Diet of ship rats following a mast event in beech (

Diet of 98 ship rats (Rattus rattus) was investigated by examination of stomach contents. Rats were trapped (as bycatch in stoat traps) from June to December 2006, in the Dart Valley near Lake Wakatipu, New Zealand, after a Nothofagus beech mast. Plant material was found in 43% of all stomachs, invertebrate fragments in 67%, feathers in 8%, hairs in 46% and skin with hairs attached in 12%, and animal (vertebrate and invertebrate) tissue in 76%. Hair samples examined by scanning electron microscopy were from mice, and rat and/or mouse DNA was found in all (10) samples subjected to DNA extraction. Mice may be an important food resource for rats following beech masts, when mouse population densities are high. Presence of feathers indicates predation of roosting or nesting birds, or scavenging. Consumption of beech seed beyond the time of germination may be due to caching of seed.     

Neighbourhood analyses of tree seed predation by introduced rodents in a New Zealand temperate rainforest

House mice Mus musculus and other introduced rodents represent a novel source of predation on tree seeds in New Zealand forests. In the northern temperate forests where these rodents are native, spatial and temporal variation in tree seed production can result in dramatic fluctuations in the distribution and abundance of seed predators, with subsequent feedbacks on the distribution and abundance of seedlings. We use neighbourhood models to examine variation in rodent predation on seeds of 4 tree species of the temperate rainforests of New Zealand as a function of 1) spatial variation in local canopy composition and 2) spatial and temporal variation in mouse activity. We placed seeds throughout mapped stands of mixed forests in alluvial valley bottoms and on elevated marine terraces in the Waitutu Forest, South Island. The risk of predation on seeds of 2 dominant canopy trees – rimu Dacrydium cupressinum and mountain beech Nothofagus solandri var . cliffortioides – peaked in neighbourhoods dominated by those species and by silver beech N. menziesii , particularly in a year of plentiful seed rain from these species. The risk of predation on rimu and beech seed was also related to measures of local mouse activity. These relationships suggest that the highest local abundance of mice was concentrated in rimu and beech neighbourhoods because of the food provided by seed rain from those trees. Predation on seed of miro Prumnopitys ferruginea , which is eaten by rats but not mice, was low in rimu neighbourhoods and where mouse activity was high. These patterns may reflect spatial segregation in the activity of rats versus mice within stands. Our results suggest that the spatial distribution of canopy trees translates into predictable patterns of variation in mouse activity and seed predation. Heterogeneity in rodent activity and seed predation within stands may have important implications for tree population dynamics.     

Age-Specific Prevalence and a Possible Transmission Route for

The prevalence of infestation of the skulls of stoats with the parasitic nematode Skrjabingylus nasicola was previously described in a national survey by King and Moody (1982). Since then, more samples from Craigieburn Forest Park and from the Eglinton Valley, Fiordland, have been collected, and a method of determining the actual ages of adult stoats has been developed. The extended samples are here examined for a relationship between infestation and age, which could not previously be tested. Prevalence generally increases with age, significantly so at Craigieburn. Stoats which had lived through one or more beech (Nothofagus solandri:) mast years at Craigieburn were significantly more likely to be infested, when the effects of age were allowed for. The hypothesis is advanced that the paratenic host for S. nasicola in New Zealand is the feral house mouse, Mus musculus, which is more numerous after a heavy beech seed fall.     

Predicting the incidence of mohua predation from the seedfall,mouse, and predator fluctuations in beech forests

Abstract

Predator control will be required to save many mohua (Mohoua ochrocephala) populations from extinction. However, control may be required only in years when stoat (Mustela erminea) densities are high. To manage local stoat populations effectively, a reliable predictor of high risk years is required. We examined whether different levels of beech seedfall and mouse capture rates were related to the levels of mohua predation recorded in the Hawdon Valley, Arthur's Pass National Park, and the Eglinton Valley, Fiordland National Park, between 1989 and 1994. During this period there was only one full beech mast year in each study area during autumn. The full mast seedfall in Hawdon Valley was predominantly of mountain beech (Nothofagus solandri var. cliffortioides) and red beech (N. fused), and in Eglinton Valley it was predominantly silver beech (TV. menziesii). During the following summer, mouse and stoat densities, and the predation rate of adult mohua, all increased considerably. There was very little predation on adult mohua in the summers following poor seedfalls when mouse and predator densities remained low. In 1993, a partial mast did not trigger a mouse or stoat irruption.

We conclude that counts of beech seedfall and indices of mouse density are potential predictors of an impending irruption of key predators. Winter mouse density appeared to be the most reliable indicator, because neither stoats nor mice respond to seedfall alone. A combination of these indicators could be used as a basis for management decisions on whether to undertake stoat control to protect mohua populations in the future. However, more information is required on the seedfall thresholds that may trigger sufficient increases in mouse and stoat numbers and, consequently, bird predation.     

Ecology of the stoat in

We studied the ecology of a high-density population of stoats in Fiordland, New Zealand, in the summer and autumn of 1990-91 following a Nothofagus seeding in 1990. Results are compared with findings from the same area in 1991-92, a period of lower stoat density. In the high-density year, minimum home ranges (revealed by radio-tracking) of four females averaged 69 ha and those of three males 93 ha; range lengths averaged 1.3 km and 2.5 km respectively. Neither difference was statistically significant. For combined sexes, average range area in the high-density year was significantly less, and range length was significantly shorter, than in the following year. When we compared stoat diet in the high-density year with that in the following two years, there were no significant differences in the frequencies of occurrence of birds or invertebrates in stoat guts. Overall, bird remains were found in 56% of guts, and invertebrates in 28%. Possum remains occurred in 6% of male stoats but were never found in females. Mice were only detected in stoats in the high-density year, when they occurred in 54% of guts. Lagomorphs occurred significantly more often in the guts of stoats during lower-density years (26%) than the high- density year (7%). Seedfall in Nothofagus forest is synchronous and periodic. Following seedfall, mouse density rises dramatically, followed by a sharp rise in stoat numbers. It has been suggested that mice feed on the abundant seed and that stoats in turn increase because of the large numbers of mice available to them. We suggest that the situation is more complex and that increases in not only mouse, but also bird (and possibly invertebrate), densities may contribute to the high productivity of stoats in the year following a Nothofagus seedfall.     

Synchronicity,periodicity and bimodality in inter‐annual tree seed production along an elevation gradient

Distinctive inter‐annual patterns of tree seed production can include spatial synchronicity, periodicity, and high variability among individuals within a population. Synchronicity and high variability are now commonly used to define mast seeding, with ‘strict’ mast seeding further distinguished by annual seed production that is either often large or nil and thus bimodal. Here we test for synchronicity, periodicity, and bimodality using 43 years of annual total and viable seed counts, along four transect lines, sampling an elevation gradient (480–1340 m) in a monospecific New Zealand mountain beech Nothofagus solandri var. cliffortioides forest. We expect most support for periodicity and bimodality at relatively high elevation sites that are most resource limited and known to have the greatest variability in seed production. While there was weak evidence for differences in viable seed counts along the elevation gradient, this was not the case for total seed counts. A significant year‐effect on seed counts provided some evidence for synchronization, but the correlations of total or viable seed counts rapidly declined (from 0.96 to 0.58) with increasing elevation difference among transect lines. Although we detected a seven‐year periodicity in total and viable seed counts at each elevation, we also detected other period lengths at most elevations. We did not find evidence for our expectation of increased period length and bimodality in relatively unproductive high elevation mountain beech forests because they would take more time to recover from seeding events. As a consequence, if resource limitation is an important driver of mountain beech seed production its influence must be strongly regulated by other factors to determine the distinctive characteristics (periodicity and synchronicity but not bimodality) of inter‐annual variation in seed production.     

Marten and fisher responses to fluctuations in prey populations and mast crops in the northern hardwood forest

Many forest tree species produce seed (mast) crops that are consumed by a variety of wildlife species and these pulsed resources may mediate interactions among predator and prey populations. In the northern hardwood forests of New York, we investigated interactions among mast production, prey abundance, and harvests of American martens (Martes americana) and fishers (Martes pennanti) during 1988–2009. Mast production for beech (Fagus grandifolia), sugar maple (Acer saccharum), and mountain ash (Sorbus americana) was synchronous and an alternate-year pattern in production was evident for most of the time series. We documented considerable temporal variation in summer small mammal relative abundance and our numerical response models received substantial support for 5 of the 8 species, indicating lagged responses to autumn mast crops. Trap response of martens to the autumn production of beech mast and mountain ash berries was immediate and numerical responses to the relative abundance of small mammal prey occurred during the preceding summer. The age structure of the marten harvest differed based on the dominant alternate-year pattern of summer prey relative abundance and autumn mast production (χ²₄ = 33.06, P < 0.001). The proportion of juvenile marten in the autumn harvest was 52% and 34% following summers when small mammal relative abundance was high and low, respectively and these differences resulted in a persistent cohort effect that was apparent until age 3.5. Trap response of fishers to the autumn production of beech mast was immediate and numerical responses to the relative abundance of Sciurid prey occurred during the preceding summer. Marten and fisher harvests fluctuated similarly among New York, Maine, and New Brunswick, which may indicate regional synchronization of mast crops and responses of martens and fishers to similar prey dynamics. A better understanding of how food availability influences demographic responses and trapping vulnerability of martens and fishers would aid our ability to manage harvests of these species on a sustained yield basis. © 2011 The Wildlife Society.     

Seed survival on experimental dishes in a central European old‐growth mixed‐species forest – effects of predator guilds,tree masting and small mammal population dynamics

Predation of tree seeds can be a major factor structuring plant communities. We present a three year study on tree seed survival on experimental dishes in an old‐growth forest in central Europe in Austria. We addressed species specific, spatial and temporal aspects of post‐dispersal seed predation. Seeds of Norway spruce Picea abies, European beech Fagus sylvatica, and silver fir Abies alba were exposed on dishes in different types of exclosures which allowed access only to specific guilds of seed predators. Removal experiments were carried out in two old‐growth forests and a managed forest (macro‐sites), including micro‐sites with and without cover of ground vegetation. We conducted the experiment in three consecutive years with a mast year of beech and spruce before the first year of the study. The seed removal experiments were combined with live trapping of small mammals being potential seed predators. Our experiments showed a distinctly different impact of different predator guilds on seed survival on the dishes with highest removal rates of seeds from dishes accessible for small mammals. We observed differing preferences of small mammals for the different tree species. Seed survival in different macro‐ and micro‐habitats were highly variable with lower seed survival in old growth forests. In contrast to our assumption, and in contrast to the satiation hypothesis which assumes higher seed survival in and directly after mast years, seed survival was lower in the year following the mast year of beech when a population peak of small mammals occurred and higher in intermast periods when subsequently small mammal population crashed. This suggests a higher importance of sporadic masting shortly after mast years in intermast periods for establishment of forest trees provided that pollination efficiency is high enough in such years. Combined with the high seed mortality observed after the mast year, this corroborates the important role of seed predation for forest dynamics. An altered synchrony or asynchrony of masting of different tree species and changed masting frequencies through climate change may thus lead to strong and non‐linear effects on forest dynamics.     

Is energy supply the trigger for reproductive activity in male edible dormice (<Emphasis Type="Italic">Glis glis</Emphasis>)?

In edible dormice (Glis glis) reproduction is synchronised with the intermittent masting of the European beech (Fagus sylvatica). In years of mast failure dormouse males seem to anticipate future low food availability and fail to develop functional testes. We hypothesised that the availability of high-quality food is linked to male reproductive capacity, because of high male energetic demands during gonad maturation. We therefore evaluated the relationship between beech seed production and male reproductivity in the field between 1993 and 2005. In order to know whether the energy content of the food as such triggers sexual capacity, we supplemented high-quality food in the field for 3 years and investigated reproductive output, reproductive capacity, and body mass changes. Results revealed that male reproductive capacity was positively linked with beech seed production. Body mass changes of reference males during the high reproductive year further revealed high energetic demands of male reproduction, which were counter balanced in food-supplemented males. However, in contrast to our assumptions, artificial food supply during a year of mast failure failed to evoke high reproductivity in edible dormice. The availability of high-quality food can therefore be ruled out from being the primary trigger for sexual activity in male edible dormice.     

Molecular data do not support a southern hemisphere base of Nothofagus powdery mildews

Three powdery mildew species present on Nothofagus (viz. Erysiphe magellanica, E. nothofagi and E. patagoniaca) are endemic to South America and have unique ascomatal appendages that are not found in powdery mildews of the northern hemisphere. We determined the nucleotide sequences of the rDNA internal transcribed spacer regions and D1/D2 domains of the 28S rDNA of these three powdery mildew species to reveal their phylogenetic relationships with powdery mildews of the northern hemisphere. Although the molecular phylogenetic analyses indicated that the three Nothofagus powdery mildews are closely related to each other they did not group into one clade in either the ITS or 28S trees. Kishino-Hasegawa, Shimodaira-Hasegawa and Templeton tests could not significantly reject the constrained trees that were constructed based on the assumption that the Nothofagus powdery mildews would form a single clade. Based on this result and the evidence that all Nothofagus powdery mildews are endemic to South America and have similar morphological characteristics, it is likely that these three species diverged from a single ancestor present on Nothofagus. Calibration of evolutionary events with molecular clocks suggested that the Nothofagus powdery mildews split from the northern hemisphere relatives 22-16 million y ago (Ma) in the middle Miocene, and divergence among the Nothofagus powdery mildews occurred 17-13 Ma. These results do not support a southern hemisphere base of the Nothofagus powdery mildews.     

Fluctuation of nut production and seedling appearance of a Japanese beech (Fagus crenata Blume)

The nut productivity, density of fallen nuts, seedling appearance and seedling survival of a Japanese beech (Fagus crenata Blume) were investigated at three localities, Mt Gozaisho, Mt Hodaka and Mt Bandai, Japan, from 1976 to 1992. Two patterns of cycles, a short cycle and a long one, were confirmed in the beech nut productivity. Synchronization in the long cycle was recognized both on Mt Hodaka and Mt Bandai. On Mt Gozaisho, the beech nut productivity was quite low, and the seedlings disappeared within 1 year. The phenomenon on Mt Gozaisho seemed to be caused by the low matter production mainly due to erosion and poor soils. A large number of seedlings appeared in the next spring of heavy mast years on Mt Hodaka and Mt Bandai. The large beech nut productivity contributed to the large seedling supply, and this enhanced the survival probability of beech seedlings. This demonstrates the possibility that beech seedlings survived longer even under dense dwarf bamboos, particularly if the seedling supply was large.     

Seed production and outbreaks of non-cyclic rodent populations in deciduous forests

Summary In a 10-year study period, outbreaks of the bank vole, Clethrionomys glareolus, Schreber only occurred in years following huge seed production of European beech, Fagus sylvatica. Intensive winter reprodution preceded the outbreaks, in contrast to a normal breeding season from April through September. No winter reproduction occurred in nearby populations from habitats without mast production. During the winter, the average weight of C. glareolus remained high in the mast forests and the age structure resembled that of a summer breeding population. Despite excess energy requirements of winter breeding, survival rates were similar to that of non-breeding winter populations. In mast years, rodent consumption in the beech forest was estimated as 1.0–10.3% of endosperm production available to postdispersal seed predators. Between mast years rodent consumption made up 30–100% of endosperm production available. Mast years occurred at irregular intervals and seed production seems to be synchronized between individual trees over large areas and induced by climatic events. These phenomena lead to seed predator satiation.     

Fallow deer impacts on Wakatipu beech forest

This study uses data from forty-nine 20 m × 20 m permanent plots measured in 1976, 1982, 1989 and 1997-2002 in Wakatipu Forest, western Otago. We relate changes in red (Nothofagus fusca), silver (Nothofagus menziesii) and mountain beech (Nothofagus solandri var. cliffortioides) forest vegetation to the presence of fallow deer (Dama dama). Vegetation composition is likely to have been altered prior to plot establishment, and results show that there was little change in vegetation composition during the study. There are some signs of fallow deer reducing silver beech seedling abundance at some plots, but most beech stands appear to be in the late phase of development and undergoing self thinning, so are probably not immediately vulnerable to suppression of canopy regeneration. In the future, widespread disturbance is likely to release plants in the understorey from competition for light and nutrients, and at that stage fallow deer browsing of beech species may be able to alter successional pathways more than has occurred over the past two decades. Seedling and sapling density of the palatable Griselinia littoralis (broadleaf) was probably insufficient to ensure successful regeneration. Comparisons of seedling densities with other mixed beech forests throughout New Zealand suggest that fallow deer density will need to be nearly zero in Wakatipu Forest before regeneration of all palatable subcanopy hardwood species is assured.     

Linking songbird nest predation to seedling density: Sugar maple masting as a resource pulse in a forest food web

The ecological literature presents considerable evidence for top‐down forcing on the maintenance of species diversity. Yet, in temperate forests, bottom‐up forces often exert a strong influence on ecosystem functioning. Here, we report on the indirect influence of a pulsed resource, sugar maple (Acer saccharum) seed production, on nest survival in a migratory songbird. We hypothesized that seed production in year t would determine daily nest survival rate in year t + 1 through its effects on seed‐eating rodents. We used the density of sugar maple seedlings (with cotyledons) in year t + 1 as a proxy for seed production in year t and predicted that it would be inversely related to songbird nest survival the same year. We estimated the density of sugar maple seedlings, eastern chipmunk (Tamias striatus) activity, and daily nest survival rate in the ovenbird (Seiurus aurocapilla) over four successive years in a northern hardwood forest of New Brunswick, Canada. Seedling density varied by two orders of magnitude between years, whereas an index of chipmunk activity changed by an order of magnitude. Both variables were positively correlated and negatively correlated to daily nest survival rate. A logistic‐exposure model including only seedling density received the greatest level of support (lowest AIC_c). Previous studies have reported the effect of sugar maple masting on seed‐eating rodent populations, but the strong link we report between seedling density and songbird nest survival is novel. A nocturnal seed‐eating nest predator, deer mouse (Peromyscus maniculatus), was not considered in our models, which may explain why chipmunk was not the best predictor of daily nest survival rate. The trophic linkages we observed are remarkably strong for a temperate forest ecosystem and might become more prevalent in northeastern North America, at least on calcium‐rich soils, with the loss of large‐diameter beech trees as a result of beech bark disease.     

Decline in capture rate of stoats at high mouse densities in New Zealand

We present two statistical models documenting variations in density indices of stoats and of mice in New Zealand southern beech (Nothofagus spp.) forests. They confirm previous, simpler correlations showing that the summer capture rate of stoats increases with spring mouse density index up to about 20–25 mouse captures per 100 trap-nights (C/100TN). However, at much higher mouse densities (60–80 C/100TN), observed in the Grebe and Borland Valleys in southern Fiordland in 1979/80 and again in 1999/2000, fewer stoats were caught than expected. These models quantify a serious decline in capture rate of stoats during periods of high mouse abundance over the range 25-80 C/100TN. At such times, management strategies aiming to protect threatened birds by intensive lethal trapping of stoats during the nesting seasons may be least effective just when they are most needed.     

Predation on native birds in New Zealand beech forests: the role of functional relationships between Stoats Mustela erminea and rodents

In the Holarctic, predation by mustelids on birds is often linked to population cycles of rodents (especially voles and lemmings) because birds may be buffered against mustelid predation at high rodent densities. By contrast, interguild relationships between introduced mustelids and rodents can have very different consequences for native birds in ecosystems where mustelids have been introduced. Here, we consider the interactions between Stoats Mustela erminea , feral House Mice Mus musculus and native birds in New Zealand beech Nothofagus spp. forests. We conclude that buffering to protect birds from Stoat predation normally fails in these systems, because peak populations of mice in these forests are low by Holarctic standards, and mice usually do not become sufficiently abundant to distract increased numbers of Stoats from preying on birds. However, temporary buffering is possible during rare episodes of extreme mouse abundance.     

Negative effects of density on space use of small mammals differ with the phase of the masting‐induced population cycle

Home range size generally decreases with increasing population density, but testing how this relationship is influenced by other factors (e.g., food availability, kin structure) is a difficult task. We used spatially explicit capture–recapture models to examine how home range size varies with population density in the yellow‐necked mouse (Apodemus flavicollis). The relationship between population density and home range size was studied at two distinct phases of population fluctuations induced by beech (Fagus sylvatica) masting: post‐mast peak in abundance (first summer after mast, n = 2) and subsequent crash (second summer after mast, n = 2). We live‐trapped mice from June to September to avoid the confounding effects of autumn seedfall on home range size. In accordance with general predictions, we found that home range size was negatively associated with population density. However, after controlling for the effect of density, home ranges of mice were larger in post‐mast years than during the crash phase. This indicates a higher spatial overlap among neighbors in post‐mast years. We suggest that the increased spatial overlap is caused by negative density‐dependent dispersal that leads to high relatedness of individuals within population in the peak phase of the cycle.     

An interactive effect of simultaneous death of dwarf bamboo, canopy gap, and predatory rodents on beech regeneration

To clarify the interactive effect of the simultaneous death of dwarf bamboo (Sasa kurilensis), forest canopy gap formation, and seed predators on beech (Fagus crenata) regeneration, we analyzed beech demography from seed fall until the end of the first growing season of seedlings in an old-growth forest near Lake Towada, northern Japan. The simultaneous death of S. kurilensis took place in 1995. We established four types of sampling site differing in forest canopy conditions (closed or gap) and Sasa status (dead or alive). Beech seed survival and emergence ratio were both highest in gaps with dead Sasa (gap-dead), because rate of predation was lowest. Seedling survival during the first growing season was also highest in the gap-dead treatment, because of less predation and less damping off. As a result, even though density of seed fall was lowest in the gap-dead treatment, the living seedling density there was highest at the end of the first growing season. Predation, which caused the greatest mortality during the seed and seedling stages, was significantly lower at both sites in gaps and sites with dead Sasa. This was probably due to changes in the behavior of rodents in response to the structure of the forest canopy and undergrowth. Both the death of Sasa and canopy gap formation allowed seedlings to avoid damping off because of the high light availability. The indirect effect of the simultaneous death of Sasa and canopy gap formation in reducing predation contributed more to beech regeneration than their direct effect in increasing light for the seedlings.     

The effects of food availability and distance to protective cover on the winter foraging behaviour of tits (Aves: Parus)

To maximize fitness, many animals must trade off their need to forage efficiently against their need to avoid predators. We studied such a trade-off in four species of tits (Paridae) in a forest near Oxford, UK. During winter, tits form flocks which increase feeding efficiency and reduce predation risk. These flocks feed extensively on beech (Fagus sylvatica) seeds, the abundance of which may be critical for winter survival. Because these seeds drop to the ground, where birds are exposed to sparrowhawk (Accipiter nisus) attack, tits need to trade off their need to find seeds against the proximity to protective cover, provided by dense clusters of hawthorn (Crataegus spp.). The quality of the beech crop differs markedly between trees and years. During a year of abundant beechmast, most tits searched for seeds close to protective cover. This 'safety-first' strategy precluded visits to superabundant food patches if they were too far from protective cover. Among beech trees near to cover, tits tended to prefer those with high seed density. Tits benefited from foraging under trees with high seed density because this correlated significantly with seed mass per square metre and because mean search times decreased with increasing seed density. Finally, we show experimentally that great tits, Parus major, can discriminate between edible (viable) and inedible (empty) seeds.