By Jamie Steer 12/04/2017

In this two-part series, Dr Jamie Steer ponders whether the ‘deer are like moa’ debate has passed its use-by date.

Writing on the impacts of introduced deer in the Transactions of the New Zealand Institute in 1892, the Reverend P. Walsh argued that New Zealand’s native forests were poorly equipped to deal with grazing mammals. Taking the pre-human forest as his Edenic baseline, he felt that species like deer should be removed from the wild as soon as possible.

Later, in the 1920s, the influential local botanist Leonard Cockayne argued along similar lines, noting with horror that deer were gobbling up his favourite plants.

Around the same time, ‘enclosure plot’ studies were first established in the country. Sections of native forest were fenced off from grazing mammals and the vegetation within these plots was compared to that outside.

The results soon ‘proved’ that grazing mammals damaged the forest because plant growth was more lush inside the fence than out. Clearly, argued the opponents of deer, the New Zealand forest would be healthier without ungulates and, importantly, more representative of the desired pre-human state.

Save the deer

Sensing danger to their favoured quarry, deerstalkers swiftly countered with an alternative theory. They suggested that, until humans wiped them out around the 1300s, the numerous species of native moa had ecological effects similar to grazing mammals.

They proposed that introduced herbivorous mammals were now regulating the forest in similar ways to moa, performing similar functional roles, and so keeping the forests closer to their pre- human state.

Red deer stag

In 1958, the visiting American biologist William Graf agreed with these suggestions. He noted that New Zealand had produced “some of the finest hedging plants in use today in the United States,” and joked that

“…if the oft-produced statement about vegetation evolution in the absence of grazers and browsers is to be taken at face value, one would have to conclude that these hedge plants must have evolved in the presence of wild hedge shears.”

He therefore agreed that grazers must be necessary to regulate such exuberant growth.

Another supporter, forester Gerald Hocking, writing in the New Zealand Journal of Forestry in 1953, similarly suggested that, far from damaging native forests, introduced mammals such as deer were “an integral part of the bionomics of our forests.”

These early contributions laid the foundations for later claims that introduced ungulates (and deer in particular) were helping the forest return to a more natural state.

This position later provided a useful ecological case against attempts to eradicate deer, especially in the 1970s when commercial deer hunting was at its peak and deer populations were at their lowest in decades.

With extermination looking like a genuine risk, hunters argued that deer were necessary to restore the natural composition of the forest. Removing them would not return New Zealand’s forests to their natural state, because previously those forests had been heavily browsed by moa. The forest needed new browsers, meaning that deer and conservationists should be seen as partners, not rivals.

Deer are pretty much like moa

In the 1980s, support for this view reached its peak. In spite of the reservations of many ecologists, deer in New Zealand were often seen as necessary herbivores. It was widely acknowledged that extinct species such as moa probably had large-scale and long-standing effects on ecosystems, and that their disappearance had dramatically altered forest structure and composition throughout the country.

As botanist Peter Wardle wrote in the New Zealand Journal of Botany in 1985,

“We must now accept that the pre-Polynesian forests of New Zealand could have been as different from the forests of the immediately pre-European era as the latter were from the native forests of today.

Writing in New Zealand Wildlife in 1989, ecologists K.W. Fraser and Les Bacheler thus argued that

“… some level of browsing and grazing pressure may be necessary to maintain the truly indigenous vegetation of New Zealand. Consequently, conservation managers may need to ensure that wild animal populations [such as deer] are maintained as a viable and effective facet of conservation management.”

Although prominent game animal biologist and historian Graeme Caughley was less emphatic, he too suggested that deer would have similar effects to moa and that, crucially, forests with deer would be more like pre-human forests than those without them.

But the debate continues…

White-tailed deer fawn

Despite all this, debate since has become increasingly polarised. Common to each pole, however, is the notion that the desirable state for New Zealand ecosystems is a pre-human one.

Those in favour of deer as functional equivalents to moa – mostly hunters – continue to argue that ecosystems containing deer are more similar to pre-human ecosystems. Those against – mostly mainstream conservationists and conservation biologists – argue that deer do not fill a similar role to moa and therefore only move ecosystems further away from their pre-human condition.

Deer advocates have sometimes been mocked and belittled by their opposition. Writing in the FMC Bulletin in 2003, Rob Brown, for instance, argued that

“Hoofed animals do not eat the same quantity or even vegetation types as browsing moas. The shooters who believe this must either not walk round in the forest or have their eyes closed. Any forest which has too many deer has an abundance of unpalatable species such as pepperwood in its middle structure. It takes a monumental dose of self denial [sic] and self interest to honestly believe this is how the forest would have looked with the presence of browsing moa.”

And Ann Graeme, writing in Forest & Bird in 2007, commented similarly on the ways that deer differ from moa

“… the browsing deer strike at the heart of the forest’s integrity – its next generation. Deer nibble the tiny seedlings, nipping off the growing tips and destroying the infant trees on which the forest depends … Moa walked on big, broad feet, not unlike gumboots. Deer have hard little hooves… [that] are far more damaging to the forest floor.”

Read part two of ‘Are deer sort of like moa?’….

This post is adapted from an article originally published in New Zealand Hunting & Wildlife, the quarterly magazine of the New Zealand Deerstalkers’ Association Inc.

Featured image: Sambar deer stag. See Creative Commons.