of the F1s are full siblings, but born three years apart). The same two male brown bears both mated with the F1 female to produce the four backcross individuals, with three littermates being sired by one male and a single, older 3/4 grizzly bear coming from a mating between the F1 female and her father. Arviat bear It was widely reported that a bear shot in 2016, near Arviat on the western shore of Hudson Bay, was a hybrid, with news agencies stating that this was an outcome of climate change. This bear was light in colour, but 'blonde' grizzly bears are common on the Barren Grounds, and the Arviat bear did not have other features characteristic of hybrids. The Arviat bear was subsequently confirmed by genetic analysis to be a pure brown bear. Range expansion of brown bears as a possible contributing factor It is currently unknown why grizzly bears are being found in the habitat of polar bears. Although a grizzly bear was killed on Banks Island in 1951, it has until recently been rare for this species to stray far north of the coast of mainland Canada. In 1991 one or more grizzly bears were documented hunting seals and polar bears on the sea ice near Melville island, over 500 km from the mainland coast. In 2003 and 2004 a geological team working on Melville Island obtained photographic and DNA evidence of a grizzly bear in the area. Their report also collated information on several other sightings in the Canadian Arctic Archipelago. Grizzly bears have apparently also been extending their range east across the Barren Grounds towards Hudson Bay, and south towards northern Saskatchewan and Manitoba. Between 2003 and 2008 seven individuals were spotted in Wapusk National Park south of Churchill, Manitoba, an area used by polar bears for maternity dens and as a refuge during the ice-free season on Hudson Bay. Ancient hybridization The genetic methods used to confirm the family relationships and ancestry of the hybrid bears from northern Canada date back to the early 1990s, and are not powerful enough to reveal ancient history. However, the newer methods of genomics analyze thousands of sites in the genome, allowing the history of individual fragments of chromosomes to be traced back to particular populations (or species in the case of hybridization). Genomic studies of brown bears and polar bears have revealed that gene flow from polar