Only intensive cull will reduce deer numbers

The only way in which contraception could work would be to prevent the movement of deer into the municipality.

Re: Deer a shared responsibility, (July 31).

I would like to add some comments, as a biologist, to the contrasting proposals to manage the blacktail deer population in Oak Bay.

The number of deer in any region will reach a rough equilibrium dependent on the balance between the amount of browse available and the level of predation.

In other words the more vegetation the greater the number of fawns born, and the more deer to consume the more the carnivores can reproduce. The two groups balance out, usually with a time lag.

In the case of Oak Bay two observations apply:

1. We have eliminated natural predators, and the automobile is an inefficient substitute.

2. Left alone the deer population will continue to expand towards the limit set by the food supply.

The trap-and-kill method of management employed briefly last winter could certainly reduce the deer population. But since deer evolved to compensate for predation the reduction will be temporary. More fawns will be born and adults will move in from adjacent regions.

Only an intensively applied cull over several years could effectively reduce deer numbers. Given the political opposition to deer culls this is not practical.

An alternative to killing animals that has been suggested is to treat does with a contraceptive.

This will not reduce the number of deer but will result in fewer fawns.

The treated does will eventually die of old age and their place and that of their never-born offspring will be taken by the migration of deer into Oak Bay. The rule is: if there is food they will come.

The use of a contraceptive will not reduce the deer population in Oak Bay and thus seems pointless.

The only way in which contraception could work would be to prevent the movement of deer into the municipality.

Given the experience of the Australians in analogous circumstances with a rabbit-proof fence (but rabbits cannot jump an 8ft fence) I do not give much credence to isolating Oak Bay from outside deer which would be required.

This is merely the opinion of a scientist. Others are entitled to their own opinions.

Joe Harvey

Oak Bay