Sperm whales undertake the deepest dives of any air-breathing animal, with welfare considerations spanning the extraordinary physiological demands of their foraging lifestyle and human-caused threats.
Sperm whale welfare combines the extraordinary natural physiological challenges of extreme deep diving with human-caused threats that cause direct welfare harm. The diving physiology of sperm whales represents one of the most remarkable biological achievements on Earth - oxygen storage in blood and muscle, metabolic suppression during diving, and cardiovascular adaptations that allow functioning at pressures that would kill surface-adapted mammals in seconds. While natural foraging involves physiological stress, this represents evolved biological capacity rather than welfare compromise in the conventional sense. Human-caused welfare harms are more clearly problematic: military sonar causes acoustic trauma and behavioral disruption that has been linked to atypical strandings of sperm whales with signs consistent with decompression injury - suggesting that sonar disrupts the controlled ascent behaviour that prevents nitrogen bubble formation. Pollutant accumulation in sperm whale tissues - including PCBs, DDT, and heavy metals - causes immune suppression, reproductive failure, and potentially neurological harm. The cognitive complexity of sperm whales, with the largest brain of any animal, strengthens the welfare case for taking these threats seriously.