Abstract
Simple SummaryFeral cats (Felis catus) have a devastating impact on Australian native fauna. Several programs exist to control their numbers through lethal removal, using tools such as baiting with toxins. Adult male cats are especially difficult to control. We hypothesized that one way to capture these male cats is to lure them using female cats. As female cats are seasonal breeders, a method is needed to artificially induce reproductive (estrous) behavior so that they could be used for this purpose year-round (i.e., regardless of season). Estrogens can be given to cats to induce estrous behavior, but it is not known for how long this elevates the blood concentrations of estradiol. Following the administration of a long-acting estrogen, estradiol cypionate, to nine captive feral cats, blood estrogen concentrations remained elevated for several days. This information will be useful to ongoing studies that are investigating ways to reduce the abundance of feral cats in Australia, especially adult male cats.The control of feral cats (Felis catus) in Australia is a key biological conservation issue. Male cats are more difficult to control than female cats. Collared and tagged female cats displaying estrous behavior have been considered as a way to lure male cats and reveal their locations. As female cats are seasonal breeders, artificial induction of estrous behavior following the administration of a long-acting estrogen could improve their use for this purpose. Estradiol cypionate was intramuscularly administered to nine entire non-pregnant female feral cats, of unknown estrous status, at 0.1, 0.3, or 0.5 mg/kg. Mean peak serum concentrations of estradiol-17β were 365 pg/mL (0.1 mg/kg), 1281 pg/mL (0.3 mg/kg), and 1447 pg/mL (0.5 mg/kg). The time-course of estradiol-17β concentrations after various doses of estradiol cypionate was assessed using non-compartmental and non-linear mixed-effects methods. At the highest-studied dose (0.5 mg/kg), the 50th percentile of estradiol-17β concentrations exceeded 0.1 ng/mL for 11.8 days, and 0.05 ng/mL for 14.6 days. The duration increased with increasing dose. No signs of toxicity were noticed in any cat during the study. This information will be useful to ongoing studies that are investigating ways to reduce the abundance of feral cats in Australia, especially adult male cats.
Highlights
Control of feral cats (Felis catus) is considered a key conservation issue in Australia due to the threat they pose to many endangered animal species through predation and disease transmission [1].Many Australian conservation organizations use broadcast sodium fluoroacetatepoison baits to kill feral cats [2,3]
Higher doses of estradiol cypionate were generally associated with higher maximum serum concentrations of estradiol-17β (Figure 1) and larger areas under their respective serum concentration time curves (Table 1)
This study has provided the first report of the disposition of estradiol-17β and the histological appearance of the ovaries and uteri in female feral cats of unknown cycle stage, following the intramuscular administration of estradiol cypionate
Summary
Control of feral cats (Felis catus) is considered a key conservation issue in Australia due to the threat they pose to many endangered animal species through predation and disease transmission [1]. Poison baits to kill feral cats [2,3]. It is rare (or undocumented) for all feral cats to be killed by a baiting program. Targeting male cats for lethal control has become a recent focus for feral cat control programs [4]. A cogitated approach for effective control of male cats that warrants consideration is to use reproductively cycling female cats as a lure. A number of methods to attract feral cats have been assessed and scent-based lures (anal gland preparations) were found to be the most effective [5]
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