Combining Aspirin with Cholecalciferol (Vitamin D3) – A Potential New Tool for Controlling Possum Populations

Abstract

The introduced Australian brushtail possum is a major vertebrate pest in New Zealand, with impacts on conservation and agriculture being managed largely through poisoning operations. Cholecalciferol (vitamin D3) is registered for use in controlling possums and despite its many advantages it is expensive and relatively inhumane. Combination of a high proportion of aspirin with a low proportion of cholecalciferol was effective in killing high proportions of groups of acclimatised, caged possums: this is attributed to both an unexpectedly high toxicity of the type of cholecalciferol used, and a proposed synergistic mechanism between the two compounds. Death was caused by localised damage to heart ventricles by aspirin, and inhibition of tissue repair by both aspirin and cholecalciferol. The observed toxicosis had lower impact on the welfare of possums than either compound administered alone, particularly aspirin alone. Residue analyses of bait remains in the GI tract suggested a low risk of secondary poisoning by either compound. The combination of cholecalciferol and aspirin has the potential to meet key requirements of cost-effectiveness and humaneness in controlling possum populations, but the effect of the combination in non-target species has yet to be tested.

An efficacy test of cholecalciferol plus diphacinone rodenticide baits for California voles (Microtus californicusPeale) to replace ineffective chlorophacinone baits

“…It has also been suggested that the acute toxicant, because of its more rapid "knock down" time, might result in sickened animals retreating to burrows or other refugia before the anticoagulant takes effect and causes their death. Morgan et al (2013) noted that dosing brushtail possums (Trichosurus vulpecula) with cholecalciferol combined with aspirin (an anticoagulant) resulted in more rapid mortality than dosing with aspirin alone. In the case of burrowing rodents such as voles, this could potentially reduce the risk of predators and scavengers having access to poisoned carcasses.…”

Cage Efficacy Trials with Cholecalciferol Plus Diphacinone and Cholecalciferol Plus Brodifacoum Baits Using Richardson’s Ground Squirrels

“…Finally, there is an increasing concern about the humaneness of some rodenticides (mainly with anticoagulants; e.g., Lapidge et al 2009). Hence, various researchers in the U.S. and elsewhere are investigating alternative formulations and/ or active ingredients (Eason et al 2010a, Eason et al 2010b, Blackie et al 2013, Morgan et al 2013, Witmer et al 2013.…”

Aerial Prefeeding Followed by Ground Based Toxic Baiting for More Efficient and Acceptable Poisoning of Invasive Small Mammalian Pests

“…However, this is considered an unlikely explanation as cholecalciferol assayed at 0.86% (i.e. 7.5% above specification) in a peanut paste, with no added masking flavour (such as cinnamon that was used in the present trials), proved highly effective in a cage trial, with the 10 possums tested consuming on average 37.2g of bait resulting in 100% mortality [ 24 ].…”