Francesca Parrini

Seasonal variations of spatial behaviour in female Alpine ibex (Capra ibex ibex) in relation to climatic conditions and age

The spatial behaviour of female Alpine ibex Capra ibex ibex L. 1758, was analysed in Gran Paradiso National Park (Italy). Data were collected on 14 radiocollared females from September 2000 to August 2002, using radio-tracking and direct observations. Seasonal spatial behaviour was influenced by environmental conditions, in particular climatic factors. In the presence of thick snow cover, females significantly reduced winter home range sizes. Snow cover limited ibex mobility and reduced localization altitudes. Annual home range and winter home range sizes were inversely related to age. Temperature modified the use of space by females during summer. During the hottest summer females moved over larger ranges at higher altitudes. Annual home range sizes (mean 186.2 ha ± 71.7 in 2000 and 182.2 ha ± 70.0 in 2001) and seasonal home range sizes were significantly smaller than those of reintroduced populations, moreover they were smaller that those of males calculated in a close study area in Gran Paradiso National Park.

Scale-dependent selection of greenness by African elephants in the Kruger-private reserve transboundary region, South Africa

Foraging behaviour and habitat selection occur as hierarchical processes. Understanding the factors that govern foraging and habitat selection thus requires investigation of those processes over the scales at which they occur. We investigated patterns of habitat use by African elephants (Loxodonta africana) in relation to vegetation greenness to investigate the scale at which that landscape attribute was most closely related to distribution of elephant locations. We analysed Global Positioning System radio-collar locations for 15 individuals, using the Normalized Difference Vegetation Index as a representation of vegetation greenness in a Geographic Information Systems framework. We compared the importance of vegetation greenness at three spatial scales: the total home range, the seasonal home range and the 16-day home range. During the wet season, seasonal home ranges for both sexes were associated with intermediate greenness within the total home range; there was no evidence of selection based on greenness at finer scales. During the dry season, the strongest associations were within the 16-day home range: individual locations for males tended to be in areas of intermediate greenness, and those for females were in areas of intermediate and high greenness. Our findings suggest that the role of vegetation greenness varies with the scale of analysis, likely reflecting the hierarchical processes involved in habitat selection by elephants.

A categorization of recent network approaches to analyse trophic interactions

Summary Network analysis, a branch of discrete mathematics that quantifies the structure of links between a set of nodes, is emerging as a powerful methodology to approach complex ecological interactions. There has been a rapidly increasing body of research targeting the topological description of trophic interactions. Here we categorize studies applying a topological approach to empirical trophic networks, with the aim of identifying recent trends and deficiencies in this approach to analyse trophic interactions. There were biases in the taxonomic groups addressed and in the methodological approaches used for data collection and analyses. Studies on antagonistic interactions were generally focused on a single kind of bipartite interaction, and most studies compared network attributes across time, ecosystems or treatments. We encourage a broader use of both interlinked and unipartite networks that would allow for describing indirect effects of trophic interactions, as well as time series of networks across seasons and phenological states of organisms. We also noted shortages of studies identifying interaction structures across levels of organization, on the correspondence between network structure and function, and particularly of studies on the behaviour of trophic networks in the face of environmental perturbations, which could provide guidance for preserving ecological interactions.

Capra ibex (Artiodactyla: Bovidae)

Abstract Capra ibex Linnaeus, 1758, is a bovid commonly called the Alpine ibex that is sexually dimorphic. Body mass and scimitar-shaped horns are more than twice as large in males as in females. There are 8 extant species in the genus Capra. C. ibex is endemic to the Alpine Range of central Europe, was eliminated throughout its range except the Italian Alps, and has since been translocated to the Alps of Austria, France, Germany, Italy, Slovenia, and Switzerland at elevations of 1,600–3,200 m. Habitat selection by C. ibex is mainly influenced by the gradient and extension of mountain slopes. It is not a species of special conservation concern and has increased to >20,000 individuals

Termite mounds vary in their importance as sources of vegetation heterogeneity across savanna landscapes

Questions Termite mounds are well known to host a suite of unique plants compared with the surrounding savanna matrix. However, most studies testing the significance of mounds for ecosystem heterogeneity have been conducted at single sites. Mound effects on savanna heterogeneity across varying landscapes are less well understood, and how effects might vary across geological types and mounds of different sizes is as yet unknown. Location Gonarezhou National Park, Zimbabwe. Methods We studied effects of termite mounds on vegetation spatial heterogeneity across two geologies (granite and basalt), including effects of mound size and the spatial extent of termite influence. Herbaceous vegetation was sampled on mounds and savanna matrix plots, and along distance transects away from mounds. Soil nutrients on mounds and in the matrix were also compared between geologies. Results Soil nutrients were more concentrated in large mounds compared with the matrix on granite, but not on basalt, with mounds therefore acting as nutrient hot-spots on nutrient-poor granite only. Large and medium sized mounds hosted compositionally different grass species to the matrix on granite, but not on basalt. Large mounds on granite also had significantly lower grass and forb species richness compared with the matrix. However, small mounds on granite, and all mound size categories on basalt, did not have an effect on grass and forb species richness or assemblage composition, an observation attributed to a lack of difference in soil nutrients between the mounds and matrix. Conclusion Our study shows that the significance of termite mounds to ecosystem spatial heterogeneity is strongly influenced by geology and mound size, with mound effects on herbaceous plant species heterogeneity more pronounced in dystrophic geologies and around large mounds. Future studies should take greater cognisance of landscape context and mound size when seeking to understand the contribution of termite mounds to ecosystem structure and function. This article is protected by copyright. All rights reserved.

Disturbance and Habitat Factors in a Small Reserve: Space use by Establishing Black Rhinoceros (Diceros bicornis)

Continued persistence of black rhinoceros (Diceros bicornis) will likely depend on the cooperation of many reserves and the application of metapopulation models to manage across reserves. The suitability of any reserve, however, depends on factors that promote and constrain occupancy. Constraining factors, particularly human disturbance, are of concern in small reserves because constraints have potentially greater effects, relative to reserve size, than in large reserves. We investigated landscape use by black rhinos at Zululand Rhino Reserve. South Africa, as a function of elevation, slope, patch type, areas burnt and factors associated with disturbance (distances to nearest water point, human settlement, boundary fence, and roads). Estimated home ranges consistently demonstrated avoidance of human settlements, fragmentation of home ranges and sometimes multi-modal core areas. Resource selection functions confirmed that use of areas increased with greater distance from human settlements (log-odds = 1.3831 ± 0.4623 [95% Cl]) and from perennial water points (2.2859 ± 0.8261). Space use was greater for thicket (1.0072 ± 0.5775) and closed savanna (0.8656 ± 0.6153) than for other patch types. Managers who plan reintroductions of black rhinos should consider availability of forage and cover, disturbances that might restrict access to resources, and effects of reserve size on those disturbances.

Contrasting termite diversity and assemblages on granitic and basaltic African savanna landscapes

Termites are recognised soil ecosystem engineers in the tropics and sub-tropics, making the understanding of their distribution a priority. However, there is a poor understanding of how differences in soil properties and plant biomass productivity affect termite species diversity. We compared the diversity of termites between two soils of differing geological provenance (basalt and granite), and consequently contrasting nutrient content, but subject to similar climatic conditions in a semi-arid Zimbabwean savanna. Basaltic soils contained more dead wood, and were more nutrient-rich than granitic soils, with significantly higher exchangeable Ca and Mg, and available P, and a less acidic pH. However, despite this higher soil nutrient status on basalts, functional and taxonomic termite diversity was higher on granites, although termite abundance was similar between the geological formations. Termite assemblages differed between the geological formations, with very little overlap. We conclude that termite diversity is highly influenced by soil productivity, with nutrient-poor soils having higher diversity, potentially due to reduced competitive exclusion or differences in species adaptation to soil conditions.

Early post-release movement of reintroduced lions (Panthera leo) in Dinokeng Game Reserve, Gauteng, South Africa

Reintroductions have been increasingly used in carnivore conservation. Animal movement influences fitness and survival and is the first behavioural response of reintroduced animals to ‘forced dispersal’ in a new habitat. However, information available on early post-release movement of reintroduced carnivores remains limited. We studied movements of 11 reintroduced lions (Panthera leo) in Dinokeng Game Reserve, South Africa, in their first season of release and investigated changes in movements over time. Movement patterns of lions were more diverse than expected and varied between sexes and individual groups. Some lion groups returned to the area surrounding the release site after initial exploration and avoided human settlements, suggesting that vegetation and human disturbances influenced dispersal upon release. Cumulative home range size continued to increase for all lions despite individual differences in movement patterns. We highlight the importance of considering the variation in individual-specific behaviour and movement patterns to assess early establishment and reintroduction success.

Drivers of population dynamics in sable antelope: forage, habitat or competition?

Similar to declines in antelope species across African conservation areas, sable (Hippotragus niger) at Kgaswane Mountain Reserve, South Africa, has exhibited a negative trend in abundance since 2000. To investigate the cause of decline, we assessed three hypotheses: seasonal forage abundance, habitat conditions and interspecific competition. We considered the evidence for each hypothesis by analysing reserve survey data, rainfall records and historical burn data with hierarchical models that incorporated potential density-dependent effects and environmental covariates. After accounting for the effects of sable abundance, we found that sable population growth was most strongly related to the interspecific competition covariates and to waterbuck (Kobus ellipsiprymnus) count in particular. Also, the strength of the relationship was shaped by the trend in sable numbers and whether the population was before or after peak abundance: the strongest indication of interspecific competition occurred after sable had reached peak abundance. The interaction between abundance of sable and that of potentially competing species emphasizes the importance of accounting for density-dependent processes, and in particular longer-term phases in abundance, when judging the roles of other factors that affect species abundance.