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.

Effect of disease-selective predation on prey infected by contact and external sources

We propose and analyze a simple mathematical model for susceptible prey (S)–infected prey (I)–predator (P) interaction, where the susceptible prey population (S) is infected directly from external sources as well as through contact with infected class (I) and the predator completely avoids consuming the infected prey. The model is analyzed to obtain different thresholds of the key parameters under which the system exhibits stability around the biologically feasible equilibria. Through numerical simulations we display the effects of external infection and the infection through contact on the system dynamics in the absence as well as in the presence of the predator. We compare the system dynamics when infection occurs only through contact, with that when it occurs through contact and external sources. Our analysis demonstrates that under a disease-selective predation, stability and oscillations of the system is determined by two key parameters: the external infection rate and the force of infection through contact. Due to the introduction of external infection, the predator and the prey population show limit-cycle oscillations over a range parametric values. We suggest that while predicting the dynamics of such an eco-epidemiological system, the modes of infection and the infection rates might be carefully investigated.

Seed dispersal and predation in the endemic Atlantic rainforest palm Astrocaryum aculeatissimum across a gradient of seed disperser abundance

Tropical forests have been subject to intense hunting of medium and large frugivores that are important in dispersing large-seeded species. It has been hypothesized that in areas with extinction or low abundance of medium and large-bodied animals the density of small rodents may increase. Therefore, this increment in the density of small rodents may compensate for the absence or low abundance of medium and large frugivores on seed removal and seed dispersal. Here, we fill up this gap in the literature by determining if seed removal, seed dispersal, and seed predation by small rodents (spiny rats, Trinomys inheringi and squirrels, Sciurus ingrami) are maintained in defaunated areas. We accessed seed removal, seed dispersal, seed predation, and seedling recruitment of an endemic Atlantic rainforest palm, Astrocaryum aculeatissimum, in a gradient of abundance of agoutis. We found that seed removal, scatter hoarding, and seed predation increase with the abundance of agoutis. In contrast, the proportion of dispersed but non-cached seeds decreased with the abundance of agoutis. We did not find any effect of the abundance of agoutis on seed dispersal distance, but we did find a positive trend on the density of seedlings. We concluded that small rodents do not compensate the low abundance of agoutis on seed removal, scatter hoarding, and seed predation of this palm tree. Moreover, areas in which agoutis are already extinct did not present any seed removal or scatter hoarding, not even by small rodents. This study emphasizes both the importance of agoutis in dispersing seeds of A. aculeatissimum and the collapse in seed dispersal of this palm in areas where agoutis are already extinct.

Opportunistic vertebrate predation by the Squirrel Glider Petaurus Norfolcensis

The Squirrel Glider Petaurus norfolcensis is classified as an exudivore/insectivore feeder, with staple dietary items including insects, insect exudates and plant exudates. During a study of the foraging ecology of the species in northern Victoria, an adult female glider was observed to harass a nesting Common Bronzewing Phaps chalcoptera, ultimately removing the bird before consuming eggs within the nest. A description of this observation is provided and vertebrate predation by the Squirrel Glider is discussed in relation to other published accounts. Vertebrate predation by the Squirrel Glider is considered infrequent and opportunistic, but may provide an additional protein and energy source for lactating females.

Attempted predation on a Large-tailed Nightjar (Caprimulgus macrurus) by an Eastern Marsh-Harrier (Circus spilonotus) in coastal Vietnam

This note describes a predation attempt on a Large-tailed Nightjar (Caprimulgus macrurus) by an Eastern Marsh-Harrier (Circus spilonotus) at Nha Trang Airport (109º 11'0"E, 12º 14'0"N),V ietnam. Observationst ook place from 0650-0700 H on 28 February 2004.

Ctenotus regius (Regal Striped Skink) : Predation

Documents predation of Regal Striped Skink (Ctenotus regius) by Grey Butcherbird (Cracticus torquatus) in the mallee of northern Victoria

Predation on a blotched bluetongue lizard (Tiliqua nigrolutea) by a highlands copperhead (Austrelaps ramsayi) in the Blue Mountains, Australia

This note documents a predation event on a juvenile Blotched Bluetongue Lizard (Tiliqua nigrolutea) by a Highlands Copperhead (Austrelaps ramsayi) in the Blue Mountains, Australia.  The diet of elapid snakes in the genus Austrelaps consists mainly of frogs and small skinks. Adults of the larger Tiliqua species may be too large for Austrelaps species to consume, and juveniles of these larger Tiliqua are possibly approaching the larger end of consumable prey items for Austrelaps.

Predation of a small passerine by the Purple-winged Roller Coracias temminckii, an endemic species of Sulawesi

The usual diet of the Purple-winged Roller, a species endemic to Sulawesi, is grasshoppers, locusts, beetles and small lizards. This note describes an observation of this species preying on an adult Eurasian Tree Sparrow Passer montanus. The presence of birds in the diet of other roller species is discussed.

Aquatic plant shows flexible avoidance by escape from tuber predation by swans

Deeper burial of bulbs and tubers has been suggested as an escape against below-ground herbivory by vertebrates, but experimental evidence is lacking. As deep propagule burial can incur high costs of emergence after dormancy, burial depth may represent a trade-off between sprouting survival and herbivore avoidance. We tested whether burial depth of subterraneous tubers is a flexible trait in fennel pondweed (Potamogeton pectinatus), facing tuber predation by Bewick's swans (Cygnus columbianus bewickii) in shallow lakes in winter. In a four-year experiment involving eight exclosures, winter herbivory by swans and all vertebrate summer herbivory were excluded in a full-factorial design; we hence controlled for aboveground vertebrate herbivory in summer, possibly influencing tuber depth. Tuber depth was measured each September before swan arrival and each March before tuber sprouting. In accordance with our hypothesis, tuber depth in September decreased after excluding Bewick's swans in comparison to control plots. The summer exclosure showed an increase in tuber biomass and the number of shallow tubers, but not a significant effect on the mean burial depth of tuber mass. Our results suggest that a clonal plant like P. pectinatus can tune the tuber burial depth to predation pressure, either by phenotypic plasticity or genotype sorting, hence exhibiting flexible avoidance by escape. We suggest that a flexible propagule burial depth can be an effective herbivore avoidance strategy, which might be more widespread among tuber forming plant species than previously thought.

Edge effects in patchy seagrass landscapes : the role of predation in determining fish distribution

Predation is often described as an underlying mechanism to explain edge effects. We assessed the importance of predation in determining edge effects in seagrass using two approaches: a video survey to sample predators at small scales across seagrass edges, and a tethering experiment to determine if predation was an underlying mechanism causing edge effects. Underwater videos were placed at four positions: middle of seagrass patches; edge of seagrass; sand immediately adjacent to seagrass and sand distant from seagrass. Fish abundances and the time fish spent in view were measured. The main predatory fish (Australian salmon, Arripis spp.) spent more time over adjacent sand than other positions, while potential prey species (King George whiting, Sillaginodes punctata (Cuvier), recruits) were more common in the middle of seagrass patches. Other species, including the smooth toadfish, Tetractenos glaber (Freminville), and King George whiting adults, spent more time over sand adjacent to seagrass than distant sand, which may be related to feeding opportunities. King George whiting recruits and pipefish (Stigmatopora spp.) were tethered at each of the four positions. More whiting recruits were preyed upon at outer than inner seagrass patches, and survival time was greater in the middle of shallow seagrass patches than other positions. Relatively few pipefish were preyed upon, but of those that were, survival time was lower over sand adjacent to seagrass than at the seagrass edge or middle. Video footage revealed that salmon were the dominant predators of both tethered King George whiting recruits and pipefish. The distribution of predators and associated rate of predation can explain edge effects for some species (King George whiting) but other mechanisms, or combinations of mechanisms, are determining edge effects for other species (pipefish).

Assessing effects of diel period, gear selectivity and predation on patterns of microhabitat use by fish in a mangrove dominated system in SE Australia

The relative value of temperate mangroves to fish, and the processes driving patterns of microhabitat use within this habitat, are unknown. There are 3 quickly identifiable microhabitats within temperate Australian mangroves: (1) forest (the area of mangroves with trees); (2) pneumatophores (the area directly seaward of the forest without trees but with pneumatophores [aerial roots]); and (3) channel (the area directly seaward of the pneumatophores without gross structural attributes such as trees or pneumatophores). Duplicate fyke and gill nets were both initially used to sample fish in the 3 microhabitats described above. Sampling took place across the seaward edge of mangroves on 10 sampling occasions (5 night and 5 day), in a large estuarine system in SE Australia. Fish assemblages (693 fish from 20 species and 15 families) varied significantly (p < 0.05) between the forest and the channel, and between diel periods for each gear (net type), but there was little difference in the assemblage structure of fish between forest–pneumatophore or pneumatophore–channel microhabitats. Juvenile lifestages (61% of all fish) and commercially important taxa (76%) were common. Abundance, biomass and species richness of fish were generally lower in the forest than the other microhabitats, but this pattern varied significantly (p < 0.05) between diel periods, among sampling occasions, and with water depth. Highly quantitative pop nets provided a preliminary assessment of whether differential gear selectivity caused patterns between microhabitats, but less rich fish assemblages were again recorded in forests than in pneumatophores. The importance of predation in structuring fish assemblages across microhabitats was assessed by measuring survival of juvenile fish tethered in 3 predation treatments (predator exclusion, cage control, and uncaged). Survival rates were high across the predator treatments and did not vary among microhabitats. The variation in fish assemblages across microhabitats within mangroves was not consistent with a model of mangrove structure providing a refuge for juvenile fish from predation, but instead could indicate differences in efficiency of gear types among microhabitats and/or other ‘edge effect’-driven processes such as the provision of food and/or shelter.

Predator behaviour and predation risk in the heterogeneous Arctic environment

1. Habitat heterogeneity and predator behaviour can strongly affect predator–prey interactions but these factors are rarely considered simultaneously, especially when systems encompass multiple predators and prey.

2. In the Arctic, greater snow geese Anser caerulescens atlanticus L. nest in two structurally different habitats: wetlands that form intricate networks of water channels, and mesic tundra where such obstacles are absent. In this heterogeneous environment, goose eggs are exposed to two types of predators: the arctic fox Vulpes lagopus L. and a diversity of avian predators. We hypothesized that, contrary to birds, the hunting ability of foxes would be impaired by the structurally complex wetland habitat, resulting in a lower predation risk for goose eggs.

3. In addition, lemmings, the main prey of foxes, show strong population cycles. We thus further examined how their fluctuations influenced the interaction between habitat heterogeneity and fox predation on goose eggs.

4. An experimental approach with artificial nests suggested that foxes were faster than avian predators to find unattended goose nests in mesic tundra whereas the reverse was true in wetlands. Foxes spent 3·5 times more time between consecutive attacks on real goose nests in wetlands than in mesic tundra. Their attacks on goose nests were also half as successful in wetlands than in mesic tundra whereas no difference was found for avian predators.

5. Nesting success in wetlands (65%) was higher than in mesic tundra (56%) but the difference between habitats increased during lemming crashes (15%) compared to other phases of the cycle (5%). Nests located at the edge of wetland patches were also less successful than central ones, suggesting a gradient in accessibility of goose nests in wetlands for foxes.

6. Our study shows that the structural complexity of wetlands decreases predation risk from foxes but not avian predators in arctic-nesting birds. Our results also demonstrate that cyclic lemming populations indirectly alter the spatial distribution of productive nests due to a complex interaction between habitat structure, prey-switching and foraging success of foxes.

Effect of Direct and Indirect Cues of Predation Risk on the Foraging Behavior of the White-Footed Mouse (Peromyscus leucopus)

Understanding predator-prey dynamics requires an understanding of how prey assess predation risk. This study tested the effect of microhabitat, moon stages, and mammalian predator urines (Vulpes vulpes [Red Fox], Mustela vison [Mink], and Procyon lotor [Raccoon]) on the degree of predation risk perceived by Peromyscus leucopus (White-footed Mouse). Giving-up densities from artificial food patches were used to quantify perceived predation risk. White-footed Mice exhibited a strong preference for cover microhabitat and for the new moon stage. However, the mice did not significantly alter their foraging behavior in response to the predator urines compared to a water control. Additionally, mice foraged less on colder nights. The results suggest that mammalian predator urines may not provide reliable information on actual predation risk for the White-footed Mice and that the mice extensively use indirect cues to assess predation risk.