HomeMy WebLinkAboutSchmitz, O DEIS.pdf YALE UNIVERSITY
School of Forestry
& Environmental Studies
14 December 2010 Greeley Lab
370 Prospect Street
Board of Trustees New Haven, CT 06511
Cayuga Heights NY oswald.schmitz@yale.edu
Dear Trustees,
I am,herewith,commenting on the plan to control white-tailed deer within the town limits of the Village of Cayuga
Heights. In providing this comment, 1 wish to affirm that I am not being paid by anyone for this service. I am providing
feedback in my capacity as an ecologist who has studied white-tailed deer for my PhD dissertation and subsequent
research. I have published 6 peer-reviewed papers and book chapters dealing with white-tailed deer ecology and
population management.
I have looked at all of the documents provided at the website for the draft environmental impact statement(DEIS)
http://www.tiiiiiiiillerassociates.COIII/pLtblici-evio k/cavu"ahei fitter, . I am working under the understanding that this is the
official document for which comment is request. Below I identify specific informational content in the documents and
offer subsequent comment.
In the document 2.0 DESCRIPTION OF THE PROPOSED ACTION the proposed deer population control effort in the
Village of Cayuga Heights(VCH)is based on the following premises. (1)Many studies in the past 20-25 years suggest
that high deer densities affect plant species composition,biodiversity and forest regeneration(pages 2-2,2-3). (2)A
substantial deer density can significantly influence wildlife habitat and deer foraging can compromise the ability of an
ecosystem to recover, leading to alteration of forest composition and structure(page 2-3).(3)Deer populations above 10
deer per square mile are undesirable if the management goal is to achieve maximum biodiversity(page 2-3). (4)To
minimize losses of animal and plant diversity, the management target should be 30 deer or fewer within VCH,or a
density of 15 deer per square mile or fewer(Page 2-4).
Comment.
Re: (1)The document is correct in stating that research over the past 20-25 years has examined how deer can affect
species composition,biodiversity and forest regeneration. However,many of these studies are in a single location and
could thus be conflated by human land use type and land-use history so that deer cannot be concluded to be a leading
factor determining the impact in any one of these studies(see Rutherford and Schmitz 2010,Journal of Wildlife
Management 76:1257-1263). Indeed,such conflation of land use on deer populations has been alluded to in 2.3 Project
Background... which claims that agricultural practices and forest management has improved and expanded deer habitat
and suburbanization of landscapes has created edge habitats preferred by deer(page 2-2).
Re: (2)It is correct that high deer densities can significantly influence habitat and forest composition and structure.
However,our research(Rutherford and Schmitz 2010),conducted in a similar landscape as VCH,and includes several
replicated town sites,again shows that these damage levels are unrelated to deer density per se across a wide range of
deer densities. This means that lowering deer densities will not by itself lessen deer impacts on habitat and vegetation.
Furthermore,the DEIS never provides criteria for quantifying and assessing damage levels that are acceptable or
unacceptable. Hence,there are no a priori criteria to judge success of management aimed at lessening"damage".
Re: (3&4)The document is correct that deer densities above 10-15 per square mile can be quite damaging in some areas.
But,again,there is wide variation in damage levels,meaning that 10-15 is not a damage threshold,as implied by the
document.
The document identifies several management goals including(5)VCH should adopt a cultural carrying capacity goal of
15 deer per square mile(page 2-7). (6)VCH should begin a Phased Options Approach(POA)beginning with sterilization
of 20-60 does and subsequent culling of unsterilized does(Page 2-7). (7)POA must be implemented in each of the first 5
years of the management program(Page 2-8)and may require continuous implementation in perpetuity(Page 2-9).
Comment
Re: (5) 1 see no evidence that this population size goal is attainable for 2 reasons. First,the document itself states that
deer population [sizes]are difficult to ascertain accurately due to daily and seasonal movements(page 2-4). Thus,there
is no evidence provided that accurate estimates of deer will be obtainable to judge the success of the management.
Second,because of the acknowledged daily and seasonal movements, the deer population in VCH may not be closed—
meaning deer may not be confined within the town boundaries,but may enter and leave VCH. There is further evidence
to suggest that VCH does not have a closed population. The current reported deer population sizes(Letter to VCH
Trustees from Paul Curtis Dated 12/9/2009—Appendix A)indicates that the deer population size(presumably within
VCH boundaries—the exact area of the population estimate is not specified)is very high by deer population standards.
However,the population was only sampled in the spring(according to the letter)so the seasonal movement of deer
remains unclear. One might expect that under such high abundances,that deer birth rates would slow because of
competition for food(called density-dependent feedback). The claim that the deer population is still growing
prodigiously(according to the letter)means there is incomplete understanding about the population dynamics on this
landscape. One possibility is that deer are moving seasonally into and out of the VCH from the surrounding landscape,
are highly abundant seasonally,but are not resident within the VCH. The fact that this alternative cannot be ruled out has
implications for(6)and(7).
Re: (6)Sterilization, if it works at all,will only work for a closed population. The fact that the DEIS has not provided
evidence that the VCH deer population is a closed population means that sterilization,and hence a POA as defined in the
document could be altogether untenable. Furthermore,if the population is open,then it will be difficult to reach a target
"stable"population size of 15 deer per square mile,even within a single culling period. Because culled deer could be
rapidly replaced by deer from the landscape surrounding VCH,there is a likelihood that even a 5 year time horizon will
be insufficient to reach a target population size. It may never be reached with an open population and culling efforts
focused only on a small part of the greater landscape.
Re: (7)The document is correct in suspecting that the PDA will need to be implemented in perpetuity,especially if the
VCH deer population is not a closed population.
In summary,there is insufficient evidence provided in the documentation to show that the management effort will achieve
its stated objective deer population size of 15 per square mile within VCH. Evidence to support the assertion that a deer
population size reduction will lessen impacts on ecosystems(habitat and vegetation)within VCH is also insufficient.
Furthermore,the DEIS needs to consider the conflating effects of human land use as a driver of deer movements and
population growth on this landscape. That is,deer populations may be the consequence of human impacts on the
landscape rather than a cause of impacts to humans.
Sincerely,
14
Oswald J. Schmitz, PhD
Oastler Professor of Population&Community Ecology