Initially I had to work on the use of Warfarin to poison squirrels. The likely outcome of any use of poison in English woodlands worried me, particularly after my work on the high fox mortality during the winter of 1959-60, which was found to be caused by foxes eating the corpses of birds that had died from feeding on grain treated with organochlorine insecticides. This was before the publication in 1962 of Rachel Carson's Silent Spring. But the landowning public wanted it and politicians were feeling the pressure.

Apart from developing a method of poisoning squirrels, which did not put too many other animals and birds at risk, my main work was to try and find why squirrels stripped bark off trees in June and July. This was the main problem caused by the American squirrel in England. I did this research at Imperial College Field Station, Silwood Park near Ascot with the encouragement and supervision of Professor Humphrey Hewer.

My main conclusion was that it was caused by a combination of factors - (1) food was scarce at that time of year (June-July), (2) major movements of squirrels seeking vacant habitat occurred at that time, and (3) that bark chipping and persistent gnawing (wire in traps, food items, wood) was a normal aggressive signal between squirrels. This persistent gnawing response can become exaggerated into prolonged stripping and bark feeding under conditions of intolerable stress when combined with hunger. Serious bark damage was precipitated when moving squirrels became hungry and were involved in an unusual amount of aggressive behaviour, particularly between migrants and the local residents.

Groups of migrating squirrels were found to end up mainly in re-growth areas lacking stable squirrel populations, where they would strip bark for a period of several days, taking many square metres of bark off the trees in the process. Observations on squirrels involved in bark stripping showed that they were involved in an unusual amount of aggressive interaction and chasing, and that the areas below where they fed often stank with the smell of wet, fly-covered squirrel droppings - the bark diet seems to give them diorrhoea. Within a few days most of the bark-stripping squirrels disappeared, maybe dispersing further or were lost to predation and disease.

If my assessment was true, poisoning prior to the damage season, if anything, could increase damage, because it would have the effect of leaving patches of woodland without a resident squirrel population in regions where there is a large surplus of squirrels. This would encourage migrant squirrels to enter in greater numbers.

Poison laid during a squirrel damage event has little effect, because animals involved in bark-stripping seem to ignore food, or poison laid down for them. This supports the notion that it has more of a social than ingestive importance.

It is strange that bark damage is rare in the eastern USA, the grey squirrel's native country. The likely reason is that it lives in a comparatively rich environment. They inhabit areas with a huge range of seed trees - especially oaks and hickories. There are also many competing sciurids which partition the habitat according to specialities. There are also more predators. Early summer food is less likely to be a problem with such a variety of food sources, especially if predators mop up excess squirrels.

The laying of poison for squirrels in English woodlands was legalised soon after I left.

Taylor, J. C. (1966). Home range and agonistic behaviour in the grey squirrel. In: Play, Exploration and Territory in Mammals P. A. Jewell & C. Loizos Eds. Symposia of the Zoological Society of London No. 18: 229-235.

Taylor, J. C. (1968). The use of marking points by Grey Squirrels. J. Zool., Lond. 155: 246-247.

Taylor, J. C. (1969). Social Structure and behaviour in a grey squirrel population. Ph.D. Thesis, University of London.

Taylor, J. C. (1970). The Influence of Arboreal Rodents on their Habitat and Man. European and Mediterranean Plant Protection Organisation Publications Series A. No. 58: 217-223.

Taylor, J. C. (1975). An example of how variations in behaviour can invalidate population estimates. Australian Mammalogy. 1: 403-404.

Taylor, J. C. (1976). The Squirrels of Silwood Park. (Unpublished manuscript revised 1997. Copies lodged in the Elton Library, University of Oxford, and Imperial College Field Station, Silwood Park.)

Taylor, J. C. (1977). The frequency of grey squirrel (Sciurus carolinensis) communication by use of scent-marking points. J. Zool. 183: 543-545.

Taylor, J. C. (1978). Sciurus. The story of a grey squirrel. Collins, London.

Taylor, J. C. (1979). A trap which selectively catches itinerant squirrels. J. Zool., Lond. 188: 288-290.

Taylor, J. C. (1979). The introduction of exotic plant and animal species into Britain. Environmental review No. 7. Biologist 26: 229-236.

Taylor, J. C. (1990). Transgressors not welcome. Country Life. Dec. 48-49.

Taylor, J. C., H. G. Lloyd and J. F. Shillito (1968). Experiments with warfarin for grey squirrel control. Ann. Appl. Biol. 61: 312-321.