Behavioural correlates of urbanisation in the Cape ground squirrel Xerus inauris

Urbanisation critically threatens biodiversity because of habitat destruction and novel selection pressures. Some animals can respond to these challenges by modifying their behaviour, particularly anti-predator behaviour, allowing them to persist in heavily transformed urban areas. We investigated whether the anti-predator behaviour of the Cape ground squirrel Xerus inauris differed in three localities that differed in their level of urbanisation. According to the habituation hypothesis, we predicted that ground squirrels in urban areas would: (a) be less vigilant and forage more; (b) trade-off flight/vigilance in favour of foraging; and (c) have shorter flight initiation distances (FID) when approached by a human observer. Observations were made in winter and summer at each locality. As expected, ground squirrels in urbanised areas were less vigilant and had shorter FIDs but did not trade-off between foraging and vigilance. In contrast, a population in a non-urbanised locality showed greater levels of vigilance, FID and traded-off vigilance and foraging. A population in a peri-urban locality showed mixed responses. Our results indicate that Cape ground squirrels reduce their anti-predator behaviour in urban areas and demonstrate a flexible behavioural response to urbanisation.     

Comparing community structure on shells of the abalone Haliotis midae and adjacent rock: implications for biodiversity

This paper concerns the effects on biodiversity of depletion of the South African abalone Haliotis midae, which is a long-lived species with a large corrugated shell that provides a habitat for diverse benthic organisms. We compared community structure on H. midae shells with that on adjacent rock at three sites (Cape Point and Danger Point sites A and B) and at two different times of the year at one of these sites. Shells of H. midae consistently supported communities that were distinctly different from those on rock. In particular, three species of non-geniculate (encrusting) corallines, Titanoderma polycephalum, Mesophyllum engelhartii and Spongites discoideus, were all found either exclusively or predominantly on shells, whereas another non-geniculate coralline, Heydrichia woelkerlingii, occurred almost exclusively on adjacent rock. The primary rocky substratum, however, supported a higher number of species than abalone shells. Possible reasons for the differences between the two substrata include the relative age, microtopography and hardness of the substrata; the abundance of grazers on them; and the relative age of different zones of the abalone shell, which support communities at different stages of succession. Diversity on shells was lowest in zones that were either very young or very old, in keeping with the intermediate disturbance hypothesis. The distinctiveness of shell epibiota will increase β diversity despite having a lower α diversity than that of adjacent rock. Decimation of H. midae by overfishing therefore has implications for biodiversity conservation.     

Carboxymethyl cellulose thiol-imprinted polymers:Synthesis,characterization and selective Hg(Ⅱ) adsorption

Sulfur containing ion imprinted polymers(S-IIPs) were applied for the uptake of Hg(Ⅱ) from aqueous solution. Cysteamine which was used as the ligand for Hg(Ⅱ) complexation, was grafted along the epichlorohydrin crosslinked carboxylated carboxymethyl cellulose polymer chain through an amide reaction. The adsorption ability of S-IIPs towards Hg(Ⅱ)was investigated by kinetic and isotherm models, which, corresponding, showed that the adsorption process followed a pseudo-second-order, fitted well with the Langmuir isotherm with a maximum adsorption capacity of 80 mg/g. Moreover, thermodynamic studies indicated an endothermic and spontaneous reaction with the tendency of an enhanced randomness at the surface of the S-IIPs with temperature increases. S-IIPs indicated a high degree of selectivity towards Hg(Ⅱ) in the presence of Cu~(2+), Zn~(2+), Co~(2+), Pb~(2+)and Cd~(2+).Furthermore, the efficiency of S-IIPs was also evaluated against real samples showing86.78%, 91.88%, and 99.10% recovery for Hg(Ⅱ) wastewater, ground water and tap water,respectively. In this study, the adsorbent was successfully regenerated for five cycles, which allows for their reuse without significant loss of initial adsorption capability.     

Ageing of chromium(III)-bearing slag and its relation to the atmospheric oxidation of solid chromium(III)-oxide in the presence of calcium oxide

Slag arising in ferrochromium and stainless steel production is known to contain residual levels of trivalent chromium. As the chromium is normally bound in the slag matrix in various silicate or spinel phases, and hence not easily mobilised, utilisation or controlled disposal of such slag is generally considered unproblematic. Experimental test work with a number of slag materials indicates, however, that very gradual oxidation of trivalent to hexavalent chromium does occur when the slag is exposed to atmospheric oxygen, rendering a quantifiable but small portion of chromium in this much more mobile and toxic form. Mechanisms and rates of the oxidation reaction were investigated in a number of long-term studies using both original slag materials and artificial mixes of chromium and calcium oxides. Powders of these materials, some of them rolled into balls, were left to age under different conditions for periods of up to 12 months. In the slag samples, which contained between 1 and 3 wt.% chromium, 1000–10 000 μg Cr(VI) were found per gram of chromium within 6–9 months of exposure to an ambient atmosphere. The rate of the oxidation reaction decreased exponentially, and the reaction could generally be said to have ceased within 12 months. In mixtures of calcium and chromium oxides the oxidation reaction is presumed to occur at the boundaries between chromium oxide and calcium oxide phases through diffusion of oxygen along the grain boundaries and of Cr³⁺ across the boundaries, resulting in the formation of calcium chromate. In the slags, where calcium and chromium oxide can form a solid solution, the oxidation is likely to occur at the exposed surface of grains containing this solution.     

Carbon footprint analysis for increasing water supply and sanitation in South Africa: a case study

This study investigates the environmental burdens due to the provision of potable water and sanitation in the eThekwini Municipality (Durban), South Africa. This was achieved by employing LCA studies for the individual parts of the urban water system (impoundment, water treatment, distribution, collection, sewage treatment and water recycling). Based on the results of the individual LCAs a base case was constructed.For the provision of potable water and sanitation to new customers, which have not been previously served, two different scenarios (200 000 new customers in an urban environment with waterborne sewage and in a peri-urban environment with on-site sanitation) and three different options (maximising use of existing assets, recycling water and building new infrastructure) were considered and analysed. With regard to the impact scores calculated for both scenarios (urban and peri-urban), the recycling of water is followed by maximising the use of existing assets as the most environmentally friendly options. The construction of new infrastructure carries a higher environmental burden and the use of bottled water for drinking (an additional scenario) carries the highest environmental burden.     

Male mate guarding in a socially monogamous mammal,the round-eared sengi: on costs and trade-offs

Mate guarding is predicted to be one of the driving forces for the evolution of monogamy, but supporting evidence in free-living mammals is rare. The goals of our study were three-pronged. First, we tested if mate guarding, measured as intrapair distance, occurs as a behavioral tactic in round-eared sengis (Macroscelides proboscideus), a socially monogamous species lacking paternal care and in which females breed asynchronously, producing 2–3 litters during an 8-month long breeding season. Second, we determined if mate guarding involves costs which we identified as changes in male body mass. Third, we investigated whether variation in individual investment in mate guarding depended on the males’ body mass and the number of neighboring males. Field data were collected in a semidesert in South Africa using radio-tracking, trapping, and direct observations during three successive breeding seasons. Mate guarding strongly depended on the females’ reproductive state, and all males started to guard their mates prior to and during estrus, as exemplified by reduced intrapair distance. Mate guarding incurred costs: overall, males lost about 5% of body mass. Male body mass loss and initial body mass were negatively related to the intensity of precopulatory mate guarding. Furthermore, during estrus intrapair distance was inversely correlated with the number of neighboring males. The results show that mate guarding is the predominant male tactic in round-eared sengis. However, since mate guarding imposed costs, males may balance benefits and costs associated with guarding by varying their effort in relation to their physical capabilities and the competitive environment.