Counting the costs of white rhino poaching : we are likely underestimating the indirect and long-term impacts

No abstract available.https://zslpublications.onlinelibrary.wiley.com/journal/14691795hj2023Mammal Research InstituteZoology and Entomolog

Rival assessment by territorial southern white rhinoceros males via eavesdropping on the contact and courtship calls

Eavesdropping on vocal signals allows animals to gather information about conspecifics. For males, eavesdropping can be a low-risk method for determining the dominance status (e.g. territorial or subordinate) and motivation (e.g. mate seeking) of rivals. Adult southern white rhino males, Ceratotherium simum, are territorial and, in addition to other vocalizations, use contact and courtship calls when communicating with females. Although male territories are exclusive, the owners may tolerate up to three resident subordinate males. However, rival males sometimes intrude. Moreover, these intrusions may lead to rivals interacting with females. We investigated whether territorial males eavesdrop on vocal signals directed towards females by intruding males to determine their dominance status (territorial or subordinate) and motivation (contact calling an anoestrous female or approaching a female in oestrus during courtship). To do this, we first recorded and analysed contact and courtship calls of adult southern white rhino males and determined that these calls signal the males' dominance status and motivation. Playback trials revealed that territorial males differentiated between the calls of subordinate and other territorial males, showing a shorter latency to approach and longer searching behaviour (i.e. walking and running) after the playback of a subordinate's call. The reason for this response could be that the intruding subordinate male might be looking to challenge the territorial male for his territory. However, subordinates probably pose the lowest risk to the resident male in terms of fighting ability. In contrast, the reactions of the territorial males to the calls of other territorial males suggest that the presence and not the motivation of an intruding male was the most important factor influencing the male's reaction. We conclude that territorial males eavesdrop on the acoustic signals of trespassing males to gather information about these rivals, which can help them to better defend their territory.The National Research Foundation, a donation from Mark McCann, the Department of Zoology, Palacký University Olomouc and the Internal Grant Agency of Palacký University Olomouc.http://www.elsevier.com/locate/anbehav2021-08-01hj2020Mammal Research InstituteZoology and Entomolog

The deterrent effects of individual monoterpene odours on the dietary decisions of African elephants

DATA AVAILABILITY : The data for this work was deposited into the Institutional Repository of the University of Pretoria at https://doi.org/10.25403/UPresearchdata.20226015.v1 and https://doi.org/10.25403/UPresearchdata.20461833.v1African savanna elephants use pre-ingestive olfactory cues when making dietary choices, and previous research has observed that elephant diet choice is negatively correlated with vegetation species that contain high concentrations of monoterpenes. However, the frequency and concentration of monoterpenes can vary dramatically across plant species. Thus, we aimed to explore the efects that the odours of individual monoterpenes have on elephant diet choice and how these efects vary with concentration. To do this, we conducted three odour-based choice experiments focusing on eight common monoterpenes found in the woody plants in Southern African savannas. In the frst experiment, we tested whether elephant diet choice for a frequently consumed plant (Euclea crispa) was infuenced by the addition of the odour of an individual monoterpene at a set concentration. In the second experiment, we explored the relative deterrence of each monoterpene. Lastly, we tested how elephant diet choice varied as a function of the addition of individual monoterpene odours at 5%, 10%, and 20% concentrations. We found that the elephants avoided most individual monoterpenes at high concentrations, with the exception being α-pinene. Furthermore, we found that the odours of some individual monoterpenes were, in fact, more deterrent than others. In the third experiment, we found that the elephants avoided β-pinene, limonene, ocimene, γ-terpinene, and terpinolene across all concentrations, but only avoided sabinene and linalool at high concentrations. Ultimately, our results show that the odour of individual monoterpenes may deter elephant consumption, but that this deterrent efect depends on both the monoterpene and its concentration.National Research Foundation of South Africa and the Rory Hensman Conservation and Research Unit. Open access funding provided by University of Pretoria.http://link.springer.com/journal/10071Mammal Research InstituteZoology and Entomolog

Are there phylogenetic differences in salivary tannin-binding proteins between browsers and grazers, and ruminants and hindgut fermenters?

While feeding, mammalian browsers (primarily eat woody plants) encounter secondary metabolites such as tannins. Browsers may bind these tannins using salivary proteins, whereas mammalian grazers (primarily eat grasses that generally lack tannins) likely would not. Ruminant browsers rechew their food (ruminate) to increase the effectiveness of digestion, which may make them more effective at binding tannins than nonruminants. Few studies have included a sufficient number of species to consider possible scaling with body mass or phylogenetic effects on salivary proteins. Controlling for phylogeny, we ran inhibition radial diffusion assays of the saliva of 28 species of African herbivores that varied in size, feeding strategy, and digestive system. We could not detect the presence of salivary proline-rich proteins that bind tannins in any of these species. However, using the inhibition radial diffusion assay, we found considerable abilities to cope with tannins in all species, albeit to varying degrees. We found no differences between browsers and grazers in the effectiveness of their salivary proteins to bind to and precipitate tannins, nor between ruminants and nonruminants, or scaling with body mass. Three species bound all tannins, but their feeding niches included one browser (gray duiker), one mixed feeder (bush pig), and one grazer (red hartebeest). Five closely related species of small ruminant browsers were very effective in binding tannins. Megaherbivores, considered generalists on account of their large body size, were capable of binding tannins. However the grazing white rhinoceros was almost as effective at binding tannins as the megaherbivore browsers. We conclude, contrary to earlier predictions, that there were no differences in the relative salivary tannin-binding capability that was related to common ancestry (phylogeny) or to differences in body size.The National Research Foundation of South Africa, the Gay Langmuir Bursary from the University of KwaZulu-Natal and the Herrick Trust of Kent State University.http://www.ecolevol.orgam2020Mammal Research InstituteZoology and Entomolog

The biological, social, and political complexity of conserving oribi antelope Ourebia ourebi in South Africa

The endangered oribi antelope Ourebia ourebi is highly dependent on privately owned lands for its continued survival in South Africa. Despite the fact that conserving oribi may result in costs to farmers in the form of land use restrictions and pressures from illegal hunting, there is evidence that South African farmers are willing to conserve oribi on their lands. However, to date, no research has been conducted to examine farmers’ understanding of how to manage their lands for oribi or their motivations for conserving this species. We conducted 50 in-depth interviews with private landowners in KwaZulu-Natal, South Africa, to investigate why farmers are willing to protect oribi, their perceptions of the threats to the species, and their understanding of how land should be managed to benefit oribi. Respondents’ willingness to conserve oribi was driven primarily by an affinity for the species and wildlife in general. Respondents perceived illegal taxi hunting to be the greatest threat to oribi. Taxi hunts are organized, illegal hunting events that involve multiple participants and packs of dogs, who hunt at night on farms without the permission or knowledge of farmers. Although some respondents managed their lands specifically to benefit oribi, most were unsure which land management practices would support oribi conservation efforts. Farmers require legal support to more effectively conserve oribi. In addition, they would benefit from outreach and awareness programs on how to manage their lands for oribi.http://www.int-res.com/journals/esr/esr-homeam2022Mammal Research InstituteZoology and Entomolog

Changes in feeding behavior and patch use by herbivores in response to the introduction of a new predator

Top-order carnivores are naturally returning, or are being reintroduced, in a number of places where they have previously been extirpated. To explore how prey species adjust their antipredator behavior in response to these predators, we measured giving-up densities (GUDs) in experimental feeding patches and time spent vigilant for greater kudu (Tragelaphus strepsiceros), sable antelope (Hippotragus niger), and warthogs (Phacochoerus africanus) before and after an introduction of wild dogs (Lycaon pictus). Before the introduction, the only predators in the system were cheetahs (Acinonyx jubatus). After the release, none of the prey species changed their microhabitat preference, in that they all preferred open grasslands to mixed tree and bush-clumps and bush-clumps. However, kudu and sable fed more intensively (i.e., achieved lower GUDs) and had lower vigilance in open grasslands, while reducing their feeding effort (i.e., higher GUDs) and increasing their vigilance near denser vegetation. When the wild dogs denned in the study site, potentially increasing contact with the prey species, the time kudu spent vigilant and their GUDs increased significantly across all patches, and continued to increase over time. In contrast, sable and warthogs stopped feeding from the experimental patches altogether during this period. The change in feeding intensity and vigilance levels by kudu likely reflected an additive antipredator response to both cheetahs and wild dogs, whereas sable and warthogs only responded to the increased risk from the wild dogs. Our results indicate that the addition of wild dogs influenced the foraging-safety trade-off for the 3 prey species, but that the antipredator behaviors utilized by these species to mitigate predation risk varied within the newly established 2-predator system.The National Research Foundation (grant number 77582 to AMS), UKZN, GreenMatter, and the Tswalu Foundation.http://jmammal.oxfordjournals.org2019-04-03hj2018Mammal Research InstituteZoology and Entomolog

Evaluating oribi translocations for conservation : the importance of translocation guidelines

At a global scale, anthropogenically-mediated disturbances have resulted in the extirpation of species and declines in both population and range size. Furthermore, land transformation and habitat fragmentation have limited the ability of species to disperse naturally throughout their ranges. To compensate for both this defaunation and disruption of animal movement patterns, rewilding and restoration are becoming increasingly important approaches to conserve and promote biodiversity. Central to both of these concepts, as well as wildlife management and conservation in general, is the translocation of species.The National Research Foundation (90783), the Endangered Wildlife Trust, and a Gay Langmuir bursary from the University of KwaZulu-Natal.https://sawma.co.za/african-journal-of-wildlife-researcham2022Mammal Research InstituteZoology and Entomolog

Is a reduction in the individual vigilance of mothers a key evolutionary driver of group formation in white rhinos?

A key benefit and evolutionary driver of group living is reduced predation risk. In white rhinos, groups comprise adult females, their calves and one to six unrelated subadults. Subadults benefit from group living through exposure to novel areas, and protection from territorial males (i.e. ‘buddy system’). In contrast, it is unclear whether mothers benefit from group living. To determine if they benefit, or if there is simply no cost, we recorded the vigilance of white rhino mothers in different-sized groups. We predicted that as group size increased, calves would have lower predation risk and mothers would reduce their vigilance. In contrast, we found that vigilance did not decrease as group size increased. Our findings thus indicate that decreased vigilance is not a benefit that white rhino mothers gain from living in groups. Also, costs of group formation are minimal for mothers as their large body size and ability to feed on a wide range of grasses reduces competition with other group members. As a result, we suggest that the benefits obtained by subadults, coupled with the lack of costs to adult females, are the main drivers of group formation in white rhinos.We thank Ezemvelo KZN Wildlife and the staff of the Hluhluwe-iMfolozi Park for permission to undertake the study. We acknowledge funds made available by the University of Pretoria (P.W.B), and the National Research Foundation (NRF) (A.M.S.). Any opinion, findings and conclusions or recommendations expressed are those of the authors and therefore the NRF does not accept any liability in regard thereto. The experimental procedure was purely observational and noninvasive, and consistent with the University of Pretoria and South African animal ethic protocols. Finally, we thank Graham Kerley and an anonymous reviewer for their valuable comments.http://africanzoology.journals.ac.za/am2013ab201

The olfactory landscape concept : a key source of past, present, and future information driving animal movement and decision-making

Odor is everywhere, emitted across the landscape from predators, prey, decaying carcasses, conspecifics, vegetation, surface water, and smoke. Many animals exploit odor to find food, avoid threats, and attract or judge potential mates. Here, we focus on odor in terrestrial ecosystems to introduce the concept of an olfactory landscape: real-time dynamic olfactory contours reflecting the patchy distribution of resources and risks, providing a key source of information used by many animals in their movement and decision-making. Incorporating the olfactory landscape into current frameworks of movement ecology and animal behavior will provide a mechanistic link to help answer significant questions about where, why, and when many animals move, and how they do so efficiently in both space and time. By understanding how animals use the olfactory landscape to make crucial decisions affecting their fitness, we can then manipulate the landscape to modify ecological interactions and, ultimately, ecosystem consequences of these interactions.An Australian Research Council ARC Discovery Grant.https://academic.oup.com/biosciencehj2023Mammal Research Institut

Plant volatiles are a salient cue for foraging mammals : elephants target preferred plants despite background plant odour

To forage nonrandomly, animals must discriminate among food items. Foods differ in look, smell and taste, providing cues for foragers with appropriate senses. Irrespective of the sensory modality, however, foragers can only use cues effectively if they can detect sensory signals above background noise. Recent evidence shows that foraging mammalian herbivores can detect plant odours, but their capacity to select preferred plants in a noisy olfactory background is unknown. Using choice trials, we tested whether the African elephant, Loxodonta africana, uses plant odour as a salient cue despite increasingly complex and challenging background odours. We first established their preference for familiar plant species. We then tested their capacity to discriminate and select preferred plants based on odour alone. We found that elephants successfully chose preferred species even when presented with complex background odours from nonpreferred plants mimicking multispecies vegetation patches. Elephants also succeeded despite our attempt to mask distinguishing odours with large amounts of a synthetic green leaf volatile. GC–MS analysis confirmed that volatile organic compound profiles differed between plant species. In demonstrating that elephants exploit plant odours even when the signal from preferred plants is embedded in sensory noise of background odours, we provide crucial behavioural evidence that olfaction provides an efficient mechanism for selective, nonrandom foraging. Whether mammalian herbivores recognize novel odours, for example from newly invading plant species, or when air pollution degrades odours of familiar plants, needs investigating. Accounting for the capacity of mammalian herbivores to use plant odour cues will improve models of both their foraging behaviour and the ecosystem impacts of their foraging.A.S. and M.H.S. were supported by the South African National Research Foundation (Grants #: 90691, 90448 & 97262).http://www.elsevier.com/locate/anbehav2020-09-01hj2019Mammal Research InstituteZoology and Entomolog