Hormonal and behavioural stress responses to capture and radio-collar fitting in free-ranging pampas deer (Ozotoceros bezoarticus)

Abstract

This study evaluated the short-term hormonal and behavioural responses to capture and radio-collarfitting in free-ranging pampas deer (Ozotoceros bezoarticus). Twenty adult deer (eleven females and nine males) were captured in the South Pantanal wetland (Brazil) and equipped with VHFradio-collars(marked deer). Untreated adult deer of the same sex were randomly chosen as the control group (nine females and nine males). On the day following capture, an observer followed all deer for faecal collection and behaviour evaluation. Faecal samples were immediately refrigerated and frozen at -20°C (within a maximum of 12 h. Faecal glucocorticoid metabolites (FGM) were measured using an II-oxoaetiocholanolone enzyme immunoassay. A qualitative behaviour assessment and the consequences of capture were evaluated using pre-defined terminologies and scores. Flightdistance was recorded using a range finder. FGM increased from 19-22 h after capture onwards and peak concentrations were five times (median) higher as the respective baseline values. FGM values of marked deer were significantly higher at 22-25 and 25-28 h compared with controls. Marked male but not female deer had significantly higher FGMvalues at 22-25 and 25-28 h compared with their baseline values. Marked deer were significantly more fearful, less sociable and defensive than controls. The absences of significant increases of FGM in the captured female deer may indicate that females are less prone to capture stress. The significantly more fearful, and less sociable and defensive patterns observed in marked deer may be relevant during capture of lactating females or in areas with high predator pressure.