Early impact on southern sheep stations
Rabbits caused a major drop in productivity on the early sheep stations, as they ate out the feed, leaving little for the sheep. At Kawarau Station near Cromwell, rabbiters took 244,000 rabbit skins in 1884 and 283,000 in 1885. Because of this infestation, the productivity of the station declined dramatically. The lambing percentage (number of lambs per ewe in a flock) fell from 70% before the rabbit influx to 45% in 1885, the death rate of the flock rose from 3.5% to 10.5%, and the wool cut per sheep dropped by 0.56 kilos.
Mt Nicholas Station, at Lake Wakatipu, carried 20,000 sheep through the 1870s, but rabbits ate out the feed and by 1888 the flock was reduced to 2,000. At the head of Lake Wakatipu John Butement had 37,000 sheep on North Station in 1880. Rabbits grazed out the vegetation where Butement wintered his flock, and in 1888 he was forced to drop his sheep numbers to 17,600. The following year he was bankrupted. The mortgagor could not find a purchaser for the leases, so they were abandoned.
Between 1877 and 1884, farmers gave up 75 runs in Otago because of the impact of rabbits. By 1887, 1,346,554 acres (545,000 hectares) had been abandoned in the province.
Parts of Canterbury escaped the worst of the first rabbit plague – but after the First World War stocking rates fell in some places in the same way as they had earlier in Otago and Southland. In 1917 W. Nosworthy took over Mesopotamia station, which had carried 23,000 sheep since about 1880. However, as the rabbit population grew, the flock was reduced to 5,000 by 1921.
Rabbit vs sheep
Ten rabbits eat as much feed as a 55-kilogram ewe. In 1880 the owner of Earnscleugh Station reckoned his run was infested with over 400,000 rabbits. Until then he had carried about 24,000 merino sheep, weighing about 36 kilograms each. The rabbit population on Earnscleugh equated to more than 66,000 sheep.
Cost of losses
Attempts have been made to put a dollar value on the cost of rabbits to the New Zealand economy. One estimate for 1995 was $14 million to $22 million for control and $8 million for loss of production. In 1999 annual production losses due to rabbits were estimated at $50 million.
These estimates ignore the cost to other resources, and the damage to the environment. Scientist G. Norbury has noted that ‘rabbits clearly impose significant costs to production, but there is no way at present to assess the marginal costs and benefits of rabbit control’. 1