Predicting functional responses in agro‐ecosystems from animal movement data to improve management of invasive pests

Abstract

Functional responses describe how changing resource availability affects consumer resource use, thus providing a mechanistic approach to prediction of the invasibility and potential damage of invasive alien species (IAS). However, functional responses can be context dependent, varying with resource characteristics and availability, consumer attributes, and environmental variables. Identifying context dependencies can allow invasion and damage risk to be predicted across different ecoregions. Understanding how ecological factors shape the functional response in agro‐ecosystems can improve predictions of hotspots of highest impact and inform strategies to mitigate damage across locations with varying crop types and availability. We linked heterogeneous movement data across different agro‐ecosystems to predict ecologically driven variability in the functional responses. We applied our approach to wild pigs (Sus scrofa), one of the most successful and detrimental IAS worldwide where agricultural resource depredation is an important driver of spread and establishment. We used continental‐scale movement data within agro‐ecosystems to quantify the functional response of agricultural resources relative to availability of crops and natural forage. We hypothesized that wild pigs would selectively use crops more often when natural forage resources were low. We also examined how individual attributes such as sex, crop type, and resource stimulus such as distance to crops altered the magnitude of the functional response. There was a strong agricultural functional response where crop use was an accelerating function of crop availability at low density (Type III) and was highly context dependent. As hypothesized, there was a reduced response of crop use with increasing crop availability when non‐agricultural resources were more available, emphasizing that crop damage levels are likely to be highly heterogeneous depending on surrounding natural resources and temporal availability of crops. We found significant effects of crop type and sex, with males spending 20% more time and visiting crops 58% more often than females, and both sexes showing different functional responses depending on crop type. Our application demonstrates how commonly collected animal movement data can be used to understand context dependencies in resource use to improve our understanding of pest foraging behavior, with implications for prioritizing spatiotemporal hotspots of potential economic loss in agro‐ecosystems.

Influence of biotic and abiotic factors on home range size and shape of invasive wild pigs (Sus scrofa)

“…However, since our study area does not include any agricultural fields, further research using an adapted protocol that accounts for the influence of crops on home range size and shape would be beneficial. 77…”

Connecting the Dots: Behavioral State Resource Selection in Wild Pigs in the Southeast United States

“…Sex has been found to be an important predictor of wild pig home range size, with males typically having a larger home range and greater movement rates than females [33]. Also, wild pigs have demonstrated seasonal differences in home range size and habitat selection based on resource availability [19,26,34]. Therefore, we expected sex-speci c and seasonal-speci c differences in the movement parameters associated with each behavioral state and differences in transition probabilities among states throughout the diel period.…”

“…Wild pigs move in deliberate manners choosing different resource patches depending on their current needs (rest, forage, mates, etc.) relative to what is available and whether or not the tradeoff for accessing these resources is energetically reasonable [17][18][19]. When targeting these resources for speci c behaviors or needs, wild pig movements tend to be methodical, as they often consistently use the same trails and interact with the same areas on the landscape [20,21].…”

Individual differences in habitat selection mediate landscape level predictions of a functional response

“…Thus, our approaches to forecasting animal distributions must be similarly robust to the influences of individual variation and habitat availability on space use. The relationship between use and availability of habitat often changes over gradients of availability, and this ideaknown as the functional response in habitat selection (Mysterud and Ims 1998)is becoming central to forecasting the distributions of populations in new environments (Clark et al 2019;Muhly et al 2019;Wilber et al 2020). However, population-level space use is underpinned by individuals that do not necessarily respond uniformly to environments with different habitat availability (Leclerc et al 2016).…”