Context

Hares are not widespread across Public Conservation Land (PCL) in New Zealand. However, they still have significant impacts on the recruitment and survival of palatable plant species. Therefore, estimates of their national distribution and abundance can help direct control efforts on PCL, and also provides important baseline information against which future assessments and different management interventions can be compared.

Key findings

Occupancy

Occupancy represents whether a hare was present or absent at a site through detection of faecal pellets. As can be seen from Figures 1 and 2, hare occupancy on PCL was:

• 24.1% (95% credible interval (CI) = 22.3 - 26%).
• stable.
• higher in non-woody ecosystems.
• lower in National Parks.

Figure 1: Hare occupancy on public conservation land (PCL) over the last five seasons. Different ecosystem types (woody, non-woody) and conservation status (national park, non-national park) are represented by different line types and colours, respectively. Click on the legend to select different combinations and hover over an individual point to show the value and 95% credible interval.

+−

Simple

Terrain

Satellite

plot level

present/absent

park level

Mean FPI

0
(0,1]
(1,5]
(5,10]
(10,15]
(15,20]
>20

Leaflet | Tiles © Esri — Esri, DeLorme, NAVTEQ

Figure 2: Observed hare faecal pellet indices (FPIs) on public conservation land (PCL) over the last five seasons. FPI is an index of relative abundance and gives a sense of distribution/occupancy across PCL. Switch between satellite and terrain view by clicking on the tile in the upper right corner of the map. Choose the ‘present/absent’ layer to outline in black areas that have hares present and choose ‘park level’ to switch to aggregated park averages. True locations have been randomly jittered to protect species and the integrity of the plot.

Definitions and methodology

DOC has developed a national monitoring programme to assess status and trend of biodiversity across of all of the land it manages with a particular emphasis on terrestrial monitoring. The programme collects data on indicators and measures of ecological integrity outlined in the Department’s Biodiversity Outcomes Assessment Framework (PDF, 1.07 MB).

The terrestrial monitoring programme has been established at approximately 1400 plot locations spaced evenly across PCL. Each year, approximately 280 plots are measured with every plot being measured once over a 5-year rotation cycle. This spatially extensive monitoring programme has been designed to provide unbiased, repeatable, national-scale estimates of priority ecological integrity indicators and measures. See Table 1 the sample sizes in different ecosystems during the five seasons from 2013-2017.

The data were modelled using a Bayesian zero-inflated negative binomial with zero inflation being informed by occupancy at a site. Both occupancy $(z_{i,j})$ and FPI $(y_{i,j})$ depended on ecosystem (woody, non-woody), park status (national park, non-national park), and time at site $i$ and transect $j$. The model was specified as follows $$\begin{array}{rcl} y_{i,j}|z_{i} = 1 & \sim & NB(\mu_i, r) \\ x_{i,j}|z_{i} & \sim & bernoulli(p \times z_{i}) \\ z_{i} & \sim & bernoulli(\psi_{i})\\ \mu_{i} & = & \frac{r}{r + \lambda \times z_{i}}\\ log(\lambda_{i,j}) & = & \alpha_{0} + \alpha_{1}woody_{i} + \alpha_{2}time_{i} + \alpha_{3}time_{i}woody_{i} + \alpha_{4}park_{i} \\ logit(\psi_{i,j}) & = & \beta_{0} + \beta_{1}woody_{i} + \beta_{2}time_{i} + \beta_{3}time_{i}woody_{i} + \beta_{4}park_{i} \\ \end{array}$$ with priors $$\begin{array}{rcl} \alpha & \sim & \mathcal{N}(0, 1000) \\ \beta & \sim & \mathcal{N}(0, 1000) \\ r & \sim & \Gamma(0.01, 0.01)\\ p & \sim & B(1, 1)\\ \end{array}$$

Table 1: Number of plots observed annually for the different ecosystems and conservation status that this report describes.

Data quality

This measure is classified as a National indicator.

Relevance

This measure relates to indicator 1.3.2 - invasive species dominance.

Accuracy

This measure complies with the data quality guidelines used in New Zealand’s Environmental Reporting framework.

Outcomes Monitoring Framework

DOC’s Outcomes Monitoring Framework provides a platform on which DOC and others can assess outcomes in a clear, structured and transparent way (Lee et al., 2005). It has been developed as a logical hierarchy that is based on broad, overarching Outcomes, beneath which are nested Outcome Objectives, Indicators, Measures and Data Elements to provide ever increasing levels of detail. The framework is scalable, as the indicators and measures remain compatible and consistent whether applied locally, regionally or nationally. The recently updated framework provides a roadmap for gathering information to meet the specific objectives of DOC and other agencies (McGlone and Dalley, 2015). The provision of a national framework with agreed outcomes, indicators and measures supports collaboration with land management and regulatory agencies, allowing for more integrated environmental policy and ‘State of the Environment’ reporting. DOC has partially implemented a national monitoring and reporting system, whereby priority indicators and measures are routinely used to report on progress against the objectives and outcomes. This factsheet reports on a measure for the 2017/18 year.

Glossary of terms

• Credible interval (CI): A 95% CI indicates that the true mean lies inside the interval with 95% probability given the posterior probability distribution.
• Method - Faecal pellet count: Faecal pellet index (FPI) method involves counting the number of faecal pellets along four 150-m-long transect lines. The estimate of the relative abundance is the total number of pellets counted per line. FPI has been shown to be linearly and positively related to known abundance of mammals.
• Occupancy: Whether or not a site is being used by a species so that it is available to be observed in the sampling period.