Behavioural flexibility does not prevent numerical declines of harvester ants under intense livestock grazing: responses of harvester ants to habitat degradation

RODRIGO POL; GABRIELA VARGAS; LUIS MARONE

ECOLOGICAL ENTOMOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017

0307-6946

1. Human-induced rapid environmental change may decrease food resourcesand create unfavourable conditions for native species. Organisms showing a flexible foraging behaviour can exploit novel or alternative foods and are more likely to persist, whereas less flexible organisms might suffer starvation and numerical reductions.2. This study assessed whether declines in the quality and availability of seedsprompted by grazing provoke behavioural and numerical responses in Pogonomyrmexmendozanus ants, and aimed to test whether behavioural flexibility buffers habitat degradation and prevents numerical declines.3. Heavy grazing caused seed reductions, especially of the highly consumed andpreferred grass seeds, and triggered two kinds of ant responses. Ants expanded their diet by incorporating a greater proportion of non-seed items, and they reduced foraging activity. As a consequence, the rate of food intake per colony lessened, particularly that of carbohydrate-rich seeds like grass seeds. Colony density under heavy grazing also fell.4. Habitat degradation triggered a cascade of mechanisms that starts with a decrease in the seed resources and continues with changes in ant behaviour. However, behavioural responses were insufficient to prevent ant numerical declines. The results of this study suggest that the reduction in the colony density under habitat degradation was provoked by ant nutritional deficit and starvation, and predict a deterioration in body condition, colony performance and reproduction of ants, which deserve further assessment.