Daily salivary cortisol levels in response to stress factors in captive common bottlenose dolphins (Tursiops truncatus) a potential welfare indicator
DOLPHINS in a captive setting can be occasionally subjected to a variety of potentially stressful situations. The stress response comprises a variety of biological reactions to internal or external stimuli elicited when an individual perceives (real or not) a threat to its homoeostasis (Moberg and Mench 2000) The stress response is a complex interplay of behavioural and physiological strategies to cope with changes in the environment (Tsigos and Chrousos 2002, Sheriff and others 2011) Noise can act as a stressor to dolphins because cetaceans rely heavily on sound for many important life functions. This reliance on sound means it is quite likely that exposure to noise will have some detrimental effects on these life functions (Wright and others 2007) Observed effects of noise on marine mammals include: changes in vocalisations, respiration, swim speed, diving and foraging behaviour; displacement; avoidance; shifts in migration path; stress; hearing damage and strandings, but responses of marine mammals to noise can often be subtle and barely detectable (Weilgart 2007) If there is no obvious change in behaviour, stress is difficult to assess in dolphins, both individually and as a group. In order to detect the presence of stress responses in these situations, the endocrine response to stressors is assessed evaluating the hypothalamic pituitary adrenal (HPA) axis activity in dolphins and other cetaceans (Wright and others 2007, Amaral 2010) The HPA axis is a key element of the stress response and, when activated, the resultant hormonal cascade increases the levels of glucocorticoids (GCs)
Veterinary Record