Applied Research and Development Branch http://sit.mnr.gov.on.ca Note Number 3 2006 Martyn E. Obbard1, Marc R.L. Cattet2, Tim Moody3, Lyle R. Walton4, Derek Potter1, Jeremy Inglis5, and Christopher Chenier 6 1 Wildlife Research and Development Section, Ontario Ministry of Natural Resources, Trent University, DNA Building, 2140 East Bank Drive, Peterborough, ON K9J 7B8 2 Canadian Co-operative Wildlife Health Centre, Department of Veterinary Pathology, Western College of Veterinary Medicine, 52 Campus Drive, Saskatoon, SK S7N 5B4 3 Enforcement Branch, Ontario Ministry of Natural Resources, 300 Water St., 1st Floor North, Peterborough, ON K9J 8M5 4 Northeast Science and Information Section, Ontario Ministry of Natural Resources, Hwy. 101 E., P.O. Bag 3020, South Porcupine, ON P0N 1H0 5 Ontario Ministry of Natural Resources, Pembroke District, 31 Riverside Dr., Pembroke, ON K8A 8R6 6 Ontario Ministry of Natural Resources, Cochrane District, 2 Third Ave., PO Box 730, Cochrane, ON P0L 1C0 Temporal Trends in the Body Condition of Southern Hudson Bay Polar Bears INTRODUCTION Ecological change in the Arctic as a result of climatic warming has been suggested as a significant threat to the conservation of polar bears (Ursus maritimus) (Lunn et al. 2002). The impacts of climatic warming on Canadian polar bear populations may occur first near the southern edge of the range in James Bay and Hudson Bay (Stirling and Derocher 1993, Arctic Climate Impact Assessment 2004, Derocher et al. 2004). In particular, the break-up of sea ice earlier in the year is believed to reduce opportunities for polar bears to feed and store fat needed for prolonged fasting during the ice-free season (Stirling et al. 1999). If polar bears have access to their primary prey, ringed seals (Pusa hispida) (Stirling and Archibald 1977), for a shorter period then it is likely that they will have difficulty gaining sufficient body mass during the ice-covered period, which may have effects at both the individual and population level. For example, Stirling et al. (1999) documented a long- term decline in body condition and evidence of reduced reproductive success in polar bears from the Western Hudson Bay population, which they attributed to a trend towards earlier melting of the sea ice in summer in western Hudson Bay. More recently, Gough et al. (2004) and Gagnon and Gough (2005) demonstrated trends towards earlier break-up in James Bay, along the southern shore of Hudson Bay, and in western Hudson Bay during the period 1971-2003. Trends towards later freeze-up were found for northern and northeastern Hudson Bay (Gagnon and Gough 2005) trends in other areas of Hudson Bay were not statistically significant but were in the direction of later freeze-up. Over the past 3 decades, break-up dates are occurring earlier by about 9.5 days per decade in northern James Bay and by between 5 and 8 days per decade along the southern Hudson Bay coast of Ontario. Declining body condition in Western Hudson Bay polar bears (Stirling et al. 1999) and the recently documented trends in break-up and freeze-up dates for eastern Hudson Bay and James Bay suggest that there

C L I M A T E C H A N G E R E S E A R C H I N F O R M A T I O N N O T E 2 Figure 1. Adult male polar bear apparently in poor body condition sighted along the Ontario coast near Fort Severn, fall 2005. (Photo credit: T. Miles) should be evidence of declines in body condition of bears from the Southern Hudson Bay population. Indeed, there are recent anecdotal reports of polar bears sighted along the Ontario coast that are perceived to be in poor condition (M. E. Obbard, unpublished data Fig. 1). Here we investigate evidence for change in body condition in Southern Hudson Bay polar bears by comparing data from an earlier study conducted from 1984-86 (Kolenosky et al. 1992) with data from recent field work conducted from 2000-05. STUDY AREA AND METHODS The study area extended along the Ontario coastline from Hook Point (ca. 54�� 50'N 82�� 15'W) on northwestern James Bay to the Hudson Bay coast at the Ontario���Manitoba border (ca. 56��50'N 89�� W) (Fig. 2). The study area included offshore spits and small islands, and inland areas up to 40 km inland from the coast. From 1984-1986, polar bears were captured by darting from a Bell 206L helicopter and immobilised using a mixture of ketamine hydrochloride and xylazine hydrochloride (Lee et al. 1981). Immobilisation was reversed by intravenous injection of yohimbine hydrochloride (Ramsay et al. 1985). From 2000-2005, bears were immobilised by darting from a Bell 206L helicopter using Telazol�� (ZT) (Stirling et al. 1989), or a mixture of Telazol�� and xylazine hydrochloride (XZT) (Cattet et al. 2003). The xylazine in XZT immobilisations was reversed with atipamezole (Cattet et al. 2003). Handling procedures were approved annually by the Animal Care Committee of the Ontario Ministry of Natural Resources (OMNR) and followed the guidelines of the American Society of Mammalogists (Committee for Field Methods in Mammalogy 1987). Standard morphometric measurements were taken, including straight-line body length (SLBL) and total body mass (TBM). SLBL was measured to the nearest centimetre as the dorsal straight-line distance from the tip of the nose to the end of the last tail vertebra using a metal measuring tape. All bears were measured while sternally recumbent with the back legs extended behind and the front legs forward. TBM was measured to the nearest 500 g by suspending the bear from either a spring-loaded weigh scale (1984-86), or an electronic load cell scale (2000-05). During weighing, bears were placed in a semi-supportive sling and lifted by chain pulley until clear of the ground (Fig. 3). A Body Condition Index (BCI) value (Cattet et al. 2002) was calculated for each