Capture Methods in Five Subspecies of Free-Ranging Bighorn Sheep: An Evaluation of Drop-Net, Drive-Net, Chemical Immobilization and the Net-Gun

Abstract

Six hundred thirty-four bighorn sheep (Ovis canadensis) were captured in the western United States between 1980 and 1986, using four different methods: drop-net (n = 158), drive-net (n = 249), chemical immobilization (n = 90) and net-gun (n = 137). The net-gun was found to have considerable advantages over the use of ground nets and chemical immobilization methods for capturing bighorn sheep. Evaluation of specific outcome categories for individual sheep, including normal, compromised (stress-induced), mortality from capture myopathy (CM), and accidental mortality, revealed significant differences in these rates between capture groups (P less than 0.05). The use of the net-gun resulted in the lowest proportion of compromised sheep at 11% (15/137), had no CM mortality, and resulted in a 2% (2/137) accidental mortality. The use of drop-nets resulted in 15% compromised sheep (24/158), a CM mortality rate of 2% (3/158), and an accidental mortality rate of 1% (2/158). A similar proportion of sheep were compromised with the drive-nets (16%, 39/249). This method also had the highest CM mortality rate at 3% (7/249), and an accidental mortality rate of less than 1% (2/249). Chemical immobilization resulted in the most compromised sheep at 19% (17/90), had a CM mortality rate of 2% (2/90), and caused the most accidental deaths at 6% (5/90). Drop-nets and drive-nets were comparable when combining total mortality with rates for compromised bighorn sheep, 18% and 19%, respectively (29/158 and 48/249). Chemical immobilization had the highest combined measure of risk at 27% (24/90) and net-gun lowest at 12% (17/137).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative evaluation of effort, capture and handling effects of drive nets to capture roe deer (Capreolus capreolus), Southern chamois (Rupicapra pyrenaica) and Spanish ibex (Capra pyrenaica)

“…Moreover, it is expensive and potentially dangerous, particularly in wild steep environments where the animal can fall over a cliff (Kock et al 1987b;Abderhalden et al 1998;Kenny et al 2008). Reported mortality for this method ranges from 0% to 26% (Kock et al 1987b;Locati et al 1991;Peracino and Bassano 1993;Abderhalden et al 1998;Pérez et al 2003;Dematteis et al 2008).…”

“…Remarkably, mortality associated with drive nets is highly variable, depending on the type of net, the surveillance by operators, the time the animals remain entangled in the net and the type of immobilising or tranquillising drug administered (Beasom et al 1980;Kock et al 1987b;Sullivan et al 1991;Berducou 1993;Schemnitz 1994;Peterson et al 2003;Powell and Proulx 2003).…”

Anaesthesia of free-ranging Northern chamois (Rupicapra rupicapra) with xylazine/ketamine and reversal with atipamezole

“…Reported mortality rates for chemically captured free-ranging Caprinae, under a variety of scenarios, varied between 0% and 26%, most of which being around 5% (Bergerud et al 1964;Houston 1969;Kock et al 1987;Jolicouer and Beaumont 1986;Gauthier 1993b;Jorgenson et al 1990;Peracino and Bassano 1993;Perez et al 1997;Kilpatrick and Spohr 1999;Bassano et al 2004;Dematteis et al 2008). In free-ranging Northern chamois captured using medetomidine-ketamine (Walzer et al 1998) and xylazine alone (Peracino and Bassano 1993;Dematteis et al 2008), mortality rates were 9.1%, 8% and 4.6%, respectively.…”

How safe is mist netting? evaluating the risk of injury and mortality to birds

“…While researchers often assume that the benefits of information gained outweigh the potential risk to individual animals, the impacts are not always quantified (Wilson & McMahon 2006). Some methods such as blood and diet sampling in birds (Carlisle & Holberton 2006;Brown & Brown 2009;Voss, Shutler, & Werner 2010), branding and tagging in seals (McMahon, van den Hoff, & Burton 2005;Baker & Johanos 2006) and radiotelemetry in mammals and birds (Kock et al 1987;Bailey et al 1996;Del Giudice et al 2005;Arnemo et al 2006;Barron, Brawn, & Weatherhead 2010) have been scrutinized carefully to determine potential effects on survival, reproduction and behaviour, whereas other methods such as the use of mist nets to capture wild birds have rarely been evaluated (Wilson & McMahon 2006;Jennings et al 2009). Procedures that affect the welfare of animals raise ethical considerations and can compromise research objectives by introducing bias into data collection and should be considered when interpreting results (Dugger et al 2006;Wilson & McMahon 2006;Saraux et al 2011).…”