‘Pill’ could aid deer control

It might sound silly to suggest a form of “the pill’’ for animals, or some other means of contraception to keep ou burgeoning deer population down. Not all that fanciful, however.

A reason cited regularly for the growth in deer numbers is that deer have no natural enemies here.

Wolves and lynx could be introduced as predators, but no marks for guessing how the IFA and farmers in general would react to that proposal! A non-runner.

But something must be done, as deer have become a nuisance, going onto farmland and other private property, damaging woodland, being a risk for spreading lyme disease, and becoming involved in road traffic accidents.

Anyone walking in Killarney National Park, Co Kerry, recently must have noticed a huge herd grazing on a hill at Knockreer, close to the town.

The grass in the surrounding acres had been eaten bare and, unsurprisingly, some people are now questioning the range’s capacity to sustain upwards of 1,000 deer in Killarney alone.

Shooting is the usual means of controlling the deer population and that, too, can be
controversial. There are, however, scientific ways of keeping numbers down — contraception for example. Experiments have been
carried out in the USA, including surgical sterilisation, use of synthetic hormones, and
a vaccine, PZP, to prevent fertilisation.

There can be practical difficulties, such as trapping deer for the implanting of hormones, and, according to the Humane Society of the United States, PZP is the most widely-used system and has the best potential for success.

PZP can be delivered to adult female deer by syringe or remotely using darts shot from a dart gun.

In one area of South Carolina, the vaccine helped reduce the deer population by 60% over five years.

Costs can be high, nevertheless, from $300 (€251) to $1,000 (€837) per animal.

Given the size of the Irish deer population, cost would be an inhibiting factor, as deer
biologist Tim Burkitt, who worked for several decades with our National Parks and Wildlife Service, pointed out. “I think research work in the US has still not found a solution and more research is needed,’’ he said.

In Britain, opinion among experts is mixed. PZP is accepted as being effective, but where deer numbers are too high, contraception would not reduce numbers in the absence of other means of removal until older females die naturally, which could take many years.

There’s also the view it would be necessary to contracept the majority of females in a given population over a five to 10-year period before a numbers reduction could be achieved. And, even then, any reductions would be modest.


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