Using dung counts
Much of the monitoring of deer density that is carried out by the Forestry Commision on their land in Scotland is done on contract by Strath Caulaidh Ltd. using a dung counting method. The Forestry Commission has commissioned Strath Caulaidh Ltd. to write up, and publish, their methods.
A paper has been published which justifies the use of the faecal accumulation rate method rather than the faecal standing crop method (Campbell, D., Swanson, G.M. and Sales, J. (2004). Comparing the precision and cost-effectiveness of faecal pellet group count methods. Journal of Applied Ecology, 41, 1185-1196).
A full description, and justification, of the method has also been published (Swanson, G, Campbell, D & Armstrong, H. (2008). Estimating deer abundance in woodlands: the combination plot technique. Forestry Commission Bulletin no. 128. Forestry Commission, Edinburgh.)
Photo: Pilkington Thorn Optronics Ltd
Using thermal imaging
Thermal imagers detect the radiant heat energy emitted from warm-bodied animals, and can make nocturnal and camouflaged animals highly conspicuous. Large mammals can be detected at distances of up to 2 km. Heat energy cannot however pass through solid objects, so animals can be concealed by vegetation. Since 1995, methods have been developed to obtain estimates of population density and trend using distance sampling, which compensates for the proportion of animals concealed in vegetation. Observations are made at night, when deer are more likely to make use of fields or open areas.
This approach has proved very effective in the lowlands, where dense coniferous thicket vegetation is less extensive than in the uplands. Thermal imaging can also provide information on deer species composition, group sizes and habitat use, and recent research suggests that these factors need to be taken into account when assessing deer impacts at a given density.
Options are currently being sought to improve methods of density estimation using thermal imaging, to make field methods as simple as possible, and to broaden the application of information that can be obtained.
For further information
Contacts
About using dung counts
Dr Helen Armstrong
Centre for Human and Ecological Sciences
Forest Research
Northern Research Station
Roslin
Midlothian EH25 9SY
Tel: +44 (0)131 445 6954
Fax: +44 (0)131 445 7335
Email: helen.armstrong@forestry.gsi.gov.uk
About using thermal imaging
Dr Robin Gill
Centre for Human and Ecological Sciences
Forest Research
Alice Holt Lodge
Farnham
Surrey GU10 4LH
Tel: +44 (0) 1420 22255
Fax: +44 (0) 1420 23653
Email: robin.gill@forestry.gsi.gov.uk
