Abstract
Fecal cortisol determination has been used in many domestic and exotic species to monitor adrenal activity. The aim of this study was to set up a radioimmunoassay (RIA) to measure fecal cortisol in the bottlenose dolphin and identify possible sources of variability. Serum samples (N=120) were collected by behavior at least once a month and fecal samples (N=472) were collected 1 to 4 times a week over a period of 1 year from 3 females and 2 males of bottlenose dolphins aging 7-10 years. Leucocytes were checked any time a blood sample was collected. Concurrently, appetite and attitude scores of the animals were recorded (scores ranged from 1=low/bad to 5=very good). The effects of sex, season and group separation, and the relationships between fecal cortisol and attitude and appetite were studied.
On average, fecal cortisol was significantly greater (P<0.01) in males (range: 0.3-15.8 pmol/g faeces) than in females (0.2-4.8 pmol/g faeces), while differences in serum cortisol were not so pronounced between females and males. No correlation between fecal and serum cortisol was detected. No correlation between fecal cortisol and leucocytes was detected, while serum cortisol had a negative correlation with eosinophils (R=-0,255, P<0.01).
The season has a significant effect on serum cortisol level (P<0.01) that showed an opposite trend compared to fecal cortisol. In males, fecal cortisol was significantly higher in summer (P<0.01) and when animals were kept separated in two groups (P<0.001). No relationship was observed between cortisol level and appetite and attitude. Both attitude and appetite were influenced by the season (P<0.05).
The determination of fecal cortisol concentrations is suitable to evaluate adrenal activity in dolphins allowing more frequent sample collection with no discomfort noticed from the animal. However, more research is needed to better characterize the physiological and environmental conditions that can affect fecal cortisol levels, and the relationship between the hormone content in feces and serum.