Can rare positive interactions become common when large carnivores consume livestock?

Livestock populations in protected areas are viewed negatively because of their interaction with native ungulates through direct competition for food resources. However, livestock and native prey can also interact indirectly through their shared predator. Indirect interactions between two prey species occur when one prey modifies either the functional or numerical responses of a shared predator. This interaction is often manifested as negative effects (apparent competition) on one or both prey species through increased predation risk. But indirect interactions can also yield positive effects on a focal prey if the shared predator modifies its functional response toward increased consumption of an abundant and higher-quality alternative prey. Such a phenomenon between two prey species is underappreciated and overlooked in nature. Positive indirect effects can be expected to occur in livestock-dominated wildlife reserves containing large carnivores. We searched for such positive effects in Acacia-Zizhypus forests of India's Gir sanctuary where livestock (Bubalus bubalis and Bos indicus) and a coexisting native prey (chital deer, Axis axis) are consumed by Asiatic lions (Panthera leo persica). Chital vigilance was higher in areas with low livestock density than in areas with high livestock density. This positive indirect effect occurred because lion predation rates on livestock were twice as great where livestock were abundant than where livestock density was low. Positive indirect interactions mediated by shared predators may be more common than generally thought with rather major consequences for ecological understanding and conservation. We encourage further studies to understand outcomes of indirect interactions on long-term predator-prey dynamics in livestock-dominated protected areas.     

A survey of environmental features in a section of the Vellar-Coleroon estuarine system,south India

A survey was conducted on 15th November, 1970, in mangrove forests and backwater regions of a section of the Vellar-Coleroon estuarine complex; a total of 19 stations were occupied. Detailed investigations on nutrients, pigments, and plankton were carried out. The following ranges in values were recorded: salinity, 10.40 to 30.50; pH, 7.50 to 8.30; temperature, 29.50° to 30.50°C; total phosphorus, 0.72 to 3.34 g at/l; inorganic phosphate, 0.19 to 1.59 g at/l; ammonia, 0.34 to 0.36 g at/l; nitrite, 0.11 to 0.25 g at/l; nitrate, 2.85 to 6.94 g at/l; silicate, 18.49 to 134.92 g at/l. Dissolved oxygen content ranged from a minimum of 3.69 ml to a maximum of 5.44 ml/l. Chlorophyll a ranged from an undetectable amount to 1.01 mg/m³, chlorophyll b from 0.02 to 0.85 mg/m³, chlorophyll c from 0 to 0.41 mg/m³ and carotenoids from 0 to 0.74 MSPU/m³. The plankton displacement volume ranged from a negligible amount to 3.60 cm³/m³; seston varied between 0.29 and 0.91 g/l. Phytoplankton was abundant at 3 stations; at other stations zooplankton was abundant. Coscinodiscus, Asterionella and Ditylum were the dominant forms among the phytoplankton; Oithona, Acrocaanus, Euterpina, Centropages, Corycaeus, Lucifer and Oikocreura were dominant among the zooplankton. Phytoplankton and zooplankton populations, as percentage of the total plankton, varied between 3.70 and 89.00% and between 11 and 96.30%, respectively. Average gross production values in the mangrove and back-water stations were 7.56 and 3.33 g C/m³/day, and the net production values 6.29 and 2.67 g C/m³/day, respectively.     

Water Transport in Polylactide and Polylactide/Montmorillonite Composites

Polylactide–montmorillonite composites were fabricated by melt-blending followed by compression molding, and water permeability of the composites was studied by both experiments and theoretical models. The water permeation in composites decreases with increasing concentration of montmorillonite. Specifically, at a concentration of 10 wt% of montmorillonite, the water permeation is 34 % less than in the neat polymer. Transmission electron microscopy (TEM) and wide-angle X-ray scattering (WAXS) results show that most of the montmorillonite particles are well-dispersed and randomly exfoliated in the polymer matrix. A fit of theoretical models to the permeation data estimates that montmorillonite platelets are mostly exfoliated in the polymer matrix and oriented randomly, which matches with results from WAXS and TEM.