I.M.A. Heitkonig

Stability of wooded patches in a South African nutrient-poor grassland: do nutrients, fire or herbivores limit their expansion?

Patches of wooded vegetation in nutrient-poor grassland characteristically contain high soil moisture and nutrient availability compared with surrounding grassland. These `islands of fertility? appear stable in size, suggesting that tree recruitment at the patch boundary is limited. We hypothesize that tree establishment in adjacent grassland is limited by (1) competition for resources, (2) fire or (3) herbivory. In a South African grassland, we measured moisture availability and conducted a bioassay experiment to analyse whether soil nutrient limits tree recruitment at the patch boundary. We thus measured nutrient concentrations of maize plants grown in patch, boundary and grassland soil. To investigate whether browsing or fire affected tree seedlings at the patch boundary, we burned plots including patches, and used fences to exclude browsers. Neither soil moisture nor nutrient availability at the boundary differed from inside the patches, suggesting that tree recruitment at the boundary is not resource limited. Both fire and browsing combined caused a significantly lower tree seedling growth at the patch boundary, suggesting that these two factors can impede tree recruitment. The balance between positive feedback mechanisms facilitating tree recruitment, and the negative impact of fire and browsing can explain the apparent stability of these islands of fertility.

Optimization of wildlife management in a large game reserve through waterpoints manipulation: a bio-economic analysis

Surface water is one of the constraining resources for herbivore populations in semi-arid regions. Artificial waterpoints are constructed by wildlife managers to supplement natural water supplies, to support herbivore populations. The aim of this paper is to analyse how a landowner may realize his ecological and economic goals by manipulating waterpoints for the management of an elephant population, a water-dependent species in the presence of water-independent species. We develop a theoretical bio-economic framework to analyse the optimization of wildlife management objectives (in this case revenue generation from both consumptive and non-consumptive use and biodiversity conservation), using waterpoint construction as a control variable. The model provides a bio-economic framework for analysing optimization problems where a control has direct effects on one herbivore species but indirect effects on the other. A landowner may be interested only in maximization of profits either from elephant offtake and/or tourism revenue, ignoring the negative effects that could be brought about by elephants to biodiversity. If the landowner does not take the indirect effects of waterpoints into consideration, then the game reserve management, as the authority entrusted with the sustainable management of the game reserve, might use economic instruments such as subsidies or taxes to the landowners to enforce sound waterpoint management.

Aversive responses of captive sandbar sharks Carcharhinus plumbeus to strong magnetic fields.

This experimental study focused on the possible deterrent effect of permanent magnets on adult sandbar sharks Carcharhinus plumbeus. Results showed that the presence of a magnetic field significantly reduced the number of approaches of conditioned C. plumbeus towards a target indicating that adult C. plumbeus can be deterred by strong magnetic fields. These data, therefore, confirm that the use of magnetic devices to reduce shark by-catch is a promising avenue.

Disease transmission in animal transfer networks

Infectious diseases transmission is strongly determined by who contacts whom. Bovine tuberculosis (bTB) caused by Mycobacterium bovis is a worldwide burden for animal populations. One of the major transmission mechanism between herd is the transfer of infectious animal. In East Africa, pastoralists may receive or bestow livestock to create and strengthen social relationships. Here, we used a network approach to examine the relative importance of such cattle transfer in the transmission of bTB. First, a total of 2550 cattle from 102 herds were tested using the comparative intradermal tuberculin test to assess the presence of bTB infected cattle in the herd. A herd was considered bTB positive if it had at least one tuberculin reactor animal. Next, we calculated the centrality of each herd in the cattle transfer network using four established measures of social network centralization: degree, betweenness, closeness and fragmentation. The relationships between the network centrality measures and bTB infection were examined using generalized linear mixed models (GLMM). We found that a herds in-degree in the social network was positively correlated with the risk of being infected with bTB (b=4.2, 95%CI=2.1-5.7; p<0.001). A herd that was close to many others (i.e., had a higher closeness index) had a larger chance of acquiring bTB infection (b=2.1, 95%CI=1.4-2.8; p<0.001). Betweenness centrality was also positively associated with the presence of bTB infection. There was a negative relationship between the fragmentation index and bTB infection (b=-2.7, 95%CI=-4.9-1.3; p<0.001). The study clearly demonstrated that the extent to which a herd is connected within a network has significant implications for its probability of being infected. Further, the results are in accordance with our expectation that connectivity and the probability that a herd will transmit the disease to other herds in the network are related.

Wildlife as insurance against rainfall fluctuations in a semi-arid savanna setting of southeastern Zimbabwe

This paper presents modeling approaches for wildlife conservation in a semi-arid savanna setting where there are frequent occurrences of drought. The model was used to test the extent to which wildlife income offers opportunities to reduce fluctuations in income as a result of variations in annual rainfall. For the application of the model the wildlife and agro-pastoral systems of southeastern Zimbabwe were simulated. Results show that wildlife income has the potential to compensate for some of the losses in expected income from livestock during droughts. However, wildlife income becomes second best to irrigated agriculture in stabilizing income in areas that show highly fluctuating rainfall. Possible reasons for this include high costs of exploiting the wildlife resource, and the small fraction of wildlife revenues received by households and communities. In order to search for sustainable solutions in areas such as the southeastern low veld of Zimbabwe, it is also important to be aware that the current human population and livestock densities are far above current sustainable levels. Our results therefore suggest that current and future efforts to conserve biodiversity are doomed to fail if there are no efforts made to decongest areas surrounding parks of high densities of human and herbivore populations, and to let local households earn more revenues from wildlife.

Effect of patches of woody vegetation on the role of fire in tropical grasslands and savannas

In tropical grasslands and savannas, fire is used to reduce woody vegetation expansion. Woody vegetation in these biomes is often patchily distributed, and micro-climatic conditions can largely vary locally with unknown consequences for fire effects. We hypothesised that (1) fire has higher temperature and maintains high temperatures for a longer period at the windward side than at the leeward side of wooded patches, (2) this difference increases with patch size, (3) fire has a larger effect on woody vegetation at the windward side than at the leeward side of wooded patches and (4) this effect increases with patch size. We planted tree seedlings around wooded patches in a grassland and burnt these plots. We found that fire had a lower temperature and had an elevated temperature for a shorter time period at the leeward side of wooded patches than at the windward side. Also, we found smaller effect of fire on the seedlings at the leeward side. We conclude that patches of woody vegetation can have a large effect on the role of fire in tropical grasslands and savannas. This effect suggests a ‘safe zone’ for seedlings at the leeward side, which consequently promotes woody vegetation expansion. This paper contributes to understanding of the effect of patchiness of woody vegetation on the role of fire in tropical grasslands and savannas in reducing woody vegetation expansion.

Parasite Prevalence in Lemurs: The Effect of Anthropogenic Disturbance and Natural Stress Factors from a Multi-Scale Perspective

DOI: 10.1159/000354129 298 5th Congress of the European Federation for Primatology researchers usually argue that one of the distinguishing features of non-human primates’ gestures is their high degree of flexibility, which can be considered in different ways: (1) ‘means-end dissociation’, which refers to the use of a particular gesture in different functional contexts and/or several gestures for one specific context, and (2) gesture sequences which consist of combinations of two or more gestural signals. Both strategies enable non-human primates to adjust their gesture use to their partner’s behaviour and to increase the range of potential meanings that can be conveyed by combining the components of a more or less limited gestural repertoire. Because of their flexible use, however, very few gestures have a specific meaning, but their meaning is defined by the context in which they occur. Thus, in contrast to many vocalizations of non-human primates, their gestures are (1) less context-specific and do not represent functionally referential signals and, related to this, (2) gesture sequences do not represent meaningful combinations used for other functions than their single components. Therefore, I will first provide an overview of recent research on the flexible use of gestures in great apes to demonstrate how they create meaning in their interactions with others. I will then discuss how these findings relate to evidence from vocal studies with the aim to identify ‘blind spots’ and biases that currently constrain a fruitful debate about the origins of human language.Comparative studies of primate grasping and manipulative behaviours in captivity are numerous but there has been little research on hand use in the wild. Hand use during wild non-locomotor behaviours may reveal increased ranges of joint mobility or manipulative behaviours that have been previously ignored or underestimated. Manipulative behaviours in apes can strongly correlate with different habitats at the species and population level. Chimpanzees more often use tools in the wild and thus are thought to be more manipulative than gorillas. However, captive studies have demonstrated high dexterity in both taxa. We investigate hand use during manipulation (e.g. food processing, tool-use) in wild mountain gorillas (Gorilla beringei, Bwindi Impenetrable National Park, Uganda) and wild chimpanzees (Pan troglodytes verus, Tai National Park, Cote d’Ivoire). We used video data collected in the wild that included 32 gorilla (n=9 individuals) and 53 chimpanzee (n=11 individuals) instances of manipulative tasks. Digital images were extracted and analysed frame by frame. Preliminary results show that hand grips are similar between gorillas and chimpanzees during the manipulation of common food objects, such as long plant stems or branches. During the manipulation of species-specific food objects, gorillas use variable thumb-index grips during the manipulation of thistles and small plant stems, while chimpanzees use similar grips during nut-cracking. These preliminary results suggest that Bwindi mountain gorillas have similarly high dexterity as that of Tai chimpanzees despite not being tool-users. Gorillas frequently use precision grasping more to obtain small rather than large food items, which is similar to chimpanzees and other non-human primates.Previous studies have shown a positive relationship between proximity to humans or habitat fragmentation and parasitic levels in non-human primates (NHPs). However, to date few have explicitly explored links between parasite load and stress conditions. To better understand the links between parasite prevalence and NHP immune system efficiency and stress levels, faecal samples of Alouatta palliata and the critically endangered Ateles geoffroyi geoffroyi were non-invasively collected in northern Costa Rica. We investigated whether the presence of gastrointestinal parasites was related to the abundance of hormones (cortisol and testosterone). Samples were gathered across three areas differing in the frequency and diversity of human presence, i.e. around the Cano Palma Biological Station, near villages and at ecotourism sites. Two grams of each faecal sample were stored in a sugar saturated solution with 10% formalin to conserve the parasites; the remaining matter was dried to preserve DNA and steroid hormones. The samples enabled the quantification of parasites as well as testosterone and cortisol levels using ELISA as proxies of general health status and stress levels. Data on parasite abundance and hormone levels were contrasted across the two species and the three different sampling areas. Furthermore, we assessed the genetic exchange among the different groups of primates sampled. We genetically analysed the samples using 12 microsatellites previously validated by the University of Costa Rica. We verified whether transmission of parasites among the groups could be possible concomitant to the genetic exchange. This study aimed to better understand and assess the impact of human factors on NHP health and across NHPs with different socio-ecological characteristics.DOI: 10.1159/000354129 290 5th Congress of the European Federation for Primatology considerably between species for any given body size. Numerous hypotheses have been put forward to explain this variation. In recent years, we have tested predictions that flow from a framework focusing on the energetic aspects of having a large amount of the metabolically expensive brain tissue. In this talk, I will give an overview of our findings from broad comparative phylogenetic studies in mammals, and their implications for our understanding of non-human and human primate evolution. In sum, we found evidence for two pathways to increase relative brain size compared to the ancestral state. First, a species may change its lifestyle to allow for a stable increase in its total energy budget, e.g. by changing its diet. Alternatively, or in combination with the first pathway, a species may allocate more energy to the brain and less to other expensive functions such as offspring production. Ultimately, this option results in very low population growth rates even in good conditions, as found in great apes. A further increase in brain size would not be compatible with demographically viable populations in these large-brained primates. However, using comparative evidence from mammals, we demonstrate that help from non-mothers can alleviate this trade-off between reproductive effort and brain size. Nevertheless, the energetic constraints on brain size evolution will only be overcome in species that can actually benefit from enhanced cognitive abilities. While such benefits are potentially ubiquitous, we would expect them to be undermined by unavoidable mortality in some socioecological conditions, and by the difficulty of transferring knowledge across generations in some social systems. A combined test of all these considerations remains a challenge, largely due to the shortcomings of the distinct datasets, but I will present the newest data and results from our current projects.Throughout their range across Africa, chimpanzees (Pan troglodytes) are threatened with extinction due to habitat destruction, disease and unsustainable levels of hunting and capture, in spite of being protected by national and international laws. In recent years, the bush meat and the pet trade have resulted in a significant increase in the number confiscated orphan chimpanzees. The Chimpanzee Conservation Centre (CCC), located in the High Niger National Park (HNNP), is the only Pan African Sanctuary Alliance (PASA)-accredited sanctuary caring for chimpanzee orphans in Guinea, West Africa. This sanctuary has been rehabilitating confiscated chimpanzees since 1997. With the aim of reinforcing the wild chimpanzee population of the HNNP and to enhance park protection, the CCC, in 2008, released a first group of 12 chimpanzees into the Mafou core area of the park. Five of those individuals have since settled at the release site and continue to be monitored. In August 2011, the CCC was able to re-enforce this resident group with the successful addition of 2 adult females. Post-release monitoring of these individuals involved distance monitoring using simple VHF and/or ARGOS and GPS store-on-board radio collars. Here, we present data downloaded in 2011–2012 from the GPS store-on-board collars of 2 adult males and these 2 additional adult females. These data allowed us to analyse their social dynamics, party composition, habitat preferences, day range and home range use. Our results indicate that these females integrated successfully into the resident group and that the behaviour of these wild-born released orphan chimpanzees mirrors that of wild counterparts inhabiting similar savannah dominated landscapes, suggesting that they have adapted appropriately to their release conditions.