If you’re reading this, you’re probably a human being. As such, while there are exceptions, you’re likely more than five feet long and weigh more than 120 pounds. With the exception of decent-size white-tailed deer, you’re larger than any wild, land-dwelling animal on the Vineyard.
Moreover, you’re the beneficiary of cultural patterns and technology that make you relatively impervious to variations in the natural environment around you. As a result, you can afford very coarse perceptions of your surroundings. When you pass a woodland, you see a woodland; a stream, and you see a stream. That suffices.
It’s worth reflecting on how unusual this is. Most of our terrestrial arthropods, for instance, are much less than an inch in length. An area that you cross in a few of your erect-primate strides is an entire landscape to a small beetle, with plenty of room for meaningful differences in structure, temperature, or humidity.
As a naturalist, I fight hard against my inborn obtuseness. To find wildlife — let alone to understand it — you need to learn to view the world from a new perspective. Variation on an incredibly small scale can matter to wild plants and animals, even making the difference between life and death. With so much at stake, everything from worms to birds perceives a world that is far more nuanced than what humans tend to see.
A woodland contains an infinity of distinct niches; each square foot of stream has its own substrate composition, temperature regime, and pattern of depth and water velocity. In contrast to blunt human perception, wildlife survives by noticing and responding to these differences, finding what works, avoiding what doesn’t, fleeing what’s lethal.
Red-legged grasshoppers in my yard, for example, get dramatically thinned out by a night in which our porch thermometer records temperatures in the upper teens. But a few individuals usually survive, and it takes colder temperatures, or at least repeated or prolonged exposure to cold, to finish off the last of these grasshoppers. In mild seasons, I find this species into early January.
Part of the explanation is surely differences in health among the grasshoppers that are present to start with. Some individuals, a bit larger than others, retain heat better. Others, having fed more successfully, have stored more fat in their tissues, providing insulation and energy.
But another part of the explanation probably lies in small-scale differences in the conditions under which particular grasshoppers confront a cold night. Some may be under leaves or dead vegetation offering particularly good insulation from the cold. Others, perhaps, hunker down in a spot where a lot of microbial activity is taking place — a process of decay, generating a small amount of heat that can make a difference of a critical degree or two.
The point is that humans look at a thermometer and see a uniform 15° night. A grasshopper skips the thermometer, but sees, instead, habitat rife with variation, albeit subtle and at a very small scale. Individuals with good instincts, or perhaps just good luck, end up in tiny patches that are marginally warmer than the rest of the yard. And that helps buy them an extra week or two of life.
In the case of my grasshoppers, variation on a spatial scale of inches or feet and reflecting only minor differences in temperature are enough to matter. Even over such small distances, though, differences can be dramatic. A patch of ground that receives full sun may exist right next to a patch that is fully shaded. But these patches differ widely in amount of light received, average temperature, and humidity. A careful look will likely reveal significant biological differences between the two spots. The joy and the challenge of studying nature is learning what species likes to be where. Each micro-habitat has its own ecology.
There is no limit to what sort of variation might matter to a plant or animal. Ants, for instance, many of which excavate vast underground nests, exhibit an incredibly nuanced understanding of soil, each species zeroing in on a preferred particle size and degree of wetness. Allegheny mound ants, for example, which mass the spoil from their tunnels into heaps that may be 5 feet across and 18 inches high, unerringly find the same type of coarse, well-drained sand to dig in. But you — do you even think about soil structure as you walk around?
A patch of loose sand, seen by a beetle, is a boulder field the size of a county. A pebble on that patch, too small for us to notice, offers concealment from predators, or cooling shade on an excessively hot day. One of the pleasures of studying nature is making the imaginative leap of seeing the world as wildlife sees it: a profoundly nuanced matrix of risk and opportunity, shaping what occurs where and when.