Browsing vs grazing debate continues

I’M responding to Tony Orman (ODT, 18.10.18) on the native versus exotic biota debate.

I agree, herbivore numbers are important, particularly when the vegetation is illadapted to tolerate their selection and/or feeding method.

In my vegetation survey of Mt Aspiring National Park in the late 1960s, huge deer numbers in remote areas had devastated the forest understorey and my subsequent vegetation monitoring throughout the park has shown a steady recovery.

I also contributed to the 1986 symposium with Caughley, that Mr Orman quotes: I contrasted the selection of palatable plants by a few deer on Fiordland’s Secretary Island with general recovery in Mt Aspiring Park.

I question Mr Orman’s estimated moa numbers from Caughley’s paper and also the relevance of Landcare’s current deer estimates compared with those of the precommercial hunting days.

With the Cupola Basin grasshopper study, Mr Orman fails to note that, compared to ‘‘dense grassland’’ areas, native grasshoppers were 29 times more abundant on ‘‘eroded sites’’ where there had been ‘‘[m]odification of the habitat by introduced ungulates’’.

Also, I can find little comment in the 16 papers published from this 1986 symposium to support Mr Orman’s claim that the ‘‘browsing habits of introduced animals (e.g. deer) were not too dissimilar from those of lostavifauna (moas and others)’’.

Graeme Caughley for one, states: ‘‘Moas would not have had the same effect as deer.’’

And as for Mr Orman’s final salvo: I appear ‘‘afflicted with an ‘antiintroduced phobia’’’, I freely admit to subscribing to the media statement (5.9.18) from Kaitieki: ‘‘We promote the wellbeing and maintenance of native species above introduced species.’’ Alan Mark, FRSNZ

Dunedin ...................................