TROUBLED WATERS - Whale and Dolphin Conservation Society

Thyroid function in cetaceans can also be affected by stressful conditions, but interpretation should
take account of sex and age (St. Aubin et al. 1996). For examples see; a) beluga whales
(Delphinapterus leucas): St. Aubin and Geraci 1988, 1992; b) captive white-sided dolphins
(Lagenorhynchus obliquidens): Ridgeway and Patton 1971; c) bottlenose dolphins (Tursiops truncatus):
Orlov et al. 1988; see also St. Aubin et al. 1996.
As in most vertebrates, stress can alter immunocompetence in cetaceans (see Romano et al. 1992,
1993, 1994; St. Aubin et al. 1989, 1990; Medway et al. 1970; Townsend 1999; reviewed in Curry
1999). Suppression of natural killer cell activity is reported in beluga whales (De Guise et al. 1997),
and capture stress can suppress leukocytes and blood iron levels (Geraci and Medway 1973, St. Aubin
and Geraci 1989). Thomson & Geraci (1986) report high mortality associated with capture and
confinement stress in various small cetaceans, including Phococoena phococoena (Dudock van Heel,
1962), Phocoenoides dalli (Ridgeway, 1966) and Delphinus delphis (Walker, 1975).
Muscle damage and exertional myopathy in cetaceans
Muscle damage was found in dolphins after capture experiments and is likely, therefore, to arise in
other cetaceans. Muscle activity during pursuit and capture can affect blood enzymes – creatinine
kinase (CK), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and blood urea
nitrogen (BUN) and potassium levels in cetaceans. Colgrove (1978) diagnosed EM following the
transportation of a bottlenose dolphin, with first signs appearing 22 hours post-transport. Young et
al. (1997) found 11 blood and serum parameters linked to stress in net-caught wild and healthy
captive bottlenose dolphins, which matched those for terrestrial animals suffering from EM. The
authors conclude that dolphins are susceptible to EM. Thurnbull and Cowan (1998) speculate that
the deaths of small cetaceans following capture for marine collections may be linked to EM.
Dolphins may be particularly prone to stress-related cardiomyopathy or contraction band necrosis
(CBN). CBN is characterized by lesions associated with hypercontracted myocardial cells, which in
turn have been linked to elevated catecholamine concentrations (Reichenach and Benditt, quoted in
Thurnbull and Cowan 1998). They can occur following traumatic circumstances ranging from
psychological stress and drowning to exertional myopathy and are considered to contribute to their
fatal outcome. Identical lesions occurred in a sample of stranded cetaceans of nine species. The
authors attributed these lesions to physiological and psychological stress linked to stranding, disease
and injury. Elevated CK levels in some dolphins killed during purse-seining are considered indicative
of “muscular exertion or muscle damage” which may result in unobserved post-release mortality
(Stuntz and Shay 1979 quoted in Curry 1999). More recent evidence for potential stress-related
injury or unobserved mortality emerged for dolphins involved in purse seine fishing operations
(NOAA 2002).
Conclusions
The degree of exercise imposed on whales during whaling may fall outside the species’ adaptive range.
“Even species that have evolved for efficient running, either for predator avoidance or for predation, may
develop exertional myopathy following intense or prolonged muscular activity associated with extreme stress
during air or ground pursuit.” (Williams and Thorne 1996). Whalers depend on gaining a minimum
distance between themselves and whales for successful harpooning. From what is known about the
behavioural response of cetaceans to ships, this range is likely to fall below what would naturally be
maintained by wild cetaceans in many cases. Pursuit as part of whaling may, therefore, be stressful
The potential stress effects of whaling and the welfare implications for hunted cetaceans
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