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The Island's exploding deer population is fueling concerns about public health and forest health — but reducing the herd is only one piece of a much larger fight against ticks.
The Island is facing a public health crisis. Positive alpha-gal tests at Martha's Vineyard Hospital climbed from two in 2020 to 740 last year, with 416 more already by June this year. The Island now carries the highest rate of tick-borne disease in Massachusetts.
Tick Free MV, the non-profit founded at the end of last year, conducted a drone survey of the Island’s deer this winter, and they found that there are 4,681 deer on the Island, a density of roughly 49 deer per square mile, nearly three times what Mass Wildlife biologists consider healthy. They say the Island can sustain 1,500 deer or fewer, at 12 to 18 per square mile, requiring a cull of close to 70%.
Tick Free MV's Executive Director, Virginia Barbatti, is candid that even a 70% reduction won't solve the tick problem outright. “But once we reduce the herd,” she says, “other interventions will finally have a chance of working.” One interesting option for ongoing tick control is the Centers for Disease Control and Prevention's 4-Poster Bait Station, which lures deer with corn and brushes tick-killing chemicals onto their necks and heads. Controlled burns can also suppress ticks while restoring carbon to the soil. On Chappaquiddick, the New England Center of Excellence in Vector-borne Diseases (NEWVEC), a coalition of researchers from across the Northeast, is developing a project to test medications that could make deer resistant to ticks, similar to medications available for pets. This fall, NEWVEC will test the drugs’ efficacy on a captive herd at the UMass Amherst campus, before potentially deploying them on Chappy in Spring 2027. These and other strategies are complements to herd reduction, but none is practical while the population stays this large.
Meanwhile, TickFree MV and the Agricultural Society continue working on more cold-storage and processing infrastructure, and they support the MassWildlife Hunters Share the Harvest program. MassWildlife pays the processing fee to the state-approved processor for venison donated through the program, while Tick Free MV offers hunters an additional incentive to donate their deer: $100 per buck and $150 per doe. Island Grown Initiative will distribute donated venison through its food pantry.
The size of our deer population has consequences beyond the serious human health concerns associated with ticks. Luanne Johnson and Matt Pelikan of BiodiversityWorks feel strongly that the Island has let the deer population go unmanaged for decades, with severe damage to the ecosystem. A forest can look tidy, but in fact that tidiness reflects the damage. A healthy forest needs a mid-story of young trees and shrubs, which the deer strip bare, leaving what experts call a “regeneration debt:” Without a mid-story, a forest is no longer able to restore itself. Many ground-nesting birds (such as ovenbirds, wood thrushes, and whippoorwills) have lost their brush cover and quietly disappeared. Even the deer, with this population density, aren't thriving: with insufficient food, their body condition declines, and fawns come into hard winters undersized.
While some people point out that white-footed mice are a primary source of ticks' Lyme infection, Pelikan notes that deer are “the preferred host for the tick's final blood meal,” meaning that both mice and deer play critical roles in the spreading of tick-borne illness. “It's genuinely a multi-host problem,” Pelikan says.
What about Lawn-Spraying? Does It Help, and Is It Environmentally Safe?
An increasing number of Islanders are hiring companies to spray their own lawns against ticks, and nobody entirely agrees on whether it works or what it costs the rest of the ecosystem.
The chemical option, pyrethroid-based products like bifenthrin or lambda-cyhalothrin, is the industry standard, and it works. It kills ticks on contact and keeps working for weeks. But it also kills other things: pyrethroids act on a nervous-system pathway shared broadly across insects and arachnids, meaning that bees, butterflies, and other pollinators exposed to a treated lawn are vulnerable, too.
The organic option, usually a cocktail of cedarwood, lemongrass, geraniol, and other essential oils, is marketed as safer and is genuinely gentler on wildlife: it breaks down faster and doesn't linger the way synthetic pyrethroids do. But its effectiveness against ticks is contested. A University of Rhode Island study that tested cedar oil and similar natural products found only a minimal knockdown of 0–24%, but their findings were inconsistent. Local applicators on the Vineyard, by contrast, report field results with closer to 70–80% effectiveness, with monthly reapplication and the way in which the spray is applied (pressurized systems, not just a light misting), making an important difference.
Pelikan worries about the effect of spraying on arthropods, especially spiders, which are soft-bodied and sensitive. “Spiders are vital predators — remove them and you unleash flies, beetles, wasps, etc. They’re crucial for balance. So people must weigh reduced tick risk against ecological impact. For some, a 30% spider loss is acceptable to protect grandchildren; others may opt out. Both responses are valid.”
Johnson is concerned that “spraying — even organic — can kill pollinators. Soapy water can glue bees’ wings … And spraying isn’t foolproof. A deer or turkey can drop a fresh tick between sprays, creating new infestations.”
BiodiversityWorks has launched a two-year study funded by the New Tudor Foundation to better understand the effectiveness and impact of organic versus chemical treatment.
There is no single fix for the tick crisis, but people are working on a holistic, multi-pronged approach. The idea that one silver bullet will solve the problem is wishful thinking. The deer harvest will not, by itself, end the tick problem on Martha's Vineyard, but state and local wildlife experts believe it will make an important and urgently-needed impact.
