Assessment of diurnal urinary cortisol excretion in Asian and African elephants using different endocrine methods

Abstract

Longitudinal urine samples were collected from Asian and African elephants to assess sample processing and immunoassay techniques for monitoring adrenal activity. Temporal profiles of urinary cortisol measured by RIA and EIA, with and without dichloromethane extraction, were similar; all correlation coefficients were >0.90. However, based on regression analyses, cortisol immunoactivity in extracted samples was only 72-81% of that of unextracted values. Within assay technique, RIA values were only 74-81% of EIA values. Collection of 24-hr urine samples demonstrated a clear diurnal pattern of glucocorticoid excretion, with the lowest concentrations observed just before midnight and peak concentrations occurring around 0600-0800 hr. These results indicate that elephants fit the pattern of a diurnal species, and that glucocorticoid production is affected by a sleep-wake cycle similar to that described for other terrestrial mammals. Cortisol can be measured in both extracted and unextracted urine using RIA and EIA methodologies. However, unexplained differences in quantitative results suggest there may be sample matrix effects and that data generated using different techniques may not be directly comparable or interchangeable.

Circadian Rhythm of Salivary Cortisol in Asian Elephants (Elephas maximus): A Factor to Consider During Welfare Assessment

“…The diurnal pattern of urinary cortisol excretion has been well characterized for Asian and African elephants (Brown et al, 2010). When comparing the salivary cortisol levels found in this study with those reported by Brown et al (2010), a similar pattern of cortisol secretion was observed.…”

“…In diurnal animals, cortisol secretion is affected by the sleep-wake cycle, with cortisol concentrations being highest early in the morning and lowest at night, whereas nocturnal animals show the opposite pattern (Brown et al, 2010;Czeisler & Klerman, 1999;Fulkerson et al, 1980;Luboshitzky, 2000;Thun, Eggenberger, Zerobin, Luscher, & Vetter, 1981).…”

“…Irvine and Alexander (1994), who worked with horses, and Suzuki et al (2003), who worked with dolphins, found that both species had the highest cortisol concentrations in the morning and the lowest hormone levels in the evening and at night. In elephants, Brown, Kersey, Freeman, and Wagener (2010) found that urinary cortisol excretion showed high levels in the morning, which decreased during the evening. Studies on salivary cortisol levels in pigs (Ekkel et al, 1996;Ruis et al, 1997) demonstrated that the concentration of cortisol was also higher during the morning and lower in the evening.…”

“…The aim of this study was to test whether salivary cortisol levels of the Asian elephant (Elephas maximus) vary between morning and evening and to take into account this possible variation when using this method as a tool to assess the welfare of captive individuals of this species (see also Brown et al, 2010).…”

Rating Methodology, Personality Axes, and Behavioral Plasticity: A Case Study in African Lions

“…Zoo researchers often utilize glucocorticoid measures as a way to assess how animals cope with captive stressors (Armstrong & Santymire, 2013;Brown, Kersey, Freeman, & Wagener, 2010;Burgener, Gusseta, & Schmidb, 2008;Loeding, Thomas, Bernier, & Santymire, 2011). A link between personality measures (behavioral responses that are consistent across time) and the physiological stress response (i.e., the hypothalamic-pituitary-adrenal (HPA)) axis activity) has been termed a coping style (Koolhaas et al, 1999).…”