The impacts of introduced House Mice on the breeding success of nesting seabirds on Gough Island

Invasive species are the main threat to island biodiversity; seabirds are particularly vulnerable and are one of the most threatened groups of birds. Gough Island, a UNESCO World Heritage Site in the South Atlantic Ocean, is an Important Bird and Biodiversity Area, and one of the most important seabird colonies globally. Invasive House Mice Mus musculus depredate eggs and chicks of most seabird species on the island, but the extent of their impact has not been quantified. We used field data and bootstrapped normal distributions to estimate breeding success and the number of surviving chicks for 10 seabird species on Gough Island, and compared estimates with those of analogous species from predator‐free islands. We examined the effects of season and nest‐site location on the breeding success of populations on Gough Island, predicting that the breeding success of Gough birds would be lower than that of analogues, particularly among small burrow‐nesting species. We also predicted that winter‐breeding species would exhibit lower breeding success than summer‐breeding species, because mice have fewer alternative food sources in winter; and below‐ground nesters would have lower breeding success than surface nesters, as below‐ground species are smaller so their chicks are easier prey for mice. We did indeed find that seabirds on Gough Island had low breeding success compared with analogues, losing an estimated 1 739 000 (1 467 000–2 116 000) eggs/chicks annually. Seven of the 10 focal species on Gough Island had particularly high chick mortality and may have been subject to intense mouse predation. Below‐ground and winter breeders had lower breeding success than surface‐ and summer‐breeders. MacGillivray's Prion Pachyptila macgillivrayi, Atlantic Petrel Pterodroma incerta and Tristan Albatross Diomedea dabbenena are endemic or near‐endemic to Gough Island and are likely to be driven to extinction if invasive mice are not removed.     

Population cycles in voles and lemmings: state of the science and future directions

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NEOSQUIRREL: a data set of ecological knowledge on Neotropical squirrels

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A desert octodontid rodent,Tympanoctomys barrerae,uses modified hairs for stripping epidermal tissue from leaves of halophytic plants

Desert rodents that consume halophytic plants must have adaptations for coping with the high salt content of the leaves. A kidney capable of excreting very concentrated urine is one method. Another is removal of the hypersaline epidermis by means of chisel-like incisors prior to ingestion of the leaves. Tympanoctomys barrerae has evolved a unique refinement of the latter adaptation. It possesses two bundles of stiffened hairs on either side of the palate just caudal to the incisors. The bundles vibrate against the lower incisors, removing the epidermis from the leaves. The efficiency of the operation is significantly greater than with the use of incisors alone. Such a device has not been described in any other mammal. The facial muscles associated with the lips, the cheek vibrissae, and the oral cavity are described in T. barrerae and the nonhalophilic octodontid Octomys mimax. M. buccinatorius pars intermaxillaris is the only muscle in direct contact with the bristle bundles. Other anatomical features found in T. barrerae that may be associated with this feeding device are: 1) a much enlarged and mobile lower labial pad operated by Mm. buccinatorius pars orbicularis oris, pars longitudinalis profunda, and mandibularis cranialis profunda; 2) two oral glands not described in other rodents; and 3) a shortened tongue. Although, taken as a whole, this epidermal stripping device is unique to T. barrerae, most of its features have evolved by modification of structures present in the facial region of more generalized rodents.     

Annual cycles of four flea species in the central Negev desert

Bionomics of fleas (Siphonaptera) parasitizing rodent hosts, mostly the gerbil Gerbillus dasyurus (Wagner) and the jird Meriones crassus Sundevall (Gerbillidae), were investigated in the central Negev desert of Israel. Populations were sampled weekly (by Sherman trapping of hosts) from August 2000 to July 2001. Among 1055 fleas of nine species captured, four species predominated (94%). Two species of Pulicidae, Xenopsylla dipodilli Smit and X. ramesis (Rothschild), reproduced perennially, whereas adults of Nosopsyllus iranus theodori Smit (Ceratophyllidae) and Stenoponia tripectinata medialis Jordan (Hystrichopsyllidae) occurred only in cool months (October-March). During their main activity season on the most infested host species (estimated from > 300 trap-nights/month), prevalence of these four flea species reached 40-70%, 20-30%, 100% and 50-70%, respectively, with infestation intensities of 2-2.7, 7-12, 2-3.5 and 2.5-7 fleas per infested rodent, respectively. Xenopsylla dipodilli oviposition peaked during autumn with parous rate > 80% by September-October. During December-April, the majority of X. dipodilli females were immature and/or nulliparous (defined as having mature ovaries but no follicular relics). In contrast, X. ramesis had two reproductive peaks, in mid-spring and autumn, evidenced by the influx of immature females in late spring and summer (30-40%) and in winter (20-30%) after maximal parous rates: 80-100% in March-April and 95-100% in October-November. Nosopsyllus iranus theodori and Stenoponia tripectinata medialis adults occurred only during cool months. At the beginning of activity, during October-November, the sex ratio of N. i. theodori was strongly biased to females (86%) that were immature and/or nulliparous. In winter, adult females were 52-65% parous and 10-32% immature. In March, as the adult population of N. i. theodori declined, 78% of females were parous and 12% immature. Seasonal activity of S. t. medialis (November-March) was shorter than for the other three species; females were predominantly nulliparous in November (80%), after which the proportion of parous females increased gradually to 84% in February. Two females of S. t. medialis collected in March were mature but nulliparous, suggesting that this species of flea might 'oversummer' (as pupae or teneral adults) in the cocooned stage.     

The biology and use of the African brush-tailed porcupine (Atherurus africanus, Gray, 1842)as a food animal. A review

The brush-tailed porcupine (Atherurus africanus) is a hystricomorph rodent, which frequents the forests of West and Central Africa. With an average weight of 3 kg, it is a favourite source of meat for urban and rural populations of Gabon, Nigeria, Cameroon or Congo. Hunted in large quantities, its price is often higher than that of other game or domestic animals. Although its current productivity in captivity is limited to a single young per birth and two to three births per year per female, this species could be a good candidate for minilivestock programmes in African forest areas if its current reproductive potential in captivity could be improved. Further research should be encouraged on its biology and reproduction since the current level of hunting for this species is probably not sustainable. Captive breeding programmes could play a role in assessing a better knowledge of the species' biology, and in reducing the effects of intensive hunting in areas where this activi ty is no longer sustainable.     

Consistencies in post-dispersal seed predation of temperate fleshy-fruited species among seasons, years and sites

1. Seed predation of 12 fleshy-fruited species was recorded in experimental dishes under early successional forest in south-west Germany (four seasons 1992 and 1993) and in south England (summer 1995). On each occasion, 200 dishes were laid out, each containing five seeds of a given species. The mean time for three or more seeds to be removed was taken as a measure of granivore preferences. We tested correlations of these preferences with several physical and nutritional seed traits.
2. Live trapping and selectively accessible dishes indicated that rodents were the major granivores ( Apodemus sylvaticus, Apodemus flavicollis, Clethrionomys glareolus ); no predation by birds or insects was observed. The rank order of the rodents' seed preferences was consistent among sites, seasons and years, but mean predation differed between species, sites and seasons. Seed predation was highest in summer and lowest in winter. Possible implications of the seasonal pattern in predation risk are discussed.
3. The preferences of rodents were significantly correlated with the species-specific viability of seeds (i.e. percentage of sound seed) in five of eight experiments and with the percentage of water in the embryo-plus-endosperm fraction (EEF) in four of eight experiments. Surprisingly, preferences were not correlated to seed mass, EEF mass or nitrogen concentration. Predation was lowest among toxic species ( Berberis vulgaris, Euonymus europaeus, Sambucus nigra ) and among species with woody endocarps ( Cornus sanguinea, Crataegus spp.).     

Geographical range size and host specificity in ectoparasites: a case study with Amphipsylla fleas and rodent hosts

Aim  To identify the factors that determine the geographical range sizes of ectoparasites with different degrees of host specificity.
Location  The study used data on the distributions of fleas of the genus Amphipsylla and their rodent hosts across the Holarctic.
Methods  All known points of occurrence of 32 flea species and 51 species of their rodent hosts were mapped. The shape and size of the geographical range of each species were estimated using a combination of the minimal convex polygon technique and modelling with the garp algorithm. Factors determining the geographical range sizes of the fleas were identified using stepwise multiple regression analysis.
Results  The geographical range size of fleas that are strongly host-specific across their entire ranges correlated positively with the geographical range size of the fleas' principal hosts, and negatively with the geographical range size of the fleas' potential competitors. The geographical range sizes of both (1) fleas that are locally host-specific but that shift their host preferences geographically, and (2) host-opportunistic fleas were positively correlated only with the area of the geographical ranges of their principal hosts. Strongly host-specific fleas occupied 0.2–80.0% of the geographical range of their principal hosts, whereas this figure was 0.9–83.7% in locally host-specific fleas and 16.6–63.7% in host-opportunistic fleas.
Main conclusions  The main determinant of the geographical range size of a flea species is the size of the geographical range of its hosts. The role of potential competitors in determining the geographical range size is stronger in host-specific than in host-opportunistic fleas. Cases in which the geographical range of a parasite is smaller than the geographical range(s) of its host(s) owing to narrower parasite environmental tolerances are much more frequent in host-opportunistic than in host-specific fleas.     

The Interplay of Habitat and Seed Type on Scatterhoarding Behavior in a Fragmented Afromontane Forest Landscape

Scatterhoarding by rodents, whereby seeds are collected and stored for later consumption, can result in seed dispersal. Seeds may be covered in litter on the forest floor (cached) or buried. This is particularly so in the Neotropics for large, nutritious seeds, and where primary dispersers are rare or missing. In African forests, contemporary anthropogenic pressures such as hunting, forest degradation, and fragmentation are contributing toward major declines in large frugivores, yet the potential for scatterhoarding to mitigate this loss is largely unknown. In this study, we used thread‐marked seed to explore the balance between seed predation and dispersal by rodents in Afromontane forest. We studied two tree species in three habitats: (1) continuous forest; (2) continuous forest edge, and (3) small, degraded riparian forest patches. We found that seed removal rates were high and almost the same in all three habitats for both tree species, but that the predation/dispersal balance differed among habitats. In continuous forest, more seeds of each species were scatterhoarded than depredated, and rates of scatterhoarding differed between the two species. In all habitats, burying seeds up to 2 cm belowground was more common than caching. Distances seeds were moved was approximately five times greater in continuous forest than in forest edge or riparian patches. We found strong evidence to suggest that the African pouched rat, Cricetomys sp. nov was responsible for the scatterhoarding.     

Species diversity and population dynamics of rodents in a farm‐fallow field mosaic system in Central Tanzania

A Capture‐Mark‐Recapture study was undertaken in Central Tanzania to compare variations in community structure and population dynamics of rodents in two types of habitats. The study was conducted in fallow field mosaic habitat dominated by perennial and annual grasses (grid BEA) and a more heterogeneous habitat (grid BEB) which was previously woodland cleared of most trees with vegetation dominated by shrubs, bushes, scattered trees and perennial grass. The relative abundance of rodents in BEA was: Mastomys natalensis (73.5%) > Aethomys chrysophilus (8.9%) > Gerbilliscus vicina (7.3%) > Arvicanthis neumanni (6.1%) > Acomys spinosissimus (4.1%) and for grid BEB: M. natalensis (67.6%) > G. vicina (11.2%) > A. neumanni (10.3%) > A. chrysophilus (7.6%) > A. spinosissimus (2.9%). Graphiurus sp., Mus minutoides, Saccostomus mearnsi, Lemniscomys striatus and L. griselda were rare and only occasionally trapped in BEB. Spatial variations in population density were non‐significant except for A. chrysophilus. Significant temporal variations within grids were observed, with synchrony of population peaks for some species. The rare species boosted species richness of grid BEB rather artificially, without significantly contributing to higher species diversity. Temporal variations in Simpson’s Diversity indices between grids were non‐significant except for three out of twenty‐one trapping sessions.