Southeastern US Snake Species are Vulnerable to Egg Predation by Red Imported Fire Ants (Solenopsis invicta)

Abstract: Invasion and spread of Red Imported Fire Ants (RIFA; Solenopsis invicta) is cited as a possible cause for enigmatic reptile declines in the southeastern United States. Reptiles are negatively affected by RIFA through predation of eggs, hatchlings, and adults. We used short-term (12-h) field trials early in incubation to evaluate whether RIFA could successfully depredate intact eggs from six species of native terrestrial oviparous snakes: North American Racer (Coluber constrictor), Speckled Kingsnake (Lampropeltis holbrooki), Prairie Kingsnake (L. calligaster), Rough Greensnake (Opheodrys aestivus), Black Ratsnake (Pantherophis obsoletus) and Great Plains Ratsnake (P. emoryi). Then we used an artificial nest field experiment at the end of incubation to test whether RIFA predation differed between a species that has apparently declined in areas of its range where RIFA has invaded (L. holbrooki) and a species that has apparently not declined (C. constrictor). We measured pip–hatch and incubation time for each species in the laboratory to determine whether differences in time between pipping and hatching (pip–hatch time) could account for interspecific differences in RIFA predation on eggs. Overall, RIFA predation rates on snake eggs were high for all species (25–67% during early trials, 50–100% at end of incubation), although P. obsoletus was only depredated after hatching in the field. Coluber constrictor had significantly shorter pip–hatch times than other species, but probability of predation by RIFA did not differ for C. constrictor and L. holbrooki. Our study provides novel observations of RIFA predation and suggests that time spent in nest, eggshell characteristics, and nest microhabitat may be more important than pip–hatch time in mediating vulnerability of snake eggs to RIFA predation.