Deer Deterrents

A diversity of methods of deterring deer from browsing or grazing plants and crops has been attempted. Unfortunately, exhaustive, controlled field experiments are limited to proprietary compounds applied to plantation forests. As a result much of what is known is drawn from the experiences of gardeners, foresters and nursery managers and this is likely to be insufficient for plant protection under every situation.

Chemical repellents are regulated in the UK by the Control of Pesticides Regulations (1986).  Rather bizarrely, lion dung and human hair (two oft quoted deer repellents) fall under the control of these regulations and have not been approved for use as pesticides!

Chemical repellents fall into two broad categories: barrier repellents, which provide a "chemical fence" to deer and are applied around the area to be protected, and feeding repellents, which are applied to individual plants to prevent feeding.

Barrier repellents

Renardine - Of the barrier repellents formulated against wildlife only Renardine is approved under the Control of Pesticides Regulations (1986) for use in the UK. The problem is that Renardine has been demonstrated to be ineffective at deterring deer!

Creosote - Although not intended as a barrier against deer, some gardeners have reported success when hanging creosote soaked rags around their gardens. Unfortunately, just as many gardeners have reported its inefficacy.

Moth balls - Again, not designed as a deer deterrent and, furthermore, totally ineffective.

Human hair - Unwashed human hair stored in tights or muslin and hung in bushes at deer head-height have been used to protect gardens from deer. Success has been highly variable and what effectiveness hair may have is thought to be reduced by rainfall and age. It is considered best to replace human hair monthly. However, controlled experiments by the Forestry Authority found human hair to be ineffective in protecting areas of plantation forest.

Lion dung - In its raw state lion dung has the problem of being incredibly smelly and difficult to degrade. Another problem is that it has been shown to be ineffective against deterring deer. However, a concentrated liquid extract of lion dung has been formulated and initial trials indicate that it may be successful in keeping deer out of silage fields for several weeks. This product is not yet on the market since safety trials are ongoing.

Scented soap - Hanging many medium to large bars of heavily scented soap amongst plants is thought by some to be effective in repelling deer. A benefit is that soap does not need to be replaced until it has completely dissolved. Evidence comes from a limited number of uncontrolled trials and met with variable success.

Human urine - Problems of collection and application of sufficient quantities aside, human urine loses what effectiveness it may have after rain. Again, evidence for its efficacy is limited to anecdote and a few uncontrolled trials.

Feeding repellents

These work by rendering potential food plants unpalatable to deer. Commercial compounds, such as Scuttle, Curb and Aaprotect can be expensive and meet with variable success. Trials have shown most to be effective, especially for low-density deer populations. However, some suffer from the need for regular re-application, especially after rain and toxicity of some may be a problem in gardens.

Visual and sonic deterrents

In general neither sonic nor visual deterrents work. Deer are rapidly adaptable and soon get used to sonic sirens, scarecrows, streamers etc. However, deer damage has been reported to be limited in the direct path of the beam of security lights, although they do not prevent entry by deer altogether. Furthermore, developments in variable pitch sonic sirens and a motion-triggered device that squirts the intruder with a jet of water have yet to be trialed for deer in the UK but may meet with a degree of success.

Physical barriers

In short, too many problems and limited efficacy are associated with deterrents that they generally do not provide protection from deer damage under all, if any, situations. The only effective barriers against deer are properly erected and maintained deer fences and individual tree/plant guards.

Minimum specifications for deer fences

Species	Mesh size (mm)	Height (m)
Muntjac/CWD	75 x 75	1.5
Roe	200 x 150	1.2
Fallow	220 x 200	1.5
Red/Sika	220 x 300	1.8

Further reading

Pepper, H.W. (1992) Forest fencing. Forestry Commission Bulletin 102. HMSO.

Pepper, H.W. et al. (1985) Individual Tree Protection. Forestry Commission Arboricultural Leaflet 10, HMSO.