Interestingly, many pursuits by wild bears have been observed in or near ponds, lakes and rivers (Iles et al., 2013; LJG & RFR our unpublished data), with the bear often lying in shallow streams and ponds immediately after the pursuit (Fig. 5). Immersion in water has been shown to reduce a polar bear's core body temperature substantially both before and after sustained exercise (Øritsland, 1969; Frisch et al., 1974). In general, the thermoregulatory costs of exercise for polar bears can be somewhat dissipated by certain behaviours, but these costs probably often constrain the duration and speed of a wild goose chase, especially during warm summer days. Figure 5:A subadult male polar bear in the Mast River (Wapusk National Park) after killing at least five flightless snow geese in three chases. After the chases, the bear walked into the river, lay down and drank periodically. Photographed on 13 July 2013 by R.F.R.