Fox Population Impact Calculator

Control Work Inputs

Foxes removed

Estimated % females

Month of removal

Projection period

Longer projections show how survival and reproduction compound. Treat later years as indicative, not a property survey.

Net Model: Mortality Rates

Pup mortality (to breeding age)

65% to breeding age is an uncited modelling assumption. The cited longevity statement does not estimate age-specific mortality.

Adult annual mortality

40% annual adult mortality is an uncited modelling assumption, not an Australian mortality estimate.

The shaded band changes each mortality rate by plus or minus 5 percentage points.

Net range (mortality plus/minus 5%)

Prevented Population Over Time

Interpreting subsequent generations:The shaded range reflects uncertainty in the two unsourced mortality assumptions. It widens over time because survival and reproduction compound, so it is most useful for showing the direction and relative scale of avoided population growth.

This calculator estimates the population growth prevented by removing red foxes (Vulpes vulpes). It is a population counterfactual, not an estimate of prey killed, lambs saved, or a dollar value. The cited sources do not establish a per-fox prey, livestock or dollar rate that applies across properties.

Model structure: monthly cohort simulation tracking adult females, adult males and pups to breeding age. PestSmart reports breeding between June and October and a 51 to 53 day gestation. The model approximates that with one litter, spread evenly across the default August to December birth window. Litters average 3 to 6 pups, so the default is 4.5. The model assumes a 50:50 offspring sex ratio.

Maturity and mortality are assumptions, not cited rates. PestSmart says females can breed before one year, while most yearlings in high-density areas do not produce pups. The 10-month maturity default is therefore adjustable, not a reported average. PestSmart also states that many foxes do not survive beyond two years and few exceed six years in the wild, but this does not provide age-specific mortality rates. The 65% pup and 40% adult annual defaults are plainly labelled, adjustable modelling assumptions, not NSW measurements.

What this does not model: this is a closed-population counterfactual. All removed foxes are treated as breeding-capable adults, and it excludes reinvasion, immigration, density dependence, food limitation and follow-up control. It shows the relative scale of avoided population growth, not a lasting population reduction on a property.

What control protects: NSW Government identifies foxes as a major threat to native animals and livestock, including poultry, lambs and goat kids. Fox predation is a NSW key threatening process and has contributed to regional declines and extinctions of native mammals and ground-nesting birds. Foxes may also surplus-kill prey. These outcomes depend on local prey, habitat and control coverage, so the calculator does not reduce them to a speculative per-fox total.

Sources (Australian, with NSW sources prioritised):

NSW Government, Foxes: NSW biodiversity and livestock impacts, surplus killing, and key threatening process context.
NSW Government, Best practice guidelines for fox control: reinvasion risk and the need for ongoing, cross-tenure control.
PestSmart, Fox biology, behaviour and ecology: Australian breeding season, gestation, litter size, maturity and longevity.
NSW Scientific Committee, Predation by the European red fox: formal NSW key-threatening-process listing.