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Wild About Utah: Spider Mountain

Spiders hang on webs attached to a UPR satellite dish.
Lyle Bingham

Recently, I accompanied Friend Weller, chief radio engineer for Utah Public Radio, on a visit to what local radio engineers affectionately call Spider Mountain. We sought to determine why the Utah County translator would intermittently go off air for minutes to hours. Friend speculated that wasps or spiders were to blame. He explained that this translator receives the signal from Logan via satellite and rebroadcasts it for lower Utah County on 88.7 MHz. It is one of more than 30 translators that re-transmit UPR where mountains block the original signal.

We drove up a gravel road to the top of the dry, desert mountain known locally as West Mountain. This cheatgrass-covered mountain rises 1900 feet from the waters on the south end of Utah Lake. At the base, there are fruit orchards, but climbing higher, we saw few plants rising above the cheatgrass. Near the top, more than 12 structures support antennas that transmit and relay signals across portions of Utah and Juab counties.

As we slowly climbed the gravel road in the UPR pickup, large bodies began to appear, moving on silk threads attached, like guy wires, to anything with height. Mobile spiders guarded each thread. When we passed, they took what appeared to be offensive positions. These spiders’ delicate legs easily span two inches. A unique black and white pattern of diamonds and dots on their back identifies them as western spotted orb weavers. The larger-bodied, gray spiders are females with legs attached to a 3/4 inch body. The narrower-bodied males measure half an inch. When they move, flashes of red show on the undersides of their legs. These same spiders live along the shores of Utah Lake and the Great Salt Lake.

The exterior of the equipment building was covered with spiders, as were the transmitting antennae above and the large receiving satellite dish nearby. We could see the problem. Spiders were blocking the signal to the satellite dish feed horn. Using a broom, we gently relocated them. Many took quick exits, dropping on threads of silk from the horn to the dish below, then running to the edge and rappelling to the ground. Others took more defensive or combative positions, only to be invited off with the broom or a gloved hand. After the eviction, we sprayed around the horn and the dish supports.

On previous trips, we had often wondered what these spiders eat. This time we found small flying insects, akin to those found along the shores of Utah Lake. They are likely carried up the mountain on wind currents. Up-hill winds develop every day as the sun warms the surface of the mountain. This time of year, the spiders don’t lack nourishment.

And how did the spiders get up there? Their progenitors were also likely carried uphill on silk parachutes. Once there, the spiders found the tallest location, strung their lines, and thrived on other unfortunates delivered by the same winds. You see, spiders, like predatory birds, are helpful pest control. For a spider, hanging high above the ground on a mountain top is a great place to be. There, the spiders can catch anything that blows or flies by. No wonder they grow so large and multiply so profusely on top of Spider Mountain.