Abstract: Mortality is high in zoo-housed black rhinoceros (Diceros bicornis), and the reproductive rates of captive white rhinoceros (Ceratotherium simum) are unsustainably low. To determine the possible role of stress in the causation of these problems, we analyzed weekly fecal samples collected for 1 year from black (10 males and 16 females) and white (six males and 13 females) rhinoceroses at 16 zoos for corticoid metabolite concentrations. Fecal corticoid profiles were examined in relation to behavior as rated by keepers in a questionnaire, luteal phase ovarian cycles of females (Brown et al., 2001), and socioenvironmental factors. We compared individual fecal corticoid profiles by examining hormone means and variability (i.e., standard deviation (SD) and coefficient of variation (CV)). For the black rhinos, higher mean corticoid concentrations were found at zoos where rhinos were maintained in enclosures that were exposed to the public around a greater portion of the perimeter. Higher variability in corticoid excretion was correlated with higher rates of fighting between breeding partners and higher institutional mortality rates. Black rhino pairs that were kept separated exhibited lower corticoid variability and less fighting activity when they were introduced during female estrous periods compared to pairs that were kept together every day. For white rhinos, significantly lower mean corticoids were found for individuals that rated higher on “friendliness to keeper.” Higher corticoid variability was found in noncycling as compared to cycling white rhino females. Noncycling females exhibited higher rates of stereotypic pacing and lower frequencies of olfactory behaviors. Interindividual differences in mean corticoids in both species appeared to be related to responsiveness to humans, whereas corticoid variability was related to intraspecific social relationships. More importantly, high corticoid variability appeared to be an indicator of chronic or “bad” stress, because of its association with potentially deleterious consequences in each species (i.e., fighting and mortality (black rhino), and reproductive acyclicity (white rhino)). Our results provide evidence that social stressors may cause chronic stress in black and white rhinos, and that this contributes to the captive-population sustainability problems observed in each species. Zoo Biol 0:1–18, 2005. © 2005 Wiley-Liss, Inc.

Abstract: Recognition of information from acoustic signals is crucial in many animals, and individuals are under selection pressure to discriminate between the signals of conspecifics and heterospecifics or males and females. Here, we first report that rhinos use information encoded in their calls to assess conspecifics and individuals of closely related species. The southern (Ceratotherium simum) and critically endangered northern (C. cottoni) white rhinos are the most social out of all the rhinoceros species and use a contact call pant. We found that southern white rhino pant calls provide reliable information about the caller’s sex, age class and social situation. Playback experiments on wild territorial southern white rhinoceros males revealed that they responded more strongly to the pant calls of conspecific females compared to the calls of other territorial males. This suggests that pant calls are more important form of communication between males and females than between territorial males. Territorial southern males also discriminated between female and territorial male calls of northern species and reacted more intensively to the calls of northern than southern males. This might be caused by a novelty effect since both species naturally live in allopatry. We conclude that white rhinos can directly benefit from assessing individuals at long distances using vocal cues especially because their eyesight is poor. Pant calls thus likely play a significant role in their social relationships and spatial organization. In addition, better understanding of vocal communication in white rhinos might be helpful in conservation management particularly because of their low reproduction in captivity.

Abstract: How animals use space has important consequences for feeding ecology, social organization, mating strategies and conservation management. In white rhinoceros, female home ranges are much larger than male territories, suggesting that movement patterns are influenced by factors other than resource distribution. In this study we placed radiotransmitters on 15 female white rhinoceros, recording 1758 locations and collecting behavioural data during 1671 observation sessions, making this the largest data set of its kind in this species. We investigated how habitat variables and male territories influenced female movement and reproductive behaviour. Female home ranges were approximately 20 km2 and core areas were 5 km2, with male territories roughly the same size as female core areas. Female range size did not vary with season, but the pattern of space use did vary. Females used grassland habitat preferentially, utilizing these areas significantly more than expected based on availability. Findings relevant to the mating strategy include: (1) the amount of grassland in a male's territory predicted female use of the territory; (2) the time that a female spent in a male's territory was a significant predictor of reproductive activity with the male, indicating that females probably mate with the most familiar male; and (3) the temporal pattern of female space use suggests that females did not increase mate sampling behaviour nor did they become more choosy about which males they visited when reproductively active. These findings suggest that males may maximize reproductive success by defending areas containing more grassland habitat.

Abstract: We investigated how plains zebras moved across a large natural landscape by analysing the movement paths of nine zebra mares foraging out from spatially confined waterholes during the dry season in the Makgadikgadi Pans National Park, Botswana. Since it was essential to investigate directed movement over a range of spatial scales to determine the correct movement behaviour and strategy, we used Nams's scaling test for oriented movement. Zebras followed directed movement paths in the lower to medium spatial scales (10 m–3.7 km) and above their visual, and possibly olfactory, range. The spatial scale of directed movement suggests that zebras had a well-defined spatial awareness and cognitive ability. Seven zebras used directed movement paths, but the remaining two followed paths not significantly different to a correlated random walk (CRW). At large spatial scales (>3 km) no distinct movement pattern could be identified and paths could not be distinguished from a CRW. Foraging strategy affected the extent of directed movement: zebras with a confined dispersion of grazing patches around the central place directed their movements over a longer distance. Zebras may extend the distance at which they can direct their movement after improving their knowledge of the local environment.

Abstract: Abstract Only few quantitative reports exist about the concentrations and induction of immunoglobulin A (IgA) in mucosal secretions of horses. Despite this, it is widely assumed that IgA is the predominant immunoglobulin on mucosal surfaces in the horse. Here, two new monoclonal antibodies (mAbs) against equine IgA, clones 84-1 and 161-1, were developed and characterized in detail. Both IgA mAbs specifically bound monomeric and dimeric equine IgA in different applications, such as Western blots and fluorescent bead-based assays. Cross-reactivity with other equine immunoglobulin isotypes was not observed. The new IgA mAb 84-1 was used in combination with the previously characterized anti-equine IgA mAb BVS2 for the development and validation of a fluorescent bead-based assay to quantify total IgA in equine serum and various secretions. The IgA assay's linear detection ranged from 64 pg/ml to 1000 ng/ml. For the quantification of IgA in serum or in secretions an IgA standard was purified from serum or nasal wash fluid (secretory IgA), respectively. The different standards were needed for accurate IgA quantification in the respective samples taking the different signal intensities of monomeric and dimeric IgA on the florescent bead-based assay into account. IgA was quantified by the bead-based assay established here in different equine samples of healthy adult individuals. In serum the median total IgA was 0.45 mg/ml for Thoroughbred horses (TB, n = 10) and 1.16 mg/ml in Icelandic horses (ICH, n = 12). In nasopharyngeal secretions of TB (n = 7) 0.13 mg/ml median total IgA was measured, and 0.25 mg/ml for ICH (n = 12). Saliva of ICH (n = 6) contained a median of 0.15 mg/ml, colostrum of Warmbloods (n = 8) a median of 1.89 mg/ml IgA. Compared to IgG1 and IgG4/7 quantified in the same samples, IgA appeared as the major immunoglobulin isotype in nasopharyngeal secretions and saliva while it is a minor isotype in serum and colostrum. The newly developed monoclonal antibodies against equine IgA and the resulting bead-based assay for quantification of total IgA can notably improve the evaluation of mucosal immunity in horses.