Individual strategies for survival
By Mark Brazil | Sep 6, 2000
Around her in the leafless, wintry trees sit more monkeys, all members of her troop. Grandmothers sit with their daughters and their daughters with their infants, while a few adult males keep to themselves on the periphery of the group.
These, in the temperate forests of northern Aomori Prefecture, are the northernmost monkeys in the world: Japanese macaques. Most of their relatives live in more southerly, warmer parts of Asia, in the subtropical and tropical regions. Over millennia, macaques entered the bridge of land off the Asian coast and moved north through what became the Japanese islands, arriving in the far north of Honshu perhaps only 20,000 years or so ago. Over the long span of their northward migration, they have steadily adjusted their lifestyles, adapting to the steady pulsing and swinging of the temperate seasons.
Now they live in an intensely seasonal part of the world, surrounded by other creatures similarly adapted, where their relatives at home in the Indian, Chinese and Indonesian tropics could never survive. The northernmost macaques, of Aomori Prefecture’s Shimokita Peninsula, have adapted to the temperate seasonality of their forest. They move through their forest home with a deep knowledge and understanding based on generations of experience, while the forest moves through the cyclic pattern of the seasons, each part of the whole responding to the slow annual change in the climate.
The restless year of the temperate forest is the backdrop against which various actors take the stage. The macaques, in their range from Yakushima to Shimokita, experience the temperate region from its borders with the subtropics to the south, all the way to its northern limit. In the mountainous parts of their range, they share their forests with another temperate creature: the Japanese serow, the goatlike antelope known here as kamoshika (Capricornis crispus). The macaques and the serow have adapted their patterns of survival to cope with both heavy winter snows and high summer heat; their behavior and seasonal strategies are readily observable.
Much harder to see are the individual struggles and strategies within the forest itself. How is it, in Japan’s northern temperate forests, that certain tree species gain dominance over others, without ever completely crowding them out? How is it that beeches, oaks, maples and mountain ashes coexist and provide a canopy to shade not merely the macaques and the serow, but also the many other species of animals and plants that make up the temperate forests?
Such apparently simple questions reveal how little we still know about the natural world around us. We cannot yet provide an answer.
Each insect, each plant, each mammal and bird has a strategy, a lifestyle that distinguishes it from the next. Each species adapts to the whole, while forging its own niche to live in. Most follow general patterns, common in the temperate region. They move in phase with each other: lying dormant during winter; awakening in spring to blossom and bloom; spending summer amid plenty; then laying down stores in the autumn, before facing yet another winter.
Yet there are some species that are aware of the same triggers and impulses, but respond differently to them. They go their own way, dancing to a different tune.
One such species, a small, rather insignificant-looking plant, has a life struggle that is out of phase with the forest; it follows its own strategy. It is known as naniwazu in Japanese (Daphne kamtschatica): I have been unable to find a common English name for it. Naniwazu is deciduous, with rather thick, glossy leaves, a little like ivy, but growing on a tough, somewhat rubbery stem less than knee high.
Like all plants, naniwazu competes for the most precious resource, light, which it needs for photosynthesis and growth. In these temperate forests, the open canopy of winter allows a flood of light down to the forest floor, but then as the trees break into leaf in spring, they slowly enmesh the sky until only dappled light seeps through. There a profusion of plants compete for the limited light, making do with the much filtered shower of photons.
In the midst of this struggle and rush for light, naniwazu has a different strategy. Its rhythm is the same, but its timing is different. Naniwazu is one jump ahead of the pack. As winter’s snows melt, naniwazu’s already-green leaves appear from beneath it, ready to absorb and process the bright light streaming down to the forest floor, and produce its delicate yellow flowers before the colorful spring ephemerals are even ready to begin growing.
Insects active early in the year are its pollinators. Having enlisted their help, naniwazu remains one step ahead of the game by drawing energy back in from its leaves, which turn yellow and drop, just when the other shrubs and trees are pushing forth their light-filtering foliage.
So by the height of summer, when the temperate forest canopy is shading much of the forest floor, naniwazu is already a season or two ahead, its leaves dropping as if it were autumn, and its striking red berry appearing as if it were nearly winter.
As the Earth tilts the temperate zone toward autumn, the speckling of light on the forest floor grows to a shower and then a flood, as the trees begin to lose their leaves in the autumn winds. While light and leaves are falling faster and faster, naniwazu is readying itself for spring. By the time the sun is lower in the sky and the first snows begin to cover the forest, its leaves are budding. Beneath the snow its leaves remain green, ready to steal a march on the next changing of the seasons.
The varying patterns, the differing lifestyles of plants and animals, bridge the seasons of this temperate part of the world. Early flying insects take advantage of seasonal strategists such as naniwazu, and are replaced by others as the degrees of light and heat change through spring into early summer. Migrant birds arrive, feeding on the later flying insects, many of which are crucial to the pollination of the summer-flowering plants, and so the links go on and on.
Fewer, rarer, yet more conspicuous to us humans are the larger mammals. Mammals such as the macaques and serows, which do not hibernate, are reduced to feeding on poor-quality food during winter, scraping a living from tree bark and tightly closed buds. Imagine just how much they must enjoy the plenty that spring finally offers. Every few days different species appear, lush and filled with the energy of growth, providing macaque and serow alike with sufficient energy to see them through their own breeding cycle.
After spring’s cornucopia, summer days are long, before autumn brings its seasonal harvests. The flood of fruits and nuts is almost too much; the forest animals cannot possibly gather and eat them all. This autumnal glut is a crucial strategy of the forest. The trees and shrubs that follow it survive generation after generation because they produce so many seeds that some always survive the net of foragers drawn to the supply.
In that way the plants perpetuate themselves while providing the means for the animals of the temperate forests to survive too. Where we humans interfere, by removing the forest or its autumnal harvest, or altering the mix of tree species, we have a significant impact on the larger animals that depend on the forest for their survival.