Although helping behavior is ubiquitous throughout the animal kingdom, actual rescue activity is particularly rare. Nonetheless, here we report the first experimental evidence that ants, Cataglyphis cursor, use precisely directed rescue behavior to free entrapped victims; equally important, they carefully discriminate between individuals in distress, offering aid only to nestmates. Our experiments simulate a natural situation, which we often observed in the field when collecting Catagyphis ants, causing sand to collapse in the process. Using a novel experimental technique that binds victims experimentally, we observed the behavior of separate, randomly chosen groups of 5 C. cursor nestmates under one of six conditions. In five of these conditions, a test stimulus (the “victim”) was ensnared with nylon thread and held partially beneath the sand. The test stimulus was either (1) an individual from the same colony; (2) an individual from a different colony of C cursor; (3) an ant from a different ant species; (4) a common prey item; or, (5) a motionless (chilled) nestmate. In the final condition, the test stimulus (6) consisted of the empty snare apparatus. Our results demonstrate that ants are able to recognize what, exactly, holds their relative in place and direct their behavior to that object, the snare, in particular. They begin by excavating sand, which exposes the nylon snare, transporting sand away from it, and then biting at the snare itself. Snare biting, a behavior never before reported in the literature, demonstrates that rescue behavior is far more sophisticated, exact and complexly organized than the simple forms of helping behavior already known, namely limb pulling and sand digging. That is, limb pulling and sand digging could be released directly by a chemical call for help and thus result from a very simple mechanism. However, it's difficult to see how this same releasing mechanism could guide rescuers to the precise location of the nylon thread, and enable them to target their bites to the thread itself.

Grasslands being used in sheep farming systems are managed under a variety of agricultural production, recreational and conservational objectives. Although sheep grazing is rarely considered the best method for delivering conservation objectives in seminatural temperate grasslands, the literature does not provide unequivocal evidence on the impact of sheep grazing on pasture biodiversity. Our aim was therefore to review evidence of the impacts of stocking rate, grazing period and soil fertility on plant communities and arthropod populations in both mesotrophic grasslands typical of agriculturally improved areas and in native plant communities. We therefore conducted a literature search of articles published up to the end of the year 2010 using 'sheep' and 'grazing' as keywords, together with variables describing grassland management, plant community structure or arthropod taxa. The filtering process led to the selection of 48 articles, with 42 included in the stocking rate dataset, 9 in the grazing period dataset and 10 in the soil fertility dataset. The meta-analysis did not reveal any significant trends for plant species richness or plant community evenness along a wide stocking rate gradient. However, we found frequent shifts in functional groups or plant species abundance that could be explained by the functional properties of the plants in the community. The meta-analysis confirmed that increasing soil fertility decreased plant species richness. Despite the very limited dataset, plant species richness was significantly greater in autumn-grazed pastures than in ungrazed areas, which suggests that choosing an appropriate grazing period would be a promising option for preserving biodiversity in sheep farming systems. Qualitative review indicated that low grazing intensity had positive effects on Orthoptera, Hemiptera (especially phytophagous Auchenorrhyncha) and, despite a diverse range of feeding strategies, for the species richness of Coleoptera. Lepidoptera, which were favoured by more abundant flowering plants, also benefited from low grazing intensities. Spider abundance and species richness were higher in ungrazed than in grazed pastures. In contrast, there are insufficient published studies to draw any firm conclusions on the benefits of late grazing or stopping fertilization on insect diversity, and no grounds for including any of this information in decision support tools at this stage.Keywords: biodiversity, grazing period, insect, stocking rate, soil fertility ImplicationsThere is a general trend toward a gradual intensification of ruminant production to meet the increasing demand for livestock products (Bouwman et al., 2005), which logically raises major concerns over the environmental consequences involved. Grassland intensification entails higher livestock densities and fertilizer application rates to increase soil productivity, which negatively affects the diversity of resident plant communities. Grasslands are being managed under a variety of agricultural production and conservation objectives;...

Grassland butterflies are on the decline throughout Europe. We tested an 'alternative rotational stocking' (ARS) strategy based on theoretical and practical aspects of grassland ecology, designed to increase butterfly diversity while also meeting farmers' production objectives. This management strategy implies taking animals away from one subplot of the rotation during the main flowering period. Its feasibility and benefits on butterfly diversity were tested by comparing ARS with continuous stocking (CS) in plots grazed by cattle at the same stocking rate: high in 2005 and 2006 then lenient in 2007 and 2008. At the high stocking rate, butterfly abundance (21AE9 vs. 8AE3, P < 0AE01) and butterfly species richness (7AE4 vs. 3AE7, P < 0AE001) were significantly higher in ARS than in CS plots, matching the increase in pasture flowering intensity and sward structural diversity. ARS was led according to the pre-planned schedule in 2005, but in 2006, the number of heifer grazing days in ARS was reduced by 19% because of unfavourable spring grass growth. At the lenient stocking rate, ARS was less beneficial for butterflies (abundance: 17AE4 vs. 13AE0, P < 0AE10; species richness: 5AE9 vs. 5AE2, P = 0AE35) but would present less risk for farmers in terms of providing livestock with sufficient forage. Alternative rotational stocking thus has potential to be integrated into grassland-based systems, but would require earlier grazing on the excluded subplot of the rotation in the event of unfavourable grass growth during spring.

Permanent grasslands are an important habitat for insect communities, including pollinator populations which are in pan-European decline. Here, we investigated the benefits of temporarily excluding sheep from pastures on butterfly (Lepidoptera: Rhopalocera and Zygaenidae) and bumblebee (Hymenoptera: Bombidae) communities in two semi-natural grasslands differing in soil fertility and surrounding landscapes. We compared the impact of continuous grazing against rotational grazing (RG) at the same stocking rate but in which a subplot was excluded from the rotation during the main flowering period. We predicted that the diversity of flower-visiting insect community would be improved by RG due to the preservation of flower-rich patches and the maintenance of sward heterogeneity. Benefits of RG management were mainly evidenced on bumblebee density and species richness, with some additional effects on local density of butterflies during the subplot-exclusion period. Temporarily excluding sheep from pastures during peak flowering could thus offer an opportunity to preserve the diversity of flower-visiting insects, in spite of weaker benefits than could have been expected from previous surveys with cattle.

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