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Energetic cost of foraging in the ant Rhytidoponera aurata in tropical Australia
Author(s) -
Gissel Nielsen Mogens
Publication year - 2001
Publication title -
physiological entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 57
eISSN - 1365-3032
pISSN - 0307-6962
DOI - 10.1046/j.0307-6962.2001.00242.x
Subject(s) - foraging , biology , respirometer , nest (protein structural motif) , ecology , forage , range (aeronautics) , zoology , respiration , botany , engineering , aerospace engineering , biochemistry
. The energetic costs of foraging by the ant Rhytidoponera aurata (Roger) were investigated both in the laboratory and field. The cost of running was estimated for workers under controlled conditions in the laboratory. Ants were placed in a ring‐shaped respiration chamber, connected to a through‐flow respirometer, in which they could run freely while their speed and respiratory rates were monitored simultaneously. The energetic costs were measured for workers while running at different speeds, and the same individuals were then used to measure the additional costs of carrying loads. Loads consisted of pieces of platinum one to two times the body mass of the ant, glued to the ants' thoraxes. These were relatively small loads compared to their natural food items. The mean cost of locomotion was 166 mJ/mg/km, and the mean cost of load carriage was 179 mJ/mg/km. A field experiment was carried out in three biotypes in open forest in Northern Territory, Australia, where worker R. aurata forage only during daylight hours at air temperatures ranging from 31 to 36 °C. Food items were placed randomly within the territory of a nest, and the duration and distance of its transportation to the nest by a forager was recorded. There were no significant differences in the frequencies with which ants selected different sized food items in the range 15–165 mg, whereas items weighing 5 mg were selected less often. The relationship between the speed of running and size of a food item transported was linear but this differed in each of three types of ground vegetation recognized. The energy cost of load carriage was extremely small compared with the energetic benefit, e.g. the energy content in a 165 mg food item is equivalent to the cost of carrying it over a distance of 78 km taking 129 days under laboratory conditions. Thus, the main limiting factor in energetic terms for this species is not the retrieval of food items, but the foraging time required to find a food source.