Little is known about the levels of stress experienced by African buffalos affected by injury, disease, or socio-ecological and anthropogenic factors. To be able to start filling this gap, we examined the suitability of two 11-oxoaetiocholanolone enzyme-immunoassays (EIAs) detecting 11,17 dioxoandrostanes (11,17-DOA) as well as faecal glucocorticoid metabolites (FGMs) with a 5b-3a-ol-11-one structure (3a,11oxo-CM), respectively, for monitoring stress-related physiological responses in African buffalo. An adrenocorticotrophic hormone (ACTH) challenge in one male and one female housed at Mokopane Biodiversity Conservation Centre, South Africa, showed a threefold increase in circulating cortisol levels in a sample taken 40 min post-injection. Corresponding 11,17-DOA levels increased tenfold (female) and 15-fold (male) above baseline, and 3a,11oxo-CM concentrations increased ninefold (female) and 12-fold (male) above pre-injection levels, indicating that both EIAs are suitable for measuring FGMs in African buffalo.In addition, 11,17-DOA levels monitored during the adaptation process of individual housing revealed an up to 14-fold elevation in FGMs. Storage of faeces at ambient temperature for up to 16 h post-defecation resulted in an significant increase in 11,17-DOA levels 2 h after defecation. Finally, higher individual baseline 11,17-DOA concentrations were found in samples defecated overnight, indicating a possible diurnal effect in excretion of FGMs in African buffalo.
The oxpecker-ungulate association of sub-Saharan Africa is an example of a complicated interspecific association subject to variation in outcome. Oxpeckers (Buphagus spp.) are unusual birds because they not only glean ticks from an array of African ungulates, but they are one of the few avian species known to wound-feed from their living hosts. The conditions under which oxpeckers wound-feed and the mechanisms generating variation in this association are unclear. We took a unique approach to studying the relationship by conducting a series of feeding preference experiments on twelve captive red-billed oxpeckers (B. erythrorhynchus). We assessed how oxpecker feeding behaviour is influenced by changes in tick abundance and tick type. In cafeteria-style experiments, oxpeckers fed equally on ticks and liquid bovine blood. In experiments using donkeys as the host animal, oxpeckers spent more time wound-feeding when a less-preferred tick type was available and when tick abundance was low compared to when a preferred tick type was available and when tick abundance was high. However, oxpeckers still wound-fed even when offered a large number of the ticks they prefer. Additional experiments incorporating tick species of different stages and multiple ungulate species are necessary to fully reveal the dynamics of this association.
Little is known about the levels of stress experienced by African buffalos affected by injury, disease, or socio-ecological and anthropogenic factors. To be able to start filling this gap, we examined the suitability of two 11-oxoaetiocholanolone enzyme-immunoassays (EIAs) detecting 11,17 dioxoandrostanes (11,17-DOA) as well as faecal glucocorticoid metabolites (FGMs) with a 5b-3a-ol-11-one structure (3a,11oxo-CM), respectively, for monitoring stress-related physiological responses in African buffalo. An adrenocorticotrophic hormone (ACTH) challenge in one male and one female housed at Mokopane Biodiversity Conservation Centre, South Africa, showed a threefold increase in circulating cortisol levels in a sample taken 40 min post-injection. Corresponding 11,17-DOA levels increased tenfold (female) and 15-fold (male) above baseline, and 3a,11oxo-CM concentrations increased ninefold (female) and 12-fold (male) above pre-injection levels, indicating that both EIAs are suitable for measuring FGMs in African buffalo.In addition, 11,17-DOA levels monitored during the adaptation process of individual housing revealed an up to 14-fold elevation in FGMs. Storage of faeces at ambient temperature for up to 16 h post-defecation resulted in an significant increase in 11,17-DOA levels 2 h after defecation. Finally, higher individual baseline 11,17-DOA concentrations were found in samples defecated overnight, indicating a possible diurnal effect in excretion of FGMs in African buffalo.
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