Mast seeding, the intermittent, synchronous production of large seed crops by a population of plants, is a well-known example of resource pulses that create lagged responses in successive trophic levels of ecological communities. These lags arise because seed predators are thought capable of increasing reproduction and population size only after the resource pulse is available for consumption. The resulting satiation of predators is a widely cited explanation for the evolution of masting. Our study shows that both American and Eurasian tree squirrels anticipate resource pulses and increase reproductive output before a masting event, thereby increasing population size in synchrony with the resource pulse and eliminating the population lag thought to be universal in resource pulse systems.

Vertebrate population dynamics, social organisation and space use often are closely associated with the distribution of critical resources, such as food. Tree squirrels are ideal models to study these relationships, since both key demographic parameters (reproduction, survival and dispersal) and spatio-temporal variation in food supplies (measured as seed-crop size) can be reliably estimated. In this paper we test the following two predictions underlying the association between annual food abundance and demography in six alpine red squirrel populations, both with and without time-lag effects: 1) between-season and between-year fluctuations in survival rate, population density and increase parallel those in food availability; and 2) individuals follow a resource tracking strategy and increase in density mainly the year after a rich seed-crop. Red squirrels occurred at higher densities in Scots pine forest, characterised by stable seed-crops, than in Norway spruce with more abundant but more variable seed crops. Fluctuations in numbers were positively correlated with food availability, measured as annual conifer seed-crop sizes. Overall, adult survival rates were higher than those of subadults, and survival substantially fluctuated between seasons and years. Autumn densities and rates of population increase (summer-autumn) were strongly correlated with the same year's autumn seed-crop, while correlations with the previous year's seed-crop (time-lag models) were either weak (population density) or absent (population increase). Results of this paper show that fluctuations in red squirrel densities in habitats with strong temporal variation in seed production are more closely linked with food availability than in more stable habitats. In addition, in the Alpine conifer forests squirrel population sizes, in autumn, increase in synchrony with food resources, eliminating the population lag normally present when resources are produced in pulses

As migratory animals, sustainable management of African elephant populations, both within and around protected areas, is a major challenge in the conservation policy of many African countries. We captured seven female elephants, representative members of family groups, in different parts of Tarangire National Park (TNP), Tanzania, and used GPS satellite radio-tracking (November 1997-June 2000 to monitor their space and habitat use and seasonal migrations throughout wet and dry seasons. Patterns of home range overlap revealed the existence of two large clans that occupied the north-central and southern parts of TNP, respectively. At the end of the dry season, elephants from the southern clan migrated about 100 km southeast of the park boundary, those from the northern clan remained mostly inside the park, or used periodically wet-season core areas in the nearby Game Controlled Areas. No natural mortality occurred during the study, but two elephants were poached outside the park. Human disturbance also affected activity patterns, and elephants were less active at day outside than inside the park. Home range size varied from 477 to 1078 km 2 for the northern elephants, and from 1630 to 5060 km 2 for the southern elephants. Migration routes were characterised by higher cover (open and closed forest) than core areas. Our results indicate that elephant management must be considered across park boundaries and that migration corridors must be protected against human disturbance and land cultivation. Society problems linked to elephant conservation can be solved by creating alternative, sustainable, use of natural resources that enhance the livelihood of local communities.

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Introduced mammals can cause extinction of native species due to replacement competition, disease, predation or hybridization. We studied the colonization of Piedmont (NW-Italy) by American grey squirrel (Sciurus carolinensis) and its effect on the native red squirrel (Sciurus vulgaris). Presence/absence data (2x2 km squares), of both species were (re)constructed using questionnaires, literature, existing databases, unpublished information, and direct monitoring with hair-tubes. In 1970 red squirrels were still widespread and greys were restricted to forests near the introduction site. By 1990, grey squirrels had increased their range to 220 km 2. , which coincided with the disappearance of native squirrels from 33 squares inside this range. The invasive species continued its spread occupying an area of 2,016 km 2 in 2010; within this area red squirrels went extinct in 88 squares. Overall, from 1970 to 2010 red squirrel went extinct in 62% of 2x2 km squares (ca. 1,689 km 2 ), and were replaced by grey squirrels. The spread of the alien species was slow in the first twenty years, but doubled in the successive two decades. Nevertheless spread was slower than in Ireland and England. Grey squirrel adapt to climate and habitats in both North and South Europe, causing extinction of the native red squirrel. A EU LIFE co-funded project with the aim to control the grey squirrel in North Italy and recent trade-restrictions and trade-ban are a first step in reducing the risk of grey squirrels invading other countries, but their effectiveness will have to be evaluated.

This paper summarizes the ecological and evolutionary interactions for seed trees and Holarctic tree squirrels. The squirrel-seed interactions prior to dispersal and hoarding of seeds as well as those in which squirrels exert a significant positive effect on dispersal and establishment of seeds are reviewed. Across all Holarctic systems, three primary selective pressures that tree squirrels exert on tree seeds are recognized: two as seed predator and one as seed disperser. The close evolutionary relationship between several species of tree squirrels and tree species on which they feed, including the influence of tree squirrels on seed and tree characteristics and the effects of seeds on the demography, behaviour and social system of the squirrels are considered. It is suggested that in some systems tree squirrels might be considered keystone consumers as a result of their disproportionate influence on seed fates.

Introduced hosts populations may benefit of an "enemy release" through impoverishment of parasite communities made of both few imported species and few acquired local ones. Moreover, closely related competing native hosts can be affected by acquiring introduced taxa (spillover) and by increased transmission risk of native parasites (spillback). We determined the macroparasite fauna of invasive grey squirrels (Sciurus carolinensis) in Italy to detect any diversity loss, introduction of novel parasites or acquisition of local ones, and analysed variation in parasite burdens to identify factors that may increase transmission risk for native red squirrels (S. vulgaris). Based on 277 grey squirrels sampled from 7 populations characterised by different time scales in introduction events, we identified 7 gastro-intestinal helminths and 4 parasite arthropods. Parasite richness is lower than in grey squirrel's native range and independent from introduction time lags. The most common parasites are Nearctic nematodes Strongyloides robustus (prevalence: 56.6%) and Trichostrongylus calcaratus (6.5%), red squirrel flea Ceratophyllus sciurorum (26.0%) and Holarctic sucking louse Neohaematopinus sciuri (17.7%). All other parasites are European or cosmopolitan species with prevalence below 5%. S. robustus abundance is positively affected by host density and body mass, C. sciurorum abundance increases with host density and varies with seasons. Overall, we show that grey squirrels in Italy may benefit of an enemy release, and both spillback and spillover processes towards native red squirrels may occur.

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