Appendix C Biosecurity Risk Assessment Rodents

Appendix C2 Appendix C Biosecurity risk assessment – Rodents Status Rodents have successfully colonised almost every continent having spread across the world with human settlement (Banks and Hughes 2012).Globally, their population numbers and their distribution continues to expand. During the last Millennium, island ecosystems have been affected significantly by the introduction of rodents from Europe and the Indian subcontinent. By 2009, rodent species had variously invaded over 80% of the world’s major island archipelagos (Russell, Towns et al. 2008, Commonwealth of Australia 2009, Harris, Gregory et al. 2012). Rodents are widely accepted as a major cause of species extinctions, extirpation and native species decline in island ecosystems (Groombridge 1992, Towns, Atkinson et al. 2006, Commonwealth of Australia 2009). Rodents are considered as highly successful and have the potential to invade and become established on new islands at an alarming rate (Commonwealth of Australia 2008). In 2009, invasive rodents had been eradicated from 350 islands in 21 countries (Commonwealth of Australia 2009). In Australia, the most commonly introduced rodent species are the ship or black rat (Rattus rattus)1, the Norway rat (R. norvegicus), the Pacific rat (R. exulans) and the house mouse (Mus musculus)2. The origin and timeframe of when most exotic rodent species invaded is unclear but it is likely that they arrived on European ships (Banks and Hughes 2012). The Australian Government listed exotic rodents on islands as a key threatening process under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) in 2006 (Commonwealth of Australia 2009). In 2009, a threat abatement plan for rodents (rats, mice) occupying islands less than 100 000 hectares in area was written (Commonwealth of Australia 2008). It sets the Australian Government priorities and strategic directions for the management of rodents (priority actions to prevent invasion at Addendum A). The house mouse and ship rat are by far the most common rodents on Australian islands (Commonwealth of Australia 2009) and are known to be present on 120 of ~8300 islands in Australia (Commonwealth of Australia 2008). To date, exotic rodents have been eradicated from 39 islands, almost all from Western Australia (Commonwealth of Australia 2009). Ship rats are present on Christmas Island in the Indian Ocean. They transported trypanosomes, a unicellular parasitic flagellate protozoa, to the island which were responsible for the rapid extinction of the islands two endemic mammals (Banks and Hughes 2012), the Maclear's rat (Rattus macleari) and the bulldog rat (Rattus nativitatis) (Director of National Parks 2013). Rat baiting and monitoring control programs have been underway in the settlement areas of Christmas Island since 2012 and are currently ongoing (Director of National Parks 2013). Both ship rats and house mice have established on the southern atoll of the Cocos (Keeling) Islands (Home Island, West Island and other Islands in the atoll). Ship rats (combined with feral cats) caused the extirpation of the Cocos Buff-banded Rail (CBBR) from the southern atoll (Commonwealth of Australia 2009). Rodent control methods used in the CKIs include:

1 The ship rat (black rat, roof rat) is a species-complex of up to five genetically distinct forms. The two most globally common forms are recorded in Australia: the Oceanic form of Rattus rattus and an Asian form, Rattus tanezumi. Research is under way at the South Australian Museum to identify where these different types occur in Australia and their origin (Banks and Hughes 2012).

2 The genus Mus is comprised of four subgenera- Pryomus, Coelomys, Mus and Nannomys - containing ~40 species and an unknown number of subspecies (ISSG 2010). Direction Island-Rattus spp. trial and eradication program, 2012 (current rodent status is unknown) West and Home Islands - domestic baiting products used to control rodents around their occupant residences West and Home Islands - Cocos (Keeling) Islands Shire conduct intermittent control programs using DX verminator (P. Chase, 2013, pers. comm., 10 Oct). Rodent populations in the southern atoll pose a considerable threat to the values of North Keeling Island (Pulu Keeling National Park), which is currently free of rodents. In 2012 three Suspected Illegal Entry Vessels (SIEVs) landed at Pulu Keeling National Park (PKNP). A monitoring program carried out between June 2012 and February 2013 concluded that rodents were not present on PKNP but monitoring is continuing. The risk of their introduction and establishment on PKNP provides the purpose for this biosecurity risk assessment. Biology There has been an extensive amount of literature written on rodent biology. Exotic rodent morphological characteristics are in Addendum B. For the below assessment, ship rats and house mice will be used as proxy species for all exotic rodents and their biology is listed below. Ship rat (Rattus spp.) The following features are broadly characteristic of Rattus spp.: colour variation can be charcoal grey to black or light brown above and cream or white below with a sleek smooth coat a pair of chisel shaped incisors with hard yellow enamel on the front surfaces a long pointed head (can be more rounded in juvenile) large thin ears (20mm+) that reach middle of eye when bent forward a scaly tail that is much longer than the head and body combined a size range between: body 165-205 millimetres (mm), tail 185-255 mm and weight 95–340 grams (g) reproduction is placental, sexual and the cycle is endogenous likely modulated by nutrition and, possibly, population density. Small numbers of rodents have been known to colonise islands in less than two years breeding age from 3 months, producing 10 litters of 3–10 (av. 5–8) per year, gestation 20– 22 days (Russell, Towns et al. 2008, Invasive Species Specialist Group 2011, Australian Museum 2013). House mouse The following features are broadly characteristic of Mus spp.: colour variation from light brown to dark grey coat a body up to 65-95 mm length, hairless long 60-105 mm tail and weight up to 30 g large prominent black eyes, round ears, a pointed muzzle with long whiskers and feet small in relation to body size prominent incisor teeth that grow continuously, length controlled by gnawing require between 3–5 g food (vegetable matter- fleshy roots, leaves, stems, insects) daily can live and breed without water but require 15% water content in food to survive generally nocturnal but can be active in daytime hours reproduction is placental, sexual and the cycle is endogenous likely modulated by nutrition and, possibly, population density life span 1–2 years, breeding age from 5 weeks, producing 10 to 12 litters of up to 10 per year, gestation between 19–21 days breed throughout the year and mostly commensal in wild populations (Invasive Species Specialist Group 2010, NSW Government 2011, NSW Government 2013). Ecology The following aspects of rodent ecology are particularly relevant in terms of assessing the risk of introduction to Pulu Keeling National Park (PKNP) and their potential impact on island biodiversity. Ship rats and house mice will be used as proxy species for all exotic rodents. they thrive in most natural habitats including agricultural areas, coastland, natural forests, planted forests, range/grasslands, riparian zones, ruderal/disturbed, scrub/shrublands, urban areas have adapted to a range of environmental conditions and reach high densities in habitat with dense groundcover requirements include adequate food and water, stable environmental temperatures, soil moist enough to burrow, nesting conditions favourable, and diseases, parasites and predation are low (Mitchell and Balogh 2007, Invasive Species Specialist Group 2010, Invasive Species Specialist Group 2011).

Establishment risk There are a range of factors relevant to the assessment of the risk of introduction and the potential establishment of rodents on PKNP. These are considered below. Departure points The following table outlines the major pathways that rodents could use to invade PKNP (Table 1). It shows the areas of current establishment, those where there is potential for naturalised distribution, the potential pathways and the likelihood of introduction. There are no exotic (or native) rodents on PKNP; however there have been biosecurity breaches in the past. It is foreseeable the island could form part of the future range of rodent species. The following information has been used to identify where threat prevention work is needed. Table 1 Rodent species invasive pathways and risk Pathway Likelihood of Origin Est.? Air Sea introduction Perth (Australian Mainland) Y Y N Very unlikely Broome (Australian Mainland) Y Y N Very unlikely Darwin (Australian Mainland) Y Y N Very unlikely Fremantle (Australian Mainland) Y N Y Very unlikely Christmas Island2 Y Y Y Very unlikely Cocos Home Island Y N Y Possible Cocos Horsburgh Island Y, N1 N Y Possible Cocos West Island Y N Y Possible Remaining islands within the Y N Y Possible southern atoll Indonesia3 Y N Y Possible Sri Lanka3 Y N Y Possible 1 House mouse present, potential for naturalised distribution of the ship rat. 2 Control programs underway in 2012–13. 3 Suspected Illegal Entry Vessels (SIEVs).

The risk of introduction by sea conveyance via the local pathway from CKIs is high as rodents have naturalised on the southern atoll. If effective threat prevention strategies including quarantine protocols were introduced and carried out, the risk of introduction could be lowered. However, illegal entry/landing onto PKNP poses a significant threat because people who enter illegally are unlikely to adopted recommended quarantine measures. Currently, there are no direct domestic conveyance pathways, either air or sea, between the mainland and PKNP, however, rodents are naturalised at all domestic origin points. For these reasons the risk via domestic pathways has been identified as low. The risk of introduction by SIEVs via the international sea pathways is high to the lack of ability to control the arrival of rodents using threat prevention strategies.

Transportability Rodents can only be transported large distances by human means. Historically, rodents transported by sea conveyance have been known to travel hundreds to thousands of kilometres (km) and survive (Russell, Towns et al. 2008). Ports can be high activity areas for rodents that arrive in shipping containers or local rodents that are attracted to the site (Russell, Towns et al. 2008). If boats are not actively checked for rodents before leaving for PKNP, this could significantly increase the risk of a rodent being transported by vessel and making it ashore. Rodents, specifically rats can invade islands by self dispersal. Swimming in warm waters some species can travel between 300 metres (m) and 2 km when conditions are favourable (Russell, Towns et al. 2008, Harris, Gregory et al. 2012). They can also travel to islands in cargo and equipment that is brought ashore or swim from a boat moored to the shoreline (Russell, Towns et al. 2008). Vessels of concern for potential to transport rodents to PKNP include: those used to transport Parks staff, which are moored at the Home and West Island piers for sporadic periods of time during and between uses local vessels and yachts (with or without permits) that travel to PKNP to fish in its marine waters and/or anchor close proximity to the islands beaches. These are within easy swimming distance of some rodents foreign fishing vessels illegally operating in Australia’s waters SIEVs travelling from Sri Lanka (less frequently Indonesia) that land or shipwreck on PKNP Although the frequency of trips from the southern atoll to PKNP is low the transport of rodents is still a cause for concern. If responsible persons do not perform adequate checks of their vessels and rodent/s are on board, the transport of one or a few rodents from the southern atoll is possible. Predicting the potential for transport by SIEV is more difficult but due to the unpredictable nature of SIEV arrivals and their potential cargo, rodent introduction is possible. The extent of the damage rodents would be able to do is limited if only one rodent is transported and the individual is not pregnant. The likelihood that a pregnant female or that a male and female would be transported simultaneously and breed is unlikely. However, if this did occur the consequences would be greatly amplified. Climatic suitability Rodents have naturalised across many continents and in varying climates. They are well adapted to the tropical climate of the CKIs which now forms part of their naturalised range. Hence, the climate of PKNP is considered highly suitable. Habitat suitability Rodents are habitat generalists. The natural values and threatened flora and fauna of PKNP would be placed at threat if rodents were introduced because they would quickly reproduce and exploit all habitat types. The known habitat preferences and presence of rodents in the CKIs, combined with lack of reproduction limiting factors and a suitable predator suggest that habitat is highly suitable. Impact on biodiversity The ability for rodents to invade, occupy and negatively impact islands is well documented (Capizzi, Baccetti et al. 2010, Banks and Hughes 2012, Harris, Gregory et al. 2012). The severity of rodent impact on island ecosystems and the diversity of species affected vary depending on the species that was introduced. Impacts to ecosystem biodiversity from rodent establishment are listed below (compiled from literature written on the ship rat and house mouse but could be extrapolated to many rodent species, with varying levels of impact). predation on a variety of different kinds of native wildlife, with varying size up to prey as large as their own body competition and disease could have a role in species decline, extirpation and extinction opportunistic feeders on food sources on PKNP could include vegetation, seeds, fungi, small vertebrates and the young or eggs of larger invertebrates, primarily seabirds and the endangered CBBR rat and mouse direct predation on seabirds and CBBR could lead to extinction and endangerment: any burrow nesting species and ground dwelling species could be greatly impacted. Smaller species would be more vulnerable than larger species (prey size range 27 g–2855 g) disruption of recruitment of the palm trees via fruit, root and seedling predation (Auld, Hutton et al. 2010). This could result greater weed species success as vectors of disease they could introduce helminths, bacteria, viruses and protozoa that could impact on the seabirds (Banks and Hughes 2012) contribute to native invertebrate population suppression and local extirpation (Banks and Hughes 2012) support hyper-predation processes by alien species, such as Feral Cats (if introduced) (Banks and Hughes 2012) other indirect impacts to ecosystem services are possible (Wanless, Angel et al. 2007, Commonwealth of Australia 2008, Holly P. Jones, Tershy et al. 2008, Commonwealth of Australia 2009, Ratcliffe, Mitchell et al. 2009, Meek, Hawksby et al. 2011, Banks and Hughes 2012) when mice are the only introduced species on an island their behaviour becomes similar to that of rats with consequently larger impacts on native species and ecosystems (Invasive Species Specialist Group 2010). The contribution of PKNP to Australia’s biodiversity assets is out of proportion to its area as it represents a less-disturbed example of a typical Indian Ocean coral atoll ecosystem. It provides refuge for threatened and migratory species that would be impacted by rodent introduction. If any of the above adverse biodiversity impacts occurred, there would be significant changes to the islands ecosystems. Based on this, if the species naturalised the consequences could be catastrophic. The EPBC listed endemic subspecies the Cocos Buff-banded rail (Gallirallus philippensis andrewsi) has been translocated to Horsburgh Island. If the translocation project were compromised by rodents predating on rail chicks or the introduction of pathogens or disease that adversely impacted the survivorship of the population the long-term consequences could be major. The principles of Harris and Gregory et al. (2012) suggest that if an incursion occurred and was subsequently eradicated the reinvasion risk is low. The long-term benefits of eradication would well outweigh the initial financial costs and logistic difficulties (Ratcliffe, Mitchell et al. 2009). Threat prevention and surveillance strategies should be introduced to encourage successful quarantine and detection/ interception methods. In the event that rodents established on PKNP a complete eradication program should be launched. Eradication methods have been well-tested in Western Australia and across the world (Commonwealth of Australia 2009) and any control program must use methods and baits that do not compromise the islands’ natural values. Additionally, potential non-target species impacts should be assessed.

Conclusions It is possible that rodents could be introduced to PKNP via the local pathway by human transport from the southern atoll. However, it is unlikely that a male and female would be introduced at the same time and an individual cannot successfully reproduce unless already pregnant. However, if rodents reproduced on PKNP, the likelihood of establishment would be almost certain. Rodents have naturalised across many continents and in varying climates, which is a cause for concern. The climate and habitat of PKNP is considered highly suitable. The consequences of rodent introduction and establishment on PKNP have been assessed as catastrophic respectively. This is based on the diversity of biodiversity impacts that would occur, which would reduce the natural values of PKNP. Based on the above assessments, introduction of rodents via the local pathway represents a VERY HIGH biosecurity risk to PKNP. The outcomes of this assessment are summarised in matrix below. RODENT INTRODUCTION AND ESTABLISHMENT RISK MATRIX Consequences Moderat Insignificant Minor Major Catastrophic Likelihood of Introduction e Almost certain Mediu Very Will probably occur once in 1 Low High Extreme month m High Likely Mediu Very Will probably occur once in 6 Low High Very High months m High Possible Will probably occur once in 2 Low Low Medium High High years Unlikely Minima Mediu Will probably occur once in 10 Minimal Low High years l m Very Unlikely Minima May occur only once in 50 years Minimal Low Low Medium or more l

Consequences Moderat Insignificant Minor Major Catastrophic Likelihood of Establishment e Almost certain Mediu Very Will probably occur once in 1 Low High Extreme month m High Likely Mediu Very Will probably occur once in 6 Low High Very High months m High Possible Will probably occur once in 2 Low Low Medium High High years Unlikely Minima Mediu Will probably occur once in 10 Minimal Low High years l m Very Unlikely Minima May occur only once in 50 years Minimal Low Low Medium or more l Addendum A Actions to prevent invasion or reinvasion of rodent species on islands less than 100 000 ha (Commonwealth of Australia 2009) Actions to prevent invasion or re-invasion Priority and timeframe 4.1 Develop generic contingency plans for reaction to any new High priority, short term rodent invasions 4.2 Apply quarantine systems on rodent-free islands and where High priority, ongoing eradication is achieved 4.3 Develop island-specific contingency capabilities for islands at High priority, short term high risk of invasion 4.4 Reduce risk of rodents gaining access to key vessels at key Medium priority, medium term ports 4.5 Identify and reduce the frequency of rodent infestation on key Medium priority, medium term Australian vessels, i.e. those regularly berthing on priority islands 4.6 Survey rodent species and prevalence on foreign boats that Medium priority, short term present risks to Australian islands 4.7 Develop and test on-island prophylactic (e.g. permanent bait High priority, short term and ongoing stations at high-risk sites) and reactive (e.g. surveillance and prompt control after any detection of rodents) strategies to detect and deal with incursions 4.8 Develop fast response capabilities to react to shipwrecks on High priority, short term priority islands 4.9 Actively involve island residents and ship owners in the High priority, long term management of incursion risks

Addendum B Australian exotic rodent morphological characteristics (Commonwealth of Australia 2009) Morphological Species characteristic Rattus rattus R. norvegicus R. exulans Mus musculus Body weight (g) 95-340 200-400 30-100 10-25 Ears Large, and cover eyes Do not cover eyes Smaller than for Smaller than for when pulled when pulled R. rattus but also the rats forwards forwards cover eyes when pulled forward Belly fur N/A N/A White-tipped with N/A (characteristic for grey underneath R. exulans) Tail Much longer than Clearly shorter About the same as About the same head/body length than HBL; thick HBL; thin and as HBL; uniformly (HBL);uniformly dark with pale uniformly dark grey brown underside Tail length (mm) 185-245 150-215 125-135 75-95 No. of nipples 10-12 (usually 10) 12 8 10 References Auld, T. D., I. Hutton, M. K. J. Ooi and A. J. Denham (2010). "Disruption of recruitment in two endemic palms on Lord Howe Island by invasive rats." Biological Invasions(12): 3351-3361. Australian Museum. (2013). "Animal Species: Black Rat " Retrieved 4 Novemeber 2013, from http://australianmuseum.net.au/Black-Rat. Banks, P. B. and N. K. Hughes (2012). Rats in the ranks: the introduced black rat in Australia. ECOS, CSIRO Publishing. Banks, P. B. and N. K. Hughes (2012). "A review of the evidence for potential impacts of black rats (Rattus rattus) on wildlife and humans in Australia." Wildlife Research 39(1): 78- 88. Capizzi, D., N. Baccetti and P. Sposimo (2010). "Prioritizing rat eradication on islands by cost and effectiveness to protect nesting seabirds." Biological Conservation(143): 1716-1727. Commonwealth of Australia (2008). Background document for the threat abatement plan: To reduce the impacts of exotic rodents on biodiversity on Australian offshore islands of less than 100 000 hectares. Canberra, Department of Environment, Water, Heritage and the Arts. Commonwealth of Australia (2009). Threat abatement plan: to reduce the impacts of exotic rodents on biodiversity on Australian offshore islands of less than 100 000 hectares. Canberra Department of the Environment, Water, Heritage and the Arts. Director of National Parks (2013). Rat baiting program: community update. The Islander. Christmas Island, Parks Australia. 2013. Groombridge, B. (1992). Global biodiversity. Status of Earth’s living resources. London, Chapman Hall. Harris, D. B., S. D. Gregory, L. S. Bull and F. Courchamp (2012). "Island prioritization for invasive rodent eradications with an emphasis on reinvasion risk." Biological Invasions(14): 1251-1263. Holly P. Jones, B. R. Tershy, E. S. Zavaleta, D. A. Croll, B. S. Keitt, M. E. Finkelstein and G. R. Howald (2008). "Severity of the Effects of Invasive Rats on Seabirds: A Global Review." Conservation Biology 22(1): 16-26. Invasive Species Specialist Group. (2010). "Global Invasive Species Database - Mus musculus." Retrieved 6 November 2013, from http://www.issg.org/database/species/ecology.asp?si=97. Invasive Species Specialist Group. (2011). "Global Invasive Species Database - Rattus rattus." Retrieved 6 November 2013, from http://www.issg.org/database/species/ecology.asp? si=19&fr=1&sts=sss&lang=EN. Meek, P. D., R. J. Hawksby, A. Ardler, M. Hudson and K. D.Tuckey (2011). "Eradication of Black Rats Rattus rattus L. from Bowen Island, Jervis Bay NSW." Zoologist 35(3): 560-568. Mitchell, B. and S. Balogh (2007). Monitoring techniques for vertebrate pests: Mice. Orange, NSW Department of Primary Industries. NSW Government (2011). Mouse monitoring and baiting. Department of Primary Industries. Primefact 1102 First Edition. NSW Government. (2013). "Mouse Biology." Retrieved 6 November 2013, from http://www.dpi.nsw.gov.au/agriculture/pests-weeds/vertebrate-pests/pest-animals-in- nsw/mouse-biology. Ratcliffe, N., I. Mitchell, K. Varnham, N. Verboven and P. Higson (2009). "How to prioritize rat management for the benefit of petrels: a case study of the UK, Channel Islands and Isle of Man." The International Journal of Avian Science(51): 699-708. Russell, J. C., D. R. Towns and M. N. Clout (2008). Review of rat invasion biology: Implications for island biosecurity. Wellington, New Zealand, Department of Conservation. Towns, D. R., I. A. E. Atkinson and C. H. Daugherty (2006). "Have the harmful effects of introduced rats on islands been exaggerated?" Biological Invasions(8): 863-981. Wanless, R. M., A. Angel, R. J. Cuthbert, G. M. Hilton and P. G. Ryan (2007). "Can predation by invasive mice drive seabird extinctions?" Biology Letters(3): 241-244.