Patterns of home range use and resource selection by eland (Tragelaphus oryx) in the Kgaswane Mountain Reserve

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2016.Resource selection by animals is a hierarchical process, reflecting the spatio-temporal heterogeneity in biotic and abiotic environmental conditions and resources. In savannah ecosystems, the availability and nutritional quality of forage resources across the seasonal cycle constitute two of the main drivers of feeding choices, seasonal movements, and, ultimately, population dynamics of large herbivores. As a consequence of the increasing insularisation of protected areas in southern Africa, the understanding of the ecological requirements of confined populations of nomadic ungulates constitutes a crucial issue for their management. The study aimed at determining the effects of forage quality and availability across the seasonal cycle on the home range occupation and resource selection by eland in an insular-like protected area, the Kgaswane Mountain Reserve (KMR) in South Africa. I focused on three spatio-temporal scales of selection: seasonal home range selection over the available landscape; habitat selection within the seasonal home range; and selection for plant species included in the diet. The main objectives at the scales of landscape and habitat selection were: 1) to determine the extent and location of the seasonal home ranges utilised by collared adult female eland in the KMR, in order to identify the seasonally favoured resource units within the available landscape; and 2) to determine the influence of environmental drivers, including the seasonal variation in forage quality and abundance, on resource selection by eland at the two different scales. Four adult female eland were fitted with GPS collars, over the course of two years. The extent and location of annual and seasonal home ranges were estimated using a-LoCoH. The influence of environmental factors, including vegetation-type, burnt areas, and NDVI, on landscape- and habitat-scale selection of used locations at peak feeding times over available scattered points was tested using mixed-effects logistic regression models. Despite the small size of the KMR, eland occupied spatially distinct dry and wet season ranges. The dry season ranges were smaller than their wet season counterparts, and During the dry season, seasonal ranges were small, and were located in moderate to very green (as indicated by NDVI values) woodland areas in respect to the available landscape. Eland selected for dry grassland, wet grassland, and open shrubland (associated with low NDVI levels) during the wet season, when they coalesced into a nursery herd and occupied a relatively large home range. The selective use of burnt areas over the available landscape units was mostly restricted to the wet season, after a green herbaceous flush had been prompted by rainfall events. Within the seasonal home ranges, eland preferentially foraged on burnt woodland and open shrubland, where re-growth of woody plants was also available. The study animals also selected for locations characterized by low vegetation greenness and biomass as a consequence of the concentration of foraging activities in open areas where low-lying browse was accessible. At the smallest scale considered for this study, the two main objectives were: 1) to determine the changes in the use of vegetation types and burnt areas during foraging activities between two different seasons; 2) to determine forage selection at the plant species scale, as influenced by the phenophase of grasses and browse. In March-April 2015 (wet-early dry transition season) and July-August 2015 (mid-dry season), feeding sites of eland were located through both VHF-tracking and scanning from vantage points. Characteristics of used feeding sites were only descriptively addressed, and included vegetation type, burning, canopy cover, and soil catenal position. The greenness and basal cover of plant species were also recorded. Availability, acceptance, and dietary contribution for each species were calculated for the two seasons, while the influence of phenological traits on plant species selection was investigated through mixed-effects logistic regression models. Woody plants were consumed in larger proportions than grasses and herbaceous forbs during the entire study period. Woody forbs and shrublets such as Lippia javanica and Athrixia elata were particularly favoured. Eland targeted species offering high proportions of green leaves. During the wet-early dry transition, the deciduous Vangueria parvifolia was particularly selected for, while the consumption of evergreen species, including Searsia lancea, increased during the dry season. Most of the observed grazing took place on flushing burns during the wet-early dry transition. The decline in grass consumption was paralleled by a considerably lowered use of the burns and of the dry grassland during the dry season, as also reflected by collars data. The results indicated that eland in the KMR adjusted their landscape and habitat selection in response to spatio-temporal variations in the availability and quality of food resources. During the wet season, flushing burns provided accessible green forage to nursery herds. Conversely, evergreen woody plants probably represented a crucial resource for eland during the limiting dry season, when herbaceous plants were mostly dormant and foliage on deciduous species was unavailable. Therefore, environmental heterogeneity at different spatial scales likely constitutes a key factor for the persistence of eland populations in small, fenced reserves.LG201

The evolutionary ecology of complex signalling systems in ungulates - diversity and flexibility in a changing world

Understanding the ultimate and proximate causes of signal diversity, complexity, and flexibility is a key issue in the study of animal communication. In this thesis, I investigated the factors affecting inter- and intraspecific variation in the visual and acoustic displays of wild ungulates, by adopting a two-pronged approach based on (1) comparative analyses with phylogenetic controls, and (2) playback experiments in the field. Comparative analyses provided the opportunity to test the validity of functional hypotheses proposed to explain the extreme diversity of sexual signals observed across ungulates (Chapter 2 and Chapter 3). Playback experiments, on the other hand, allowed for a fine-scale examination of (i) the adaptive significance of complex vocalizations (Chapter 4); and of (ii) the impact of anthropogenic disturbance on the flexibility of antipredator signalling systems (Chapter 5). In Chapter 2, I used the comparative method to identify the evolutionary drivers of courtship display complexity in male bovids and cervids. Specifically, I tested the role of multiple selection pressures in shaping the evolution of elaborate gestural signals. I found that the size of gestural repertoires (intended as a proxy for complexity) was positively correlated with the potential for male polygyny, and with the number of sympatric, closely-related heterospecifics. These patterns point to sexual selection and species recognition as the main promoters of complexity in courtship displays. Moreover, my results showed that larger male body mass was associated with smaller gestural repertoires, possibly due to energetic constraints imposed to movements in very large species. In Chapter 3, I asked why sexual dimorphism in two morphological signalling traits, namely colouration and pelage ornaments, is absent in a large number of highly polygynous bovids, contrary to expectations from sexual selection theory. I therefore tested whether lack of dimorphism could be explained by unsustainable fitness costs of ornamentation from sex-biased predation in species forming social groups containing multiple males and females (“mixed-sex herds”). Supporting this interpretation, I found that morphological dimorphism was promoted by intense male mating competition, but reduced by the propensity of sexual aggregation. Hence my results indicate that social integration in mixed-sex herds likely represents a powerful evolutionary force limiting the acquisition of dimorphic ornaments, in direct contrast with the positive drive exerted by sexual selection. In Chapter 4, I examined the adaptive value of the complex roaring display of male impala antelopes (Aepcyeros melampus). The roaring display is a signal of territorial advertisement, and consists of combinations of snorts and grunts. However, similar snorts are also used in isolation as alarm calls. Using playback experiments, I therefore focused on (i) establishing whether alarm and “advertisement” snorts where indeed the same calls; and on (ii) examining the function of snorts in the roaring display. I found that male impala reacted with similar risk-aversive responses to both alarm and “advertisement” snorts, indicating equivalence in the message conveyed by the two calls (as also supported by acoustic analyses). By contrast, grunts elicited aggressive behaviour. Roaring displays (snorts + grunts) also triggered aggressive reactions; the presence of the snorts, however, decreased the latency of male impala to respond appropriately to the following grunts. This suggests that snorts, which are originally alarm calls, have acquired a secondary role in roaring displays as “attention-grabbing elements” to the grunting component. My results therefore indicate that vocal complexity can also evolve via the co-option of pre-existing calls for secondary, derived functions. In Chapter 5, I aimed at determining whether human shields against natural predators along the borders of the Maasai Mara National Reserve (Kenya) could have reduced the alarm call responsiveness of two common antelopes, the topi (Damaliscus lunatus) and the Thomson’s gazelle (Eudorcas thomsonii). Contrary to my predictions, I found that both topi and gazelles showed stronger rather than weaker alert reactions to playbacks of conspecific alarm calls in areas exposed to human disturbance. I propose that this could be explained by the eventual association of alarm calls with low-intensity but unpredictable threats linked with human activities, which require careful evaluation by receivers. In summary, these four studies highlight how various social, ecological, and anthropogenic factors have contributed to the diversification of ungulate signalling phenotypes, and might provide useful insights to evaluate the effects of global changes on the behaviour of wild ungulate populations

Ecological Drivers of Habitat Use by Meso Mammals in a Miombo Ecosystem in the Issa Valley, Tanzania

Vast stretches of East and Southern Africa are characterized by a mosaic of deciduous woodlands and evergreen riparian forests, commonly referred to as “miombo,” hosting a high diversity of plant and animal life. However, very little is known about the communities of small-sized mammals inhabiting this heterogeneous biome. We here document the diversity and abundance of 0.5–15 kg sized mammals (“meso-mammals”) in a relatively undisturbed miombo mosaic in western Tanzania, using 42 camera traps deployed over a 3 year-period. Despite a relatively low diversity of meso-mammal species (n = 19), these comprised a mixture of savanna and forest species, with the latter by far the most abundant. Our results show that densely forested sites are more intensely utilized than deciduous woodlands, suggesting riparian forest within the miombo matrix might be of key importance to meso-mammal populations. Some species were captured significantly more often in proximity to (and sometimes feeding on) termite mounds (genus Macrotermes), as they are a crucial food resource. There was some evidence of temporal partitioning in activity patterns, suggesting hetero-specific avoidance to reduce foraging competition. We compare our findings to those of other miombo sites in south-central Africa

The Repeating Flaring Activity of Blazar AO 0235+164

Context. Blazar AO 0235+164, located at redshift z = 0.94, has undergone several sharp multi-spectral-range flaring episodes during the last decades. In particular, the episodes peaking in 2008 and 2015, that received extensive multi-wavelength coverage, exhibited interesting behavior. Aims. We study the actual origin of these two observed flares by constraining the properties of the observed photo-polarimetric variability, those of the broad-band spectral energy-distribution and the observed time-evolution behavior of the source as seen by ultra-high resolution total-flux and polarimetric Very-long-baseline interferometry (VLBI) imaging. Methods. The analysis of VLBI images allows us to constrain kinematic and geometrical parameters of the 7 mm jet. We use the Discrete Correlation Function to compute the statistical correlation and the delays between emission at different spectral ranges. Multi-epoch modeling of the spectral energy distributions allows us to propose specific models of emission; in particular for the unusual spectral features observed in this source in the X-ray region of the spectrum during strong multi spectral-range flares. Results. We find that these X-ray spectral features can be explained by an emission component originating in a separate particle distribution than the one responsible for the two standard blazar bumps. This is in agreement with the results of our correlation analysis that do not find a strong correlation between the X-rays and the remaining spectral ranges. We find that both external Compton dominated and synchrotron self-Compton dominated models can explain the observed spectral energy distributions. However, synchrotron self-Compton models are strongly favored by the delays and geometrical parameters inferred from the observations

The Third Fermi Large Area Telescope Catalog of Gamma-ray Pulsars

We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. Another 33 millisecond pulsars (MSPs) discovered in deep radio searches of LAT sources will likely reveal pulsations once phase-connected rotation ephemerides are achieved. A further dozen optical and/or X-ray binary systems co-located with LAT sources also likely harbor gamma-ray MSPs. This catalog thus reports roughly 340 gamma-ray pulsars and candidates, 10% of all known pulsars, compared to $\leq 11$ known before Fermi. Half of the gamma-ray pulsars are young. Of these, the half that are undetected in radio have a broader Galactic latitude distribution than the young radio-loud pulsars. The others are MSPs, with 6 undetected in radio. Overall, >235 are bright enough above 50 MeV to fit the pulse profile, the energy spectrum, or both. For the common two-peaked profiles, the gamma-ray peak closest to the magnetic pole crossing generally has a softer spectrum. The spectral energy distributions tend to narrow as the spindown power $\dot E$ decreases to its observed minimum near $10^{33}$ erg s$^{-1}$, approaching the shape for synchrotron radiation from monoenergetic electrons. We calculate gamma-ray luminosities when distances are available. Our all-sky gamma-ray sensitivity map is useful for population syntheses. The electronic catalog version provides gamma-ray pulsar ephemerides, properties and fit results to guide and be compared with modeling results.Comment: 142 pages. Accepted by the Astrophysical Journal Supplemen

All-sky Medium Energy Gamma-ray Observatory: Exploring the Extreme Multimessenger Universe

The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe class mission concept that will provide essential contributions to multimessenger astrophysics in the late 2020s and beyond. AMEGO combines high sensitivity in the 200 keV to 10 GeV energy range with a wide field of view, good spectral resolution, and polarization sensitivity. Therefore, AMEGO is key in the study of multimessenger astrophysical objects that have unique signatures in the gamma-ray regime, such as neutron star mergers, supernovae, and flaring active galactic nuclei. The order-of-magnitude improvement compared to previous MeV missions also enables discoveries of a wide range of phenomena whose energy output peaks in the relatively unexplored medium-energy gamma-ray band

Proximity to human settlements can reduce vigilance, but increase alarm call responses in African antelopes

Human activities can have complex effects on the antipredator behaviour of wildlife, and an understanding of the intricacies can provide important information for conservation management. In some cases, ‘human shields’ that attract wild ungulates may form around human settlements due to a lower density of large predators. However, human presence may also be associated with increased exposure to a range of anthropogenic threats, such as poaching, predation by dogs and costly interactions with livestock and their herders. Here we compared the antipredator behaviour of two savannah antelopes, topi, Damaliscus lunatus, and Thomson's gazelle, Eudorcas thomsonii, between the relatively undisturbed areas in the interior of the Maasai Mara National Reserve (Kenya) and the peripheral areas next to human settlements by the reserve boundary. We found that both antelope species were less vigilant in the more human-impacted peripheral areas, suggesting a reduction in the overall predation risk. However, both species also responded more strongly to conspecific (but not heterospecific) alarm calls in the human-impacted areas. We suggest that alarm calls in the human-impacted areas may be elicited by a more variable and unpredictable set of threats, many of which are anthropogenic, and that these require more careful assessment by the antelopes. Human presence can thus have opposite effects on different aspects of antipredator behaviour, emphasizing the need to better understand how animals perceive threats in their environment and the consequences for population performance

Molecular emission in laser-induced breakdown spectroscopy: An investigation of its suitability for chlorine quantification on Mars

The intensity of the molecular CaCl emission in LIBS spectra is examined in order to evaluate its suitability for the detection of chlorine in a Martian environment. Various mixtures resembling Martian targets with varying Cl content are investigated under simulated Martian conditions. The reactions leading to the formation of CaCl are modeled based on reaction kinetics and are used to fit the measured CaCl band intensities. MgCl bands are also investigated as potential alternatives to CaCl, but no MgCl bands can be identified in samples containing both Mg and Cl. The study confirms that CaCl is well suited for the indirect detection of chlorine, but finds a strong dependence on the concentrations of Ca and Cl in the sample. Spectra from samples with a high chlorine concentration can have low-intensity CaCl emission due to a deficiency of Ca. A qualitative estimate of the sample composition is possible based on the ratio of the band intensity of CaCl to the intensity of Ca emission lines. Time-resolved measurements show that the CaCl concentration in the plasma is highest after about 1 µs