The SquirrelWeb team wish you all a very happy and prosperous 2007. Please let us know about squirrel research being undertaken, update reports on current research, useful equipment and contacts, publications and any other items of general interest. Thank you.
It’s easy to make the right choices in a world that is predictable. For example we plan our holidays around average weather patterns and work schedules. Similarly, animals in the wild, time reproduction to match seasonal increases in food supply. However, if the world is unpredictable, making the right choice is far more difficult. That’s why only a small percentage of investors do well in the stock market.
There are a number of ecosystems that are characterized by highly unpredictable swings in the production of resources. A good example of this is the production of seed by trees in a region. Trees display a phenomenon known as “œmasting” whereby all of the trees in large regions synchronize the production of seed so in a given year trees either produce massive amounts of seed or no seed at all. This is actually an evolutionary strategy by the trees to thwart the animals that eat the trees’ seed. In “bust†years the trees try to starve their seed predators so that in “boom†years there are few seed eaters around and they are swamped by all of the seed available. The seed predators cannot respond in time to the increased production because they cannot predict when it is going to occur. The net result is that more seed escapes to germinate in a mast year as compared to a strategy where the trees produce a constant amount of seed each year.
In this scenario, the seed predators are at the mercy of the trees and they are reduced to simply tracking the resources after they come available. Enter two species of seed predators, the American and Eurasian red squirrels. Our long-term studies (15-20 years) of these species (who forage on the seeds of spruce, pine, oak, and beech trees) indicate that the squirrels are beating the trees at their own game. We found that the squirrels appear to be capable of predicting when a big mast crop is about to be produced by the trees and in anticipation of this, they produce more offspring in the form of an additional litter. So… rather than having to wait for the extra seed to be produced and available for consumption, the squirrels produce more young well before the seed is ready to eat but at a time when the youngsters, once they are weaned, can take full advantage of extremely abundant seeds. The net result is that the squirrels have the maximum number of mouths available to consume the mast crop and in so doing, thwart the trees’ swamp and starve strategy.
The squirrels have had to overcome two obstacles to counter the trees’ strategy. First, they need a reliable cue to predict the upcoming seed crop. Although we do not know what this cue is as yet, we suspect it is tied to the buds which turn into the structures that harbour the future seed (cones for spruce trees, nuts for oak and beech).
The more difficult obstacle to overcome is that the squirrels need to produce the second litter of pups at a time when environmental conditions are very tough; there are no additional resources available to pump into more offspring because the trees have been producing very little seed before the mast year. In this case the squirrels appear to invest in extra offspring not when they can (after seed is available) but when it makes sense evolutionarily (before seed is available but in time for their offspring to benefit). In other words, just as with the trees, natural selection has favored a strategy in the squirrels that leads to more offspring surviving over time. In essence, the squirrels are beating the trees at their own game.
This story is analogous to a family living from paycheck to pay check and facing decisions about how much to spend on the kids’ Christmas gifts. Add to this is the dilemma that the paycheck varies a lot from one month to the next. The tendency in this situation is for the parents to invest only as much as they can spare which would be relatively little if previous months had been tough. However, if the parents could reliably predict that the upcoming paycheck was going to be a big one, they might be willing to “break the bank†to have a good Christmas and the parents can rest easy because they know that there will be money coming in soon. This is what red squirrel mothers are doing but rather than buying presents, they are making more babies.
Stan Boutin
Department of Biological Sciences
University of Alberta
Edmonton T6G 2E9
Canada
Luc Wauters
Department Environment-Health-Safety
University of Insubria, Varese
Italy
See: Boutin, S., Wauters, L., McAdam, A., Humphries, M., Tosi, G., & Dhondt, A. (2006) Anticipatory Reproduction and Population Growth in Seed Predators. Science, 314, 1928 – 1930. Listed on thePublications web page.
The presence of alien North American grey squirrels is of extreme concern and could have potentially devasting impacts on native Eurasian red squirrels and woodland ecosyetms in central and southern Europe – see the Aliens and Current and Recent Projects web pages. A study on a recently discovered population of grey squirrels in Ticino Park, Lombardy (N Italy) has demonstrated the risk of spread of grey squirrels throughout north-central Italy and into the southern parts of Switzerland. However, population simulations suggest that eradication of the grey squirrel is still possible if an appropriate eradication strategy is put into place immediately. To this end the authors suggest that a scheme to monitor the distribution of red and grey squirrels involving the public will help to increase public awareness of the problem in the region. They conclude that the successful containment of further grey squirrel spread will require co-operation between Italian and Swiss wildlife authorities.
See: Tattoni, C., Preatoni, D., Lurz, P., Rushton, S., Tosi, G., Bertolino, S., Martinoli, A., & Wauters, L. (2006) Modelling the expansion of a grey squirrel population: implications for squirrel control.Biological Invasions, 8, 1605-1619. Listed on Publications web page.
Andrea Grill from Italy has started a new project on the phylogeography and post-glacial history of the European squirrel, Sciurus vulgaris – see the Projects Page. You may be able to help if you have tissue samples of red squirrels from known locations throughout Western, Central, Southern and Eastern Europe. If this is the case, please contact Andrea directly.
Andrea Grill
The red squirrel, Sciurus vulgaris, has declined dramatically in Europe during the last century. Nevertheless, phylogeographic data covering its entire distribution area, which provide the basis to identify the evolutionary significant units of this species and to establish an effective conservation strategy on a European scale, are still missing. Our project is directed at tracing the present phylogeographic patterns in the Western, Central, Southern and Eastern European populations of S. vulgaris, including the Balkans and European Russia. Genetic variation and differentiation of S. vulgaris populations will be assessed and past demographic changes be inferred. Western and Central European samples will be compared to samples from localities in Southern and Eastern Europe. This will finally allow us to reconstruct the genetic history of the species in Europe since the last glacial maximum and to assess the consequences of the expansion of the introduced S. carolinensis, which may be loss of genetic variation, hybridization and genetic introgression. The data collected will be used to define evolutionary significant units for the red squirrel on which conservation efforts can be targeted, and provide practical recommendations for its management in order to prevent further decline of European populations.
Dr Andrea Grill, Istituto Nazionale per la Fauna Selvatica, Laboratorio di Genetica, Via Cà Fornacetta, 9, 40064 Ozzano Emilia (BO), Italy. Tel: +39 051 6512 253. e-mail:
A conference about red squirrel conservation, organised by Scottish Natural Heritage, will be held at the Pollock Halls, Edinburgh on Monday, 27th Februiary 2006. Deputy Environment Minister Rhona Brankin will be present and will open the meeting. For further information, see www.scotland.gov.uk/News/Releases/2006/01/12090830 .
The Scottish Squirrel Survey, funded by Scottish Natural Heritage, was established in March 2005 and is coordinated by Mel Tonkin, Scottish Squirrel Survey, c/o Scottish Wildlife Trust, Cramond House, Kirk Cramond, Cramond Glebe Road, Edinburgh EH4 6NS. It aims to set up a sustainable system of survey and monitoring of red and grey squirrels throughout Scotland through using Local Squirrel Group volunteers to undertake systematic surveys. Further details can be found here Scottish Squirrel Survey Information Sheet (PDF) and here Scottish Squirrel Survey Pamphlet (PDF).
Recently, it was pointed out to us that a list of lesser known holidays published in the Washington Post included January 21st as Squirrel Appreciation Day. Apparently, this holiday only dates back to 2001. Further information about this holiday can be found at :www.holidayinsights.com/moreholidays/January/squirrelappreciation.htm
Let’s all observe and celebrate Squirrel Appreciation Day by putting out some tasty food for the critters!
Happy New Year to everyone from the Squirrelweb Team.
Squirrels in eastern Russia have apparently turned nasty and killed a dog in the centre of a park in a village called Lazo in eastern Russia. This has been attributed to a failure of the cone crops – see the full story posted on BBC News World Edition on 1st December 2005 at news.bbc.co.uk/2/hi/europe/4489792.stm. Also see the links to other stories on BBC News, such as an Inn near Worcseter being forced to take a squirrel terrine starter off their menu by animal rights protesters, and plastic snakes being used to ward off squirrels in a public garden in Devon.