HomeMy WebLinkAboutOstfield, R DEIS.pdf Cary Institute
of Ecosystem Studies
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Senior Scientist
Richard S.Ostfeld,Ph.D.
6 December 2010
To:Village of Cayuga Heights Board of Trustees
Subject:Draft Environmental Impact Statement,Cayuga Heights Deer Management
Plan
I am a research scientist who has devoted much of the past twenty years to
understanding the ecology of Lyme disease and other tick-borne infections(see
http://www.ecostudies.org/people sci ostfeld.html). I have carefully read all sections
of your DEIS pertaining to the potential impacts of management options on ticks and
tick-borne disease. The DEIS contains many inaccurate and unsupported statements
about relationships between deer,blackleg ticks (incorrectly called "deer ticks"),
�e >Ra�_ or example.page 2-10 incorrectly states that linear correlations
exist between deer and ticks. A comprehensive review of the scientific literature on the
relationship between numbers of deer and numbers of ticks reveals that the majority of
studies find no statistical correlation at all(see:Ostfeld,R.S.2011. Lyme disease: the
ecology of a complex system. Oxford University Press, New York.). The lack of a
correlation derives from the following facts: (1)deer do not infect ticks with Lyme
bacteria,and actually reduce the infection prevalence in tick populations; (2)adult
blacklegged ticks feed on at least 27 different species of mammals and are not specialists
on white-tailed deer;(3)when deer populations are culled, ticks crowd onto the
remaining deer,resulting in similar total numbers of tick meals;and (4)even when deer
affect the number of eggs laid by adult ticks and resulting abundance of larvae,
numbers of larvae do not predict numbers of nymphs(nymphs are responsible for
transmitting Lyme disease to people).
On page 3-,5 the document cites the Monhegan Island (Maine)study to project what
might happen in Cayuga Heights. This is misleading. On Monhegan Island,the deer
herd was hunted from 100 to zero individuals. No other host animals for the adult
stage of the tick were present on the island. Therefore,with no other host on which to
complete their life cycle, the blacklegged ticks declined dramatically. But when deer
have been culled on mainland sites,management never achieves extirpation of deer,
and the remaining deer plus many other hosts support adult ticks. Therefore, control of
ticks is weak to nonexistent. Moreover,although mention is made of deer thresholds in
the non-peer-reviewed literature,no scientific data support the existence of a deer
density threshold below which ticks decline to low numbers. Scientific literature on
which my statements are based can be found in the book cited above.
I refrain from commenting on other arguments concerning the benefits of culling deer.
However, to the extent that the justification is based on the notion that reduced Lyme
disease incidence will result,the document is deeply flawed.
I would be happy to address questions should any arise.
Sincerely,
Richard S. Ostfeld,PhD
Senior Scientist