Species Recovery Project – Red squirrels in Thetford Forest (completed 2003)

John Gurnell

Research into the ecology and conservation of red squirrels in Thetford Forest, East Anglia, has been going on since the 1970s. Since September 1992, I have directed a series of studies, sponsored by English Nature, the Forestry Commission and the People’s Trust for Endangered Species, that have the twin aims of studying red squirrel conservation methods that may be applied to other parts of the country, and to assist in the recovery of the very small population of red squirrels that still remains in Thetford Forest. The studies are focussed in a 1700 ha Red Squirrel Reserve, and the person in charge of the field work is Janie Steele.

Objective 1: Maintain and increase the number of red squirrels in Thetford Forest.

The population of red squirrels at Thetford has declined from a healthy population in the 1960s to only a few percent of its former value. This is probably linked to the spread of the grey squirrel, though changes to the structure of the forest may also be important (for example, the change from Scots pine [SP] to Corsican pine [CP]). Work over the past few years may, perhaps, have halted the decline, but significant improvement remains an unachieved goal. A further 3 -year project of intensive work and monitoring will inform a future decision about whether maintenance or recovery of this population is a realistic goal.

Delivery mechanisms

  • Control grey squirrels to maintain minimise numbers in the RSCA as far as practicable;
  • Update the Forest Design Plans for time to time to include ways of Improving the forest age structure and species composition of the RSCA to benefit red squirrels, e.g. the removal of broadleaves such as ride-side beech, replant some areas with SP rather than CP, and trial the use of continuous cover management in retentions of SP to provide understorey cover;
  • Restock the RSCA with wild or captive-bred red squirrels, when this can be done without a high probability of excessive mortality;
  • Supplement the food of red squirrels, when and where appropriate;
  • Control disease, using information from current research as it becomes available.


  • Control grey squirrels using live-traps, to a pre-arranged plan within the RSCA and in a 1.5km buffer strip;
  • Continue implementation of the Forest Design Plan;
  • Monitor food take at red squirrel-only supplementary food hoppers;
  • Monitor natural food resources. i.e. broadleaf food supplies each autumn and cone availability on trees throughout the year;
  • Examine habitat utilisation by red and grey squirrels using cone feeding line transects;
  • Captive breed red squirrels on site;
  • Release of red squirrels (captive-bred or wild as appropriate), with particular attention to minimising the risk of disease, and full monitoring by trapping and radiotracking.
  • Live trap and radio-track red squirrels (wild or captive bred) within the Reserve to monitor performance.

Objective 2: To determine if grey squirrel control is a management option for red squirrel conservation.

The removal of grey squirrels to benefit red squirrels has been widely proposed as a conservation tactic, but there exists only fragmentary evidence to support its use. However, detailed information about the specific effects of grey squirrel control on both red and grey populations is lacking and the work at Thetford provides the best way of obtaining this. In addition, data about effort and catch will be collected to improve understanding return for control effort. This will enable judgements to be made concerning the economics of grey squirrel control.

Delivery mechanisms

  • Measure trapping effort (time/cost), together with its costs of materials and travel;
  • Monitor grey squirrel populations (from trapping results, post-mortem etc.);
  • Monitor natural food resources and its effects on grey squirrel populations in conifer forest;
  • Link with studies on red squirrels under Objective 1


  • Record trapping effort within different zones of the grey squirrel control area;
  • Examine trapped grey squirrels and record age, breeding structure and body condition;
  • Carry out visual counts and hair tube surveys for red and grey squirrel as time permits;
  • Activities as under Objective 1

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