Summary 1.Faecal pellet group (FPG) count data are widely used to estimate animal abundance, with two alternative methods normally employed. Faecal accumulation rate (FAR) techniques measure the daily accumulation rate of pellet groups, while faecal standing crop (FSC) techniques measure overall density. To estimate abundance, both methods require estimates of the animal defaecation rate. FSC techniques also require an estimate of pellet group decomposition rate. In general, FAR techniques are considered less prone to bias while FSC methods are considered more precise and cost-effective. On balance, the majority of authors and practitioners prefer FSC methods, although little empirical evidence supports this decision. 2. FPG count data were obtained from 26 study areas to compare the precision of FAR and FSC count techniques when applied to wild deer populations in the UK uplands. The time needed to collect count data was quantified in 10 study areas. 3. The coefficients of variation (CV) of FSC pellet group count data ranged from 9% to 23% and were approximately 0·7-0·9 times those of equivalent FAR data. The precision of both methods was related to the density of pellet groups. On average, FSC count data took 80 min per plot to obtain, with FAR taking 1·6-1·9 times longer. 4. For the precision of FSC and FAR abundance estimates to be comparable in the range of conditions studied, decomposition rate trials would require a CV of 5-20%. While a number of studies report this to be possible, estimates of the time needed to obtain this level of precision generally exceed the net available time that results from the deployment of FSC rather than FSC pellet group counts. 5. Synthesis and applications . Using the levels of finance available to most deer managers in the UK uplands, deer abundance estimates obtained using FSC techniques on individual study sites up to 20 000 ha appear generally less cost-effective than FAR when compared in terms of their overall precision. As FAR methods are also thought to have less potential for bias when applied in the appropriate environmental conditions, they should be preferred over FSC when estimating deer abundance in concealing habitats.

We assessed genetic differentiation and diversity in 14 populations of sika deer (Cervus nippon) from Japan and four populations of sika deer introduced to the UK, using nine microsatellite loci. We observed extreme levels of differentiation and significant differences in diversity between populations. Our results do not support morphological subspecies designations, but are consistent with previous mitochondrial DNA analyses which suggest the existence of two genetically distinct lineages of sika deer in Japan. The source of sika introduced to the UK was identified as Kyushu. The underlying structure of Japanese populations probably derives from drift in separate glacial refugia and male dispersal limited by distance. This structure has been perturbed by bottlenecks and habitat fragmentation, resulting from human activity from the mid-nineteenth century. Most current genetic differentiation and differences in diversity among populations probably result from recent drift. Coalescent model analysis suggests sika on each of the main Japanese islands have experienced different recent population histories. Hokkaido, which has large areas of continuous habitat, has maintained high levels of gene flow. In Honshu the population is highly fragmented and is likely to have been evolving by drift alone. In Kyushu there has been a balance between gene flow and drift but all the populations have experienced high levels of drift. Habitat fragment size was not significantly associated with genetic diversity in populations but there was a significant correlation between habitat fragment size and effective population size.

Summary 1.Hybridisation with an invasive species has the potential to alter the phenotype and hence the ecology of a native counterpart. 2. Here data from populations of native red deer Cervus elaphus and invasive sika deer Cervus nippon in Scotland is used to assess the extent to which hybridisation between them is causing phenotypic change. This is done by regression of phenotypic traits against genetic hybrid scores. 3. Hybridisation is causing increases in the body weight of sika-like deer and decreases in the body weight of red-like females. Hybridisation is causing increases in jaw length and increases in incisor arcade breadth in sika-like females. Hybridisation is also causing decreases in incisor arcade breadth in red-like females. 4. There is currently no evidence that hybridisation is causing changes in the kidney fat weight or pregnancy rates of either population. 5. Increased phenotypic similarity between the two species is likely to lead to further hybridisation. The ecological consequences of this are difficult to predict.

We investigated temporal changes in hybridization and introgression between native red deer (Cervus elaphus) and invasive Japanese sika (Cervus nippon) on the Kintyre Peninsula, Scotland, over 15 years, through analysis of 1513 samples of deer at 20 microsatellite loci and a mtDNA marker. We found no evidence that either the proportion of recent hybrids, or the levels of introgression had changed over the study period. Nevertheless, in one population where the two species have been in contact since approximately 1970, 44% of individuals sampled during the study were hybrids. This suggests that hybridization between these species can proceed fairly rapidly. By analysing the number of alleles that have introgressed from polymorphic red deer into the genetically homogenous sika population, we reconstructed the haplotypes of red deer alleles introduced by backcrossing. Five separate hybridization events could account for all the recently hybridized sika-like individuals found across a large section of the Peninsula. Although we demonstrate that low rates of F1 hybridization can lead to substantial introgression, the progress of hybridization and introgression appears to be unpredictable over the short timescales.

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