Leaf cutting ants live in symbiosis with a basidiomycete fungus that is exploited as a source of nutrients for the ant larvae. Tests of fungus transport demonstrated that Acromyrmex subterraneus subterraneus workers discriminate concolonial fungus from alien fungus, and rejected the latter. Larvae and pupae of the ant were used as controls. Chemical analysis of the fungus revealed a great similarity between its hydrocarbon profile and that found on the ant brood. Experiments with lures showed that chemical extracts from the fungus are responsible for this discrimination process. Moreover, the presence of brood inside the fungus seemed to be important for discrimination of the fungus by workers. Resident workers accepted concolonial broodless fungus less than concolonial fungus inoculated with brood odor. Fungus seems to acquire colonial odor passively, simply by contact with the brood. The impact of fungus volume present in the nest on closure of the colony is discussed. We show here for the first time the importance of a symbiotic vegetal organism in colonial recognition in social insects.
An interesting way to understand and eventually improve the well-being of captive animals is to compare different living and social conditions, in order to analyze the behavioral differences between animals living in very restrictive conditions and animals enjoying more permissive ones. In the present study we performed 10 observations of six wolf enclosures with quite different living and social conditions. The rest/activity balance, behavioral diversity, and use of available space were used as welfare criteria. Results show that the proportion of time resting was higher in large, comfortable enclosures. In each park, animals used only a part of the available space, the proportion being lower in large enclosures. The behavioral diversity was little affected by the size of the enclosure, but highly related to the composition of the pack. The results underline the importance of spatial choice and social group management.
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