Living on the edge: Space use of Eurasian red squirrels in marginal high-elevation habitat.

In marginal habitats located at the edge of a species\u2019 range, environmental conditions are frequently extreme and individuals may be subject to different selective pressures compared to central populations. These so-called edge or marginal populations tend to have lower densities and reproductive rates than populations located in more suitable habitats, but little is known about local adaptations in spacing behavior. We studied space use and social organization in a population of Eurasian red squirrels (Sciurus vulgaris) in a high-elevation marginal habitat of dwarf mountain pine (Pinus mugo) and compared it with spacing patterns in high-quality Scots pine (Pinus sylvestris) forest at lower-elevation. Home ranges and core areas were larger in the marginal habitat. In both habitats, males used larger home ranges than females, but sex differences in core area size were significant only in the edge population. Patterns of core area overlap were similar in both habitats with intra-sexual territoriality among adult females and higher degrees of inter-sexual overlap, typical for the species throughout its range. However, low densities in the edge population resulted in higher female by males overlap in spring-summer, suggesting males increased home ranges and core areas during mating season to augment access to estrus females. Thus, in the marginal habitat, with low food abundance and low population densities, linked with extreme winter conditions, squirrels, especially males, used large home ranges. Finally, squirrels responded more strongly to variation in food availability (inverse relation between home range size and seed abundance), and even to fluctuations in density (inverse relation between core area size and density of animals of the same sex), in the marginal than in the high-quality habitat, suggesting high behavioral plasticity to respond to the ecological constraints in marginal habitats

Nutcrackers become choosy seed harvesters in a mast-crop year.

As an efficient seed-disperser, Eurasian nutcrackers (Nucifraga caryocatactes) generally consume and hoard mature, edible pine seeds for future use. In 2009, when the Arolla pine, Pinus. cembra, produced a mast-crop, we investigated cones discarded by nutcrackers. Most cones were only partly eaten and some mature seeds remained in the distal part. This was in contrast to years of lower seed production when nearly all seeds were harvested from the majority of cones. To determine whether nutcracker cone-discarding behaviour maximised intake rate, seed kernels and the aborted seeds rate were measured from the different cone parts. In 2009, seeds from cone-tops were on average 17% lighter than in the base and middle sections, and the proportion of aborted seeds in the top part was 81% higher than in the other sections. There was no difference in seed mass and proportion of aborted seeds in cone-tops of intact cones and cones handled by nutcrackers. Regarding each cone as a patch, cone discarding behaviour can be considered as an optimal cone-leaving rule, maximising rate of energy-intake, supporting the Marginal Value Theorem. Hence, we suggest that increased food abundance leads to more selective seed harvesting in nutcrackers

Estimating offspring production using capture-mark-recapture and genetic methods in red squirrels.

Reproductive rate is a key demographic parameter of life history and population ecology. In traditional population-ecology studies of small mammals, this and other vital rates are inferred from capture-mark-recapture (CMR) data. However, CMR assumes that immigrants at first capture can be distinguished from unmarked locally born offspring, an assumption not always met. We verified CMR estimates of locally born red squirrel (Sciurus vulgaris) offspring as a measure of reproductive rate, with candidate offspring (CO)\u2013candidate parent (mothers, CPs) assignment by CERVUS, using ten DNA microsatellite loci. Seventytwo of 122 candidate offspring (59%) were assigned to 52 of 125 CPs in six populations. Estimates of mean litter size were 1.5 young (range 1\u20133). The 50 CO (41%) not assigned to a reproducing female in the study site were considered immigrants. Parentage assignment also provided evidence of dispersal between two of our sites. Overall, CMR and CERVUS agreed in 77% of cases. Considering only the 55 juveniles determined as locally born by CMR, 50 (91%) were also assigned as local offspring with CERVUS. The main discrepancy between the two methods was that 22 subadult squirrels classified immigrants by CMR, were assigned by CERVUS to females which had reproduced in our sites. It is concluded that although in our study system agreement between CMR and CERVUS in determining local offspring was high, using genetic parentage assignment helped to correctly classify some subadults, considered immigrants by CMR, as locally born. Hence, in largescale demographic studies, combining CMR with parentage assignment will allow more precise estimates of reproduction and dispersal

The strong and the hungry: Bias in capture methods for mountain hares (Lepus timidus).

Estimating density, age and sex structure of wild populations is a key objective in wildlife management. Live trapping is frequently used to collect data on populations of small and medium-sized mammals. Ideally, sampling mammal populations by live capturing of individuals provides a random and representative sample of the target population. Trapping data may, however, be biased. We used live-capture data from mountain hares Lepus timidus in Scotland to assess sampling bias between two different capture methods.Wecaptured hares using baited cage traps and long nets on five study areas in the Scottish Highlands. After controlling for the effects of body size, individuals caught in traps were lighter than individuals caught using long nets, suggesting that the body condition of hares differed between the capture methods. This tendency may reflect an increased risk-taking of individuals in poorer body condition and less aversion to entering traps in order to benefit from eating bait. Overall, we caught more adult hares than juveniles and more female hares than males. Our results show that estimates of density and population structure of mountain hares using livecapture data could be affected by the capture method used. We suggest that live-capture studies employ more than one capture method and test for heterogeneity in capture probability to minimise potential bias and achieve reliable estimates of population parameters

Record litter size in the eurasian red squirrel (Sciurus vulgaris)

In the literature, litter size in red squirrels Sciurus vulgaris ranges between 1-6 offspring. Here we report a record litter size, in Europe, of 7 young (6 males, 1 female), marked in the nest when 10-14 days old, in a high-elevation mountain pine habitat, Lombardy Alps (Northern Italy). We discuss implications of extreme winter conditions for lifehistory strategies and possible trade-offs between high reproductive investment and short life-spa

Disease, invasions and conservation : no evidence of squirrelpox virus in grey squirrels introduced to Italy

Native red squirrels Sciurus vulgaris in Great Britain and Ireland are threatened by alien grey squirrels S. carolinensis through exploitation competition and spillover of squirrelpox virus (SQPV). By accelerating the replacement of red squirrels by the invader, SQPV represents a fundamental factor to consider when planning management and conservation strategies. In mainland Europe, grey squirrels introduced to Italy threaten the survival of the whole continental red squirrel population, but no extensive surveys for SQPV presence have been carried out in the region. We therefore investigated SQPV infection in north Italian grey squirrel populations through a combination of serological and molecular methods. Firstly, we analysed sera from 285 individuals through an enzyme\u2010linked immunosorbent assay (ELISA) to detect antibodies against SQPV. Secondly, a PCR designed to amplify a segment of the G8R SQPV gene was carried out on DNA extracted from swabs and skin tissue samples from a second set of 66 grey squirrels. ELISA tests identified four reactors (1.4%), but the subsequent PCR survey did not detect any SQPV DNA. Based on the low prevalence observed and on PCR results, we believe that the four suspected positives were the result of an ELISA cross\u2010reaction following exposure to another pox virus. Considering sample size and performances of the two methods, confidence of freedom from SQPV resulted above 99.9%. However, because of the severe impact of SQPV on red squirrels, we recommend the implementation of a passive surveillance plan for the early detection of an SQPV emergence in continental Europe

Home range dynamics of mountain hares (Lepus timidus) in the Swiss Alps.

Little is known on the ecology and behaviour of the alpine mountain hare (Lepus timidus). Between 1996 and 1997, we analysed by radiotracking the pattern of space use of 8 mountain hares from the Swiss Alps. We estimated home range size using both the kernel density estimator and the minimum convex polygon. We found smaller ranges (38 ha) compared to those reported for the species in boreal or arctic habitats, but similar to ranges in Scotland. Hares did not use a centre of major activity (core area) and showed high home range overlap, confirming their non-territorial behaviour. Smaller ranges were used during winter compared to the other seasons, whilst no difference in size was found between sexes

Parasites and biological invasions : do helminths play a role in facilitating grey squirrel (Sciurus carolinensis) settlement and in its competition with native red squirrel (Sciurus vulgaris)?

AIM: Several studies have shown that parasites can play an important role in biological invasions (Dunn AM, 2009, Adv Parasitol, 68: 161-184), mainly via two different processes. First, during the invasion process, alien species often lose part of their parasite community with a positive impact on their population growth and consequently on their settlement and spread (\u201cparasite release hypothesis", Torchin ME et al 2003, Nature, 421: 628-630). Second, parasites may mediate the impact of invasive species on native taxa ("parasite-mediated competition", Hudson P and Greenman J, 1998, Trends Ecol Evol, 13:387-390), introducing in the environment novel parasites to which native species are more susceptible or increasing the abundances of local parasite acting as additional reservoir (Tompkins DM, 2001 Parasitology, 1999: 187-193). Since 1948, the Eastern grey squirrel (Sciurus carolinensis), a North-American alien species, has been repeatedly introduced in Italy, causing local extinction of the native Eurasian red squirrel (Sciurus vulgaris), mainly through exploitation competition for food (Martinoli A et al, 2010, Hystrix It J Mamm, 21: 127-136). Our purpose is to explore gastro-intestinal helminth communities of grey and red squirrels in Italy in order to investigate the role of parasites in the settlement of the alien species and in its interaction with native one. In particular, we want to test two independent hypothesis: the parasite release and the parasite-mediated competition MATERIAL AND METHODS: We have sampled 8 populations (4 grey-only, 3 red-only and 1 red-grey area) in Piedmont and Lombardy by capturing both species with standard live-trapping techniques. Grey squirrels were euthanized immediately after capture, while red squirrels were marked and released after samples collection. Grey squirrels were then dissected and their intestinal content examined using standard parasitological techniques. For red squirrels, we performed coprological analysis and tape tests to obtain indirect information on their gastro-intestinal parasites. To provide a check-list of red squirrel parasites, we also dissected several roadkills collected from different sites in Northern Italy. RESULTS: We dissected 142 grey squirrels in which we identified four different species of gastro-intestinal nematodes: Strongyloides robustus, Trichostrongylus calcaratus, Trichuris muris and Aonchotheca annulosa (prevalence: 74%, 13%, 6% and 2%, respectively). The species richness we observed is lower compared to what is reported for grey squirrel in their native range (Raush R and Tiner JD, 1948, Am Midl Nat, 39: 728-747). S. robustus is a parasite common and abundant in North-American squirrels (Bartlett CM, 1995, Folia Parasit, 42:102-114), but never recorded in Europe until now, thus likely brought here by grey squirrels during the invasion process. On the contrary, T. calcaratus, T. muris and A. annulosa should be considered as non-specific or accidental species, the latter two acquired by the grey squirrel here in Europe. As regards red squirrels, coprological analysis, tape tests and 26 roadkills collected in red-only areas have shown the presence of only one nematode, Rodentoxyuris sciuri (prevalence: 96%), typical of this species and already recorded in red squirrels in Europe (Hugot JP et al, 1996, Int J Parasitol, 26: 147-149). On the other hand, in red-grey areas, coprological analysis and roadkills examination have shown the presence of S. robustus in red squirrels, suggesting parasite transmission from the grey squirrel to the native species. CONCLUSION: Our results lend support to the parasite release hypothesis, as grey squirrels in Italy are missing several helminths species usually present in North-America. Moreover, the lack of species-specific parasites is suggested by the presence of some accidental species, probably exploiting vacant niches. Concerning parasite-mediated competition, we found that S. robustus can be transmitted to the red squirrel, but so far we haven't found any evidence of helminths spillover from red to grey squirrel. To confirm that S. robustus actually plays a role in grey squirrel impact on the native species, further investigation on the pathogenic effect of this nematode on red squirrels is needed

Estimating and comparing food availability for tree-seed predators in typical pulsed-resource systems: alpine conifer forests.

Alpine conifers produce pulsed resources for the community of tree-seed consumers. Here, we describe field and statistical methods to estimate spatio-temporal variation in seed-crops in forests with different species composition. Annual and between-site variation in seed production was high and characterised by occurrence of mast-crops followed by seed-crop failure the following year. Seed-crops of different species did not fluctuate in parallel. Please see also: Plant Biosystem 143(3), Page 643 for Corrigendu