|1. Sodium is an essential dietary element and preferential foraging for
high concentrations of sodium by inland herbivorous and omnivorous ants suggests
it may be limiting. If so, increased sodium availability through altered deposition
and anthropogenic sources may lead to increased colony and population growth and
cascading ecological impacts.
2. For red imported fire ants, Solenopsis invicta Buren, the present study tests:
(i) whether colonies from coastal and inland sites differ in their responses to NaCl
baits; and (ii) whether supplemental NaCl increases growth of fire ant colonies in the
3. Fire ants in inland sites with low sodium deposition responded roughly an order
of magnitude more strongly to high concentrations of NaCl baits than did fire ants in
coastal sites with high sodium deposition.
4. Laboratory colonies of fire ants, however, showed no signs of sodium limitation
or benefits of increased sodium. The link between behavioural responses to baits in
the field and effects on colony growth deserves further investigation to assess the
ecological impacts of altered sodium availability|