Have you ever heard silence? I mean real silence, not just the peacefulness found by leaving town and walking into the woods for a bit, but the actual empty sound of silence. A lack of noise that makes your ears ring, your heart beat more noticeably and seems to freeze your entire surroundings. The sound of absolutely nothing. True silence.
Here at the Kenai National Wildlife Refuge, we've been listening across 2 million acres from the Visitor Center to the Caribou Hills to remote lakes in wilderness and everything in between. Why? To find out what we hear. Believe it or not, sound has effects on the landscape and it affects us. Sure, it sounds simple (no pun intended), but think about how much noise you hear on a daily basis: traffic, ravens, wind, people talking, dogs barking. Or maybe the sound of your snowshoes or skis cutting snow, the bear bell on your pack, a gurgling stream, the buzzing of insects. The point is, there's a lot of noise out there, and all of it forms our "soundscape".
So you're probably wondering what we've been hearing on the Refuge. We've been deploying recorders, the SM2 model made by Wildlife Acoustics Inc., throughout the refuge to gauge how much human activity is contributing to the soundscape. We spread the SM2s across the refuge to get the best distribution of sound possible, recording 20 seconds every hour throughout winter (December-April).
SM2s are small, making it easy to place them in a variety of different habitats with very little disturbance to that area. Depending on the temperatures, these recorders can run without maintenance for over a month while storing sound recordings on a simple SD card. With two small microphones sticking off the sides (see photo), SM2s look a little funny at first, but equipment like this allows biologists to collect a large amount of data across the landscape with minimal impacts to those areas.
Recordings taken last winter in Caribou Hills, along Tustumena Lake Road and Skilak Wildlife Drive, and at Paddle Lake revealed interesting sounds. These four sites, representing a handful of the dozens of sites we sampled, are exposed to different kinds and levels of human-caused sounds: snowmachines in Caribou Hills, snowmachines and vehicle traffic near Tustumena and Skilak Lakes, and maybe a few ice anglers at the end of Swan Lake Road.
We collected 6,409 recordings in total from these four sites. Within each recording, sounds were individually identified and then grouped based on if they were natural or man-made sounds. We heard a lot of airplanes, ravens, wind, and other typical sound, but the noise we heard the most often? Silence.
Silence made up 73 percent of these recordings. Given how much noise we are surrounded by every day all the time, this came as a surprise. The other 27 percent of the sound samples consisted of a variety of different noises. Natural sounds alone occurred more than twice as often as man-made sounds, but still only accounted for 16 percent of the total recordings from these stations.
When we did hear something other than silence, we heard a lot of different things. Twenty-eight sound sources were identified with additional unidentified noises that we lumped into an "unknown" category. Aircraft was the most frequently-heard human noise, making up 79 percent of human sound at these four sites. Snowmachines were detected in 14 percent of these recordings. Human voices, vehicles, gunshots and ice augers made up an even smaller portion, but were expected to be heard. In two surprising instances, we heard stereo music and fireworks on New Year's Eve!
The majority of natural sounds were caused by wind and rain, followed by birds. Over 15 different avian species were identified with great horned owls and common redpolls occurring most frequently. Although hearing common bird species on the recordings came as no surprise, we did detect several less common species as well such as white-winged crossbills, pine grosbeaks and boreal owls. Even the golden-crowned kinglet, a rare species during winter, was heard.
Although we documented some amazing and surprising sounds in these recordings, these sounds still only make up a small portion of the daily sounds, or lack thereof, that occur on the refuge. Given how many different sounds we detected, it's amazing that there is still so much silence. From day to day, how much silence do you hear? It's certainly a rarity.
My daily life is filled with a constant hum, and even when I go outside to escape it, either nature creates noise for me or I do simply through my actions. I found real silence this winter, but only after stopping while snowshoeing and actively listening for it.
Here on the Refuge, we are fortunate to experience a still mostly wild and pristine landscape, but that's not to say that silence will always be there. While the singing of birds and the buzzing of insects are reminders of the natural world we live in, as we encroach more and more into these wild areas, our sounds follow us, and with it, a diminishing of the wilderness experience.
If you haven't experienced the sound of silence before, I recommend finding it before it disappears.
Bennie Johnson recently graduated with a degree in Wildlife Science from Virginia Tech and is wrapping up a biological internship at the Kenai National Wildlife Refuge. You can find more information about the Refuge at http://kenai.fws.gov or http://www.facebook.com/kenainationalwildliferefuge.