Experimental protocol to repel opossums (Didelphis marsupialis) through an artisanal odor repellent device

26 27 Background: The human-opossum (Didelphis marsupialis) conflict has increased during the 28 last decades mainly due to natural habitat loss and mediated by the opossum’s generalist and 29 opportunistic habits. Objective: A potential solution to reduce this conflict is to discourage 30 the opossums presence in human settlements without affecting the welfare of both parts. With 31 this purpose we developed an artisanal odor device with three different chemicals: citronella, 32 ammonia and creolin, and tested their effectiveness to drive away opossums. Methods: We 33 first attracted local opossums using fruits or canned sardines as bait in two areas, an urban 34 natural park (n = 2 sites), and in a peri-urban forest reserve (n = 4 sites), both in Envigado, 35 Antioquia, Colombia. Posteriorly we installed the odor device with one of three chemicals 36 on each site and for two weeks. The cycle was repeated with all chemicals in all sites. The 37 number of opossums per night was recorded daily using camera-traps with bait and 38 bait+chemical. Results: We found that ammonia and creolin were associated to fewer 39 opossums/night, even when the sites were still baited, and that citronella did not decrease the 40 presence of opossums/night when added to the baited sites. In addition, the number of 41 opossums per night was higher in the urban park relative to the forest reserve. Conclusion: 42 We suggest to further test the repellent effect of ammonia and creolin on real human-opossum 43 conflict scenarios, however caution is warranted given its irritant, flammable, and corrosive 44 properties. 45