Abstract
After centuries of absence, the Eurasian red squirrel (Sciurus vulgaris) is recolonizing and expanding throughout Portugal. We implemented an online community-based project, which enabled us to obtain unprecedented records on the Eurasian red squirrel distribution, not only allowing us to map its current extent area but also to reconstruct its southward range expansion during the past years in Portugal. Possible origins of dispersion are forested areas in the northwestern and eastern Spanish borders and sites of reintroductions in Lisbon, Porto, and Coimbra. This well-established public engagement platform sets a successful example of integrated efforts between society and academy in gathering data on species distribution.
Introduction
Wildlife observation is one of the oldest hobbies in humanity, earlier connected to hunting activities and later contributing to natural history (More 1979). When nature observation was split into hobby and science, the latter as a profession, the use of citizen efforts by academics became relatively rare (Silvertown 2009a). However, in recent decades, wildlife monitoring by professionals alone has been challenged by the fast environmental changes, lack of human resources, and limited funds (Sutherland et al. 2015). At the same time, thanks to the emergence of new technologies and social media which enabled communication between millions of people, wildlife projects are now able to gather a massive effort of citizens, with a tremendous impact on biodiversity monitoring and on our understanding of species distribution (Bonney et al. 2009; Sullivan et al. 2009; Dickinson et al. 2010; Newman et al. 2012). In just a few years, the use of citizens’ efforts became a cost-effective approach in wildlife monitoring (e.g., Shorten 1954; Bonney et al. 2009; Silvertown 2009b; Goldstein et al. 2014).
Squirrels, which are highly appreciated by their esthetic value, have been used to implement citizen science projects in several European countries (e.g., Goldstein et al. 2014; Gurnell et al. 2014). Although the Eurasian red squirrel’s (Sciurus vulgaris) biology and conservation status are well known in most of Europe (Bosch and Lurz 2012; Shuttleworth et al. 2015), there is a lack of knowledge about this species distribution (“Wallacean shortfall” sensu Brown and Lomolino, 1998) still in Portugal, where it was indeed absent for almost four centuries (Mathias and Gurnell 1998). This extinction has been related to the combination of intense farming and tree logging for the naval industry, resulting in habitat destruction and fragmentation (Mathias and Gurnell 1998). The recolonization of the Portuguese territory started during the 1980s, when large areas of pine woods became available through reforestation (Mathias and Gurnell 1998), and after two decades the species was distributed in the north of the country (Ferreira et al. 2001). During the 1990s, squirrel reintroductions took place in three urban parks in the north and central Portugal (Vieira et al. 2015). However, the current extent of the Eurasian red squirrel expansion is still unknown (Rocha et al. 2014). Updating the known distribution of the Eurasian red squirrel in Portugal is a need and an opportunity to test social media as a tool for public engagement. We implemented an online community-based project to engage the public in collecting Eurasian red squirrel data across Portugal. These citizen records were used to analyze the Eurasian red squirrel potential extent of occurrence in Portugal during the last 15 years.
Methods
Public engagement occurred mainly through a page titled “O Esquilo Vermelho em Portugal” (The Red Squirrel in Portugal) on the Facebook social media website from November 2013 onwards. The page was dedicated to sharing information about the species, gathering records of the Eurasian red squirrel in Portugal, mainly by photographic or video evidence, and promoting continuous public interaction by answering questions and asking for details on the records. In addition to the Facebook page and in order to reach a broader public, an online questionnaire was set in February 2014 using the Google Drive platform, which remained active until April 2015. Respondents provided information on the date and location of the record, habitat type, and individual morphological characteristics confirming the accuracy of squirrel species identification. Accuracy of identification was also ensured by the previous knowledge of no occurrence of other squirrel species in Portugal (Rocha et al. 2014). Continuous public awareness on the invasive gray squirrel threat and morphological differences between this species and the native Eurasian red squirrel are provided through our social media page. Respondents were given the opportunity to report more than one record per questionnaire and were specifically asked to inform about historical sightings of squirrels (the following options were provided: before 2000, 2001–2005, 2006–2010, and after 2010). Any dubious record lacking proper information on species and/or sighting locality was removed from our database. Finally, to reduce temporal bias in the records’ distribution for data before 2000, we collected complementary data from local nature photography blogs, as well as personal communications directly to the authors. Both the online questionnaire and the social network page were broadly disseminated by national and local media, through radio, newspapers, and magazines, as well as other social networks, thus reaching a wider and more diversified public throughout the country.
To produce current distribution map of the Eurasian red squirrel, we grouped records with the same locality name or GPS coordinates. Each record represents a different locality. Whenever GPS coordinates were not included in the record, these were obtained in Google Earth using the locality and additional information provided by citizens, such as the location of roads and woods. Maps were produced in software QGIS 2.14.1 considering water masses, land cover, and political layers for Portugal from source GLC2000 on DIVA-GIS (Hijmans et al. 2001). Additionally, total sighting data was grouped into the abovementioned four groups of 5-year intervals and we used a 95% Kernel interpolation function to plot records per each 5-year interval. To verify the quality of sighting data, they were compared to previous studies referring to the Eurasian red squirrel distribution in Portugal (Mathias and Gurnell 1998; Ferreira et al. 2001; Vieira et al. 2015).
Results
During this survey, a total of 1487 public reports were collected: 33 sightings obtained during the exhaustive research on online platforms, 38 sightings reported via e-mail, 336 sightings directly reported through the dedicated social network page, and 1080 sightings extracted from the 535 responses to the online questionnaire. These reports included sightings relative to 668 different localities throughout Portugal (Fig. 1).
Map of public engagement records (black dots) of the Eurasian red squirrel in Portugal, referring to the 668 different localities reported in this study. Stars represent reintroductions during the 1990s at (1) Parque Biológico de Gaia, (2) Jardim Botânico de Coimbra, and (3) Parque Florestal de Monsanto. Darker colors throughout the map represent forested and natural areas and lighter colors represent agricultural and edified areas
There was a significant growth in the number of records from 2000 to 2015 (Fig. 2). Records were mostly concentrated near the coastal regions from the extreme northwest down to Lisbon as well as between Douro and Tejo rivers (Fig. 2).
Kernel distribution (95%) of public engagement records of the Eurasian red squirrel in Portugal during the past 15 years. Darker colors indicate higher concentration of records. Stars represent reintroductions in Porto, Coimbra, and Lisbon during the 1990s
Discussion
This public engagement project enabled us to obtain unprecedented data on the Eurasian red squirrel in Portugal, establishing its potential current distribution and possible routes of expansion during the past years. Sighting data of Eurasian squirrels until 2000 matched with previous known distribution north of Douro River and in the vicinity of three urban parks where reintroductions took place during the 1990s (Mathias and Gurnell 1998; Ferreira et al. 2001; Vieira et al. 2015). This match between complete censuses and public records is a good sign for data quality control. In the last 15 years, the Eurasian red squirrel rapidly expanded throughout the center of Portugal. Distribution of records suggests possible origins of dispersion linked to the Spanish borders. Other works also suggested the Eurasian red squirrel recolonization in northern Portugal was related to the reforestation of large pine wood areas (Mathias and Gurnell 1998; Ferreira et al. 2001) and indeed current records are mainly related to forested and natural areas (Fig. 1). Eastern borders with Spain also seem to be a path of expansion. Rocha et al. (2014) showed an eastern distribution connected to Spanish populations and our results demonstrate that probably these populations expanded to central and southern Portugal. Moreover, reintroductions in three urban parks may have also contributed to the ongoing expansion of this species, since squirrels were seen in nearby areas after reintroductions (Vieira et al. 2015). However, it is unlikely that reintroductions were the main factor in this expansion because the number of reintroduced individuals was low and local populations seemed to be declining (Vieira et al. 2015). The new records south of Tejo River during recent years suggest a continuous expansion through forested places that can shelter this species. Coupled with the squirrel good dispersal capabilities (Wauters et al. 2010), the transformation of Portuguese landscape into forested monocultures during the last two decades (ICNF 2013) may have also favored the rapid expansion of this species. The most recent expansion south of Tejo River has sparse points possibly due to the lack of suitable forest habitats although limitations in our methods should not be ignored (see below). Further squirrel monitoring using a combination of public engagement and traditional surveying methods (e.g., van der Merwe et al. 2005; Goldstein et al. 2014; Rudd et al. 2016) will help to establish the borders in the species’ expansion through the Portuguese territory.
Multiple advantages arise from public engagement-based projects, especially those using social media as this project, including the low-cost implementation, wider public participation, less need of standardized surveys, faster data gathering and the potential to collect large datasets across a wider geographic area (Newman et al. 2012; Goldstein et al. 2014). Although data quality is limited, public engagement can be used when control data obtained through standardized surveying protocols is available (Galloway et al. 2006), as the censuses used in this study (Mathias and Gurnell 1998; Ferreira et al. 2001). Despite the mentioned advantages, some drawbacks can also be pointed out from these projects, including concentration of records in residential areas and temporal bias. Indeed, oversampling in residential and accessible areas, contrasting with undersampling in inaccessible areas, has already been discussed by Dickinson et al. (2010). Here, there is a lack of sightings in some countryside areas that do not necessarily mean local absence. Besides accessibility, presence of elder human population in the Portuguese countryside could explain this bias since this group is not expected to have usual access to social networks. We used both national and local media to reach a wider and more diversified public, but specific dissemination actions in these areas might be further implemented to help overcome this issue. Although partial historical reconstruction of the Eurasian red squirrel expansion was possible, it should be highlighted that most of reported records were from the last 5 years. There is a risk of relying on people’s memory regarding when they saw the animal. But we believe that by given broad temporal intervals (5-year intervals), we are decreasing this potential bias. We also tried reducing temporal bias by including records from nature photography blogs. Continuously keeping the public engaged and interested in essential to reconstruct the time course of species’ expansion (Rudd et al. 2016).
This well-established public engagement platform sets a successful example of integrated efforts between society and Academia to gather noteworthy data on this species distribution in Portugal. Public engagement is the first step towards citizen long-term monitoring which is expected to be a cost-effective tool in mapping wildlife. Together with standardized targeted surveys, these public initiatives greatly improve biological datasets and contribute to strengthen conservation strategies by increasing citizens’ interest and visibility among stakeholders.
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Acknowledgements
We are extremely grateful to the public for voluntarily providing information on the Eurasian Red Squirrel. We are also grateful to Dr. Lucas Wauters, and the citizens Romão Machado, Otilia Tavares, Susana Bilber, and Rui Ferreira for supporting this project. We thank Craig Shuttleworth and one anonymous reviewer for their valuable comments on this manuscript.
Funding
RGR has a research grant from FAPES, Brazil (ref: 0650/2015). BPV has support from Science Without Borders program (CNPQ/CAPES, Brazil). This work was supported by CESAM RU (UID/AMB/50017), which is co-financed by the University of Aveiro (Department of Biology), FCT/MEC through national funds, and FEDER (PT2020 Partnership Agreement).
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Rocha, R.G., Vieira, B.P., Rodrigues, V. et al. Public engagement offers insights on the Eurasian red squirrel distribution. Eur J Wildl Res 63, 87 (2017). https://doi.org/10.1007/s10344-017-1145-y
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Keywords
- Citizen science
- Cost-effective methods
- Conservation
- Sciurus vulgaris
- Social media