Microclimatic Conditions Regulate Surface Activity in Harvester Ants <Emphasis Type="Italic">Messor barbarus</Emphasis> |
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Authors: | Francisco M Azcárate Eva Kovacs Begoña Peco |
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Institution: | (1) Departamento de Ecología, Universidad Autónoma de Madrid, C. U. Canto Blanco, E-28049 Madrid, Spain;(2) Kiskunsag National Park, H-6000 Kecskemét, Hungary |
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Abstract: | This paper analyses the effect of microclimatic factors (internal soil temperature, surface temperature and surface relative
humidity) on surface activity of Messor barbarus harvester ants. We selected 44 colonies in an area of Mediterranean grassland
near Madrid (Central Spain), which were monitored for activity between March 1998 and September 1999. Results indicate that
microclimatic factors are good predictors of colony activation and intensity of activity. Colonies became active above certain
critical values of internal soil temperature and relative humidity. For active colonies, surface temperature was the main
regulatory factor for worker departure rate, which peaked at around 25–30°C. Worker speed was positively correlated with surface
temperature, although the relationship was weaker for large-sized workers. Microclimatic factors were not enough, however,
to predict task allocation outside the nest. The explanation for this aspect of ant behavior probably requires the inclusion
of biotic factors in the models. |
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Keywords: | mediterranean grasslands ant colonies temperature relative humidity task allocation |
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