Circadian rhythm of salivary cortisol secretion in female zoo-kept African elephants (Loxodonta africana)

Publication Type:
Journal Article
Year of Publication:
Miguel Casares, Gema Silván, Maria Dolores Carbonell, Cati Gerique, Leticia Martinez-Fernandez, Sara Cáceres, Juan Carlos Illera
Zoo Biology
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Salivary samples were collected over a 24-hr period from one group of six juvenile (7–12 years) and one group of three adult (24–25 years) African elephant females, Loxodonta africana, and the cortisol concentration was measured in unextracted samples by EIA. Samples were collected during May, June, and November 2012 (n = 147) using cotton swabs at 4-hr intervals from 20:00 to 20:00 of the next day (seven samples per animal in each trial). The animals are kept under standard zoo management: the herd is maintained in their indoor enclosures until 10:00 and then released into the outdoor enclosures until 21:00–21:30 (May/June) and 18:30–19:00 (November). No adult elephant bull was present at the zoo during this time. The results demonstrate a clear diurnal pattern of cortisol secretion with the lowest concentration observed at 20:00 (2.03 ± 0.08 ng/ml saliva) and the peak concentrations at 08:00 (5.26 ± 0.35 ng/ml saliva). Although the cortisol values were higher in the adult cows compared to the juvenile cows in the May–June period, the differences were not significant. However, the values obtained in November from the juvenile group were significantly higher (P < 0.05) than the concentrations measured in this group in June. In conclusion, salivary cortisol in zoo elephants follows a circadian rhythm (sleep–wake cycle) adapted to daily zoo husbandry routines. Zoo Biol. 35:65–69, 2016. © 2016 Wiley Periodicals, Inc.


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