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Federal Register / Vol. 86, No. 146 / Tuesday, August 3, 2021 / Rules and Regulations
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available on the internet at www.regulations.gov, Docket No. FWS
R8ES20190006.
Subalpine Habitat Suitability, Snowpack Levels, and Coyote Presence Over the past 75 years, average annual temperatures in the Sierra National Forest which overlaps the southwestern portion of the Sierra Nevada DPSs range have increased by about 1.0 to 1.5
C Meyer et al. 2013, p. 2. In the Lake Tahoe region northern Sierra Nevada mountain range in California, the average number of days per year for which the average temperature was below-freezing has decreased from 79 in 1910 to about 51 in 2010 Kadir et al.
2013, p. 102. These increased average temperatures coupled with periodic drought conditions can result in changed habitat conditions in subalpine habitat. For example, direct measurements of primary productivity in a subalpine meadow in Yosemite have shown that mesic medium wet and hydric wet meadows both tend to increase productivity in response to warmer, drier conditions Moore et al.
2013, p. 417. Xeric dry meadows tend to increase productivity due to warmth, but decrease due to drier conditions Moore et al. 2013, p. 417. A
comparison of tree biomass and age in subalpine forests now and about 75
years ago also points to increased productivity over time Kadir et al.
2013, p. 152. Specifically, small trees with comparatively more branches increased by 62 percent, while larger trees decreased by 21 percent, resulting in younger, denser stands Kadir et al.
2013, p. 152. This overall increase in biomass occurred consistently across the subalpine regions of the Sierra Nevada mountain range and across tree species. The primary cause was an increase in the length of the growing season Kadir et al. 2013, p. 152.
A study of coyotes and montane red foxes in the Lassen area of California found that coyotes moved out of high elevation areas during the winter, possibly due to deep snow Perrine 2005, p. 74. Red foxes also moved to somewhat lower elevations in winter, but tended to remain at higher elevations than coyotes average 1,878
m 6,161 ft versus average 1,690 m 5,545 ft for coyotes Perrine 2005, p.
96. Studies in Alberta and Maine have also documented elevational separation of coyotes and red foxes Perrine 2005, p. 84. A study of coyotes in Sonora Pass, however, where Sierra Nevada DPS foxes occur, found that coyotes outnumber DPS foxes during the summer in the high elevation areas most used by Sierra Nevada DPS foxes, and
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also found several coyotes that were occupying the high-elevation areas yearround Quinn and Sacks 2014, p. 12;
Quinn 2017, pp. 67. Areas unoccupied by coyotes may serve as refugia for red foxes Perrine 2005, p. 84, so the coyotes occupying high elevation areas near Sonora Pass during the winter may be negatively impacting Sierra Nevada DPS foxes by restricting them from hunting areas or den sites, by the threat of direct predation on adult foxes or cubs, and by generally reducing the carrying capacity of the area available for the foxes Quinn and Sacks 2018, p.
18. The extent of the impact is of course unclear, but given the current small estimated size of the Sierra Nevada DPS population, any death or reproductive failure resulting largely from coyote presence could affect the overall viability of the DPS as a whole.
In the central portion of the Sierra Nevada mountain range, average recent April 1 snowpack levels in Yosemite which overlaps a portion of the known Sierra Nevada DPS sightings have been just above 60 cm 23.6 in Curtis et al.
2014, p. 9. To date, all Sierra Nevada DPS individuals sighted within the park have been in the areas of highest snowpack Eyes 2016, p. 2.
While snowpack conditions vary by year and location, the best available scientific and commercial information suggests that the areas where the Sierra Nevada DPS occurs have been maintaining high snowpack during winter and spring most years see section 4.1 of the SSA report Service 2018, pp. 2223. Therefore, the current condition of the snowpack depth appears adequate for the DPSs needs, except during drought years such as occurred in California and other western states from 2012 to 2017 Kim and Lauder 2017, pp 245.
Prey Availability Rodent population numbers in subalpine areas have likely increased due to an increase in primary productivity Service 2018, pp. 21, 24.
Despite several factors that may limit their availability e.g., increased presence of coyotes, the general landscape appears adequate for rodents.
Adequate leporid population numbers may be of concern given that both white-tailed jackrabbits and snowshoe hares are considered species of special concern across the Sierra Nevada by CDFW CDFW 2017, p. 51, a designation meaning they are potentially vulnerable to extirpation in California CDFW 2017, p. 10.
Regardless of rangewide leporid abundance, the best available scientific and commercial information does not
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indicate that leporid abundance is inadequate in the vicinity of the majority of known Sierra Nevada DPS
sighting locations i.e., Sonora Pass area; leporids appear currently to be relatively common and present all year in the Sonora Pass area Rich 2014, p.
1.
Habituation Based on new information received, habituation of Sierra Nevada DPS foxes to humans and human food sources may expose Sierra Nevada DPS fox individuals to harm or injury, such as from dog attacks, dog diseases, and vehicle collisions Dunkelberger 2020, p. 2. Sierra Nevada red foxes in the Southern Cascades population have been exhibiting begging behavior at the Lassen Peak parking lot Perrine 2005, p. 150. A female from that population was killed by a dog in 2002 after having previously exhibited begging behavior Perrine 2005, p. 135. The death occurred less than 175 m 600 ft from a ski chalet.
Other indicators of habituation have also been noted in the range of the Sierra Nevada DPS. The HumboldtToiyabe National Forest has several photographs of Sierra Nevada DPS foxes closely approaching hikers and snowmobilers, presumably in hopes of obtaining food Dunkelberger 2020, p.
2. Hikers within the DPSs range have also posted photographs on social media showing themselves feeding Sierra Nevada DPS foxes. Although we have no reports of Sierra Nevada DPS foxes approaching soldiers at the MWTC, trash has occasionally been left after training exercises, and tracks from Sierra Nevada red foxes, as well as fox scat containing food wrappers have been found in these debris areas Dunkelberger 2020, p. 2. The recently completed INRMP commits the MWTC
to implement measures that prevent habituation of foxes, including an education program for military personnel on these measures MWTC
2018, p. 367. As a result of these actions, we do not expect habituation on MWTC lands to significantly affect the population of the DPS. We have no information indicating loss of Sierra Nevada DPS foxes due to habituation.
Overall, the best available information suggests that habituation of individual foxes may occur, but is expected to be restricted to a few individuals over time.
Deleterious Effects Associated With Small Populations Sierra Nevada DPS population numbers are currently low 18 to 39
individuals spread across the Sonora Pass, northern Yosemite, and Mono
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