Irresistible ants: exposure to novel toxic prey increases consumption over multiple temporal scales

Abstract

As species become increasingly exposed to novel challenges, it is critical to understand how evolutionary (i.e., generational) and plastic (i.e., within lifetime) responses work together to determine a species' fate or predict its distribution. The introduction of non-native species imposes novel pressures on the native species that they encounter. Understanding how native species exposed to toxic or distasteful invaders change their feeding behavior can provide insight into their ability to cope with these novel threats as well as broader questions about the evolution of this behavior. We demonstrated that native eastern fence lizards do not avoid consuming invasive fire ants following repeated exposure to this toxic prey. Rather fence lizards increased their consumption of these ants following exposure on three different temporal scales. Lizards ate more fire ants when they were exposed to this toxic prey over successive days. Lizards consumed more fire ants if they had been exposed to fire ants as juveniles 6 months earlier. Finally, lizards from populations exposed to fire ants over multiple generations consumed more fire ants than those from fire ant-free areas. These results suggest that the potentially lethal consumption of fire ants may carry benefits resulting in selection for this behavior, and learning that persists long after initial exposure. Future research on the response of native predators to venomous prey over multiple temporal scales will be valuable in determining the long-term effects of invasion by these novel threats.

Non-avian reptile learning 40 years on: advances and promising new directions

“…In a subsequent study, sub-adult lizards did not avoid toxic ants after direct exposure, after six months (exposed as juveniles), or when they were sourced from a population invaded by fire ants for generations. Similar to the previous study, sub-adult lizards increased ant consumption during the course of the experiment (Herr et al, 2016). A third study used lab-born hatchling fence lizards to test fire ant avoidance behaviour.…”

Eastern Fence Lizards (Sceloporus undulatus) display an ontogenetic shift in relative consumption of native and invasive prey

“…Since adults have been exposed to fire ants for their entire lifetimes (likely frequently over several years) they may have learned that consuming fire ants is noxious or painful and thus learned to avoid them. However, these lizards increase consumption of fire ants with repeated exposure, arguing against learned avoidance (Robbins et al 2013;Herr et al 2016). The hatchlings were fire ant naïve and did not have had the opportunity to learn to avoid fire ants.…”

“…This innate avoidance suggests selective pressure to avoid eating these toxic ants. However, sub-adult fence lizards increased consumption of fire ants with increased exposure across multiple contexts (multigenerational, distant past, and recent exposure; Robbins et al 2013;Herr et al 2016). In all of these experiments, lizards were presented with fire ants as their only prey option, meaning their ability to distinguish fire ants from native ants, a key assumption, has not been tested.…”

Ecoimmune reallocation in a native lizard in response to the presence of invasive, venomous fire ants in their shared environment

“…Red imported fire ants are venomous, and as few as 12 fire ants are capable of killing a fence lizard (Langkilde, 2009b). Fire ants also serve as a novel prey item for fence lizards and envenomate the lizards even as they are consumed (Herr et al, 2016; Venable & Langkilde, 2019; Venable et al, 2019). In addition to sharing a broad geographic range, fence lizards and fire ants occupy open, anthropogenically disturbed habitats, resulting in frequent interactions between the two species (Langkilde, 2009a, 2009b).…”

“…Fire ants also serve as a novel prey item for fence lizards and envenomate the lizards even as they are consumed (Herr et al, 2016;. In addition to sharing a broad geographic range, fence lizards and fire ants occupy open, anthropogenically disturbed habitats, resulting in frequent interactions between the two species (Langkilde, 2009a(Langkilde, , 2009b.…”