Effects of capture stress on free-ranging, reproductively active male Weddell seals

Abstract

Physiological stress responses to capture may be an indicator of welfare challenges induced by animal handling. Simultaneously, blood chemistry changes induced by stress responses may confound experimental design by interacting with the biological parameters being measured. Cortisol elevation is a common indicator of stress responses in mammals and reproductive condition can profoundly influence endocrine response. We measured changes in blood cortisol and testosterone induced by handling reproductively active male Weddell seals (Leptonychotes weddellii) early and late in the breeding season. Weddell seals have the highest resting cortisol levels of all mammals yet showed a clear, prolonged elevation in cortisol in response to capture. Responses were similar when first caught and when caught a second time, later in the breeding season. Baseline testosterone levels declined over the breeding season but were not altered by capture. Administering a light dose of diazepam significantly ameliorated the cortisol response of handled animals without affecting testosterone levels. This may be an effective way of reducing acute capture stress responses. Male breeding success in years males were handled was no different to the years they were not, despite the acute capture response, suggesting no long-term impact of handling on male reproductive output.

Stress response of wild bottlenose dolphins (Tursiops truncatus) during capture–release health assessment studies

“…Accordingly, it is assumed that an animal showing a larger expression of cortisol in the plasma in response to capture and restraint perceives the stressor more negatively than an animal with lower cortisol levels (Walker et al, 2005). Even Weddell seals (Leptonychotes weddellii) with the highest resting cortisol levels of all mammals show a clear, prolonged elevation in cortisol in response to capture (Harcourt et al, 2010).…”

Short-term effects of tagging on activity and movement patterns of Eurasian beavers (Castor fiber)

“…blood parameters and/or faeces; Bosson et al 2012;Harcourt et al 2010;Rehnus et al 2009;Sheriff et al 2011). Indeed, capture effects might only be physiological (Kock et al 1987;Meyer et al 2008) and do not necessarily imply visible behavioural changes.…”

An Economical Custom-Built Drone for Assessing Whale Health

“…Given the large size, mass and power of whales, this approach involves high risk to both researchers and to the whale itself. Even under ideal circumstances this method is likely to disturb the animal, potentially compromising the validity of some of the measures such as stress hormones which elevate rapidly (Harcourt et al, 2010). Accordingly, alternative approaches have long been sought.…”