SquirrelWeb

Goedele Verbeyen

Investigation of the Asian Chipmunk (Eutamias sibiricus Laxmann 1769) in De Panne (Belgium)

The Asian chipmunk is being imported in Belgium as a pet since the beginning of the sixties. Now there are four free-living populations in Belgium, one in the Zoniënwoud (Brussels, estimated at 18.000 individuals in 2000!), one in Westerlo, one in a Castle park in Zwijnaarde and the one from this study in the Calmeynbos in De Panne. About 20 years ago, 17 animals were released in the Calmeynbos by the amusement park Meli. In their original distribution area these animals can, at high densities, cause a lot of damage to agricultural fields. In the Zoniënwoud a negative influence on some ground breeding birds is indicated. Because of the danger of negative consequences on the ecological system due to increasing population pressure, preventive measures have been suggested. There is the need of a more specific study of the interaction of the chipmunks with the forestal ecological system. At first step taken in this direction is this study, conducted in fall 1998, 1999 and 2000 in De Panne.

The aim of this project is to estimate chipmunk numbers and distribution and to look at their behaviour (especially feeding habits). The study includes two parts : (1) an estimation of the population density based on the transect method in the whole study area and (2) a more accurate estimation of the population density based on capture-mark-recapture data in part of the study area.

The chipmunks preferred the forested area but in years with high densities they spread out in the surrounding gardens and dunes. Estimates were about 350 chipmunks in 1998, 160 in 1999 and 70 in 2000, so there seems to be a decrease in population size. The low number of chipmunks left in 2000 were concentrated in the part of the forest with the most food. The forest is divided by a road, with remarkable differences in sex ratio between both sides: at one side, with a low chipmunk density, sex ratio was about 1:1, while at the other side, with much higher densities, there were about 4 females for 1 male.

Acqui Terme (Alessandria), Italy, 11th to 13th September 2001

Organised and hosted by Professor Italo Currado, Peter J. Mazzoglio and Sandro Bertolino (University of Turin)

Two hours south of Turin is the city of Acqui Terme, which is famous for its thermal spas and its castle that dates back to the 13th Century.

The workshop was opened by the Mayor of Acqui Terme and was filmed by a local TV Station. Approximately 40 people attended, with researchers from Spain, Portugal, the U.K., Belgium and Italy.

11th September 2001 The main topic for the talks presented on the first day was the population dynamics and effects of fragmentation on the European red squirrel (Sciurus vulgaris), and the behavioural ecology of the variable squirrel (Callosciurus finlaysonii), an introduced species from Asia. At the close of the day, delegates visited the Castle and its park containing a resident group of =14 Variable squirrels. These squirrels change colour as they age, from brown?headed individuals to white. The tip of the tail also whitens. Colour is believed to indicate the squirrels position with a dominance hierarchy. An enjoyable evening meal was had by all in one of the local restaurants.

12th September 2001. The second day of the workshop was spent at the Royal Castle of Racconigi, in Racconigi (Cuneo). The main topic of the day was the behaviour patterns and population dynamics of the European red squirrel in different habitats. After the morning session a trip was planned to visit either the Royal Castle or the Royal Park of Racconigi. The Royal Park has a resident population of grey squirrels (“Scoiattolo grigi”) which may number about 400 individuals at present. In the evening an excellent workshop dinner was held in a wine cellar in Acqui Terme. The dinner was prepared and cooked by catering students at the University.

13th September 2001 Representatives from the State Forestry Service were present at the last day of the Workshop’s proceedings in Acqui Terme. The morning talks centred on red squirrel conservation in the presence of grey squirrels and increasing the habitat suitability for reds. Prior to lunch Peter Mazzoglio’s presentation on the predicted numbers of grey squirrels in Genoa, Italy and the potential for spread into the hills around the city, opened up the main topic for the afternoon session on Alien species and the effects on the native red squirrel. Luc Wauters outlined the possible mechanisms of replacement of the red by the grey squirrels based on studies in Italy and the UK.

The afternoon session, entitled Management of the grey squirrel in U.K. and Italy and the conservati on of the red squirrel, was chaired by Mick Clout, Chair of the IUCN Invasive Species Specialist Group based at Auckland University, New Zealand. Mick talked about invasive species in New Zealand (including rats and the Brush tailed possum) and the effects on native flora and fauna. The tactics used to eradicate or contain these species was also presented. John Gurnell, Peter Lurz and Brenda Mayle gave presentations based mainly on red and grey squirrel studies in Britain, including the use of models as tools and possible ways of controlling grey squirrels. The grey squirrel situation in Italy was then introduced by Piero Genovesi along with plans for eradicating the population or managing red and grey squirrels should eradication proof intractable. Towards the end of the session, representatives from the National and Regional Park Services, the Regional Environmental Department and the Regional Wildlife Service presented talks. It was announced that the 7th European Workshop would be combined with the 3rd International Colloquium on the Ecology of Tree Squirrels to be held at the University of Newcastle upon Tyne in the UK in 2003. Delegates were reluctant to end the meeting after a very interesting and enjoyable workshop, and retired in groups to bars and restaurants to continue their discussions late into the evening.

Many thanks go to the organizers for hosting the Workshop and for their very kind hospitality.

Amanda Lloyd,
October 2001

For further details and pictures, go to www.agraria.unito.it/dip/divapr/wr.

Sandro Bertolino

The grey squirrel in Italy: species expansion and threats for neighbouring countries

Origin and spread of the grey squirrel in Italy

The grey squirrel was introduced into Piedmont (north-western Italy) in 1948, when two pairs were released at Stupinigi (province of Turin) (Bertolino et al., 2000). In 1966, 5 animals imported from Norfolk (Virginia, USA) were released into the park of Villa Groppallo at Genoa Nervi. The Piedmont population has shown a rapid increase of its range in the last decades. From their introduction until 1970 the grey squirrel was recorded only close to the release site, occupying an area of about 25 Km2 (Wauters et al., 1997). Subsequently, the species started to spread into the surrounding area: in 1990 the species’ range arrived to 243 Km2, in 1997 to 380 Km2. After 1997 the range showed a dramatic increase, and in 1999 the grey squirrel was present in an area of 880 Km2 (Wauters et al., 1997; Bertolino and Genovesi, submitted).

Competition with red squirrel and damage

The grey squirrel was introduced into Great Britain and Ireland several times from the end of the last century, causing the progressive disappearance of the native red squirrel from a wide portion of the two islands (Reynolds 1985, Gurnell and Pepper 1993), and severe damage to forests and commercial tree plantations (Rowe and Gill 1985, Dagnall et al. 1998). Bark-stripping activity inflicts wounds that severely degrade timber quality and can facilitate the penetration of insects and fungi (Kenward 1989). It is remarkable that gray squirrel produces little damage to tree in its native area in north America (Kenward 1989). Italian data confirm the competitive exclusion of the red squirrel from the grey squirrel range. A distribution survey in the area where grey squirrels are present, showed a reduction of 46% in the range of the red squirrel from 1970 to 1990, and a further decrease of 55% from 1990 to 1996 (Wauters et al. 1997a).

Eradication proposal and failure of the project

In respect to the urgency of remove the grey squirrel from Italy, in 1997 the NWI (National Wildlife Institute), in co-operation with the University of Turin, produced an action plan finalised to the eradication of the alien species. One of the first steps of the plan was the experimental removal of the small population present in the Racconigi park, in order to produce a pilot eradication scheme. The trial eradication started in May 1997, and the preliminary results were very encouraging, but some animal right groups took the NWI to court, managing to halt the project. In July 2000 the Appeal Court of Turin discharged the two officers.

Outcomes

The three years legal struggle determined the failure of the campaign. Since then, as a consequence of the suspension of the eradication campaign, the species has significantly expanded its range and nowadays the complete eradication is considered not feasible anymore (Genovesi and Bertolino 2000). In fact, the range of the grey squirrel has reached the continous wood belt of the Alps, and of the hilly system of the eastern Piedmont. The dramatic expansion of the species’ range in the last two years, and the homogeneous and continuous broadleaf woodlands characterising the Alpine region, make a colonisation of the entire alpine arch in a few years very probable. Such pessimistic prediction is also supported by the results of a model developed by Lurz et al. (submitted), that predicts that grey squirrel spread is likely to speed up once they are in the pre-alpine forest due to reduced fragmentation, and indicate two possible scenarios, with the greys across Alps and in France in 30-50 years. The NWI to produce a strategy for the control of the Grey squirrel, and after an assessment of the range expansion, the NWI proposed a strategy aimed to: 1) identify and protect key areas for the conservation of viable populations of red squirrels, 2) contain the grey squirrel in order to delay its expansion to neighbouring countries and to the mountain system of Italy (Genovesi and Bertolino 2000).

Threats to other countries

The grey squirrel has colonised in Italy a mean of 17.2 Km2 per year, similarly to the values reported for Great Britain (18 Km2/year, Okubo et al., 1989). The colonisation of new areas has not been constant since 1970, ranging from 1.1 Km2/year in the first phase, when the spread outside the wooded area of Stupinigi was hindered by the presence of extended cultivated fields with a very reduced and fragmented woods, to 10-20 Km2/year, once the species started spreading along the rivers, and recently increased to 250 Km2/year, when the grey squirrel reached the hilly areas of eastern Piedmont and the Po river (Bertolino & Genovesi, submitted). Considering these data and the model developed by Lurz et al. (submitted), a scenario with the grey squirrel through the Alps and in France in the next decades is likely.

References

• Bertolino, S., Currado, I., Mazzoglio, P.J., Amori, G., 2000. Native and alien squirrels in Italy. Hystrix Italian Journal of Mammalogy (n.s.) 11 (2), 49-58 .
• Bertolino, S. and P. Genovesi (submitted). Eradication of the grey squirrel (Sciurus carolinensis) from Italy: failure of the project and consequences for red squirrel (Sciurus vulgaris) conservation in Eurasia
• Dagnall, J., Gurnell, J., Pepper, H., 1998. Bark-stripping by gray squirrels in state forests of the United Kingdom: a review.
  In: Steele, M.A., Merritt, J.F., Zegers, D.A., (Ed). Ecology and Evolutionary Biology of Tree Squirrels. Virginia Museum of Natural History, Special Publication, n. 6, 249-261.
• Genovesi, P., Bertolino, S., 2000. Piano di Azione Nazionale per il controllo dello Scoiattolo grigio (Scirus carolinensis). Ministero dell’Ambiente, Servizio Conservazione della natura, pp. 31.
• Gurnell, J., Pepper, H., 1993. A critical look at conserving the British red squirrel Sciurus vulgaris. Mamm. Rev. 23, 125-136.
• Kenward, R. E., 1989. Bark-stripping by grey squirrels in Britain and North America: why does the damage differ? In: Putman, R.J., (Ed), Mammals as Pests. Chapman and Hall, pp. 144-154.
• Lurz P.W.W., Rushton S.P., Wauters L.A., Bertolino S., Currado I. , Mazzoglio P.J, (submitted). Predicting grey squirrel expansion in North Italy: a spatially explicit modelling approach.
• Okubo, A., Maini, P.K., Williamson, M.H., Murray, J.D., 1989. On the spatial spread of the grey squirrel in Britain. Proocedings of the Royal Society of London B 238, 113-125.
• Reynolds, J.C., 1985. Details of the geographic replacement of the red squirrel (Sciurus vulgaris) by the grey squirrel (Sciurus carolinensis) in eastern England. J. Anim. Ecology 54, 149-162.
• Rowe, J.J., Gill, M.A., 1985. The susceptibility of tree species to bark-stripping damage by grey squirrels (Sciurus carolinensis) in England and Wales. Quaterly Journal of Forestry 79, 183-190.
• Wauters, L.A., Currado, I., Mazzoglio, P.J., Gurnell, J., 1997. Replacement of red squirrels by introduced grey squirrels in Italy. In: Gurnell, J., Lurz, P., (Ed), The Conservation of Red Squirrels, Sciurus vulgaris L. People Trust for Endangered Species, pp. 79-88.