Social, Reproductive and Contextual Influences on Fecal Glucocorticoid Metabolites in Captive Yangtze Finless Porpoises (Neophocaena asiaeorientalis asiaeorientalis) and Bottlenose Dolphins (Tursiops truncatus)

Abstract

Although the use of fecal glucocorticoid metabolite (FGCM) measurements as non-invasive biomarkers for the stress response in mammals has increased, few studies have been conducted in odontocetes. We investigated if animal sex, age, pregnancy or contextual variations (season, sampling time, enrichment, social separation and presence of visitors) influenced the FGCM concentrations in presumably healthy, captive and endangered Yangtze finless porpoises (YFPs, N = 4) and bottlenose dolphins (BDs, N = 3). For YFPs, the FGCM concentrations were influenced by season (p = 0.01), diurnal variation (p = 0.01) and pregnancy (p = 0.005). Contextual variables that were associated with increases in FGCM concentrations included social separations (p = 0.003) and numbers of visitors (p = 0.0002). Concentrations of FGCMs were lower (p = 0.001) after exposure to environmental enrichment. For BDs, enrichment was associated with reduced concentrations of FGCMs (p < 0.0001). The presence of visitors also influenced this species’ FGCM concentrations (p = 0.006). These results demonstrate that changes in the FGCM concentrations in YFPs and BDs may occur in response to contextual and social changes. In combination with other behavioral and physiological assessments, measurements of FGCMs may be a useful tool for monitoring cetacean welfare. Such monitoring may help researchers identify and better understand situations that may be stressful for animals and, therefore, improve management and husbandry. Furthermore, results from our study and inferences of the FGCM concentrations in cetaceans, and their potential relationship to stress, may be extrapolated to studies of free-ranging animals, which may help detect possible environmental or anthropogenic stressors that could be affecting these populations.

Reference intervals and values for fecal cortisol, aldosterone, and the ratio of cortisol to dehydroepiandrosterone metabolites in four species of cetaceans

“…While age was a significant predictor of cortisol for Tursiops truncatus in the current study, age has not been a significant predictor in previous reports [ 16 , 34 ]. Month was a significant predictor of cortisol for Tursiops aduncus in the current study, similar to seasonal variations observed in previous work [ 31 ].…”

Biological characteristics of pregnancy in captive Yangtze finless porpoises revealed by urinary metabolomics

“…Tetrahydrocortisone is commonly measured in urine as a marker of cortisol production and metabolism [ 69 ]. In cetaceans, elevated concentrations of fecal glucocorticoids during pregnancy have been observed in the North Atlantic right whale ( Eubalaena glacialis ) [ 70 ], blue whale ( Balaenoptera musculus ) [ 38 ], humpback whales ( Megaptera novaeangliae ) [ 71 ], and YFPs [ 72 ]. Furthermore, long-term continuous monitoring by Steinman et al.…”

Activity, Social Relationships, and Maternal Care in a Bottlenose Dolphin Group under Professional Care

“…However, differences in maternal style also may have moderated the strength of other social relationships. Positive social relationships can enhance the welfare of dolphins under professional care [50,63]. Social behaviors, such as synchronous swimming, are associated with positive affective states [64].…”