Much Ado About Deer: Maybe For Good Reason

Residents and wildlife experts convened in Dobbs Ferry to discuss the effects large deer populations have on our suburban landscape—beyond eating tulips and obstructing cars.

Wildlife experts from the Mianus River George, the New York Department of Environmental Conservation and Westchester County and Tufts University presented their research Monday showing that deer cause extensive deforestation. 

The event was organized by the Dobbs Ferry Deer Committee, who have been working to devise a viable and palatable deer management solution in Dobbs Ferry. "This is not a debate," said Committee Chair Dan Evangelista. "This is an educational forum."

Residents, though, came demanding answers—specific plans to address the problem in the foreseeable future.

"I walk regularly in the woods in Irvington and I am very concerned," said Christine Plazas. "The changes in the forest over the last few years are very apparent." 

But how to bring down the numbers of deer from around 60 per square mile to an optimal 12 to 15 is a point of contention among locals.

"I believe it is discouraging to listen to conversations about  hunting when there are non-lethal alternatives," said Irvington's Diana Barella. "It is especially discouraging that the DEC may be the main obstacle to using them."

Deer: What is the situation in Westchester? 

Information presented by Rod Christie, executive director Mianus River Gorge in Bedford:

• In pre-colonial forests, the deer populations were about 14 or 15 deer per square mile. Their natural predators were wolves and mountain lions.
• There was then 75 percent deforestation as forest was turned to farmland. Nearly all predators simultaneously were extirpated.
• In the early 1900's, laws were made to protect deer and many were reintroduced from the Catskills and other areas upstate.
• As the farms were later abandoned, young forests began to emerge. There was also a huge increase in the deer population.
• Now, Westchester has mainly old forests, with significantly less herbaceous diversity than in the past. 
• A study conducted in 1965 and then again in 2004 showed that the number of species of saplings in the Mianus River decreased from 23 to 8.
• Deer are Ecosystem Engineers, meaning they create and modify habitats.
• During winter months, they start scavenging for food around residences.
• If the population is not brought down, deer will run out of food and many will starve to death.
• If action is not taken quickly, it will be too late for the forests and associated wildlife to regenerate.

Is Bow Hunting a Good Solution?

Information provided by Mark Weckel, Director of research and land management at the Mianus River Gorge, also a PhD candidate with a thesis analyzing whether controlled archery is a viable option in Westchester:

• In Westchester, there are about 60 deer per square mile, meaning you see one about every 200 yards on Rte. 9.
• Deer aren't the only cause of deforestation. Other causes include: acid rain, invasive worms, and changes in lifestyle.
• Under the the Rose Petal Hypothesis, ecologists believe they can bring down the entire population by reducing the number of does. This theory is based on the idea that deer don't travel very far.
• The pros of archery: it is the traditional approach; it does not include firearms; it is volunteer-based.
• The cons: it is controversial, volunteers can be flaky, guns are faster.
• Bow hunting won't bring down numbers overnight. Weckel's bow-hunting study in the Mianus River Gorge showed populations lowered by 25 percent in 7 years.

Is Immuno-Contraception an Effective Alternative to Lethal Control?

Information provided by Dr. Alan Rutberg, Tufts University:

• PZP is a protein extracted from pig ovaries which cause antibodies that block fertilization in animals.
• PZP must be injected.
• It has been used to varying degrees of success to control deer and wild horse populations.
• It can be delivered either by hand or through a projectile dart.
• PZP has been shown to reduce doe pregnancy rates 90 to 95 percent in the first year.
• The simple vaccine is $25 per dose. The time-released dose is $225 per dose. But the majority of the cost is in the labor. The overall cost is about $225 per deer. 

What Has the County Done?

Information provided by Dan Aitchison, wildlife curator at Westchester County:

• The county has opened
• County officials started the controlled hunting at two parks in Somers. This season, there will be more.
• It is a controlled scientific experiment.

Will the DEC Issue Permits for These Options:

Information presented by Kevin Clarke of the NYS DEC:

• The DEC has issued permits for controlled bow hunting.
• Immuno-contraception is still experimental, so the proposal would need to be part of a scientific experiment. Clarke could not comment on how difficult it would be to secure a permit for PZP without a specific proposal.
• The DEC's role isn't to choose sides.