Frequency of tail loss reflects variation in predation levels,predator efficiency,and the behaviour of three populations of brown anoles

We investigated two predictions regarding the incidence of tail regeneration in lizards for three populations of brown anoles exposed to varying predation levels from the same predator (cats). Firstly although inefficient predators are likely to increase the incidence of regenerated tails (i.e. lizards can escape through tail autotomy), highly efficient predators will kill and eat the lizard and thus leave no evidence of autotomy. At the site with no cats, only 4% of anoles demonstrated signs of tail regeneration. This value was not significantly different from the site where feral cats (i.e. ‘efficient’ predators that would capture prey to eat, as supported by behavioural observation) were present (7%). By contrast, 25% of anoles present at the site with pet cats (well‐fed domesticated cats that caught and played with anoles, i.e. were ‘inefficient’ predators) exhibited regenerated tails. Secondly, more obvious lizards are more susceptible to predation attempts. Supporting this hypothesis, our data indicate a higher incidence of regenerated tails (28%) was recorded amongst adult males (which are territorial, occupying exposed positions) compared to females and subadult males (17%) or juveniles (1%). In conclusion, the behaviour of both the predator and the lizard influences the frequency of regenerated tails in brown anoles. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 648–656.     

Airborne dispersal ofPhytoseiulus persimilis (Acarina:Phtyoseiidae) from a raspberry garden in New Zealand

Airborne dispersal of the predatory mitePhytoseiulus persimilis Athias-Henriot and its preyTetranychus urticae Koch was recorded by trapping mites in silicon grease on microscope slides mounted on a cross-shaped frame placed horizontally 2.5 m above ground level (0.5 m above the top of the crop). Both species were also recorded on raspberry foliage, and population changes there were closely mirrored by numbers caught in the trap.Phytoseiulus persimilis was trapped on slides and recovered from foliage until leaf fall which occurred 6 weeks after the last prey was found. The decline in predator numbers on the foliage closely followed the decline in prey numbers, but the decline of predators on the aerial trap more closely mirrored the decline in the proportion of sample leaves with predators.     

Quantifying fine-scale resource selection by introduced European hedgehogs (Erinaceus europaeus) in ecologically sensitive areas

Introduced predators are important drivers of ecosystem change and can threaten native species. The European hedgehog (Erinaceus europaeus) was introduced from Britain into New Zealand where it is currently widespread, including in braided-river environments of the interior cold drylands where it might threaten native species such as riparian ground-nesting birds. The establishment of hedgehogs in braided-river environments may be facilitated by adjacent pastoral landscapes that provide food, primarily invertebrates, and dry shelter. Forays by hedgehogs into native prey habitats, such as riverbed floodplains, increase predation pressure. Understanding the spatial ecology of introduced predators can improve effectiveness of control measures. We assessed spatial resource selection by hedgehogs in a braided-river environment by tracking 27 individuals for 4–8 days in summer and autumn using microGPS-backpacks. We extracted fine-scale landscape variables from a map created using very high resolution satellite imagery to model home range placement within the study area. We also assessed habitat composition and ranking within high-use areas using compositional analysis. Hedgehogs established home ranges in pastoral landscapes containing abundant edges and high vegetation productivity (mainly green pastures and shrubs), and selected pastures and patches of shrubs as high-use areas. Hedgehogs avoided riverbed floodplains, suggesting that reported predation events on ground-nesting birds might be a consequence of secondary predation or individual specialization. We recommend that predation of native species by hedgehogs might be best alleviated if trapping is focused on those areas selected by native fauna of conservation concern (e.g. riverbed floodplains), as well some biologically-determined buffer surrounding these sites.     

Co‐occurrence dynamics of endangered Lower Keys marsh rabbits and free‐ranging domestic cats: Prey responses to an exotic predator removal program

The Lower Keys marsh rabbit (Sylvilagus palustris hefneri) is one of many endangered endemic species of the Florida Keys. The main threats are habitat loss and fragmentation from sea‐level rise, development, and habitat succession. Exotic predators such as free‐ranging domestic cats (Felis catus) pose an additional threat to these endangered small mammals. Management strategies have focused on habitat restoration and exotic predator control. However, the effectiveness of predator removal and the effects of anthropogenic habitat modifications and restoration have not been evaluated. Between 2013 and 2015, we used camera traps to survey marsh rabbits and free‐ranging cats at 84 sites in the National Key Deer Refuge, Big Pine Key, Florida, USA. We used dynamic occupancy models to determine factors associated with marsh rabbit occurrence, colonization, extinction, and the co‐occurrence of marsh rabbits and cats during a period of predator removal. Rabbit occurrence was positively related to freshwater habitat and patch size, but was negatively related to the number of individual cats detected at each site. Furthermore, marsh rabbit colonization was negatively associated with relative increases in the number of individual cats at each site between survey years. Cat occurrence was negatively associated with increasing distance from human developments. The probability of cat site extinction was positively related to a 2‐year trapping effort, indicating that predator removal reduced the cat population. Dynamic co‐occurrence models suggested that cats and marsh rabbits co‐occur less frequently than expected under random conditions, whereas co‐detections were site and survey‐specific. Rabbit site extinction and colonization were not strongly conditional on cat presence, but corresponded with a negative association. Our results suggest that while rabbits can colonize and persist at sites where cats occur, it is the number of individual cats at a site that more strongly influences rabbit occupancy and colonization. These findings indicate that continued predator management would likely benefit endangered small mammals as they recolonize restored habitats.     

Optimizing control programmes by integrating data from fine-scale space use by introduced predators

The control of introduced mammalian predators (IMP) through trapping campaigns relies on operator experience to deploy traps in sites with an expected high probability of IMP presence, where the maximum number of captures is anticipated. We tested the limitations of available information on fine-scale spatial use by feral cats modelled from remote data collection methods (small-resolution satellite imagery and GPS-telemetry) in an intensive control campaign conducted over 8 years in an ecologically sensitive area of New Zealand. We calculated dichotomous optimal/sub-optimal areas for cats and found that operators placed traps in or close to optimal areas. Over a continuous range of probabilities of cat use, trap sites were not principally placed in hot spots of cat use. Logistic regression revealed that the probability of cat use was significantly associated with the probability of capture. However, regressing catch-effort against the probability of cat use showed no association between sites of high probability of cat use and higher capture rates. The incorporation in the models of bait, trap type, and habitat suitability for rabbits, as variables of operator’s choice showed that rabbit suitability, and the combination of baits/traps were significant. Results suggest that trapping feral cats is a complex process that likely relies on variables of space, time, and individual cognition. However, control programmes could improve trap deployment by identifying sites of high probability of cat use to maximize capture probability, while traps in sub-optimal areas could be removed (cost reduction), reallocated to optimal areas, or used to “fence” core conservation areas.     

Local predator composition and landscape affects biological control of aphids in alfalfa fields

The biological control service supplied to croplands is a result of the predator community present within a focal crop, which is likely influenced by surrounding landscape composition and configuration. In this study, using cage experiments in two regions near Santiago, we determined if predator communities supplied a significant biological control service in alfalfa fields, examined how the abundance of exotic and native coccinellids, as well as other key predator groups, influenced biological control of aphids and measured how landscape composition and heterogeneity at three spatial scales influenced this service. We found that predators significantly suppressed aphid populations in both regions, but the relative importance of predators versus landscape variables on biological control differed between regions. In the region where predators were abundant, biological control was higher and related to the abundance of native coccinellids and syrphids, highlighting the importance of native species as providers of crucial ecological services. In the region where predators were not abundant, biological control was lower, and it was related to landscape composition, being positively associated with the abundance of woodlots and urban habitats, and negatively associated with fruit crops in the landscape. Therefore, landscape effects on biological control service may be weaker than local factors, and only become important when local predator abundance is low.     

Spatial heterogeneity in predator activity, nest survivorship, and nest-site selection in two forest thrushes

The ability of prey to find and use predator-free space has far-reaching consequences for their persistence and interactions with their predators. We tested whether nest survivorship of the ground-nesting veery (Catharus fuscescens) and shrub-nesting wood thrush (Hylocichla mustelina) was related to the local absence of a major nest predator, the white-footed mouse (Peromyscus leucopus). Mouse-free space was defined by trap stations that failed to trap a mouse during the avian breeding season (~May through July). In addition, mouse activity was quantified at individual trap stations based on the number of captures during the same period (six 2.25-ha trapping grids, each containing 121 trap stations trapped repeatedly throughout the summer between 1998 and 2002.) Annual mouse-free space was correlated with other measures of mouse activity based on trapping data. Both mouse-free space and activity metrics were significantly related to annual rates of nest predation (i.e., nest daily mortality rate) in veery but not wood thrush. Likewise, mouse-free space and mouse activity within the nest neighborhood (~30×30 m² surrounding each nest) was significantly related to nest survivorship in veery but not wood thrush. More trap stations had consistently greater (hotspots) and lesser (coldspots) mouse activity than expected by chance, and veeries were significantly more likely to nest near stations that had below the grid-average trapping success. Our study thus documented significant spatial variability in predator activity and its relationship to nest predation and nest-site selection in a ground-nesting songbird.     

Forecasting the effect of land-use change on native and non-native mammalian predator distributions

Intensive land use can fragment continuous natural areas into smaller patches, which may be too small to support viable populations of native fauna and more susceptible to invasion by alien species. We demonstrate the utility of combining species occurrence models with land-use change models to identify areas where future development may differentially affect wildlife. Occurrence data for native (e.g., gray fox, coyote, bobcat, mountain lion, striped skunk, raccoon) and non-native (e.g., domestic dogs, domestic cats, opossums) mammalian predators were collected from 188 remotely triggered camera locations across an oak woodland and vineyard landscape in northern California. The occurrence data were used in combination with landscape variables extracted using a geographic information system to build explanatory models of predator occurrence. These statistical models were used to derive two surfaces showing relative probability of occurrence for non-native and native predators. Then, a spatially explicit land-use change model was used to examine potential future predator distributions given potential future vineyard expansion. The probability distribution models generated hypothesized low probabilities of occurrence for native predators within large vineyard blocks, but higher probabilities within isolated vineyards and also in oak woodlands. The models suggest the highest probabilities of non-native predator occurrence fell within large blocks of vineyard. Using one possible future vineyard development scenario, the distribution models illustrate areas where probability of native predator occurrence may be reduced and where non-native predators may expand due to vineyard development. This technique could be applied to prioritize acquisition of critical wildlife habitat and maintain habitat connectivity for wildlife populations.     

Skink and invertebrate abundance in relation to vegetation, rabbits and predators in a New Zealand dryland ecosystem

We explored the relationships between ground vegetation, ground fauna (native skinks and invertebrates), rabbits, and predators in a modified New Zealand dryland ecosystem. We hypothesised that vegetation cover would provide habitat for ground fauna. We also hypothesised that rabbits (Oryctolagus cuniculus) would reduce the abundance of these fauna by reducing vegetation, and by providing prey for mammalian predators (cats Felis catus and ferrets Mustela putorius) that consume ground fauna as secondary prey. We measured these variables at 30 sites across three pastoral properties in the South Island in 1996 and 2002. There were mostly positive relationships between vegetation ground cover and fauna captures in pitfall traps. Relatively few beetles and caterpillars were caught where cover was less than 80%, no millipedes were caught where cover was less than 70%, and few spiders and mostly no skinks, crickets, flies or slugs were caught where vegetation cover was less than 50%. Most grasshoppers were caught where cover ranged from 30 to 80%. Faunal species richness was also positively related to cover. This supports our hypothesis that ground vegetation provides habitat for skinks and invertebrates in this ecosystem. The introduction of rabbit haemorrhagic disease in 1997 provided a natural experiment to test the hypothesised indirect effects of rabbits on ground fauna. Declines in rabbits varied between properties, and vegetation cover and predator abundance changed according to the magnitude of these declines. However, skink and invertebrate abundance did not track these changes as expected, but instead varied more or less consistently between properties. Some fauna increased (skink captures quadrupled and cricket captures nearly doubled), others declined (flies, caterpillars and spiders), and some did not change (beetles, millipedes, slugs and grasshoppers, and faunal species richness and diversity). Therefore, rabbits, predators and vegetation did not affect changes in skinks and invertebrates in consistent ways. The dynamics of ground fauna are likely to be more influenced by factors other than those we measured.     

Modified pheromone traps help reduce bycatch of bark‐beetle natural enemies

• 1 Thanasimus formicarius and Temnochila caerulea, two of the main predators of Ips sexdentatus, a well‐known forest pest in Southern Europe, are captured in high numbers when trapping I. sexdentatus as a result of the kairomonal effect of the lures used.
• 2 A preliminary field trial showed that predators could survive for at least 1 week within trapping containers, although predator mutilation and high predator death rates were observed.
• 3 Different modifications of conventional multiple funnel and slot traps with the objective of reducing natural enemy entrance into trap containers were bioassayed in field experiments conducted over four seasons. Based on the larger sizes of predators, different designs using welded wire‐mesh screens improved performance to different extents. Providing escape windows just above the screen on multiple funnel traps gave the most promising results, including when effect sizes among all tested designs were compared.
• 4 Thus, a simple modification of the lowest funnel of the multiple funnel traps would reduce the bycatch of T. formicarius and T. caerulea, hence improving the efficiency of trapping programmes by lowering the likely impact on natural populations of these predators.

     

Predation by domestic cats in an English village

We studied predation by approximately 70 domestic cats ( Felis catus L.) in the Bedfordshire village of Felmersham over a one-year period. All the prey items brought home by virtually all the cats in the village were recorded and, where possible, identified. A total of 1090 prey items (535 mammals, 297 birds and 258 unidentified animals) were taken, an average of about 14 per cat per year. Twenty two species of birds and 15 species of mammals were identified. The most important items were woodmice (17%), house sparrows (16%) and bank voles (14%).
Old cats of both sexes caught fewer prey over the year than young cats. Female cats on the edge of the village also caught more prey than female cats in intermediate or central areas of the village; male cats showed no such effect. The type of prey caught also varied with position in the village; 'core' cats caught proportionately more birds than 'edge' cats. There was some indication in the data that cats caught fewer prey in areas where cat density was highest, but this effect was impossible to disentangle from position in the village. Weather apparently influenced hunting success. Temperature had no direct influence, but fewer prey were caught in winter; cats also caught less on wet days and windy days.
Estimates of the number of house sparrows in the village at the start of the breeding season, and the number of sparrows known to have been caught by the cats, suggest that at least 30% of the sparrow deaths in the village were due to cats. Domestic cats would appear to be major predators in this typical English village.     

Power lines,roads, and avian nest survival: effects on predator identity and predation intensity

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Continuing influences of introduced hedgehogs <Emphasis Type="Italic">Erinaceus europaeus</Emphasis> as a predator of wader (Charadrii) eggs four decades after their release on the Outer Hebrides,Scotland

Non-native predators can cause major declines or even localised extinctions in prey populations across the globe, especially on islands. The removal of non-native predators can, therefore, be a crucial conservation management tool but there can be challenges when they are viewed as charismatic in their own right. Four decades after their introduction to islands in the Outer Hebrides, Scotland, European hedgehogs Erinaceus europaeus continue to be an important nest predator for a declining population of breeding waders. Where hedgehogs were rare, clutch survival rates (assessed using nest temperature loggers) of five species of waders (dunlin Calidris alpina, lapwing Vanellus vanellus, redshank Tringa totanus, snipe Gallinago gallinago and ringed plover Charadrius hiaticula) were higher than where hedgehogs were relatively more abundant. Hedgehogs were the most frequent nest predator identified using cameras. However, factors influencing population sizes of breeding waders are complex and unlikely to be attributable to a single species of predator. The interactions between predation, land use, habitat and the changes in each deserve further attention.     

Quantifying fine-scale resource selection by introduced feral cats to complement management decision-making in ecologically sensitive areas

The feral domestic cat (Felis catus) is considered to be one of the most damaging introduced predators, responsible for the decline and extinction of numerous native species. Advanced satellite technologies enable the study of resource selection by small mammals at fine-scales through remote data. These tools can improve understanding of the spatial ecology of introduced predators in ecologically sensitive areas, such as where cats pose a threat to native species and where improvement of predator control methods is required. We studied fine-scale resource selection by feral cats in the ecologically important New Zealand braided-river ecosystem, where they pose a risk to endangered native ground-nesting birds. We collected 34 location datasets from 21 cats fitted with lightweight global positioning system-collars, and extracted landscape variables from a resource map created using very high spatial resolution satellite imagery (Quickbird) and object-base imagery analysis for image classification. We modelled second-order seasonal and annual resource selection functions and characterized landscape composition of highly-used areas using compositional analysis. At a population level, cats generally selected fine-scale landscapes that are important for their primary prey rabbits (Oryctolagus cuniculus), and for refugia. An external validation of the annual model using data from cats tracked in an independent study showed a positive correlation with model predictions. Individual cats also visited habitats used by native ground-nesting birds, and thus pose a threat to them through secondary predation or individual specialization. Cat control operations should therefore focus around areas of concentrated ground-nesting bird activity and in areas identified as high-use by cats.     

Landscape features associated to wind farms increase mammalian predator abundance and ground-nest predation

Wind farm implementation is a rapidly growing source of landscape transformation that may alter ecological processes such as predator–prey interactions. We tested the hypothesis that wind farms increase the activity of nest predators and, ultimately, increment ground-nest predation rates. We placed 18 plots in Iberian shrub-steppes (11 at control and seven at wind farm sites), each one comprised nine artificial ground-nests (three quail eggs/nest). Artificial nests were placed during two events: at the beginning (April) and at the end (June) of the breeding season in 2016 (n?=?324 artificial nests). We estimated the relative abundance of avian and large mammalian predators in the surroundings of each plot and recorded nest fate after 12 days exposure. We also measured variables at landscape and microhabitat scale that potentially affect predator abundance and nest predation. Wind farm sites contained higher cover of gravel roads and more large mammalian predators. Moreover, the abundance of large mammalian predators increased with surrounding cover of both trees and gravel-roads. Avian predator abundance and nest predation rates did not differ between control and wind farm sites, though nest predation did increase with the surrounding cover of crops and gravel roads. Lastly, nest predation was higher at the end of the breeding season and decreased with moss and lichen cover. Our results support previous evidence on the increase of mammalian predator abundance as the surface area of gravel-roads increases, pointing towards a potential mechanism for wind farms leading to rise ground-nest predation. Future wind energy projects should minimize the development of gravel-roads for wind turbine access or maintenance.

     

Removal and eradication of introduced species in a fenced reserve: Quantifying effort,costs and results

Given the difficulty of effective landscape‐scale control of introduced predators, fenced areas that exclude them (i.e. ‘mainland islands') can play an important role in conserving threatened mammal species in Australia. Despite this, the effort required to eradicate or remove introduced species from within fenced areas remains poorly quantified. This study was conducted at Mt Gibson Wildlife Sanctuary in semi‐arid Western Australia, where a 43 km predator‐exclusion fence surrounding 7832 ha was completed in June 2014. The subsequent effort expended in eradicating feral Cat (Felis catus) and removing European Rabbit (Oryctolagus cuniculus) populations was logged daily during 11 months of active population removal and 3.5 months of monitoring. The total effort expended on cat eradication, rabbit removal and monitoring included over 4800 person‐hours of work and nearly 67,000 km of driving (of which 6700 km was for spotlighting), and the conduct of over 15,000 trap nights, 2300 km of sand tracking transects, and over 7800 camera‐trap nights. Total costs (in 2015 figures) were estimated at just over AUD $390,000, which equates to approximately $50 per hectare. Cage trapping was most efficacious for catching cats, although it took nine months to capture the last individual, which was detected independently by both sand tracking transects and camera traps. This research provides baseline data on the resources required for future eradication and removal projects, particularly those within fenced reserves.     

A comparison of the Nzi,Horse Pal® and Bite‐Lite® H‐traps and selected baits for the collection of adult Tabanidae in Florida and North Carolina

Despite the veterinary and medical importance of horse flies, deer flies, and yellow flies, only a few trap types have been evaluated to monitor adult population dynamics. Currently, three trap types are being utilized (H‐trap, Horse Pal® (HP), and Nzi trap), but no head‐to‐head comparisons have been reported. Thus, we conducted comparative trapping studies in Florida and North Carolina. At two study sites in Florida, the efficacy of all three trap types was compared, but only the H‐trap and HP were compared in North Carolina. Although trap type was significant at all sites, the trap type which caught the most specimens was not the same. In Florida at the Lower Suwannee Wildlife Refuge (LSWR) site, the H‐trap caught the most specimens (2,006), followed in decreasing order by Nzi (938) and HP (541). At the Cedar Ridge Ranch site, the Nzi caught significantly more specimens (1,439) than the H‐trap (215) and HP (161), which were not significantly different from each other. In North Carolina, the H‐trap caught approximately twice as many specimens as the HP (1,458 vs 720). These trap comparison studies were followed up by a study on the efficacy of various bait combinations: (No Bait (NB), dry ice only (DI), Trap Tech Lure (TTL) only, and DI + TTL), which was conducted only at the two Florida sites with H‐traps. At both sites, bait combinations significantly affected trap collections. One pattern (DI +TTL > DI > TTL > NB) was recorded at the LSWR, while at the Cedar River Ranch the pattern was DI > DI +TTL > TTL > NB. Our data showed that trap type and bait combination significantly influence overall adult tabanid abundance as well as individual species composition.     

Geometric optimization for prey–predator strategies

This paper investigates several strategies for prey and predator in both bounded and unbounded domains, assuming they have the same speed. The work describes how the prey should move to escape from the predator and how predator should move to catch the prey. The approach is agent-based and explicitly tracks movement of individuals as prey and predator. We show that the prey escapes one or two competing predators, while might be caught in the case of three predators. The paper also describes a strategy for finding a well camouflaged static prey which emits signals.     

Antipredatory Response and Food Intake in Wood Mice (Apodemus sylvaticus) under Simulated Predation Risk by Resident and Novel Carnivorous Predators

Chemical signals left by predators are a potential source of information about the risk of predation, and small mammals are known to take them into account when making decisions. We investigated whether wood mice (Apodemus sylvaticus) are more likely to avoid the faeces of resident predators (red fox Vulpes vulpes and common genet Genetta genetta) vs. a novel predator (European pine marten Martes martes). Odour recognition would increase perceived predation risk and reduce food intake by individual mice. Wood mice response to predators was analysed by live‐trapping using two untreated controls (baited/non‐baited) and traps experimentally manipulated with three predator treatments (faeces of red fox, common genet or pine marten). Traps were baited with 4 g of toasted corn, and food intake by wood mice was determined as the amount of bait remaining in each trap. We found that traps treated with faeces of resident predators were the most avoided, and the number of captures in traps treated with pine marten faeces was similar to the control‐baited traps. The variation found in food intake was explained by the interaction between the types of treatment and breeding condition. Food intake was similar in control‐baited traps and in traps with faeces of pine marten, but when predation risk by resident predators (red fox and common genet) was simulated, breeders reduced food intake significantly as compared to non‐breeders. These results indicate that predator recognition and feeding behaviour under predation risk depend on individual factors and the balance of costs‐benefits in each particular predation risk situation at a given place and time.     

Predation risk effects on fitness related measures in a resident bird

Predation risk is thought to be highly variable in space and time. However, breeding avian predators may create locally fixed and spatially fairly predictable predation risk determined by the distance to their nest. From the prey perspective, this creates predation risk gradients that potentially have an effect on fitness and behavioural decisions of prey. We studied how breeding avian predators affect habitat selection (nest location) and the resulting fitness consequences in a northern population of resident willow tit ( Parus montanus ). Data included 429 willow tit nests over a four year period in a landscape containing a total of 33 avian predator nests. Willow tit nests were located randomly in the landscape and no predator avoidance in habitat selection or emptying of territories in proximity to predators was observed. Nestling size, however, was positively associated with distance from predator nests (n=252). Nestling mass and wing length were about 4.5% smaller close to predator nests compared to nestlings raised far from predator nests. Tarsus length also exhibited a positive relationship with increasing distance from predator nest but this was limited to habitats of young forests and pine bogs or dense mixed forests (4% increase). It is likely that habitat structural complexity influenced the perception of predation risk in different habitats. Our results indicate that willow tits do not provide reliable cues of predator free habitats for settling migrants. Nonetheless, breeding avian predators may create predictable predation risk in the landscape which is an important factor affecting reproductive success and potentially the demography of prey populations.