Volunteer surveys as a means of inferring trends in garden mammal populations

Factors influencing butterfly and bumblebee richness and abundance in gardens

Gardens are often depicted as green sanctuaries, providing refuges for wildlife displaced from the countryside due to intensive farming. While gardens have been recognized for their positive impact on biodiversity conservation, few studies have investigated the impact of pesticide usage in domestic gardens. In this study, we explored how butterfly and bumblebee populations in gardens across the UK are influenced by habitat quality, urbanisation level and pesticide use. To achieve this, we engaged with participants in Garden BirdWatch, a weekly garden wildlife recording scheme operated by the British Trust for Ornithology. Participants in the study provided data on the attributes of their garden and surrounding area and were asked to complete a questionnaire about their pesticide practices. Of the 417 gardens from which we obtained useful data, we found that 32.6 % had pesticides applied to. Urbanisation and garden quality were the main factors influencing insect populations. Butterfly richness was lower in suburban and urban gardens and butterfly abundance lower only in suburban gardens when compared to rural gardens, but this relationship did not hold for bumblebees. Abundance of butterflies and bumblebees, but not their species richness, increased with the habitat quality of gardens. Butterflies were lower in abundance and richness in more northerly gardens, which was not the case for bumblebees. Effects of pesticides were relatively weak, but butterfly richness was 7 % lower in gardens applying any pesticide. Overall, our study shows that garden butterfly and bumblebee abundance and richness are strongly influenced by both extrinsic and intrinsic factors, and that garden management can have an important positive effect on insect population.

A citizen science based survey method for estimating the density of urban carnivores

Globally there are many examples of synanthropic carnivores exploiting growth in urbanisation. As carnivores can come into conflict with humans and are potential vectors of zoonotic disease, assessing densities in suburban areas and identifying factors that influence them are necessary to aid management and mitigation. However, fragmented, privately owned land restricts the use of conventional carnivore surveying techniques in these areas, requiring development of novel methods. We present a method that combines questionnaire distribution to residents with field surveys and GIS, to determine relative density of two urban carnivores in England, Great Britain. We determined the density of: red fox (Vulpes vulpes) social groups in 14, approximately 1km² suburban areas in 8 different towns and cities; and Eurasian badger (Meles meles) social groups in three suburban areas of one city. Average relative fox group density (FGD) was 3.72 km^-2, which was double the estimates for cities with resident foxes in the 1980’s. Density was comparable to an alternative estimate derived from trapping and GPS-tracking, indicating the validity of the method. However, FGD did not correlate with a national dataset based on fox sightings, indicating unreliability of the national data to determine actual densities or to extrapolate a national population estimate. Using species-specific clustering units that reflect social organisation, the method was additionally applied to suburban badgers to derive relative badger group density (BGD) for one city (Brighton, 2.41 km^-2). We demonstrate that citizen science approaches can effectively obtain data to assess suburban carnivore density, however publicly derived national data sets need to be locally validated before extrapolations can be undertaken. The method we present for assessing densities of foxes and badgers in British towns and cities is also adaptable to other urban carnivores elsewhere. However this transferability is contingent on species traits meeting particular criteria, and on resident responsiveness.

Changes in the distribution of red foxes (Vulpes vulpes) in urban areas in Great Britain: findings and limitations of a media-driven nationwide survey

Urbanization is one of the major forms of habitat alteration occurring at the present time. Although this is typically deleterious to biodiversity, some species flourish within these human-modified landscapes, potentially leading to negative and/or positive interactions between people and wildlife. Hence, up-to-date assessment of urban wildlife populations is important for developing appropriate management strategies. Surveying urban wildlife is limited by land partition and private ownership, rendering many common survey techniques difficult. Garnering public involvement is one solution, but this method is constrained by the inherent biases of non-standardised survey effort associated with voluntary participation. We used a television-led media approach to solicit national participation in an online sightings survey to investigate changes in the distribution of urban foxes in Great Britain and to explore relationships between urban features and fox occurrence and sightings density. Our results show that media-based approaches can generate a large national database on the current distribution of a recognisable species. Fox distribution in England and Wales has changed markedly within the last 25 years, with sightings submitted from 91% of urban areas previously predicted to support few or no foxes. Data were highly skewed with 90% of urban areas having <30 fox sightings per 1000 people km(-2). The extent of total urban area was the only variable with a significant impact on both fox occurrence and sightings density in urban areas; longitude and percentage of public green urban space were respectively, significantly positively and negatively associated with sightings density only. Latitude, and distance to nearest neighbouring conurbation had no impact on either occurrence or sightings density. Given the limitations associated with this method, further investigations are needed to determine the association between sightings density and actual fox density, and variability of fox density within and between urban areas in Britain.

Combining a map-based public survey with an estimation of site occupancy to determine the recent and changing distribution of the koala in New South Wales

The present study demonstrates one solution to a problem faced by managers of species of conservation concern – how to develop broad-scale maps of populations, within known general distribution limits, for the purpose of targeted management action. We aimed to map the current populations of the koala, Phascolarctos cinereus, in New South Wales, Australia. This cryptic animal is widespread, although patchily distributed. It principally occurs on private property, and it can be hard to detect. We combined a map-based mail survey of rural and outer-urban New South Wales with recent developments in estimating site occupancy and species-detection parameters to determine the current (2006) distribution of the koala throughout New South Wales. We were able to define the distribution of koalas in New South Wales at a level commensurate with previous community and field surveys. Comparison with a 1986 survey provided an indication of changes in relative koala density across the state. The 2006 distribution map allows for local and state plans, including the 2008 New South Wales Koala Recovery Plan, to be more effectively implemented. The application of this combined technique can now be extended to a suite of other iconic species or species that are easily recognised by the public.