Land Use as a Driver of Patterns of Rodenticide Exposure in Modeled Kit Fox Populations

Abstract

Although rodenticides are increasingly regulated, they nonetheless cause poisonings in many non-target wildlife species. Second-generation anticoagulant rodenticide use is common in agricultural and residential landscapes. Here, we use an individual-based population model to assess potential population-wide effects of rodenticide exposures on the endangered San Joaquin kit fox (Vulpes macrotis mutica). We estimate likelihood of rodenticide exposure across the species range for each land cover type based on a database of reported pesticide use and literature. Using a spatially-explicit population model, we find that 36% of modeled kit foxes are likely exposed, resulting in a 7-18% decline in the range-wide modeled kit fox population that can be linked to rodenticide use. Exposures of kit foxes in low-density developed areas accounted for 70% of the population-wide exposures to rodenticides. We conclude that exposures of non-target kit foxes could be greatly mitigated by reducing the use of second-generation anticoagulant rodenticides in low-density developed areas near vulnerable populations.

Prevalence of Anticoagulant Rodenticides in Feces of Wild Red Foxes (Vulpes Vulpes) in Norway

“…This is in accordance with a study in Finland with no significant relationship between overall AR concentration and environmental variables such as farm density and industrial surroundings (Koivisto et al 2018). In contrast, San Joaquin kit fox (Vulpes macrotis mutica) demonstrated the highest AR exposure in low-density development areas (Nogeire et al 2015). These regions generally included single-family housing units, which is similar to our suburban areas.…”

Genome‐wide expression reveals multiple systemic effects associated with detection of anticoagulant poisons in bobcats (Lynx rufus)

“…In California, exposure to ARs is a statewide problem with over 70% (368/492) of birds and mammals testing positive for ARs between 1995 and 2011 (California Department of Pesticide Regulation ). AR toxicity was a leading cause of mortality in predatory and scavenging birds (Kelly et al., ) and in coyotes ( Canis latrans ) (Riley et al., ), and it is increasingly recognized as a major threat to the Pacific fisher ( Pekania pennanti ) (Gabriel et al., ; Thompson et al., ) and to the endangered San Joaquin kit fox ( Vulpes macrotis mutica ) (Nogeire, Lawler, Schumaker, Cypher, & Phillips, ). In southern California, over 90% of bobcats and mountain lions ( Puma concolor ) tested positive for ARs (Riley et al., ).…”

Modeling Exposure of Mammalian Predators to Anticoagulant Rodenticides

“…These classes implemented all other behavior necessary for the rodenticide model (see ODdox 2 ). The overall modeling strategy was somewhat similar to (e.g., Nogeire et al, 2015) in that we attempted to create distributions of predators based on habitat structure and then overlay exposure. The main differences were that we had no predator population dynamics, the scale which is much smaller in our study and more detailed, and that we used a more detailed simulation of baiting patterns, and subsequent AR vectoring and environmental decay.…”

“…For example, there is seasonal variation in the use of farm buildings by polecats, where ARs are used (Birks, 1998), which may explain the increase in AR burdens in polecats in winter in Denmark (Elmeros et al, 2015). Such a population model should be individual-based (e.g., Nogeire et al, 2015), but should also ideally be able to represent environmental and behavioral details accurately to assess individual toxico-kinetics (e.g., Topping et al, 2016). A further improvement would be the use of multiple landscapes for testing scenarios.…”