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Seven introduced deer taxa are present in New Zealand and there is interest in the dynamics of these populations. Estimating the abundance of deer is problematic, but faecal pellet counts (an index of abundance) have been conducted on New Zealand's public conservation land since the 1950s. We compiled faecal pellet count data from published and unpublished sources, and used the most common data type (presence–absence of pellets in plots along transects) to investigate decadal changes in the relative abundances of deer at the national, island (North and South) and Department of Conservation conservancy spatial scales. A quadratic model with different trends for each conservancy best explained the pellet frequency data for the period 1952–2010: pellet frequencies were highest during the 1950s–1970s and then declined to minima in the 1980s and 1990s and then increased in the 2000s. The decline in pellet frequencies was likely caused by increasing commercial deer harvesting, and the recent increases in pellet frequencies in several conservancies are likely a consequence of reduced commercial harvesting. The key limitations of faecal pellet count data collected in New Zealand (i.e. spatial and temporal variability, and that only summary statistics are often available) are discussed.
