This is an HTML version of an attachment to the Official Information request 'Evidence of Tahr damaging native fauna.'.

The effects of tahr in 
alpine and subalpine 
A summary of potential and alternative monitoring networks to assess the 
ecological integrity of subalpine and alpine vegetation exposed to tahr grazing

What we know about 
Infrastructure available to report on the effects  
the effects of tahr in 
of tahr on alpine and subalpine ecosystems:
alpine and subalpine 
 ›  Plots in alpine grasslands (n = 117) in 8 catchments in the management zone, 
established in the 1990s, remeasured several times, most recently 2013; 
remeasurement begins 2020.
 ›  Alpine and subalpine 
ecosystems in New Zealand 
 ›  Plots in alpine grasslands are environmentally and compositionally biased, adequate 
are naïve to mammalian 
for reporting change in dominant tussocks but not other less dominant species. 
herbivores, so it’s likely that 
 ›  Plots in alpine grasslands are only in 8 catchments in the management zone and 
these ecosystems will not 
cannot be used to make inference about the whole management zone.
be resilient to some of their 
effects [Forsyth et al. 2010]

 ›  Systematically-located plots on an 8-km grid across alpine and subalpine 
ecosystems across the management and exclusion zones, established 2011–2017; 
 ›  Tahr are social animals that 
remeasurement began in 2018. 
affect ecosystems differently 
 ›  Systematically-located plots are adequate to report on change in structural 
in space and time: alpine 
dominant species (tussocks, shrubs) but not for other less dominant species (e.g., 
ecosystems in summer 
small herbs eaten by tahr).
and subalpine ecosystems 
(especially shrublands) in 

 ›  Legacy datasets of transects in some alpine and subalpine ecosystems on public 
winter [Forsyth & Tustin 2005]
conservation land (established 1970s/80s), not remeasured since.
 ›  Legacy datasets of transects in subalpine grasslands on public leasehold land, 
 ›  Tahr diet in alpine and 
established in 1960s/70s, measured most recently 2000s [Day & Buckley 2013].
subalpine ecosystems 
consists mostly of tussocks 
and shrubs but also alpine 
herbs (buttercups and others) 
that are naturally uncommon 
and patchy in distribution 
[Tustin & Parkes 1988; Parkes 
& Forsyth 2008]

 ›  Tahr can have highly 
concentrated effects in alpine 
and subalpine ecosystems, 
transforming tall tussocks 
and subalpine shrublands to 
turfs at local (<300 m2) scales 
[Wilson 1976; Wardle 1977, 

 ›  As tahr abundance increases, 
the heights of dominant 
▲   Tier 1 20 x 20 plots within the tahr management units and exclusion zones as defined in the Tahr 
tussocks decline at wider 
Control Plan.
scales [Cruz et al 2017]
▲   Vegetation in one of the 117 subjectively located plots (in Zora Creek, Westland) at two points in 
time showing a reduction in tussock cover and height. Left image in 1999; right image in 2012. 
Photos: Ingrid Grüner, DOC
Cover image: Juvenile males. Photo: Dylan Higgison

Here’s the state of our capacity to report on the effects of tahr:
 ›  We can report on change in alpine tussock grasslands 
from plots established between 1990 and 1999. These 
plots showed a small but significant decline in tussock 
grass height over time [Cruz et al 2017]
 ›  New systematically-located plots (established since 
2011) provide a baseline against which changes in alpine 
and subalpine ecological integrity can be determined. 
These plots have established that there is lower shrub 
cover in the tahr management zone than the exclusion 
zone [Bellingham et al 2018]
 ›  So far, reporting of effects of tahr on ecosystems is from 
public conservation land only.
▲   Image of figure from Cruz et al showing change in tussock height.
We cannot report on: 
 ›  Resilience of alpine and subalpine species and 
ecosystems to grazing by tahr.
 ›  Whether tahr are impoverishing vegetation widely or 
transforming ecosystems widely because we lack time-
series data.
 ›  Effects on herbaceous species eaten by tahr. We need 
more information to inform what groups of plants to 
monitor and why. Our capacity to select other species to 
measure is currently statistically poor and hampered by 
a lack of knowledge about tahr’s dietary preference (we 
know that herbaceous plants like Ranunuculus species 
comprise up to a quarter of their diet by dry weight 
[Parkes & Forsyth 2008], but we are unable to determine 
whether this affects their populations).
 ›  Catchment-scale impacts of tahr and ecosystem 
resilience that integrate tahr behaviour and movements 
with vegetation changes in alpine and subalpine 
▲  Herbaceous species.

Things that could better inform 
Bellingham PJ, Wiser SK, Burge OR, Easdale T, Richardson SJ 2018. 
decisions about the ecological impacts 
Potential of Tier One and alternative monitoring networks to 
assess the ecological integrity of alpine vegetation exposed to 
of tahr and how to set thresholds for 
tahr grazing. Landcare Research Contract Report LC3328 for the 
intervention that are scientifically 
Department of Conservation.
defensible for both alpine and  
Cruz J, Thomson C, Parkes JP, Grüner I, Forsyth DM 2017. Long-
subalpine ecosystems:
term impacts of an introduced ungulate in native grasslands: 
Himalayan tahr (Hemitragus jemlahicus) in New Zealand’s 
 ›  Continue measurement of existing plots in alpine 
Southern Alps. Biological Invasions 19: 339–349.
tussock grasslands in the management zone 
Day NJ, Buckley HL 2013. Twenty-five years of plant community 
and of systematically-located plots across the 
dynamics and invasion in New Zealand tussock grasslands. 
management and exclusion zones.
Austral Ecology 38: 688–699.
 ›  Establish new networks of plots (or reinstate 
Forsyth DM, Tustin KG 2005. Himalayan tahr. In: King CM (ed) The 
old plot networks) in alpine and subalpine 
Handbook of New Zealand Mammals, 2nd edition, pp. 361–373. 
ecosystems to increase statistical power to 
Oxford University Press, South Melbourne.
detect tahr browsing effects.
Forsyth DM, Wilmshurst JM, Allen RB, Coomes DA 2010. Impacts of 
introduced deer and extinct moa on New Zealand ecosystems. 
 ›  Instigate long-term research sites that collect 
coupled data on tahr and other mammalian 
New Zealand Journal of Ecology 34: 48–65
herbivores with vegetation data in alpine 
Parkes JP, Forsyth DM 2008. Interspecific and seasonal dietary 
grasslands and subalpine grasslands that are 
differences of Himalayan tahr, chamois and brushtail possums 
heavily browsed by tahr east and west of the 
in the central Southern Alps, New Zealand. New Zealand Journal 
of Ecology 32: 46–56.
Tustin KG, Parkes JP 1988. Daily movement and activity of female 
 ›  Maintain current methods used on plots to 
and juvenile Himalayan tahr (Hemitragus jemlahicus) in the 
determine effects of tahr (to ensure continuity 
eastern Southern Alps, New Zealand. New Zealand Journal of 
and ability to maximise time-series data) 
Ecology 11: 51–59.
and evaluate suitability of other methods to 
determine effects.
Wardle P 1977. Plant communities of Westland National Park (New 
Zealand) and neighbouring lowland and coastal areas. New 
 ›  Determine the effectiveness of multiple remote 
Zealand Journal of Botany 15: 323–398.
sensing techniques to determine tahr habitats 
Wardle P 1979. Plants and Landscape in Westland National Park. 
and their impacts on them.
National Parks Authority Scientific Series No. 3, Department of 
 ›  Determine dietary preference of tahr (i.e., 
Lands and Survey, Wellington.
ascertain biomass of plant species in the wild 
Wilson HD 1976. Vegetation of Mount Cook National Park, New 
in proportion to their mass in tahr rumens), 
Zealand. National Parks Authority Scientific Series No. 1, 
including throughout seasons.
Department of Lands and Survey, Wellington.
 ›  Improve the evidence base for attributing impacts 
on vegetation to tahr, in the context of other 
herbivores. This would include determining hare 
diets in alpine or subalpine ecosystems .
 ›  Determine targets (optimum ecological integrity) 
to which to management of alpine and subalpine 
ecosystems could be aimed.
Photo: Scott Theobald (DOC)