deep and so often. Cascadia Research shows that the deeper the whales dive, the less often they dive per day, cutting their efforts by at least 40%. The challenges of deep diving are also overcome by the unique diving physiology of beaked whales. Oxygen storage during dives is mostly achieved by blood hemoglobin and muscle myoglobin. While the whale is diving, its heart rate slows and blood flow changes. This physiological dive response ensures oxygen-sensitive tissues maintain a supply of oxygen, while those tissues tolerant to hypoxia receive less blood flow. Additionally, lung collapse obviates the exchange of lung gas with blood, likely minimizing the uptake of nitrogen by tissues. Feeding The throats of all beaked whales have a bilaterally paired set of grooves that are associated with their unique feeding mechanism, suction feeding. Instead of capturing prey with their teeth, beaked whales suck it into their oral cavity. Suction is aided by the throat grooves, which stretch and expand to accommodate food. Their tongues can move very freely. By suddenly retracting the tongue and distending the gular (throat) floor, pressure immediately drops within the mouth, sucking the prey in with the water. Dietary information is available from stomach contents analyses of stranded beaked whales and from whaling operations. Their preferred diet is primarily deep-water squid, but also benthic and benthopelagic fish and some crustaceans, mostly taken near the sea floor. In a recent study, gouge marks in the sea floor were interpreted to be a result of feeding activities by beaked whales. To understand the hunting and foraging behavior of beaked whales, researchers used sound and orientation recording devices on two species: Cuvier's beaked whale (Ziphius cavirostris) and Blainville's beaked whale (Mesoplodon densirostris). These whales hunt by echolocation in deep water (where the majority of their prey is located) between about and usually catch about 30 prey per dive. Cuvier's beaked whales must forage on average at for 58 minutes and Blainville's beaked whales typically forage at deep for an average of 47 minutes. Range and habitat The family Ziphiidae is one of the most widespread families of cetaceans, ranging from the ice edges at both the north and south poles, to the equator in all the oceans. Specific ranges vary greatly by species, though beaked whales typically inhabit offshore waters that are at least 300 m deep. Beaked whales are known to congregate in deep waters off the