Monitoring adrenocortical function as a measure of stress in blue wildebeest (Connochaetes taurinus)

Abstract

Like many other wildlife species, blue wildebeest (Connochaetes taurinus) are routinely captured for relocation purposes. Several studies have shown that physiologically this is a very stressful period for wild animals and can affect several aspects of their well-being. Little is known about the level of physiological stress experienced by blue wildebeest during capture and confinement before transport. A non-invasive approach to assess adrenocortical function as a measure of physiological stress would be preferable, as animals are not disturbed during sample collection, and therefore sampling is feedback free. Currently, however, such a non-invasive measure has not been evaluated for any wildebeest species. An adrenocorticotropic hormone (ACTH) challenge test was performed on one sub-adult male and one adult female. We examined the suitability of five enzyme immunoassays (EIAs), detecting faecal glucocorticoid metabolites (fGCM) with a 5?-3?-ol-11-one (3?,11oxo-CM), 5?-pregnane-3?,11?,21-triol-20-one (37e), 11?,21-diol-20-one (corticosterone), 11,17,21-trihydroxypregn-4-ene-3,20-dione (cortisol), and 11,17-dioxoandrostane (11,17-DOA) structure respectively, for monitoring stress-related physiological responses in blue wildebeest. After evaluating all five EIAs, it was concluded that the EIA measuring 11,17-DOA performed the best for detection of fGCMs in blue wildebeest with a 21 fold increase above the baseline in the male and a 4,7 fold increase above the baseline in the female at 12 hours post ACTH injection. Under field conditions the use of the 11,17-DOA EIA allowed the monitoring of fGCM alterations when wildebeest were captured using a mass capture technique; fGCM concentrations were elevated by 1,5 times in samples collected from animals restrained for up to 10 hours in a truck compared to those collected directly after capture (P <0,001). No significant increase in fGCM concentrations was detected in faecal samples collected directly after capture from animals of the same herd captured either on day 1 or day 2 of mass capture, indicating that the presence of a helicopter during the two days of capture was not associated with a profound stress response in wildebeest that were not captured at the time but were in the vicinity of the capture. Storage of faeces in labelled plastic containers at ambient temperature for up to 48 hours post-defecation resulted in a significant decrease in 11,17-DOA levels from 8 to 48 hours after defecation. Therefore sample collection for 11,17-DOA determination in wildebeest can occur for up to 8 hours post-defecation without the risk of substantial decreases in 11,17-DOA concentrations. By identifying a suitable assay for determining 11,17-DOA concentrations in blue wildebeest, it can now be used by researchers, wildlife managers and veterinarians to reliably monitoring the physiological stress responses to capture or other management procedures with minimum interference to the animals. We have also shown that the presence of a helicopter during capture does not appear to have a lasting influence on wildebeest 11,17-DOA concentrations, but prolonged restraint for 10 hours does.