Holding ground in the face of invasion: native fence lizards (Sceloporus undulatus) do not alter their habitat use in response to introduced fire ants (Solenopsis invicta)

The introduction of non-native species is becoming increasingly common. Understanding the impact of invaders on native populations is critical for effective management. Red imported fire ants ( Solenopsis invicta Buren, 1972) were introduced to the USA in the 1930s. They will attack, and can kill, native fence lizards ( Sceloporus undulatus (Bosc and Daudin in Sonnini and Latreille, 1801)), which co-occur with these ants across much of their invasive range. I determined whether fence lizards minimize encounters with S. invicta by altering their habitat use following invasion or avoiding cues of the presence of these fire ants. I recorded the habitat use of fence lizards and S. invicta mounds across four sites with different histories of invasion, and quantified lizard avoidance of S. invicta scent. I found that lizards do not alter their habitat use following S. invicta invasion, nor do they spatially avoid their mounds. Fence lizards do avoid S. invicta scent, but this was only evident in naïve or recently invaded populations. The lack of avoidance of S. invicta by fence lizards could be explained by the high prevalence of these fire ants, making them difficult to avoid, and adaptive shifts in the escape behaviour and morphology of these lizards following invasion that permit them to survive fire ant attack.