Rebecca L. Thomas

Spatio-Temporal Variation in Predation by Urban Domestic Cats (Felis catus) and the Acceptability of Possible Management Actions in the UK

Urban domestic cat (Felis catus) populations can attain exceedingly high densities and are not limited by natural prey availability. This has generated concerns that they may negatively affect prey populations, leading to calls for management. We enlisted cat-owners to record prey returned home to estimate patterns of predation by free-roaming pets in different localities within the town of Reading, UK and questionnaire surveys were used to quantify attitudes to different possible management strategies. Prey return rates were highly variable: only 20% of cats returned ≥4 dead prey annually. Consequently, approximately 65% of owners received no prey in a given season, but this declined to 22% after eight seasons. The estimated mean predation rate was 18.3 prey cat−1 year−1 but this varied markedly both spatially and temporally: per capita predation rates declined with increasing cat density. Comparisons with estimates of the density of six common bird prey species indicated that cats killed numbers equivalent to adult density on c. 39% of occasions. Population modeling studies suggest that such predation rates could significantly reduce the size of local bird populations for common urban species. Conversely, most urban residents did not consider cat predation to be a significant problem. Collar-mounted anti-predation devices were the only management action acceptable to the majority of urban residents (65%), but were less acceptable to cat-owners because of perceived risks to their pets; only 24% of cats were fitted with such devices. Overall, cat predation did appear to be of sufficient magnitude to affect some prey populations, although further investigation of some key aspects of cat predation is warranted. Management of the predation behavior of urban cat populations in the UK is likely to be challenging and achieving this would require considerable engagement with cat owners.

Supplementary feeding of wild birds indirectly affects ground beetle populations in suburban gardens

Supplementary feeding of wild birds by domestic garden-holders is a globally widespread and popular form of human–wildlife interaction, particularly in urban areas. Vast amounts of energy are thus being added to garden ecosystems. However, the potential indirect effects of this activity on non-avian species have been little studied to date, with the only two previous studies taking place under experimentally manipulated conditions. Here we present the first evidence of a localised depletive effect of wild bird feeding on ground beetles (Coleoptera: Carabidae) in suburban gardens under the usual feeding patterns of the garden-holders. We trapped significantly fewer ground beetles directly under bird-feeding stations than in matched areas of habitat away from feeders. Video analysis also revealed significantly higher activity by ground-foraging birds under the feeding stations than in the control areas. Small mammal trapping revealed no evidence that these species differ in abundance between gardens with and without bird feeders. We therefore suggest that local increases in ground-foraging activity by bird species whose diets encompass arthropods as well as seed material are responsible for the reduction in ground beetle numbers. Our work therefore illustrates that providing food for wild birds can have indirect negative effects on palatable prey species under typical conditions.

Limitations to recording larger mammalian predators in savannah using camera traps and spoor

Traditionally, spoor (tracks, pug marks) have been used as a cost effective tool to assess the presence and in some cases the individual identity of larger mammals. Automated camera traps are now increasingly utilised to monitor wildlife, primarily as the cost has greatly declined and statistical approaches to data analysis have improved. While camera traps have become ubiquitous, we have little understanding of their effectiveness when compared to traditional approaches using spoor in the field. Here, we 1) test the success of camera traps in recording a range of carnivore species against spoor in realistic field settings (dirt roads in a South African wilderness reserve); 2) ask if simple measures of spoor size taken by amateur volunteers are likely to allow individual leopards to be tracked in the field and 3) for a trained tracker, ask if this approach may allow individual leopards to be followed with confidence in savannah habitat. We found that camera traps under-recorded mammalian top and meso-carnivores when compared with spoor in the field, with camera traps more likely to underrecord the presence of smaller carnivores (civet 64%; genet 46%, Mellers mongoose 45%) than larger (jackal sp. 30%, brown hyena 22%), while leopard was more likely to be recorded by camera trap (all recorded by camera trap only). We found that amateur trackers could be beneficial in regards to recording leopard presence; however the large variance in measurements of spoor taken by volunteers suggests that this approach is unlikely to allow the collection of further information about individual leopards. Nevertheless, the use of simple spoor measurements in the field by a trained field researcher increases their ability to reliably follow a leopard trail in difficult terrain. This allows researchers to glean further data on leopard behaviour and habitat use without the need for complex spoor analysis.

Effectiveness of mobile apps in teaching field-based identification skills

Abstract It has been suggested that few students graduate with the skills required for many ecological careers, as field-based learning is said to be in decline in academic institutions. Here, we asked if mobile technology could improve field-based learning, using ability to identify birds as the study metric. We divided a class of ninety-one undergraduate students into two groups for field-based sessions where they were taught bird identification skills. The first group has access to a traditional identification book and the second group were provided with an identification app. We found no difference between the groups in the ability of students to identify birds after three field sessions. Furthermore, we found that students using the traditional book were significantly more likely to identify novel species. Therefore, we find no evidence that mobile technology improved students’ ability to retain what they experienced in the field; indeed, there is evidence that traditional field guides were more useful to students as they attempted to identify new species. Nevertheless, students felt positively about using their own smartphone devices for learning, highlighting that while apps did not lead to an improvement in bird identification ability, they gave greater accessibility to relevant information outside allocated teaching times.

Habitat associations and breeding bird community composition within the city of Bristol, UK

Capsule Different urban breeding bird communities are associated with different habitat types, but, although community species diversity varies significantly, total bird density does not. Aims To investigate the association between breeding bird communities and habitats within Bristol, UK and how these communities vary in terms of species diversity and total bird abundance. Methods Breeding density data for 70 species in the metropolitan area of Bristol, UK were subjected to de‐trended correspondence analysis to identify the number of different communities present and their indicator species. These data were then used to identify patterns of habitat association with each community and differences in species richness and total bird density. Results Three communities were identified: a rural community associated with woodland, managed grassland and inland water; a suburban community associated with buildings and residential gardens; and an intermediate community that shared some of these habitat characteristics. Species richness, but not total bird abundance, was lowest in the suburban community. Conclusion The diversity of species in urban areas appears to be most dependent upon the availability of patches of natural and semi‐natural habitats. Residential gardens support fewer species, but those species that are present may be found at high densities.

Use of anthropogenic material affects bird nest arthropod community structure: influence of urbanisation, and consequences for ectoparasites and fledging success

AbstractNests are a critically important factor in determining the breeding success of many species of birds. Nevertheless, we have surprisingly little understanding of how the local environment helps determine the materials used in nest construction, how this differs among related species using similar nest sites, or if materials used directly or indirectly influence the numbers of offspring successfully reared. We also have little understanding of any potential links between nest construction and the assemblage of invertebrates which inhabit nests, in particular, ectoparasites. We addressed these questions by monitoring the success rates of Blue Tits Cyanistes caeruleus and Great Tits Parus major, using nest boxes in rural, urban greenspace and urban garden settings. We collected used nests, identified the arthropods present, and measured the proportions of highly processed anthropogenic materials used in nest construction. Twenty-five percent of Great Tit nest materials were of anthropogenic origin and this was consistent across habitats, while Blue Tits used little (1–2%) anthropogenic material except in gardens (~16%), suggesting that Great Tits preferentially sought out these materials. In fledged nests, an increasing use of anthropogenic material was associated with a lower general arthropod diversity and ectoparasite predator abundance (Blue Tits only), but higher levels of Siphonaptera (fleas). Higher arthropod diversity was associated with lower flea numbers, suggesting that increased diversity played a role in limiting flea numbers. No direct link was found between breeding success and either anthropogenic material usage or arthropod diversity and abundance. However, breeding success declined with increasing urbanisation in both species and increased with nest weight in Blue Tits. The interplay between urbanisation and bird ecology is complex; our work shows that subtle anthropogenic influences may have indirect and unexpected consequences for urban birds.ZusammenfassungDie Verwendung anthropogener Baumaterialien beeinflusst die Struktur der Arthropodengemeinschaften in Vogelnestern: Auswirkungen der Verstädterung und die Folgen für Ektoparasiten und Ausfliegeerfolg Für den Bruterfolg vieler Vogelarten stellen Nester einen Faktor von kritischer Bedeutung dar. Dennoch haben wir nur überraschend wenige Kenntnisse darüber, wie das lokale Umfeld zur Prägung des verwendeten Baumaterials beiträgt, wie sich diesbezüglich verwandte Arten unterscheiden, welche ähnliche Nistplätze nutzen, oder ob die verwendeten Materialien direkt oder indirekt die Anzahl der erfolgreich aufgezogenen Nachkommen beeinflussen. Auch wissen wir nur wenig über potenzielle Zusammenhänge zwischen der Nestbauweise und den Invertebratengesellschaften, speziell Ektoparasiten, welche die Nester besiedeln. Diesen Fragen gingen wir nach, indem wir die Erfolgsraten in Nistkästen brütender Blaumeisen Cyanistes caeruleus und Kohlmeisen Parus major aus ländlichen Bereichen, städtischen Grünflächen und aus Stadtgärten kontrollierten. Wir sammelten benutzte Nester, bestimmten die vorhandenen Arthropoden und maßen den Anteil der beim Bau verwendeten höher verarbeiteten anthropogenen Materialien. Etwa 25% des Nistmaterials bei Kohlmeisen stammte aus einer anthropogenen Quelle und zwar durchweg in allen Habitaten, während Blaumeisen nur wenig davon (1–2%) benutzten, außer in Gärten (~16%), was darauf hindeutet, dass Kohlmeisen diese Materialien bevorzugt sammelten. Bei benutzten Nestern hing die zunehmende Verwendung anthropogenen Materials mit einer geringeren allgemeinen Arthropodendiversität und Häufigkeit ektoparasitischer Prädatoren (nur bei Blaumeisen), jedoch größerer Mengen an Siphonapteren (Flöhen) zusammen. Eine höhere Arthropodendiversität stand mit geringeren Flohzahlen in Verbindung, was nahelegt, dass die höhere Diversität bei der Begrenzung der Flohzahlen eine Rolle spielt. Wir fanden weder einen direkten Zusammenhang zwischen Bruterfolg und der Verwendung anthropogener Materialien, noch zur Arthropodendiversität oder -häufigkeit. Allerdings nahm der Bruterfolg bei beiden Arten mit zunehmender Verstädterung ab und nahm bei den Blaumeisen mit dem Nestgewicht zu. Das Zusammenspiel zwischen Urbanisierung und der Ökologie der Vögel ist komplex; unsere Arbeit zeigt, dass geringfügige anthropogene Einflüsse indirekte und unerwartete Folgen für Vogelarten in Siedlung haben können.

Asymptomatic Host Plant Infection by the Widespread Pathogen Botrytis cinerea Alters the Life Histories, Behaviors, and Interactions of an Aphid and Its Natural Enemies

Plant pathogens can profoundly affect host plant quality as perceived by their insect herbivores, with potentially far-reaching implications for the ecology and structure of insect communities. Changes in host plants may have direct effects on the life-histories of their insect herbivores, which can then influence their value as prey to their natural enemies. While there have been many studies that have explored the effects of infection when plants show symptoms of disease, little is understood about how unexpressed infection may affect interactions at higher trophic levels. We examined how systemic, asymptomatic, and seed-borne infection by the ubiquitous plant pathogen Botrytis cinerea, infecting two varieties of the lettuce Lactuca sativa, affected aphids (the green peach aphid, Myzus persicae) and two widely used biocontrol agents (the parasitoid Aphidius colemani and the ladybird predator Adalia bipunctata). Lettuce varieties differed in host plant quality. Asymptomatic infection reduced chlorophyll content and dry weight of host plants, irrespective of plant variety. Aphids reared on asymptomatic plants were smaller, had reduced off-plant survival time and were less fecund than aphids reared on uninfected plants. Parasitoids showed reduced attack rates on asymptomatically infected plants, and wasps emerging from hosts reared on such plants were smaller and showed reduced starvation resistance. When given a choice in an olfactometer, aphids preferentially chose uninfected plants of one variety (Tom Thumb) but showed no preference with the second (Little Gem) variety. Parasitoids preferentially chose aphids on uninfected plants, irrespective of host plant variety, but ladybirds did not show any such preference. These results suggest that the reduced quality of plants asymptomatically infected by Botrytis cinerea negatively affects the life history of aphids and their parasitoids, and alters the behaviors of aphids and parasitoids, but not of ladybirds. Fungal pathogens are ubiquitous in nature, and this work shows that even when host plants are yet to show symptoms, pathogens can affect interactions between insect herbivores and their natural enemies. This is likely to have important implications for the success of biological control programs.

Increasing game prices may alter farmers’ behaviours towards leopards (Panthera pardus) and other carnivores in South Africa

Human-carnivore conflict occurs globally, particularly in regions where large carnivores predate livestock. Retaliatory killings do occur, and although predation of livestock by carnivores happens, losses from other factors such as disease or injury can be misattributed because of landowner perceptions. Game farming for both trophy hunting and eco-tourism is becoming increasingly common in South Africa, and there has been a rapid increase in the cost of game animals (in some species as much as five-fold) between 2010 and 2015. This could result in an increase in conflict between commercial game farmers and carnivores. We conducted two questionnaire surveys of farmers in 2010 and 2015 to investigate this. We asked if there had been changes in farming practices, perceived predator activity, perceived amount of livestock and commercial game losses, and actions taken towards carnivores in a South African farming community. We found no significant change in farming types in the area or losses of livestock between the years. However, there was a significant increase in perceived commercial game losses reported, even though protection of game had increased. Actions taken towards carnivores by livestock/game farmers were also significantly more negative in 2015 compared to farmers growing crops, but there was no such difference in 2010. We suggest that these changes could be a result of the increase in game prices over that period, leading to greater financial losses when an animal is predated, which in turn could increase the likelihood of retaliatory killings of carnivores.

Game fence presence and permeability influences the local movement and distribution of South African mammals

Fences are utilised throughout the world to restrict the movements of wildlife, protecting them from threats and reducing human—wildlife conflict. In South Africa the number of privately-owned fenced game reserves has greatly increased in recent years, but little is known about how fencing affects the distribution and movements of target and non-target mammals. We surveyed 2 m either side of the complete fence line of a recently established commercial game reserve in South Africa, identifying signs of animal presence (spoor, scat, foraging or other field signs) while also recording damage (holes) to the fence. Every 250 m we carried out 100 m perpendicular transects either side of the fence, recording vegetation cover and height at 10 m intervals along the transect. We found that livestock (largely cattle) were excluded from the reserve. However, 12% of records of large animal species were recorded outside of the fence line. These species had been introduced to the reserve, strongly suggesting that they had crossed the boundary into the surrounding farmland. Sixteen naturally present wild species were found on both sides of the fence, but we found more evidence of their presence inside the reserve. Observational evidence suggests that they were regularly crossing the boundary, particularly where the fence was damaged, with hole size affecting species recorded. We also found evidence that the construction of the fence had led to a difference in vegetation structure with plant richness and percentage of non-woody plant cover significantly higher inside the fence. While fencing was highly effective at preventing movement of livestock, introduced and wild animals were able to cross the boundary, via holes in the fence. This work shows that the efficacy of the most common approach to preventing animal movement around protected areas depends on the species being considered and fence condition.