. Warm-blooded animals do not live as long as cold-blooded animals. And polar bears, moose, and walruses are all warm-blooded. Regulating your body temperature is good if you want to remain active year-round at the poles, but it comes at a price. The relatively large sizes of these arctic mammals may lead you to believe that they occupy the slow lane, but their warm-bloodedness means they are effectively burning the candle at both ends. A 500lb moose does not live appreciably longer than a 5g salamander. A fully grown moose has few natural predators, but most of the energy it consumes does not go toward living longer – it is simply lost as heat. Cold-blooded animals can essentially shut down their bodies in between meals to conserve energy, and go months without food – owing to the need to stay warm, no bird or mammal can afford to eat so infrequently. This is especially true for small warm-blooded creatures, which have a much harder time regulating their temperature. This fact alone explains why there are penguins but not parakeets in Antarctica; why there are seals but not shrews at the north pole. Their relative inefficiency, combined with regular forays into risky environments in the constant quest for food, make it so that warm-blooded animal must grow to the size of an elephant or a whale if they are to enjoy a relaxed pace of life.
Desert Island Risks
Picture it. A tropical paradise, blonde sands calmly caressed by the cool blue, a gentle ocean breeze brings salt and seaweed to the nostrils, and unseen birds bring a sweet melodious symphony to the ear.
But there is trouble in paradise.
Islands may seem distant and immaterial, but these microcosms are home to some of the most precious wildlife on Earth. There are thousands of islands, each one a world in miniature. Just because life on islands have so little room to move, does in no way mean that life on islands is any less complex, intricate, and unfathomable than life on the mainland. Indeed, island inhabitants face unique pressures that provide opportunities for life to experiment and evolve, generating weird and wonderful, almost mythical creatures. Importantly for this discussion, island life can afford to take its foot off the gas. Birds on oceanic islands enjoy such a leisurely existence, many forget how to fly. The scarcity of trees and lack of predators encourages them to nest on the ground, and wings become somewhat redundant. What’s more, the ability to fly may even be a disadvantage in these remote places; it is unlikely that avian castaways will stumble upon better real estate in the surrounding area, and they may not be able to navigate back to their present locale if they up sticks and leave. Thus there is often a strong pressure to stay put. The seeds of island plants typically get heavier for the same reason; if they floated on the breeze they would simply be swept out to sea. Their inherent isolation is what makes each island unique. It is this same isolation however, that makes islands so inherently vulnerable.
Islands are the geographical equivalent of immune systems that have yet to be exposed to infection. They lack the acquired defenses to combat illness, and hence the fallout from exposure to novel diseases is often fatal. In the 21st century islands are sick, and we are to blame. However, human beings are not the disease in this analogy. Like mosquitoes, acting unknowingly as a vector for the real nasties, malaria, dengue, zika, we are in turn merely vectors for the real pathogens: cats and rats. Half of all known extinctions in human history have occurred on islands. Ninety percent of all bird extinctions have occurred on islands. Rats and cats are responsible for most of these. With so many islanders succumbing to rather mundane predators, it begs the question: ‘don’t these island creatures know an enemy when they see one?’ And the answer is, somewhat surprisingly, ‘no’. Or more accurately, ‘not anymore’. Fear is an adaptive trait, useful for avoiding predators and undue risks. However fear is an extremely costly trait, and hence animals on islands with no natural predators tend to lose their fear rather quickly. Stories abound of Dodos practically walking into the cooking pots of Dutch sailors and Galapagos finches feeding from the hand of Darwin; not so much fish in a barrel as birds on an island. Lack of fear therefore, is the characteristic that makes islanders so endearing and so endangered in the same breath.
Mass extinctions occur when the change of pace is accelerated to such an extent that most species cannot keep up; their time has literally run out. The current rate at which species are being lost is faster than practically any other time in life’s history. We are amidst the sixth mass extinction event. Human beings, and particularly industrial societies, have brought about a sense of rapidity that leaves all others in the dust. The inherently slow pace of island life results in such tropical paradises acting as the canaries in the coal mine. The likes of moas, pygmy elephants, and Irish elk, are sadly now spoken of in the past tense. And the situation is going to get worse before it gets better. Komodo dragons giant tortoises and tuataras are on the way out. People are only becoming more numerous and more mobile. It is now possible to fly halfway round the world in less than 16 hours. It is now possible to book a package holiday to Tristan da Cunha. Nowhere is safe, nowhere too remote to avoid the ongoing pandemic. We are orchestrating a transition from desert island to deserted island. Before long entire archipelagos will be reduced to nothing but rubble. Picture it. A tropical paradise, blonde sands calmly caressed by the cool blue, a gentle ocean breeze brings rotting carcasses and cat shit to the nostrils, an eerie unnatural silence fills the ear. The fate of the islands today will be the fate of the continents tomorrow. If we want to stem the loss of biodiversity on this planet, now’s the time.
The sun is rising. Huddled beneath the crown of an ancient oak, I take in my surroundings. The early-morning mist hangs on the forest floor. It will be several hours before it dissipates. It is still cool enough that I can see my breath, and the woodland birds sound lethargic, chilled from the night before. The sun’s rays are sepia-toned and fractured as they pass through a tangle of tree branches. A stag emerges from the gloom, equal parts mythical and majestic as it meanders through the copse. It wanders close enough for me to see its glistening fur, to see its nostrils flare. Closing my eyes, I hear my heartbeat. I hear rustling leaves. A branch snaps underfoot, a grouse flushes from the thicket. Not a moment to lose, I raise the bow to my eye and take aim. The time is now.