Sandro Bertolino

Spread and attempted eradication of the grey squirrel (Sciurus carolinensis) in Italy, and consequences for the red squirrel (Sciurus vulgaris) in Eurasia

In 1997, the National Wildlife Institute, in co-operation with the University of Turin, produced an action plan to eradicate the American grey squirrel from Italy, as this introduced species replaces the native red squirrel through competitive exclusion and damages trees through de-barking. The first step, a trial eradication of a small population of grey squirrels at Racconigi (Turin) to evaluate the efficiency of the removal techniques, started in May 1997. Preliminary results showed that eradication was feasible, but the project was opposed by radical animal rights groups which took the National Wildlife Institute to court in June 1997. This legal action caused a suspension of the project and led to a lengthy judicial enquiry that ended in July 2000 with the acquittal of the Institute. Nevertheless, the 3-year suspension of all actions led to a significant expansion of the grey squirrels range and thus eradication is no longer considered practical. Therefore, in the medium to long term, grey squirrels are likely to expand through continental Eurasia. This constitutes a major threat to the survival of the red squirrel over a large portion of its distribution range and will have a significant impact on forests, with economic damage to timber crops.

Animal xenodiversity in Italian inland waters: distribution, modes of arrival, and pathways

The paper provides a list of the non-indigenous animal species occurring today in Italian inland waters. Xenodiversity was found to amount to 112 species (64 invertebrates and 48 vertebrates), which contribute for about 2% to the inland-water fauna in Italy. Northern and central regions are most affected, and Asia, North America, and the rest of Europe are the main donor continents. The large majority of non-indigenous species entered Italy as a direct or indirect effect of human intervention. A difference between invertebrates and vertebrates was found for their mode of arrival (unintentional for invertebrates and intentional for vertebrates). Accidental transport, in association with both fish (for aquaculture or stock enhancement) and crops, has been the main vector of invertebrate introductions, whereas vertebrates were mostly released for stocking purposes. Overall stock enhancement (47.92%) and culture (37.5%) prevailed over the other pathways. Seventeen and 7 species of our list are included among the 100 worst invasive species of Europe (DAISIE) and of the world (IUCN), respectively. For some (but not all) non-indigenous species recorded in Italy the multilevel impact exerted on the recipient communities and ecosystems is known, even if rarely quantified, but knowledge on their chronic impact is still missing. Additional research is needed to provide criteria for prioritizing intervention against well established invaders and identify which new potential invader should be targeted as “unwanted”.

The Use of Climatic Niches in Screening Procedures for Introduced Species to Evaluate Risk of Spread: A Case with the American Eastern Grey Squirrel

Species introduction represents one of the most serious threats for biodiversity. The realized climatic niche of an invasive species can be used to predict its potential distribution in new areas, providing a basis for screening procedures in the compilation of black and white lists to prevent new introductions. We tested this assertion by modeling the realized climatic niche of the Eastern grey squirrel Sciurus carolinensis. Maxent was used to develop three models: one considering only records from the native range (NRM), a second including records from native and invasive range (NIRM), a third calibrated with invasive occurrences and projected in the native range (RCM). Niche conservatism was tested considering both a niche equivalency and a niche similarity test. NRM failed to predict suitable parts of the currently invaded range in Europe, while RCM underestimated the suitability in the native range. NIRM accurately predicted both the native and invasive range. The niche equivalency hypothesis was rejected due to a significant difference between the grey squirrel’s niche in native and invasive ranges. The niche similarity test yielded no significant results. Our analyses support the hypothesis of a shift in the species’ climatic niche in the area of introductions. Species Distribution Models (SDMs) appear to be a useful tool in the compilation of black lists, allowing identifying areas vulnerable to invasions. We advise caution in the use of SDMs based only on the native range of a species for the compilation of white lists for other geographic areas, due to the significant risk of underestimating its potential invasive range.

Population control of coypu Myocastor coypus in Italy compared to eradication in UK: a cost-benefit analysis

Abstract Invasive alien species rank among the worlds greatest threats to biodiversity and cause huge economic losses. Eradication is a key management strategy for newly introduced pests, but it is frequently discarded due to the high costs. When populations become established and conflicts increase, policy-makers often resort to permanent population control. However, no cost-benefit analyses have been carried out so far to compare the two alternatives. We present the first cost-benefit analysis by comparing the permanent control campaign of coypu Myocastor coypus in Italy with the successful eradication carried out in UK in the 1980s. Data regarding the eradication came from literature, while costs and benefits of control were quantified through a national survey. In Italy, during 1995-2000, the damage amounted to € 11,631,721, control activities cost € 2,614,408, and 220,688 coypu were removed. Control campaigns did not stop the population expansion nor the increase in damage and economic losses at a national scale. However, the efficacy of local campaigns varied among different ecosystems. According to our predictions, the Italian coypu range may expand 2.5-3.3 times, and economic losses may reach € 9-12 millions/year. A comparison between the costs of the successful eradication carried out in East Anglia (€ five million over 11 years) and the permanent control campaign in Italy (€ 14 million over only six years) shows that even very costly eradications, if successful, may have a very positive cost-benefit ratio in the long term.

Prevalence of coccidia parasites (Protozoa) in red squirrels ( Sciurus vulgaris): effects of host phenotype and environmental factors

We investigated the relative importance of environmental factors versus host phenotype in determining parasite prevalence in Eurasian red squirrels ( Sciurus vulgaris). One hundred and forty-three fecal samples of 116 different squirrels collected in 2000 and 2001 from five study areas in the Italian Alps, were examined for intestinal protozoans. Two species of Eimeria were present with a medium to high prevalence in both years and in all areas, while two other species were rare, occurring only in some areas and not in all years. Cryptosporidium parvum had a high prevalence in the two study areas of the Western Alps, while in the three areas of the Central Alps it was recorded only once. The prevalence of Eimeria sciurorum and C. parvum fluctuated in parallel with squirrel density, suggesting a possible correlation between the presence of these protozoans and host density. A gender effect on E. sciurorum prevalence at low density could be explained by different space use patterns and social organization of males and females. C. parvum occurred more frequently in young squirrels, suggesting an acquired immunity in adults, but age-related susceptibility was not found for eimerian species. The coccidian community was more similar within than between regions, and study area and year were key parameters in predicting coccidia infection. There was no evidence of competition between coccidian species, but one positive interaction between E. sciurorum and E. andrewsi was observed. Our results suggest that the effects of geographic region, area features, and year effects probably related to fluctuations in host population density, were more important than individual phenotypic host characteristics in structuring the coccidian assemblage and determining levels of parasite prevalence in red squirrel populations.

Effectiveness of coypu control in small Italian wetland areas

Abstract Introduced coypu (Myocastor coypus) damage crops and natural vegetation and undermine riverbanks. We controlled coypu with cage traps to protect vegetation in 3 wetlands in the Park of the Rivers Po and Orba (northwestern Italy). During a 3-year trial, coypu were controlled in the Natural Reserve of Valenza (NRV), an area with a low degree of colonization, but not in one with a high immigration rate. In NRV park wardens were involved for 18 man-days of work annually, and the cost was 1,518 Euros (1,867 U.S. dollars) per year. From 2001 a control program was carried on in the 3 areas. Removal densities (0.06–1.3 animal/ha) suggested that 2 trapping periods annually were adequate to slow down coypu population increase. The recovery of yellow waterlily (Nuphar lutea) in 3 plots and colonization of new ponds by vegetation indicated that coypu were maintained at a level sustainable for vegetation development.

Is coat-colour polymorphism in Eurasian red squirrels (Sciurus vulgaris L.) adaptive?

Coat-colour polymorphism, the relative frequencies of red, brown and black fur-morphs, was examined in nine populations of the Eurasian red squirrel (Sciurus vulgaris L.) in northern Italy. The proportions of the three different coat-colours differed between populations. Red morphs were most common in mixed woodlands of the Upper Po-plain, but rare in populations from the Alps. The highest frequencies of black morphs were found in subalpine conifer forests in the western Alps (Gran Paradiso) and in montane mixed conifer forests in the central Alps (Valtellina). Coat-colour did not affect juvenile survival, and there were no significant differences in mean foot length or body mass among subadults and adults of different colour-morphs. However, inter-population variation in the frequency of black morphs was positively correlated with the proportion of spruce (and/or fir) in the forest and with the density of trees. We suggest that the combination of a denser and more cryptic fur in black morphs gives them a selective advantage over other coat colour morphs in wet, dense spruce-fir forests of the Italian Alps, which could explain the within- and between population variation in the relative frequencies of coat colour phenotypes observed in this study.

ACTIVITY BUDGET AND FORAGING BEHAVIOR OF INTRODUCED CALLOSCIURUS FINLAYSONII (RODENTIA, SCIURIDAE) IN ITALY

Abstract We studied seasonal activity patterns and feeding behavior of a population of Finlaysons squirrel (Callosciurus finlaysonii) native to Indochina and introduced into Italy. Squirrels spent the majority of active time foraging, switching between resources according to availability. In winter, they fed mainly on buds or stripped bark, shifting to flowers when plants bloomed in spring, and to mature seeds and fruits from June to October. By November–December, bark-stripping became progressively more important. This activity accounted for 36.5% of the yearly feeding time. The flexibility to exploit a wide range of foods, the ability to change food habits throughout the year, and hoarding behavior are factors that could indicate a proclivity to use different habitats successfully.

Population dynamics, breeding patterns and spatial use of the garden dormouse ( Eliomys quercinus ) in an Alpine habitat

Population dynamics, breeding patterns and spatial use of the garden dormouse Eliomys quercinus were studied for 3 years in a larch woodland in the Alps. Animals were caught with live-traps, once a month from May to September, and marked with transponder tags. Population density ranged from a minimum of 8.3 individuals/10 ha to a maximum of 49.4 individuals/10 ha when juveniles became trappable. The activity season of the garden dormouse lasts 5 months and allows the animals to reproduce only once a year. Birth rates fell between the middle of June and the middle of August. The dormouse population was characterized by high stability and adults continued to live in the same area from year to year. The main factor limiting the survival of individuals was winter mortality. Survival on the trapping grid through hibernation was 36–50% for adults and c. 32% for juveniles. During the mating season, males and females were aggregated and overlapped their ranges, and after the mating season, they spread out. The tendency of the reproductive females to have separate non-overlapping ranges is indicative of a probable territorial behaviour in females during gestation and lactation.

Semiaquatic mammals introduced into Italy: case studies in biological invasion

Several semiaquatic mammal species introduced into European freshwater ecosystems are very successful colonizers and rapid invaders. There are four species established in the regional wetlands: the coypu (Myocastor coypus Molina), the muskrat (Ondatra zibethicus Linnaeus), the American mink (Mustela vison Schreber), and the Canadian beaver (Castor canadensis Kuhl). These species were imported into Europe to be farmed or were intentionally released into the wild with the aim of harvesting their furs. The Canadian beaver was erroneously released in Finland in an attempt to recover the extinct population of European beavers exterminated by overhunting in the 19th century (Nummi 1996). Three of them (coypu, muskrat, and mink) are present in Italy with a different status and pose different and complex challenges for preventing further introductions, eradicating key populations, and mitigating the impact of the populations already established in the wild. The principles of a national strategy on the non-indigenous semiaquatic species in Italy could thus provide examples for addressing other species and countries.