Ethyl‐iophenoxic acid as a quantitative bait marker for small mammals

Abstract

Bait markers are indispensable for ecological research but in small mammals, most markers are invasive, expensive and do not enable quantitative analyses of consumption. Ethyl-iophenoxic acid (Et-IPA) is a non-toxic, quantitative bait marker, which has been used for studying bait uptake in several carnivores and ungulates. We developed a bait with Et-IPA, assessed its palatability to common voles (Microtus arvalis), and determined the dose-residuerelation for this important agricultural pest rodent species. Et-IPA concentrations of 40 to 1280 μg Et-IPA per g bait were applied to wheat using sunflower oil or polyethylene glycol 300 as potential carriers. In a laboratory study, common voles were offered the bait and blood samples were collected 1, 7, and 14 days after consumption. The samples were analyzed with LC-ESI-MS/MS for blood residues of Et-IPA. Sunflower-oil was the most suitable bait carrier. Et-IPA seemed to be palatable to common voles at all test concentrations. Dose-dependent residues could be detected in blood samples in a dose-dependent manner and up to 14 days after uptake enabling generation of a calibration curve of the dose-residue relationship. Et-IPA was present in common vole blood for at least 14 days, but there was dissipation by 33-37% depending on dose. Et-IPA meets many criteria for an "ideal" quantitative bait marker for use in future field studies on common voles and possibly other small mammal species.

Developing fertility control for rodents: a framework for researchers and practitioners

“…2013; Jacoblinnert et al. 2022a). However, the variable persistence of some markers, such as iophenoxic acid analogs in wildlife species highlights the need for calibration testing of each compound as a marker for each species and for each proposed use before starting a bait delivery trial (Ballesteros et al.…”

“…2003; Jacoblinnert et al. 2022a), camera traps, and PIT tag readers. Such studies allow identifying individual and population level patterns of bait uptake in target and non‐target species, revealing the reasons for over/under dosing and then adjusting baiting strategies accordingly (e.g.…”

“…Bait markers tested on rodents include Rhodamine B, tetracyclines, ethyl-iophenoxic acid, and its analogs methyland propyl-iophenoxic acid (e.g. Jacob et al 2002;Ballesteros et al 2013;Jacoblinnert et al 2022a). However, the variable persistence of some markers, such as iophenoxic acid analogs in wildlife species highlights the need for calibration testing of each compound as a marker for each species and for each proposed use before starting a bait delivery trial (Ballesteros et al 2013).…”

Fertility control of rodent pests: recent developments from lab to field

“…Further consideration to develop a commercial product requires a food bait to be presented in an attractive and stable formulation (e.g. Jacoblinnert et al 2021a) that can be consumed by the target pest rodent at the relevant time, such as just before the onset of the breeding season (Jacoblinnert et al 2021b).…”

“…Jacoblinnert et al . 2021a) that can be consumed by the target pest rodent at the relevant time, such as just before the onset of the breeding season (Jacoblinnert et al . 2021b).…”