NEPA--Environmental Assessment

Silverton Grazing Risk Assessment
bighorn summer range. Together, there is about 4,877 acres of overlap between these
allotments and mapped summer range of the S33 herd. Within this area of overlap, about
821 acres (17%) are suitable for domestic sheep grazing.
West Needles Herd (S71):
The S71 West Needles Herd was established with animals translocated from the
Georgetown Herd in 2000, and 2002-2003. The 2007 estimated population size of the
West Needles herd was 75 animals (George et al. 2008), and reproduction and survival
have been good (Beecham et al. 2007). Bighorn sheep use the entire Animas River canyon
from Rockwood up to Needle Creek. The primary summer range of this herd is the West
Needle Mountains, and primary winter and lambing range is the Animas River canyon
from Rockwood up to the Cascade Wye.
Immediately after release, two bighorns dispersed into the S21 Ouray-Cow Creek herd.
Based on ear tag observations, several sheep dispersed into the S33 Pole Mountain/Upper
Lake Fork herd. Six or seven sheep moved into the Hermosa Cliffs area to the west of the
Animas River canyon and have remained there and produced lambs every year.
The CDOW opened S71 for hunting for the first time in 2007 with 1 ram tag issued
annually. No ewe licenses have ever been issued for this herd.
S71 is considered a translocated herd by CDOW and therefore is lower priority for
conservation at a statewide level (George et al. 2008). As a translocated population,
CDOW recognizes the existence of pre-existing domestic sheep grazing to the north, east,
and west of S71, and does not advocate closure of active domestic sheep allotments on
public land based solely on the potential for interaction between domestic and bighorn
sheep (Colorado Division of Wildlife 2009). CDOW does however, suggest working with
existing permittees grazing sheep in areas of mapped overlap with bighorn sheep summer
range to collaboratively take advantage of opportunities if/when they arise to reduce the
potential for physical contact, and the subsequent potential for disease transmission,
between domestic sheep and bighorn sheep of the S71 herd.
Under current management, the S71 bighorn herd overlaps with 6 active or vacant
domestic sheep allotments. Of these, 5 are FS allotments: West Lime (vacant), Little
Molas/West needles (vacant), Needles Mountains (vacant), Flume (vacant), and Deer
Creek/Engine Creek (active). One active BLM grazing allotment, Gladstone, overlaps with
mapped summer range for S71. Together, there is about 36,554 acres of overlap between
these 6 allotments and mapped summer range of the S71 herd. Within this area of
overlap, about 9,464 acres (26%) is suitable for domestic sheep grazing.
ALTERNATIVES CONSIDERED BUT ELIMINATED FROM FURTHER ANALYSIS
We considered the possibility of moving domestic sheep bands from currently active
allotments where the perceived risk of contact with bighorn sheep is “High” (see figure 3,
below) to other currently vacant allotments where the perceived risk of contact with
bighorns may be lower. Below is a brief discussion of the alternatives considered but
eliminated, and the reasons for their elimination.
Graysill and Flume allotments (FS, vacant allotments): These allotments have been vacant
since 1989. They have been successfully used as a forage reserve as recently as 2002 with
no adverse impacts to vegetation and soils. There are few if any conflicts with recreation.
There is a small area of overlap with mapped summer range of the S71 West Needles
bighorn sheep herd in the extreme south end of the Flume Allotment. Due to difficult
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