Nervous tick

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Hilary Miller

Whats rarer than a tuatara? Amblyomma sphenodonti, of course, the blood-sucking ectoparasitic tick that chooses to dine on our national icon, the tuatara. Charles Daugherty and Hilary Miller from Victoria University in Wellington have undertaken a nationwide survey of 28 islands inhabited by tuatara, but only found the rare tick on eight islands. Why is the tick so rare in these nat­ural populations and on islands with populations translocated for conservation purposes? An obvious cause for the absence of ticks from trans-located populations are animal husbandry practises; ticks were sometimes re­moved during island translo­cations by wildlife staff. However, in the recent transfer of 70 tuataras to Karori wildlife sanctuary the ticks naturally disap­peared. The most logical explanation is that the ticks detached from their host as part of their life-cycle but with insufficient tuatara roaming the new sanctuary they were un­able to reacquaint themselves with a suitable host. The inability to transfer between hosts at low densities may explain the demise of Amblyomma on some islands.

Detailed molecular analysis of mitochon­drial and nuclear DNA has revealed that A. sphenodonti is genetically distinct from other known Amblyomma tick species, and could even represent a new genus. Hilary’s work is fascinating, and highlights an impor­tant debate in conservation biology, one that requires us to examine ourselves: Why do we value lizards above ticks?

Tuatara have been the focus of an inten­sive conservation management programme for many years, and like all other reptiles, mammals (native), amphibians and birds (except game birds), tuatara are afforded the protection of New Zealand’s Wildlife Act. Unfortunately our endangered tick did not make it on the initial list of 32 terrestrial invertebrates that were given honorary “ani­mal” status and thus included in the sched­ule of protected animals. As such, Ambly­omma was not afforded the same attention as their iconic hosts. This is not a uniquely New Zealand phenomena—conservation programmes frequently attempt to reduce the prevalence of parasites to increase the health and breeding success of host animals. So where does this leave us? What is the value of one species compared to another? Should the mere trophic rank of parasite vs predator, vertebrate or invertebrate de­termine our conservation priorities? I guess this greys into an area of value judgements where scientific debate often comes second place. However, you never know when you might need a blood sucking tick, so I support the Noah principle of protecting all species in our global ark.

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