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Atlas of the mammals of Great Britain and Northern Ireland

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... Biological records of terrestrial mammals were sourced from a database housed by the Mammal Society (see Crawley et al., 2020). Only records from the UK or the Isle of Man, identified to species level, with date specified to day, and location at a 1 km 2 spatial scale or finer were included. ...
... In addition, a categorical covariateday-list lengthwas included in the observation sub-model to estimate sampling effort and variability in selective reporting (Szabo et al., 2010). A categorical covariate was used owing to the higher mammal species richness in the south of the UK compared with the north (Crawley et al., 2020): using a continuous list length in this scenario would result in higher detections in the south (Outhwaite et al., 2019). The day-list length categories used in this model were: (1) Single species records; (2) Short lists, records of two or three species; and (3) Comprehensive lists, records of more than three species from a site within a day. ...
... Most assessments of trends in conservation status depend on comparison of snapshot assessments taken at two time points, often separated by many years. For example, the recent British Mammal Atlas compares distributions in 1960-1992 with those in 2000-2016 (Crawley et al., 2020); population reviews typically operate on a 20-year time window (Harris et al., 1995;Mathews et al., 2018); and data intensive systematic surveys are often performed infrequently e.g. 10 years for the National Otter Survey (Crawford, 2010). Clearly, such approaches create a decadal time lag for detection of changes, with consequences for the effectiveness of interventions. ...
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Conservation action is usually triggered by detecting trends in species’ population size, geographical range, or occupancy (proportion of sites occupied). Robust estimates of these metrics are often required by policy makers and practitioners, yet many species lack dedicated monitoring schemes. An alternative source of data for trend estimation is provided by biological records, i.e., species presence information. In the UK, there are millions of such records, but biological trend assessments are often hindered by biases caused by the unstructured way in which they are collected. Recent advances in occupancy modelling that account for changes in survey effort and detectability over time mean that robust occupancy trends can now be estimated from these records. By grouping mammal species into survey assemblages — species likely to be recorded at the same time — and applying occupancy models, this study provides estimates of long-term (1970 to 2016) occupancy trends for 37 terrestrial mammal species from the UK. The inter-annual occupancy growth rates for these species ranged from -4.26% to 11.25%. This information was used to classify two species as strongly decreasing, five as decreasing, 12 as no change, 11 as increasing and seven as strongly increasing. Viewing the survey assemblages as a whole, the occupancy growth rates for small mammals were, on average, decreasing (-0.8% SD 1.57), whereas bats and deer (0.9% SD 1.30) were increasing (3.8% SD 3.25; 0.9% SD 1.30 respectively), and mid-sized mammals were stable (-0.3 SD 1.72). These results contribute much-needed information on a number of data deficient species, and provide evidence for prioritising conservation action.
... True's beaked whale, Mesoplodon mirus, has a disjunct distribution, occurring in the North Atlantic mainly between 25 o and 50 o north and in the southern oceans, principally off the coasts of eastern southern Africa and the southern coast of Australia, but with a presumed circumglobal range (Jefferson et al. 2015). It is one of six species of beaked whale, Family Ziphiidae, recorded regularly from European seas (Still et al. 2019;Crawley et al. 2020), although a single Gray's beaked whale, M. grayi, from the southern hemisphere was stranded in 1927 in the Netherlands (MacLeod, 2000). Beaked whales feed primarily on squid, which they hunt at depth off the continental shelf, so that strandings are usually rare in comparison with other cetaceans. ...
... Beaked whales feed primarily on squid, which they hunt at depth off the continental shelf, so that strandings are usually rare in comparison with other cetaceans. Sowerby's beaked whale, M. bidens, and Cuvier's beaked whale, Ziphius cavirostris, strand most frequently off the British coast (Crawley et al. 2020), but until now there have been no strandings of True's beaked whale. A previous record in January 1931 from Geirinish, South Uist, Western Isles was later re-identified as a female Cuvier's beaked whale (Fraser, 1934;McCann, 1964;Kitchener & Herman, 1995). ...
... A previous record in January 1931 from Geirinish, South Uist, Western Isles was later re-identified as a female Cuvier's beaked whale (Fraser, 1934;McCann, 1964;Kitchener & Herman, 1995). However, there have been strandings and sightings of this species in Ireland and elsewhere in Europe (Weir et al. 2004;Evans et al. 2007;Crawley et al. 2020). For example, there were 13 strandings in Ireland between 1899 and 2014 (Evans et al. 2007;McGovern et al. 2014;Coombs et al. 2019). ...
... For hedgehog, this could be due to the distribution of data (with few captures at both small and large distances) causing poor model fit and inaccurate density estimates. We estimated high densities of roe deer relative to national estimates; this result is expected because, although roe deer are widely distributed throughout the United Kingdom, North-East England (where our study was based) has a higher abundance than other areas, such as central and southeast England (Crawley et al., 2020). For stoats, our density estimate was lower than that of Mathews et al. (2018), but they noted that their estimate was unreliable due to a lack of data (and hence no CI could be produced). ...
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Accurate and precise density estimates are crucial for effective species management and conservation. However, efficient monitoring of mammal densities over large spatial and temporal scales is challenging. In the United Kingdom, published density estimates for many mammals, including species considered to be common, are imprecise. Camera trap distance sampling (CTDS) can estimate densities of multiple species at a time and has been used successfully in a small number of studies. However, CTDS has typically been used over relatively homogeneous landscapes, often over large time scales, making monitoring changes (by repeating surveys) difficult. In this study, we deployed camera traps at 109 sites across an area of 2725 km2 of varied habitat in North‐East England, United Kingdom. The 4‐month survey generated 51 447 photos of wild mammal species. Data were sufficient for us to use CTDS to estimate the densities of eight mammal species across the whole‐survey area and within four specific habitats. Both survey‐wide and habitat‐specific density estimates largely fell within previously published density ranges and our estimates were amongst the most precise produced for these species to date. Lower precision for some species was typically due to animals being missed by the camera at certain distances, highlighting the need for careful consideration of practical and methodological decisions, such as how high to set cameras and where to left‐truncate data. Although CTDS is a promising methodology for determining densities of multiple species from one survey, species‐specific decisions are still required and these cannot always be generalized across species types and locations. Taking the United Kingdom as a case study, our study highlights the potential for CTDS to be used on a national scale, although the scale of the task suggests that it would need to be integrated with a citizen science approach. In this study we use camera trap distance sampling to estimate both survey‐wide and habitat‐specific densities for a range of mammal species in north east England. We show that our density estimates are similar to other published estimates but with a higher level of precision. We discuss the opportunities and challenges of using this method for national‐level mammal monitoring, taking the UK as a case study.
Article
Finding more efficient ways to monitor and estimate the diversity of mammalian communities is a major step towards their management and conservation. Environmental DNA (eDNA) from river water has recently been shown to be a viable method for biomonitoring mammalian communities. Most of the studies to date have focused on the potential for eDNA to detect individual species, with little focus on describing patterns of community diversity and structure. Here, we first focus on the sampling effort required to reliably map the diversity and distribution of semi-aquatic and terrestrial mammals and allow inferences of community structure surrounding two rivers in southeastern England. Community diversity and composition was then assessed based on species richness and β-diversity, with differences between communities partitioned into nestedness and turnover, and the sampling effort required to rapidly detect semi-aquatic and terrestrial species was evaluated based on species accumulation curves and occupancy modelling. eDNA metabarcoding detected 25 wild mammal species from five orders, representing the vast majority (82%) of the species expected in the area. The required sampling effort varied between orders, with common species (generally rodents, deer and lagomorphs) more readily detected, with carnivores detected less frequently. Measures of species richness differed between rivers (both overall and within each mammalian order) and patterns of β-diversity revealed the importance of species replacement in sites within each river, against a pattern of species loss between the two rivers. eDNA metabarcoding demonstrated its capability to rapidly detect mammal species, allowing inferences of community composition that will better inform future sampling strategies for this Class. Importantly, this study highlights the potential use of eDNA data for investigating mammalian community dynamics over different spatial scales.
Article
A ‘call count’ survey of Water Rails Rallus aquaticus, using broadcast vocalizations to elicit a response, was carried out on Alderney over two consecutive winters. The species was found to be widespread on the island, with 34 birds found in both winters. Most, 62% in each winter, occurred in habitats associated with water, but 38% unexpectedly occupied drier habitat. The survey presents new information on Water Rail abundance, distribution and habitat use on the island, and indicates that the species does not always require access to wet ground in winter.
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