Risk analysis of Possums and Opossums in The Netherlands F. van Vliet R. Lensink Risk analysis of Possums and Opossums in The Netherlands F. van Vliet R. Lensink commissioned by: Invasive Alien Species Team (Netherlands Food and Consumer Product Safety Authority) 19 June 2012 report nr 12-001 Status: Final draft Report nr.: 12-001 Date of publication: 19 June 2012 Title: Risk analysis of Possums and Opossums in The Netherlands Authors: drs. F. van Vliet drs. ing. R. Lensink Pictures front cover Open source; see species depscription Number of pages incl. appendices: 110 Project nr: 11-708 Project manager: drs. ing. R. Lensink Name & address client: Netherlands Food and Consumer Product Safety Authority Invasive Alien Species Team Postbus 9102, 6700 HC Wageningen Reference client: Letter, dd 12 December 2011 TRC/nVWA/2011/13848 Signed for publication: drs. T.J. Boudewijn teammanager bird ecology Initials: Bureau Waardenburg bv is not liable for any resulting damage, nor for damage which results from applying results of work or other data obtained from Bureau Waardenburg bv; client indemnifies Bureau Waardenburg bv against third- party liability in relation to these applications. © Bureau Waardenburg bv / Ministry of Agriculture, Nature and Food Quality, Invasive Alien Species Team This report is produced at the request of the client mentioned above and is his property. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, transmitted and/or publicized in any form or by any means, electronic, electrical, chemical, mechanical, optical, photocopying, recording or otherwise, without prior written permission of the client mentioned above and Bureau Waardenburg bv, nor may it without such a permission be used for any other purpose than for which it has been produced. The Quality Management System of Bureau Waardenburg bv has been certified by CERTIKED according to ISO 9001:2008. 2 Preface Some possum and opossum species are known to be kept captive and traded in The Netherlands. The Invasive Alien Species Team of The Netherlands Food and Consumer Product Safety Authority has commissioned Bureau Waardenburg to assess the occurrence of opossums and possums in The Netherlands and the probability of these exotic species establishing free ranging populations in The Netherlands and the subsequent impacts. This risk analysis was carried out by: drs. F. van Vliet report; drs. ing. R. Lensink project management and report; Dr. T.M. van der Have and ir. J.W. Lammers, Invasive Alien Species Team (NVWA), supervised this study. The authors thank all who contributed. Most of the written information was found as open source on the internet; we have noted all our sources; it is our mistake if some or someone has been forgotten. 3 4 Table of contents Preface...............................................................................................................................................3 Summary ...........................................................................................................................................7 Nederlandse samenvatting............................................................................................................11 1 Introduction...............................................................................................................................15 1.1 Aim of this project ........................................................................................................15 1.2 Methods........................................................................................................................16 1.3 Species of interest .......................................................................................................17 2 Common Brushtail Possum....................................................................................................19 2.1 Biology and ecology ....................................................................................................19 2.2 Risk Analysis................................................................................................................27 2.3 Bomford and ISEIA method for Risk assessment ...................................................34 3 Striped Possum .......................................................................................................................37 3.1 Biology and ecology ....................................................................................................37 3.2 Risk Analysis................................................................................................................41 3.3 Bomford and ISEIA method for Risk assessment ...................................................44 4 Virginia Opossum ....................................................................................................................47 4.1 Biology and ecology ....................................................................................................47 4.2 Risk Analysis................................................................................................................53 4.3 Bomford and ISEIA method for Risk assessment...................................................57 5 White-eared Opossum............................................................................................................61 5.1 Biology and ecology ....................................................................................................61 5.2 Risk Analysis................................................................................................................67 5.3 Bomford and ISEIA method for Risk assessment ...................................................70 6 Gray Four-eyed Opossum......................................................................................................73 6.1 Biology and ecology ....................................................................................................73 6.2 Risk Analysis................................................................................................................78 6.3 Bomford and ISEIA method for Risk assessment ...................................................81 7 Gray Short-tailed Opossum....................................................................................................83 7.1 Biology and ecology ....................................................................................................83 7.2 Risk Analysis................................................................................................................86 7.3 Bomford and ISEIA method for Risk assessment ...................................................89 8 Small Fat-tailed Opossum ......................................................................................................91 5 8.1 Biology and ecology....................................................................................................91 8.2 Risk Analysis................................................................................................................94 8.3 Bomford and ISEIA method for Risk assessment...................................................97 9 Risk management ...................................................................................................................99 10 Conclusions and recommendations................................................................................. 101 11 Literature.............................................................................................................................. 103 6 Summary Framework This risk analysis has been carried out for possums and opossums. For at least seven species it has been proven that they occur in Western Europe (as a pet). Those species are: Possums - Common Brushtail Possum Trichosurus vulpecula - Striped Possum Dactylopsila trivirgata Opossums - Virginia Opossum Didelphis virginiana - White-eared Opossum Didelphis albiventris - Gray Four-eyed Opossum Philander opossum - Gray Short-tailed Opossum Monodelphis domestica - Small Fat-tailed Opossum Thylamys pusilla In this risk analysis the ecology of species is described as well as the probability that they could be successful in settling en spreading, as derived from their ecology and climate match. Furthermore, we give insight into the expected risk (and damage) from ecological and socio-economic viewpoints. Finally, for all species two methods of formal and transparent risk analysis are filled in. Information about occurrence in Western Europe was gathered from people and sources dealing with the trade and the keeping of possums and opossums. Information on the ecology of species was mainly found in the formal scientific literature as this is found as open source on the internet. Probability of settlement and spread The Common Brushtail Possum is an invasive exotic species in New Zealand and has proven to have negative effects on native flora and fauna. The main reason is that ground predators are lacking on these islands. The costs for control of this species are very high. It is unknown how this possum will behave in an environment were ground predators are present, as in Western Europe. There is a good climate match between its native range and Western Europe. Therefore, a settlement here could easily develop into a successful invasion, as long as management (eradication) is not conducted. The opportunistic lifestyle of this species could be an advantage in its possible success. The Virginia Opossum is