City Creek Nature Notes – Salt Lake City

November 2, 2016

November 2nd

Filed under: Grandview Peak, North American porcupine — canopus56 @ 7:21 pm

Where have All the Porcupines Gone?

3:30 p.m. During the 1980s, when I was younger, I would ride a mountain bike to the end of the road, climb Grandview Peak, and then walk and ride out by the light of a rising full Moon. Then, it was common to see five to eight North American porcupines (Erethizon dorsatum) warming themselves on the road. They were a definite hazard. Running into one a bicycle would mean certain injury, but now none are seen. This fall, a trusted acquaintance reports that a single porcupine does live in the upper canyon near mile 5.0. They are solitary and not easy to run into, despite the light-colored quills on their backs and their strong offensive odor. Unlike other herbivores like deer, they have no need to be secretive because of their quills. Where have all the porcupines gone?

Inherent population fluctuations might be one answer. In a classic study from the 1960s, Donald A. Spencer surveyed some 300 trees in Mancos Canyon, Colorado, and he used bores of porcupine injured trees to estimate porcupine populations fluctuations over 80 years. He found an approximate twenty-year periodic cycle, but it was not correlated to the solar cycle. In 2002, then graduate student Ilya Klvana of the McGill University performed a similar study for forests in eastern Quebec covering the past 130 years, and she found a correlation between the phased peaks of porcupine populations and the solar cycle and its related precipitation cycle. Data from other porcupine researchers have found fluctuating peaks, but no periodicity. Another cause for the disappearance of porcupines from City Creek may be long-term drought. The porcupines may have migrated north to find more water and healthier trees.

Man is another possible explanation for their decline. City watershed or U.S. Forest Service personnel might have declared them to be pests, either to people or trees, and then laid strychnine containing salt baits to reduce the porcupines’ numbers.

Whatever the cause of their relative absence, I miss the sanguine porcupines. They live in one place for most of their lives, they are vegetarians, and due to the strong defense that their quills provide and their diet, they do not make many enemies.

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