When it comes to what’s happening in the natural world, you don’t know what you’re missing.
No, really: If you know you’re missing something, you aren’t truly missing it, right? The natural environment around us is full of activity, and even a skilled observer is utterly oblivious to a high percentage of what’s going on.
Let me give an example. A few weeks ago, I spent two hours exploring a 30-acre tract of scrub oak on Long Point Wildlife Refuge. Along the way, I turned up about a half-dozen fork-tailed katydids, which seemed like a typical number for that much time spent in that type of habitat. If you had asked me after that excursion what I thought the status of this insect was at that location, I would have said “uncommon” — present, fairly easy to find, but pretty thin on the ground. I might have estimated a population of 100 or 200 across the site.
Two weeks later, I was on the same tract, operating a large tractor and mowing deck as part of an ecological restoration project. The machinery flushed katydids left and right: I saw easily 50 of them in my first two hours of work, covering only about two acres of the site. If you asked me now about the status of fork-tailed katydid at this site, I’d say “abundant” — occurring at high density, and virtually unavoidable. The total count on the site is surely in the high hundreds, more likely the thousands.
The two assessments are wildly different from each other, and after my first visit, I couldn’t have imagined the results of my second. When I’m bug-hunting, I typically move slowly and quietly; the goal is to prompt insects into motion so I can detect them, but not to startle them so much that they fly out of range. On the first visit, I surely passed within feet or even inches of hundreds of katydids without imagining that they were present. It was only the view from a loud, disruptive piece of equipment that revealed my error.
The fact is, human senses are rather dull, and most wildlife excels at staying hidden. Part of the elusiveness of wildlife comes from protective coloration. A resting katydid, for example, looks stunningly like a leaf; human visual acuity, and our ability to interpret what we see, simply aren’t up to the task of consistently noticing stationary katydids among an infinity of leaves.
Behavior also plays a role in limiting detectability. The wildlife we see is usually actively doing something; the motion, indeed, is often what allows us to notice things. But for a variety of reasons — to conserve energy, to avoid exposure to excessive heat or cold, and of course to avoid attracting the attention of predators — most wild creatures spend a high percentage of their time concealed and doing nothing at all. This can make them impossible for humans to notice.
I’ve developed tactics to overcome my limitations. I find, for example, that when I’m looking for insects, it’s helpful to make multiple passes through the same piece of habitat. The first pass will prompt a few individuals into motion. Meanwhile many other individuals, present but immobile, are partially roused by the disturbance. It’s only on the second or even third pass, after previous disturbance has woken them up, that these insects move. So a little patience dramatically multiplies how many individuals I can spot.
Given the ease with which wildlife is overlooked, how can we possibly assess the sizes of populations? One partial solution is to accept the fact that you’re missing a lot of individuals, but to assume that the percentage you’re missing stays consistent. This is the approach taken by projects like the Breeding Bird Survey run by the U.S. Geological Survey: A huge number of points are sampled every year, using a consistent methodology, and while the process doesn’t make any attempt to estimate how many birds are present but undetected, it does allow for meaningful year-to-year comparisons of how many birds are found. You can’t tell what the total population is, but you can tell whether it is growing or shrinking.
Another approach is to conduct intensive counts across a small area, and then extrapolate. I you mark off a 10-square-meter sample of scrub oak, and then have a crew of three or four naturalists investigate it intensively, you can probably count nearly every katydid that is present. If you’ve got 1,000 square meters of total habitat, you can multiply your findings in the 10-square-meter tract times 100 and get at least a rough estimate of the total number of katydids present. The process, though, depends on the untestable assumptions that you’re missing few, if any, individuals in your sample plot, and that the species you’re studying is evenly distributed across the entire area.
So get used to the humbling idea that however much you may think you know about the natural world, you’re missing more than you’re noticing. The harder you look, the more you’ll find. But human ability to detect wildlife is nearly always outweighed by the desire of wildlife to stay hidden.