Post by warsaw on Apr 4, 2015 2:14:00 GMT -9
Building a reliable snare cable for capturing grizzly and American
black bears
John P. Flaa1,4, Steve B. Michel2
, and Chris Borstad3
1
Mount Revelstoke and Glacier National Parks, Box 350, Revelstoke, BC V0E 2S0, Canada 2
Banff National Park, Box 900, Banff, AB T1L 1K2, Canada 3
University of British Columbia, Department of Civil Engineering, 1984 West Mall, Vancouver, BC V6T 1Z2, Canada
Abstract: Wildlife researchers and managers have been using Aldrich foot snares to capture
American black bears (Ursus americanus) and grizzly bears (U. arctos) for decades. Recently,
failures have been reported in snare cable assemblies, resulting in escapes of both black and
grizzly bears. We tested different configurations of snare cable and hardware using a hydraulic
pull machine. Snare foot loops constructed with compression sleeves or CrosbyH clips torqued
to 20.3 newton-meters (N-m) consistently exceeded minimum strength requirements for use on
large bears (.16.8 kilonewton [kN]). In our tests, anchor sections of snares using compression
sleeves and 0.794 cm swivels never failed below 30 kN. It is important to use robust,
manufacturer-rated hardware and precise methodology when building snare cables to achieve
consistent holding strength. The use of substandard components and improper torquing of
clamps can result in failure of the snare endangering both bears and capture personnel
Thousands of bears have been live-captured using
variations of the Aldrich foot snare, and relatively few
have escaped the system once captured (Johnson and
Pelton 1980, Reagan et al. 2002, Lemieux and
Czetwertynski 2006). However, in 2007, a male grizzly
bear (Ursus arctos; 200 kg when captured in 2005)
broke a foot loop while we approached it to remotely
deliver an immobilization drug. Snares failed in 2 other
recent instances, we know of, during the capture of
American black (Ursus americanus) and grizzly bears
(personal communications: B. McLellan, BC Forest
Service, D’Arcy, British Columbia, Canada, 2007; E.
Wenum, Montana Fish, Wildlife & Parks, Kalispell,
Montana, USA, 2007). An Amur tiger (Panthera tigris
altaica) snare-captured in the Russian Far East also
escaped in 2008 (C. Miller, Wildlife Conservation
Society, Vladivostok, Primorski Krai, Russia, personal
communication, 2008). When a bear escapes a snare
there is a high potential for serious injury or death both
to the bear and to capture personnel.
www.bearbiology.com/fileadmin/tpl/Downloads/URSUS/Vol_20_1/Flaa_et_al._Ursus_20_1.pdf
black bears
John P. Flaa1,4, Steve B. Michel2
, and Chris Borstad3
1
Mount Revelstoke and Glacier National Parks, Box 350, Revelstoke, BC V0E 2S0, Canada 2
Banff National Park, Box 900, Banff, AB T1L 1K2, Canada 3
University of British Columbia, Department of Civil Engineering, 1984 West Mall, Vancouver, BC V6T 1Z2, Canada
Abstract: Wildlife researchers and managers have been using Aldrich foot snares to capture
American black bears (Ursus americanus) and grizzly bears (U. arctos) for decades. Recently,
failures have been reported in snare cable assemblies, resulting in escapes of both black and
grizzly bears. We tested different configurations of snare cable and hardware using a hydraulic
pull machine. Snare foot loops constructed with compression sleeves or CrosbyH clips torqued
to 20.3 newton-meters (N-m) consistently exceeded minimum strength requirements for use on
large bears (.16.8 kilonewton [kN]). In our tests, anchor sections of snares using compression
sleeves and 0.794 cm swivels never failed below 30 kN. It is important to use robust,
manufacturer-rated hardware and precise methodology when building snare cables to achieve
consistent holding strength. The use of substandard components and improper torquing of
clamps can result in failure of the snare endangering both bears and capture personnel
Thousands of bears have been live-captured using
variations of the Aldrich foot snare, and relatively few
have escaped the system once captured (Johnson and
Pelton 1980, Reagan et al. 2002, Lemieux and
Czetwertynski 2006). However, in 2007, a male grizzly
bear (Ursus arctos; 200 kg when captured in 2005)
broke a foot loop while we approached it to remotely
deliver an immobilization drug. Snares failed in 2 other
recent instances, we know of, during the capture of
American black (Ursus americanus) and grizzly bears
(personal communications: B. McLellan, BC Forest
Service, D’Arcy, British Columbia, Canada, 2007; E.
Wenum, Montana Fish, Wildlife & Parks, Kalispell,
Montana, USA, 2007). An Amur tiger (Panthera tigris
altaica) snare-captured in the Russian Far East also
escaped in 2008 (C. Miller, Wildlife Conservation
Society, Vladivostok, Primorski Krai, Russia, personal
communication, 2008). When a bear escapes a snare
there is a high potential for serious injury or death both
to the bear and to capture personnel.
www.bearbiology.com/fileadmin/tpl/Downloads/URSUS/Vol_20_1/Flaa_et_al._Ursus_20_1.pdf