House mouse plagues in Australia Chris Dickman Introduced Rodent Pests in Australia House Mouse Black Rat Brown Rat (Mus musculus) (Rattus rattus) (Rattus norvegicus) Mus musculus in Australia • Arrived with European settlement (225 years ago)? • Now continent-wide • A pest in wheat-growing areas in southern regions • Outcompeted by native mice elsewhere • Prey source for owls, introduced and native mammalian carnivores Australian environments - 1 • Summer rain Winter or year round rain 0 500 1000 1500 2000 2500 3000 3500 Kilometers Australian environments - 2 Australian fauna – 1 Australian fauna – 2 Australian fauna – predators House Mouse life-history • Exist in small demes for long periods • These demes are in refuge sites: water, food, shelter • Rapid population turnover • Populations irrupt within 3-4 months when conditions are good, collapse within a year • Characteristics of an invasive species House Mouse reproduction • Gestation = 19 days • Sexual maturity = 5 – 6 weeks • Postpartum oestrus, 3-4 weeks between litters • Litter size = 1 –13 • Can breed year-round but not much in winter • Survival rates are low (<5%) during dry times, >40% after rain Mouse plagues in Australia Mouse plagues in Australia • >750 mice per hectare (but typically >1000 mice per hectare) • Since 1890 mouse plagues have been recorded ∼ every 10 years, but the frequency is increasing to every 4 years Where do mouse plagues occur? Darlings Downs Murrumbidgee Irrigation Area Victorian mallee How much is known about plague formation? • 70% of mouse plagues can be predicted by current models • Rainfall (early- and late-season rains), moderate temperatures, food availability, refuges are all important components of the current predictive models • Models are simple: plagues occur in regions where all native rodents & most marsupials are extinct, and mammalian predators are controlled Predicting house mouse plagues Rainfall grasses, crops, Food supplies seeds, insects ? Mouse births, deaths, demography movements 70% predictability Complicating factors Crop damage predation, disease social interactions Krebs et al. (2005) Impacts of House Mice • Economic costs • Social costs • Health costs • Environmental costs Economic costs • Significant crop loss and damage to stored grain, damage to rural town businesses (e.g., stock spoilage, destruction of electrical cabling) • Outbreak in 1993 cost up to $Aus 100 million in losses, most costs borne by grain growers • In South Australia, 350 000 ha baited with strychnine • More-recent outbreaks have cost > $Aus 100 M Farming practices and mouse plagues • Clearing remnant areas of native vegetation disadvantages predators • Mammalian predators are culled • Retaining ground cover to prevent soil loss and retain soil moisture lowers predation risk for mice • Crop rotation and continuous cropping • Irrigation provides permanently good conditions • (Pech et al. 1999; Kenney et al. 2003) Rodenticides used in Australia • Alphachlorlose (not used much) • Bodifacoum • Bromadiolone • Cholecalciferol (withdrawn) • Coumatetrayl • Flocoumafen • Sodium monofluoacetate (1080) • Strychnine • Thallium sulphate (withdrawn) • Warfarin (Ratsak) • Zinc phosphide Immunocontraception Dynamics of native mice Lessons for mouse plagues? • NE Simpson Desert, Queensland • Spinifex-dominated dunefields • Rainfall 150-200 mm year-1 • Temperatures -7 to 50°C • Fire return interval ~25 years • Long-term data 1990-present • > 25,000 mammal captures, ~22,000 lizard captures, ~9,500 frogs Boom and bust dynamics – native mice Average of Pseudomys hermannsburgensis 60 50 Sandy inland mouse Sandy inland mouse Pseudomys 40 hermannsburgensis 30 20 Captures trap (100 nights) Photo by Bobby Tamayo 10 0 1990 1991 1993 Average of1999 Notomys2001 alexis2002 2006 2008 2011 60 50 Spinifex hopping-mouse 40 30 Captures trap (100 nights) 20 10 0 1990 1991 1993 1999 2001 2002 2006 2008 2011 Captures (100 trap nights) Rainfall (mm) 10 20 30 40 50 60 300 350 400 100 150 200 250 0 50 0 1990 1990 of rain mice: effects Native 1990 1991 1990 1991 Sandy inland mouse, 1991 1992 1993 1992 Long 1992 1993 1993 1994 - 6 1994 rainfall termannual‘average’ - Average of Pseudomys Average hermannsburgensis month lag 1995 1995 1995 1996 1996 1997 1997 1997 r 1998 = 0.66*** 1998 1999 1999 1999 2000 2000 2000 2001 2001 2001 2002 2002 2002 2002 2003 2003 2004 Sandy inland inland Sandy 2004 hermannsburgensis 2005 2005 mouse Photo by Bobby Tamayo Bobby by Photo 2005 Pseudomys 2006 2006 2006 2007 2007 2007 – 2008 2008 2008 2009 1 2009 2010 2010 2010 2011 2011 2011 Captures (100 trap nights) Rainfall (mm) 60 10 20 30 40 50 300 350 400 100 150 200 250 0 50 0 1990 1990 of rain mice: effects Native 1990 1991 1990 1991 1991 Spinifexhoppingmouse, 1992 Long 1993 1992 1992 1993 - 1993 rainfall termannual‘average’ 1994 6 1994 - 1995 month lag 1995 1995 1996 1996 Average of alexis Notomys Average 1997 1997 1997 1998 1998 1999 1999 r 1999 =0.47*** 2000 2000 2000 2001 2001 2001 2002 2002 2002 2002 2003 2003 2004 2004 2005 2005 2005 2006 2006 2006 2007 2007 2007 – 2008 2008 2008 2009 2 2009 2010 2010 2010 2011 2011 2011 Captures (100 trap nights) Rainfall (mm) 0.5 1.5 2.5 3.5 4.5 100 150 200 250 300 350 400 50 0 1 2 3 4 5 0 1990 1990 Marsupials: effects of rain of rain effects Marsupials: 1990 1991 1990 1991 1991 Long 1992 Brush 1992 1993 1992 Long 1993 - 1993 rainfall termannual‘average’ 1994 - - tailedmulgara, 1994 term annual ‘average’ rainfall termannual‘average’ 1995 10 1995 Average of1995 Dasycercus cristicauda - month lag 1996 1996 1997 1997 1997 1998 1998 r 1999 1999 = 0.58*** 1999 2000 2000 2000 2001 2001 2001 2002 2002 2002 2002 2003 2003 2004 2004 2005 2005 2005 2006 2006 2006 2007 2007 2007 – 2008 2008 2008 1 2009 2009 2010 2010 2010 2011 2011 2011 Rainfall (mm) Captures (100 trap nights) 100 150 200 250 300 350 400 50 0 1 2 3 4 5 6 7 8 0 1990 1990 1990 Marsupials: effects of rain of rain effects Marsupials: 1991 1990 1991 1991 dunnart, Lesser hairy 2 1992 - 1992 6 month lag 1993 1992 1993 1993 Long 1994 r 1994 = 1995 1995 - - - term annual ‘average’ rainfall termannual‘average’ 0.33** footed 1995 Average of SminthopsisAverage youngsoni 1996 1996 1997 1997 1997 1998 1998 1999 1999 1999 2000 2000 2000 2001 2001 2001 2002 2002 2002 2002 2003 2003 2004 2004 2005 2005 2005 2006 2006 2006 2007 2007 2007 – 2008 2008 2008 2009 2 2009 2010 2010 2010 2011 2011 2011 Effects of predators Average of Pseudomys hermannsburgensis 60 Capture rate: Sandy inland mouse 50 Heavy summer rains 40 Rains 30 20 Intense per capita predation Predation Captures trap (100 nights) 10 0 1990 1991 1993 1999 2001 2002 2006 2008 2011 Conclusions • Invasive rodents such as house mice show many of the characteristics of invasive species • Plagues are predictable: shelter, rainfall → food allows increased breeding & survival • Ecological, economic, health and broader environmental coats are immense • Traditional control techniques have variable (and often questionable) effects • Need for new control measures – lessons from native rodent dynamics References • Brown P.R. & Singleton G.R. 1999 J Applied Ecology 36: 484-493 • Dickman C.R. et al. 2011 J Mammalogy 92: 1193-1209 • Kenney A.J. et al. 2003 Pages 325-328 in Rats, Mice and People, ed. G.R. Singleton et al. ACIAR Monograph series, Canberra • Krebs C.J. et al. 2005 Wildlife Research 31: 465-474 • Pech, R.P. et al. 1999 Pages 81-112 in Ecologically-based Management of Rodent Pests, ed. G.R. Singleton et al. ACIAR Monograph series, Canberra • Singleton G.R. 1989 Journal of Zoology 219: 495-515 • White T.C.R. 2002 Australian J. Agricultural Research 53: 505- 509 • Ylönen H. et al. 2003 Oecologia 135: 372-377 .