Ecology of the cattle tick (Boophilus microplus) in subtropical Australia. I. Introduction and free-living stages

Abstract

An experiment is described which compared the fluctuations in the numbers of cattle tick, Boophilus miicroplus, that resulted from direct climatic effects or from changes in host resistance. Four herds of cattle, matched for tick resistance and with different Bos indicus (zebu) content, were grazed at each of two locations, one in central Queensland (23¦ S.) and one in southern Queensland (28¦ S.), from November 1977 to May 1982. Natural tick populations were counted regularly, and host resistance was measured using artificial infestations, either twice or six times a year. Concurrent exposures of engorged ticks in pastures were used to measure the success of the ticks in producing larvae and to partition mortality during development. Two later papers report other aspccts of the experiment. These include observations on the resistance of cattle to ticks and on the relationship between tick numbers on the cattle on one hand, and the availability of larvae on pasture and survival of parasitic stages on the other. Engorged ticks produced more larvae throughout the year in central Queensland, despite laying fewer eggs. The colder and longer winter in southern Queensland greatly reduced tick reproduction. Failure of engorged ticks to survive predation and find a favourable oviposition site, egg mortality and loss of larvae in the pasture accounted for most of the reduction in the potential number of larvae produced. Reduced oviposition was also important in wintcr.