Nico L. Avenant

Correlating rodent community structure with ecological integrity, Tussen‐die‐Riviere Nature Reserve, Free State province, South Africa

Rodents form a vital component of Free State ecosystems and monitoring them may be a relatively quick and inexpensive method of indicating healthy or unhealthy ecosystem functioning. Using removal trapping, we have studied rodent seasonal abundance, species richness, Shannon diversity, and evenness of rodents in four habitats in the Tussen-die-Riviere Nature Reserve, inspected the most successful sampling method for these habitats, and report on their community structure and how it is related to an Ecological Index (≅ EI value of grassland). Both species richness and Shannon diversity increased significantly with EI value. The indicator species Mastomys coucha occurred at all plots, but contributed the largest proportion of the total captures (ca. 80%) at the plot with lowest EI value. Other results important for small mammal monitoring and collecting are that trap success and species richness was highest in autumn. This study also confirms that four days and nights continuous trapping is essential for the effective sampling of rodent communities in Free State grasslands. Our results partially support expectations that the number of specialist species increases with succession, M. coucha dominance acts as an indicator of habitat disturbance, rodent species richness conforms to Tilmans hump-shaped curve model, and adds to a baseline of diversity indices in a variety of grassland habitats.

The Effects of Captivity on the Mammalian Gut Microbiome.

Synopsis Recent studies increasingly note the effect of captivity or the built environment on the microbiome of humans and other animals. As symbiotic microbes are essential to many aspects of biology (e.g., digestive and immune functions), it is important to understand how lifestyle differences can impact the microbiome, and, consequently, the health of hosts. Animals living in captivity experience a range of changes that may influence the gut bacteria, such as diet changes, treatments, and reduced contact with other individuals, species and variable environmental substrates that act as sources of bacterial diversity. Thus far, initial results from previous studies point to a pattern of decreased bacterial diversity in captive animals. However, these studies are relatively limited in the scope of species that have been examined. Here we present a dataset that includes paired wild and captive samples from mammalian taxa across six Orders to investigate generalizable patterns of the effects captivity on mammalian gut bacteria. In comparing the wild to the captive condition, our results indicate that alpha diversity of the gut bacteria remains consistent in some mammalian hosts (bovids, giraffes, anteaters, and aardvarks), declines in the captive condition in some hosts (canids, primates, and equids), and increases in the captive condition in one host taxon (rhinoceros). Differences in gut bacterial beta diversity between the captive and wild state were observed for most of the taxa surveyed, except the even-toed ungulates (bovids and giraffes). Additionally, beta diversity variation was also strongly influenced by host taxonomic group, diet type, and gut fermentation physiology. Bacterial taxa that demonstrated larger shifts in relative abundance between the captive and wild states included members of the Firmicutes and Bacteroidetes. Overall, the patterns that we observe will inform a range of disciplines from veterinary practice to captive breeding efforts for biological conservation. Furthermore, bacterial taxa that persist in the captive state provide unique insight into symbiotic relationships with the host.

Dental microwear of sympatric rodent species sampled across habitats in southern Africa: Implications for environmental influence.

Dental microwear textures have proven to be a valuable tool for reconstructing the diets of a wide assortment of fossil vertebrates. Nevertheless, some studies have recently questioned the efficacy of this approach, suggesting that aspects of habitat unrelated to food preference, especially environmental grit load, might have a confounding effect on microwear patterning that obscures the diet signal. Here we evaluate this hypothesis by examining microwear textures of 3 extant sympatric rodent species that vary in diet breadth and are found in a variety of habitat types: Mastomys coucha, Micaelamys namaquensis and Rhabdomys pumilio. We sample each of these species from 3 distinct environmental settings in southern Africa that differ in rainfall and vegetative cover: Nama-Karoo shrublands (semi-desert) and Dry Highveld grasslands in the Free State Province of South Africa, and Afromontane (wet) grasslands in the highlands of Lesotho. While differences between habitat types are evident for some of the species, inconsistency in the pattern suggests that the microwear signal is driven by variation in foods eaten rather than grit-level per se. It is clear that, at least for species and habitats sampled in the current study, environmental grit load does not swamp diet-related microwear signatures.

Why Namibian Farmers Are Satisfied With the Performance of Their Livestock Guarding Dogs

The success of livestock guarding dogs (LGDs) in mitigating farmer–predator conflict relies on the perceptions of farmers that use them. Purebred LGDs are provided to Namibian farmers by the Cheetah Conservation Fund as a farmer–predator conflict mitigation measure. We examined the perceptions of farmers using 164 of these LGDs by analyzing data collected during face-to-face interviews from 2000–2010. Although most respondents reported reduced livestock losses since LGD introduction, satisfaction with LGD performance was more strongly linked to their observations of LGD behavior. The most commonly reported negative behaviors were staying home (29 LGDs, 18%) and chasing wildlife (25 LGDs, 15%). On subsistence farms, care provided was negatively correlated with LGD age (r = −.34, n = 35, p = .04) and LGDs reportedly staying home were provided with less care than other LGDs. Overall, LGDs performed satisfactorily on commercial and subsistence farms, and thus contributed to farmer–predator conflict mitigation.

Correlating small mammal community characteristics and habitat integrity in the Caledon Nature Reserve, South Africa

Abstract This study quantifies habitat-specific small mammal patterns in the Caledon Nature Reserve, Free State province, South Africa. Small mammal community variables were correlated with an Ecological Index, the current method used to interpret habitat integrity in Free State nature reserves. It also reports on the seasonal abundance, species richness and diversity of small mammals present in specific habitats and addresses the most successful methods to sample these taxa, such as the duration of trapping to ensure unbiased sampling, and in which season should effort be concentrated to obtain optimal results. Our results support expectations that small mammal species richness increase with Ecological Index value, the number of specialist species in Free State grasslands increases with succession up to the climax phase, and that Mastomys coucha dominance acts as an indicator of habitat disturbance. It also supports previous studies that have shown a minimum trapping period of 3 days and nights, and best trap success and species richness at the end of autumn–early winter.

Space use variation in co-occurring sister species: response to environmental variation or competition?

Coexistence often involves niche differentiation either as the result of environmental divergence, or in response to competition. Disentangling the causes of such divergence requires that environmental variation across space is taken into account, which is rarely done in empirical studies. We address the role of environmental variation versus competition in coexistence between two rodent species: Rhabdomys bechuanae (bechuanae) and Rhabdomys dilectus dilectus (dilectus) comparing their habitat preference and home range (HR) size in areas with similar climates, where their distributions abut (allopatry) or overlap (sympatry). Using Outlying Mean Index analyses, we test whether habitat characteristics of the species deviate significantly from a random sample of available habitats. In allopatry, results suggest habitat selection: dilectus preferring grasslands with little bare soil while bechuanae occurring in open shrublands. In sympatry, shrubland type habitats dominate and differences are less marked, yet dilectus selects habitats with more cover than bechuanae. Interestingly, bechuanae shows larger HRs than dilectus, and both species display larger HRs in sympatry. Further, HR overlaps between species are lower than expected. We discuss our results in light of data on the phylogeography of the genus and propose that evolution in allopatry resulted in adaptation leading to different habitat preferences, even at their distribution margins, a divergence expected to facilitate coexistence. However, since sympatry occurs in sites where environmental characteristics do not allow complete species separation, competition may explain reduced inter-species overlap and character displacement in HR size. This study reveals that both environmental variation and competition may shape species coexistence.

Quality and Quantity of the Scientific Information Available on Black-Backed Jackals and Caracals: Contributing to Human—Predator Conflict Management?

Black-backed jackals, Canis mesomelas, and caracals, Caracal caracal, are meso-carnivores impacting the livestock and game farming (wildlife ranching) industries in southern Africa. Many efforts to manage the impact of these predators are unsuccessful and no meaningful, or effective, long-term management programme has been formulated over any large area (spanning more than a single farm or a group of neighbouring farms) throughout their southern African range. This paper reports on the scientific information available on the ecology of black-backed jackals and caracals to evaluate the nature of current knowledge of these species in order to prioritize research for the development of meaningful human—predator conflict management (HPCM) strategies. From a HPCM perspective, it is evident that published field studies on black-backed jackals and caracals in southern Africa are limited in scope, spatially and temporally isolated, and generally old (appearing prior to 2005). Most studies were also mainly conducted in protected areas, with little information from farming areas. Significant ecological questions, relevant to HPCM are highlighted by our study. These questions include studying whether or not black-backed jackal and caracal territoriality persists under rangeland conditions?; Have the two predators ‘learned’ to predate on introduced livestock or wildlife?; Has reproductive behaviour changed under rangeland conditions?; and, Is compensatory breeding observed under rangeland conditions? Answers to these questions will undoubtedly contribute to the formulation of more effective HPCM strategies.

Actual and perceived collision risk for bird strikes at Namibian airports

At Namibia’s two major airports, Hosea Kutako International and Eros (domestic), 117 bird strike collision incidents were recorded between 2006 and 2010. A risk assessment, which included a proposed risk weighting methodology, was conducted at Hosea Kutako and Eros airports, which estimated the probability of an accident/collision as well as the consequence of such a collision. The assessment included surveys of bird occurrence frequencies as well as pilot interviews. The results of the risk assessments were compared with actual bird strike incidences for each species, frequency of occurrence of birds and pilot perceptions of species risk, in order to find whether risk assessment and pilot perception are reliable measures of potential bird strike incidence. White-backed Vulture Gyps africanus and Helmeted Guineafowl Numida meleagris were the highest risk species at both airports. They were also, after Crowned Lapwing Vanellus coronatus, the species most often observed by pilots. Bird strike records showed that Crowned Lapwing and Helmeted Guineafowl were also the most frequently struck birds at both airports. The study illustrates how combining risk assessment, pilot perception and bird strike history can benefit bird strike minimisation plans at airports through the rapid identification of priority bird species.

Integrating small mammal community variables into aircraft‐wildlife collision management plans at Namibian airports

Understanding ecosystems within and around airports can help to determine the causes and possible mitigation measures for collisions between aircraft and wildlife. Small mammal communities are an important component of the semi-arid savanna ecosystems of Namibia, its productivity and its ecosystem integrity. They are also a major direct attractant for raptors at airports. The present study compared the abundance and diversity of small mammals between Namibias 2 main airport properties (Hosea Kutako International Airport and Eros Airport), and among areas of land used for various purposes surrounding the airports. A total of 2150 small mammals (3 orders, 11 species) were captured over 4 trapping seasons. Small mammal abundance was significantly higher at the end of the growing season than during the non-growing season. The grass mowing regimen in current management plans at the airports resulted in a significant reduction of small mammal abundance at Hosea Kutako during the non-growing season only, thus indicating that annual mowing is effective but insufficient to reduce the overall abundance of mammal prey species for raptors. Small mammal numbers were significantly higher at Hosea Kutako Airport compared to the cattle and game farming land surrounding the airport, while no differences in small mammal densities or diversity were found for areas with different land uses at and surrounding Eros. The study suggests that the fence around Hosea Kutako provides a refuge for small mammals, resulting in higher densities. It also indicates that different surrounding land use practices result in altered ecosystem function and productivity, an important consideration when identifying wildlife attractants at airports.

The ecomorphology of southern African rodent incisors: Potential applications to the hominin fossil record

The taxonomic identification of mammalian fauna within fossil assemblages is a well-established component of paleoenvironmental reconstructions. However, many fragmentary specimens recovered from fossil sites are often disregarded as they can be difficult to identify with the precision required for taxonomic methods. For this reason, the large numbers of isolated rodent incisors that are often recovered from hominin fossil bearing sites have generally been seen as offering little interpretive value. Ecomorphological analysis, often referred to as a “taxon-free” method, can potentially circumvent this problem by focusing on the adaptive, rather than the taxonomic significance of rodent incisor morphology. Here, we determine if the morphology of the upper incisors of modern southern African rodents reflects dietary behavior using discriminant function analysis. Our model suggests that a strong ecomorphological signal exists in our modern sample and we apply these results to two samples of isolated incisors from the hominin fossil bearing sites, Sterkfontein and Swartkrans.