- We now have Ralph Green with us from Pace University.
Ralph has also been collaborating with FEMC,
trying to get our regional browse project together.
Today, Ralph will be presenting
White-tailed Deer Harvest Success
and its Impact on Forest Understory Vegetation:
Evaluating Management Program Efficacy
in Southeastern New York.
- Thank you for having me
and thank you for everyone being here this morning.
I'm Ralph Green and I'll be going over my graduate thesis
that I did for my master's in Environmental Science
at Pace University.
During my mentor, Dr. Begley-Miller who is the
director of science and stewardship
at Teatown lake reservation
I'm actually defending this next week.
So this is like a short, quick version of it.
So it is called White-tailed Deer Harvest Success
and its impact on forest understory, vegetation,
evaluating deer management program efficacy
in Southeastern New York.
So that being said, let us begin.
So it was well-documented that,
white-tailed deer are over abundant in the Northeast,
especially in New York state and
South Eastern portion of that state.
And there's a lot of literature on how overabundant deer
can have a severe impact on forest understory,
diversity and richness.
And it also said that Lethal deer management
is the most effective way to manage deer
and reduce the densities over time.
So basically the study aims to better understand the
effectiveness of White-tailed deer management programs
and improving forest understory conditions.
So continuing on with the study rules.
I want to understand these different
lethal management strategies,
whether it be recreational hunting,
or managed volunteer programs or culling,
basically to see which one of those are more successful
at decreasing overall deer density over time.
And if those changes, if they're present,
if they correlate with improved
forest vegetation conditions.
So let's go over some of the management strategies
I use in this study and then we'll get into my hypothesis.
First, we have open-access recreational firearm hunting,
you know just follows New York state regulations,
And I have a site that does that.
Then there's highly coordinated archery programs.
They follow New York state archery regulations,
but on these private reservations and preserves,
there's a line managers or stewards who
coordinate with hunters and where to go.
So we have a few sites that do that in this study,
and then there's culling,
which could be done over bait, like in this picture
or in this study we have
one site that does professional sharpshooters.
And then lastly, there's a control of there's,
sites that do not manage their deer at all,
no hunting, nothing. So none.
So getting into my hypothesis,
first they're broken down into 1A 1B similar to 2A 2B
and for the first two only.
So for the first hypothesis hypothesis, 1A:
If a site does not manage their deer,
then they'll have the highest deer densities.
And similarly with hypothesis 1B,
then they'll have the lowest forest understory,
diversity, richness, and abundance.
So, with hypothesis 2A and 2B,
in hypothesis 2A,
If the site does manage their deer,
then they'll have the lowest levels of deer density
and 2B they'll have,
a higher level of those up forest understory conditions.
So moving on to my other hypothesis,
we're going to look first,
these boxes are important.
So with recreational firearm, hunting, and culling
hypothesis 3 , it says that
it will be the most efficient form of management,
meaning, remove the most deer
and similarly to hypothesis 4
if it was the most efficient,
then it'll have the highest levels
of the forest understory conditions.
And so it kind of sets the tone for the rest of the,
prototypes and the study where no management,
obviously no efficiency, so high levels for deer,
and they'll just have
the lowest levels of forest inventory conditions.
So that places the coordinator archery programs
in the middle of with moderate efficiency
and moderate levels of the forest understory conditions.
So let's look at these programs in the sites
that I use in the study.
So they're all part of the
Environmental Monitoring and Management Alliance
in Southeastern New York.
Here we have first, in the bowl boxes,
we have the Edmond Niles Hayck Preserve
and the Rockefeller University Field Research Center.
They do not manage their deer.
And next we have the Vassar College Farm and Ecological
Preserve at the broken outbox,
They do the professional firearm cull.
and Black Rock Forest Consortium,
They do open-access firearm hunting.
Lastly with the dash boxes in the Southern
portion of the map is Ward Pound Ridge Reservation
and Teatown Lake Reservation,
And Mianus River Gorge Preserve,
who do the highly coordinated archery programs.
So we're going to look at the methods.
I will assess three criteria to determine differences
between program efficacy.
First, you're comparing harvest efficiency,
the number of deer taken per hour effort.
Second is to compare the changes in deer density
between years determined, which of these programs
most effected their deer.
And lastly is to compare the vegetation,
including woody seeding density and also their
height, the present absence at each site,
and also thinking about key understory plants.
But it really boils down to does your density,
and vegetation conditions correlate or not?
So to do this, there's a lot of data required.
So I met with this,
the seven sites in the study
and only six of them use vegetation data.
So the first step is looking at the vegetation data
and here we see what year, like who provided what,
and what years they have.
And all of the vegetation data came from
another EMMA project, which is their exclosures,
which are 10 by 10 meter plots that are paired
one's fenced and one's unfenced.
So we're here, like I said, we're seeing the,
who provided what and where it had the clock
supplemental data, which I did for most of them.
And then there's the deer density part.
So we're here seeing who provided what
and what years they have and,
what was supplemented collected and take note
of the methods used here.
Everyone uses a different method
and for whether it be winter tracking or pellet counts,
camera's shop surveys with different methods or,
infrared flyovers and just all very different.
And lastly is the harvest records,
basically their method,
but also how they recorded their harvest.
Like, sex age class, hours spent,
their deer per hour, all that.
And again, you know, what years they provided,
being note that everybody uses different tops,
like started at a different time.
So really to get to it,
we're going to look at how I collected,
well compiled and collected
the vegetation data for the study.
So, like I said, it had to do some supplemental collection
in the summer of 2020 and 2021.
And I looked at the mostly herbaceous deer preferred plants,
which I call deer indicator plants
and identified them to species,
measure them in centimeters
and kept a number of the individuals at each species.
And similarly for tree seedlings,
I identify these woody tree ceilings that were less than
3.8 centimeters diameter at breast height.
Then find them the species as well,
heightened centimeters as well,
kept status if they were living or dead
and also kept a number
of their individuals for each species.
And here's a little picture of me in the field.
So next is the deer density part where like,
there are sites that do not manage to do,
so they do not have their deer density numbers.
So I needed like, all that for all sites.
So I had the two unmanaged sites,
Rockefeller and Huyck.
I ran camera trap surveys in the fall of 20
using Jacobson's branch antlered survey method
to estimate deer.
So here's me in the field.
Here's one picture I got of a buck at Huyck.
And so now after all this data compilation and collection,
there is a curation process and help produce these analyses
that I'm going to be showing a first thing to start,
you know, with deer related stuff.
And it was one of my favorite pictures that I got
from one of my cameras and my surveys.
So first we're going to look at
the total amount of hunting hours.
You know, annual rate by each site.
I wanted to make note first, you know,
like here's the hour spent,
but this year since started programs, since like I said,
every site has to be gone at different times,
started at different times, run different lengths.
I used years since start of program to, you know,
make up for this and compare everyone equally.
So, their first year it was year zero and so on and so forth
every year after that, we 1, 2, 3, 4, 5, 6, so forth.
So, here's every site in this plotted by its program type
while there, as simple as this, the program type.
So here we have Black Rock's firearm hunting,
which has the most amount of time spent by any site
by far, steady like that.
And then, a lot lower as the archery programs
where Teatown is the lowest of the archery programs,
but the lowest site,
the lowest amount of time spent by far
is that Vassar with it's firearm pole, as you can see here,
and they're all pretty steady with their time over time.
So moving on,
let's look at deer density change over time by these sites
and we can incooperate the sites,
who do not manage their deer for reference.
So we're looking at deer per square kilometer here
again by year since program start
and with each site by it's program type
and make, I also ran an analysis of variance
and it wasn't like deer,
the deer density was significant when
you look out over time and method.
So, meaning that method and time
were significant to deer density.
So we see that the archery programs
at Teatown and Ward Pound Ridge
are significantly decreasing deer density over time.
Whereas Vassar's firearm Cull
is their estimates are all over the place.
There's a lot of variations,
so it's slightly increasing over time,
but there's variation with everybody's, you can see here,
Black Rock's firearm hunting is low and steady over time.
And Mianus has some of the lowest densities
and it's slightly decreasing over time.
So, we make note here,
so here's Huyck and they're pretty high as expected,
but here's Rockefeller,
who's a little moderate as unexpected
in sites that don't manage their deer.
So, but still, we see that the sites that manage their deer
have lower deer density over time
and the sites that don't manage their deer
are a little bit higher.
So we'll support hypotheses 1A and 2A here.
So let's move on to the harvest efficiency over time.
So now it's the same process year since start of program.
We have deer harvest per hour,
their efficiency and analysis to variance.
If found that time and method
worsening a finger on the harvest efficiency.
So we began Vassar's firearm cull by far
the most efficient program type,
but it's decreasing significantly over time.
And then we have the archery programs which you know,
a little bit lower efficiency,
but they're also slightly decreasing over time and fast,
Black Rock's firearm hunting is low,
but significantly it's just standardly low over time.
It's very constant.
But what do make note here is that
at the archery sites, like Mianus, and Teatown
they run a supplemental winter pole
over bait with archery programs
and that efficiency is increasing over time.
As you can see here at the green.
And so, we do see that Vassar's Cull
is the most efficient it's firearm is most efficient
and BlackRock's fire hunting is breeze sufficient.
So we could partially support
hypothesis 3 here with the efficiencies,
and now let's move on to
the vegetation results a little bit here.
And so we're gonna look at the site seedling densities,
per a hundred meters squared per site over time
with their program type as usual.
So it's a little bit different here
and ran an analysis of covariance
on the change of deer density and the method.
And it was not significant to
the density of seedlings at each site.
Cause like yo6u see here, here's Rockefeller,
the site does not manage deer
and they have the highest seedling density
at any site and they don't manage their deer.
So then the only sites that manage their deer
that had a positive response was
Teatown with their Archery program.
That's a really good response.
And then Vassars firearm Cull it's pretty significant,
but everyone else, not really, there's nothing there.
And even when you look at the density of Tall Seedlings,
I just classified this as seedlings
that are greater than 4cm in height.
Again, analysis of covariance
on the change of deer density and
time method were not significant to not have Tall Seedlings.
You know, their density again,
your Rockefeller is still really high.
And the only side that had a positive relationship
was Vassar's firearm Cull here,
but everyone else it's just really not significant.
So I have to reject hypothesis 1B and 2B,
about those forest understory conditions.
So only when we incorporate the deer indicator plants,
those are mostly herbaceous plants.
Then we kind of really see
the diversity of each site showing up.
And that's what this graph does here.
We're looking at the Shannon Diversity,
the diversity score of each plot, each site.
And again it's plotted against total change in deer density.
That's why we see there's an increase of diversity
as there's an increase in the total change of deer density
that was removed by programs.
But still, we see here's,
this is definitely Rockefeller here
with this higher diversity.
And this is Huyck it's a little bit lower
and their diversity scores.
It's nice to see that like Black Rock has a slight change
in deer density, but they still have high scores.
And then of course the archery programs are doing well.
And what's surprising is that Vassar's Firearm Cull,
has a lot of change in deer density,
but it's a little lower than most of those program types.
So really here in the analysis covariance on the diversity,
it is significant when you consider
the change in deer density, time and program type,
but still hypothesis 4 was based off those, the cull,
the firearm hunting and cull being some of the highest
scores and so we don't see that here.
So I have to reject hypothesis 4.
And so it's just interesting to think about
how diversity only really is interesting to look at
once we incorporate the deer indicator plants,
and what has wondering about
the seedling response that we got?
Like what can really explain for that?
So to account for it a little bit,
here we're looking at the proportion of
Woody tree seedlings found within
the controlling exposure plots across all sites.
And these species here are only found like
these are all the species out of everything we looked at.
These are all found at least 50% of the sites,
only these out of everything that we looked at.
And so here, we've broken down the proportion
within the control and exposure plots.
The orange is the exclosures and blue is the control plots.
And the score at the top here is
the deer browse accesability index.
So that means 67% of black gum seedlings
were found within exclosures.
Whereas like around 33% were found in controlled plots.
And see we go from left to right,
the browse is, like it goes up like sensitive species,
browse sensitive all the way here is more browse taller.
We see where sugar, maple, and black Oak and Ash species,
these species that more browse tolerant, whereas black gum,
witch Hazel and red maple they're browse sensitive.
And these species in the middle,
they not really showing browse sensitivity
nor browse tolerance.
So that means they can withstand browse
and they're taking up a lot of space.
And then it's also just good to think about
when we broke this down by site,
only like these three species here were the only species,
black gum, witch hazel, red maple and hickory species.
Those, we only found at four to three sites,
these species, whereas in thinking about species uniqueness,
16 species that we sample were found at only one site.
Sorry, 16 species are found at least one site.
So a lot of uniqueness going on, which could contribute to,
the response we can diversity like Rockefeller,
where they have like such high diversity
for a site does not manage their deer.
And then like let's account for the deer indicators,
plants species where, here's maple leaf fiberon,
the only non invasive plant in this group,
and it was very browse sensitive,
and a lot of these plants were browse sensitive,
like a false Solomon's seal and herrings
moves Solomon's seal a little bit.
And we moved down, we see Jack in the pulpit
and white wood aster,
starting to move a little bit closer to browse tolerance,
but they're still pretty like in that middle space.
Whereas Canada Mayflower,
it'd become a very browse tolerant in this study.
And it's just very interesting to look at.
And these are clear indications of deer browse.
Like, if you wanted to monitor deer browse
these plants are doing a pretty good job at it.
So to really wrap this up,
culling is the most efficient method
for reducing deer densities we found,
but, site really better explained variability
and the vegetation response that we got.
And of course the deer density as well
than program type did.
So I like to think about other unmeasured factors
like browsing history, soil conditions,
the land use history that, it could account.
And I have found in the literature
that could account for the differences across sites
and also inconsistent methods of measuring deer density,
cost of living the comparison type
as your precision and accuracy is all very varying
for these different methods.
And also to think about more
is like poaching maybe occurring it's very unlikely,
but it could be occurring on many sites.
And let's say sites that manage deer
do see decrease and stimulation of deer over time,
so basically deer management programs
work at reducing deer density,
but also think about that some seedlings
may not be as sensitive to change in deer density
as compared to herbaceous plants,
or those indicator plants that I've found,
and maybe it'd be best to look at more
browse susceptible species or sensitive species
instead of looking at all species like I did.
So basically wrap it up, the take home is,
management and assessment of program success
should occur at the site level,
unless standardized metrics and protocols
are implemented at the regional level.
You know, thank you for having me again.
If you have any questions,
please feel free to reach out.
Otherwise, I hope you have a great day.
- Thanks Ralph.
So we have one minute for questions.
We have one here was, firearm hunting open to dose?
Did you look at harvest of bucks versus dose?
It's well-established that
to manage your populate populations
you need to harvest dose.
- Yes, it was open to parsing dose
and I did receive like each sites break down
like the sex age classes
that were harvested within each year.
And yeah, I did look into the literature where,
if you do want to reduce or stabilize your populations, yes,
you would much rather target dose.
- Great.
And if anyone has any further questions,
you can reach out to Ralph directly or through FEMC
and we can put everyone in touch.
So thanks again, Ralph.
- Thank you.