- [Narrator] All right well, we will start with Josh Blouin.
He is with the Vermont Cooperative Fish
and Wildlife Research Unit
through the Rubenstein School of Environment
and Natural Resources at the University of Vermont.
And he will be presenting today about
Moose Habitat Selection and Fitness Consequences
during two critical winter tick life stages in Vermont.
- [Joshua] Good afternoon, my name is Joshua Blouin,
I'm a masters student at the University of Vermont,
and today I'll be discussing the second chapter
of my masters thesis,
Moose Habitat Selection and
Fitness Consequences During Two Critical Winter Tick
Life Stages in Vermont.
So due to time constraints
I just wanna very quickly give some background.
Moose populations have been declining in Vermont
and a study was initiated in 2017 that ran through 2019
to examine mortality and productivity rates
here in the State.
So 126 moose were fixed with GPS radio callers
in wildlife management units E1 and E2
in Northeastern, Vermont.
This study and Jacob Dubbo from the University
of Vermont Thesis Work found that heavy infestations
of winter ticks is really a driving force
of mortality for our population
especially in the Northeast corner of the State.
And when I say heavy infestations, I'm talking greater
than 60,000 winter ticks on a single calf
just under a year old.
So this is a really gruesome hard way
for these individuals to ultimately perish.
So what is the relationship between winter ticks and moose?
So I just wanna quickly go through this life cycle.
So we'll start when the tick larvae are climbing
onto vegetation and seeking a host, preferably a moose.
Once on the moose, these winter techs go through
two life stages, nymph and adult on the moose
taking blood meals and molting between each stage.
During the late winter early spring period,
these female ticks take their most significant blood meal
in preparation to drop-off the moose.
So after they've engorged with blood,
these female ticks drop from the moose
into preferably leaf litter,
where they then lay their eggs and the cycle continues.
I think it's really important at this stage
to point out these important winter tick life stages.
And again that is the peak questing period
and the peak drop-off periods.
So that fall questing period is that
we defined as a 50 day period
where these winter ticks are really seeking
that host or that moose and the spring drop-off period
when those female winter ticks are taking
their largest blood meal, which typically drives
those calves under a year old to mortality.
So what do we know about moose habitat selection
during these two really critical winter tick life periods?
Well one important study here in new England examined
third-order or within home range habitat selection
during the questing and drop-off periods.
And I'll talk here in just a second about what I mean
by third-order habitat selection,
but the key findings from Christine Healey's paper in 2018
found that, moose were selecting the same habitats
during both the questing and the spring drop-off periods,
which was really promoting this winter tick and moose cycle
as winter ticks tend to be fairly immobile.
So where they drop-off is typically where they're picked up.
So I wanna transition quickly into describing what I mean
by first, second and third-order habitat selection.
So in 1980, Johnson described this hierarchal manner
of habitat selection.
And it's important to note these different scales
as analysis and interpretation of selection
may change depending on which scale you're examining.
So first-order habitat selection is interested
and is more core scale examination
of where a species tends to be found.
What is their geographic range?
While second-order habitat selection is referring to
the selection of a home range
within that geographical range.
So where are animals?
Where do they tend to spend the most time
within their geographical range?
While third-order habitat selection is more interested
in this fine scale examination of habitat components
within an individual's home range.
So this is what Christine Healey was examining for
during these two time periods.
So what were moose using within their home range?
And this is also what I used in the first chapter
of my thesis when I was examining utilization
distributions for individual moose.
And so we have a better understanding of what mortality
and reproductive rates look like from this study,
as well as the suitability of habitats
from my first chapter,
and this third-order selection
during these important winter took life stages
outlined by Healey in 2018.
But an analysis of habitat selection
at these more core scales
first and second-order habitat selection
and how selection decisions
may ultimately affect the fitness of moose
could provide really important insights
for their management as they're in decline.
So the objectives of this chapter were to investigate
that first-order habitat selection of adult female moose
during those two important winter tick life stages
using multi-season occupancy framework.
And the second objective was to evaluate
fitness consequences of habitat selection
during the fall questing period for cows
who had calves that survived
versus cows who had calves that perished
due to heavy winter tick infestations.
So to get at first-order habitat selection
by adult female moose,
we imposed a grid of roughly 1700 patches
across our study area.
Each one square kilometer in size.
We then filtered our GPS radio caller by two periods
so that tick questing and the tick drop-off period
for all female moose captured during the study,
and this resulted in over 12,000 GPS locations of 74 moose.
So the next step was to identify habitat variables
of potential importance to moose occupancy.
So we used LiDAR Habitat Structure,
so this really fine scale examination
of the height classifications of vegetation
as well as these NLCD habitat composition variable.
So what is the forest type of these areas?
And so we can map these across our study area.
Here's an example of some of our composition
and structure variables as well as terrain
such as elevation and slope mapped across our study area.
So as you might imagine, incorporating both this structure
and this composition habitat variables
into a model can be rather complex
and often these relationships are correlated.
And so we created a principal component analysis
or a PCA to account for their complexity
and some often correlated relationships
between habitat structure
and composition variables.
So each principal component is explaining
or was explaining a different combination of the variables
which were ultimately driven by these loadings.
When I say loadings, the figure on the right here
is showing with arrows
how certain habitat variables are ultimately
affecting our principal component.
And I think the big picture here is to focus on
on the right, you know,
we have all of these structure and composition variables
that are pulling these principal components
in different ways, but we ultimately end up with
the map on the left
that is four primary principle components
that describes all 11 of those habitat variables.
So now that we have gritted our landscape,
created our patches or our sites
and identified our important habitat variables,
we are now interested in mapping the distribution of moose
across patches on the landscape.
So we create an encounter history
for each of those important winter tick life stages.
And you can see here from on the figure on the right
if you can imagine that gridded landscape again
the green patches are identifying patches on the landscape
that were occupied by moose during that time period
or the white patches were areas where moose were undetected,
and this encounter histories are showing changes
in occupancy patterns through time and across space.
And so these multi-season occupancy models
really allow us to examine those changes through time.
And there are four key parameters
to a multi-season occupancy model,
but for simplicity and time constraints,
we'll really focus on these three.
So the initial probability that moose occupy a patch,
is based on those habitats structure
and composition variables.
So psi is looking at, in that first year
in early 2017 that dropout period,
what is really driving that initial probability
that moose will be there and in a patch.
Next colonization and extinction parameters,
they're really focusing on what is driving changes
in occupancy over time and through space.
And so for example in the drop-off tick period in 2017,
the patches within this red rectangle are moose
there was undetected, no moose were detected there
but in the following time period,
that questing period in 2017,
some of these patches were occupied by moose.
So what is driving those colonization rates?
And same for extinction,
so patches that were colonized in 2018 drop-off period
but then in the following questing period of 2018
moose were not there.
So what is driving these changes?
So we used our presence to evaluate these changes
in occupancy patterns, across the patches and through time.
So we created a model set of 24 models
each representing an alternative hypothesis
explaining these changes in occupancy.
I don't have time to go into the model set
but just know that there was one clear top model
that was examining the probabilities of extinction
and colonization as a function of the habitat structure
and composition variables.
So this brings us to the key results for objective one.
So we mapped the probabilities of both the colonization
and the extinction rates for our top model.
So the areas of darker red in our study area
are showing higher probabilities
of either extinction or colonization,
while the white patches are showing areas
of lower probabilities.
So there are a couple of key takeaways from this figure.
Number one in the upper right-hand figure
we notice that during the fall questing period
the probability of extinction is very low
for most patches in our study area.
And this likely means that moose are moving around much more
during this time,
which makes sense given what we know
about moose behavior during the mating season.
Given that, let's focus on the time period
when moose are dropping ticks on the landscape.
So the two figures on the left.
So patches where the probability
of extinction was low and colonization was high
during the spring drop-off period,
is really showing these areas with the
highest probability of moose occupancy.
And these are really characterized
by higher proportions of young or shrub forage
mixed forest at those greater elevations.
I think it's also really important at this point to remember
that where winter ticks drop-off moose,
is likely where they will quest the following fall.
So this brings us to our next objective.
Are there important patterns or relationships
between the habitats adult female moose are selecting
during that period when they're picking ticks up
and the fate of their offspring.
So to determine these patterns of habitat selection
and the fate of their offspring,
we radio collar moose in January,
we would follow these adult females
throughout the winter into early may
when they typically gave birth to a calf,
we'd follow that calf through the summertime,
come the following January
we asked the capture crew to really target these cows
that we knew had calves.
So we had observed them all summer.
And they were able to go out and capture 10 cow calf pairs.
And what this allowed for was this inference
of where was that cow calf pair
during the fall time period when they were picking up ticks.
And now that we've collared that calf in January
we know their ultimate fate,
so some died due to heavy winter tick infestations
and some lived,
and thankfully it was split in half.
So from this two resource selection functions
were estimated one for adult females
whose calves survived age one,
and one for adult females whose calves perished
prior to age one.
So due to time, I just wanna quickly breeze
through these methods for objective two.
So we greeted the landscape
but this time at a much finer scale,
so 200 meters squared patches.
Also similar to objective one we performed this PSA
to really account for complexities
and correlation between our habitat variable.
So for each resource selection function,
we estimated used or unused patches
as a function of the different
principle components describing our habitat variables.
So for each individual, we used all of the patches they used
and a thousand randomly selected unused patches.
We then repeated this 10,000 times
to end up with a resource selection function
for each individual.
So these were then aggregated across the individuals
who had calves that lived versus those
who had calves that died.
So this brings us to our key results for objective two.
So if we look at this figure here on the X-axis
our principle components describing our habitat variables
and on the Y-axis are our estimates.
And so we can see from this box plot
that if a cow has a calf that died,
so fate equals zero,
those clear bars versus the cows with calves that survived
there are clear differences in how
they are selecting habitats
when they're picking up winter ticks.
And so this brings us to the major key result
which is females with calves that died
were selecting habitats with higher proportions
of young, mixed forest at higher elevations.
And if you remember from objective one,
these were areas where the probability of occupancy
during the time period
when they're dropping ticks was highest.
So where the highest occupancy of moose
where they're dropping their ticks,
cows that were spending the most time in those areas
where their offspring were perishing
from heavy winter tick infestations.
While the individuals with calves that survived
were selecting habitats with
adequate young deciduous forest,
but also habitats with higher proportions of mature canopy,
evergreen forest, and wetlands at lower elevations.
So their second order habitat selection patterns
were deviating from the majority of the moose
in their occupancy analysis.
So these are really exciting results
in that they show fitness consequences
of habitat selection decisions made by female moose
during that time when they're picking up ticks.
In our analysis of first and second order habitat selection
in combination with Healey's 2018
third-order habitat selection,
really gives this detailed examination
of moose habitat selection patterns
and how those selection decisions may ultimately relate
to winter tick infestations.
So in terms of management,
our model coefficients and mapped results
really help to define these potential hotspots
for both moose and for winter ticks.
And so Timber Management, for instance,
may benefit from this knowledge of potential hotspots
by encouraging habitats that benefit both moose
but limit winter tick loads.
So potentially encouraging uneven age
selective cuts for example.
In terms of winter ticks,
little is known about the ecology, abundance and management
of these winter ticks in their natural settings.
So management and research may benefit from these
the knowledge of these potential hotspots
and really focus future research that can ultimately
help break the negative impacts
of this winter tick moose cycle.
So with that, I will end my talk here today,
thank you so much for listening,
I just wanna give a real quick shout out
to some of the organizations that made this study possible
such as the Silvio Conte Wildlife Refuge,
and all the kind staff there
particularly Refuge Manager, Steve Agius,
also to VELCO for their continued support
throughout the project.
A handful of people to thank, particularly my advisors
Jen Murdoch, and Terry Donovan,
and folks from the State such as Cedric Alexander,
Scott Darling, Mark Scott, and Tony Smith.
So thank you for tuning in
and I'll be happy to answer any questions folks might have.
- [Jason] This is Jason Helf.
Can you hear me - [Joshua] Oh hey Jason
yep I can hear you.
- [Jason] It's really interesting that it looks
like the high elevation habitats may pose
to be maybe a little bit riskier
for tick acquisition for these moose,
so I'm thinking with respect to climate change,
is that potentially a good thing?
Does that suggest that these lower elevation habitats
may provide viable areas for moose longer than we think
moving into the future?
- [Joshua] Yeah, I think that's a really good question
and a good point,
because I think it's important
when we're thinking about the relationship
between winter ticks and mooses,
how weather may ultimately affect winter ticks.
And we know from some research at UVM
with Sheryl Sullivan's work and others elsewhere
in New England in kind of a laboratory setting,
that weather and cold can really impact these winter ticks
and so, yeah, maybe these higher elevation habitats
may prove to be detrimental for winter ticks
as the weather changes.
It's hard to know but I think the big takeaway is,
this is pointing towards kind of supporting the theory
of higher moose densities are kind of driving
this parasite load.
And so those cows or calves that are kind of
selecting the perimeter,
the periphery habitats that may be
seen as potentially suboptimal
in terms of forage and things,
may ultimately be really beneficial for their fitness.
And so, yeah, it's an interesting dynamic there but
it's a good question about future weather patterns
and how that might affect that the tick levels as well.