Pennsylvania Game News - February 2023 - 34

There were none here now and little
evidence of any recently. But they'd been
here before, often, and would undoubtedly
be back. A trail camera aimed at a " crossover "
- or spot river otters regularly use
to move from one water body to another
- at this location captured images of the
animals each of the past two winters.
Cool, right? Otters are playful and
charismatic, a treat to see even as still lifes.
These images, though, may serve a
higher purpose.
" With river otters, no one has come up
with a really easy way to monitor populations, "
Keller said.
A novel trail camera survey might be
that answer.
Game Commission staff deployed
more than 70 cameras, combined, across
the Northeast and Northwest regions each
winter for three years, from 2020 to 2022.
All operated for about eight weeks, from
early January through early March.
The goal was twofold: to determine
otter occupancy, meaning whether otters
were in an area, and to get a handle on
relative abundance, meaning how many
there might be at a location.
That latter metric especially is typically
a " tricky thing to get to, " Keller said.
Biologists often use mark-and-recapture
surveys - trapping animals, tagging
them, then releasing them to see what
percentage shows up in the harvest - to
monitor wildlife. That's how the Game
Commission monitors black bears.
To audit otter density specifically, some
rely on " bridge " surveys. That involves
walking up or downstream a predetermined
distance from a bridge, looking for
otter sign, then comparing that to what's
found walking a similar track around
other bridges.
Both techniques are effective, Keller
34
said, but also hugely labor-intensive and
time-consuming. Trail camera surveys,
by comparison, might prove an easy and
cost-effective alternative.
Roger Coup, Wildlife Management
Supervisor coordinating the work in the
Game Commission's Northwest Region,
agreed. They don't provide a population
estimate, he said.
" But they tell you if you've got otters
present and what the relative abundance
appears to be, " Coup said. " So they're a
good way of collecting baseline information
without having to put a lot of manpower
out in the field for a long time. "
The notion of using trail cameras in
wildlife management is relatively new.
It's only been in the last half-dozen years
or so that researchers nationwide seriously
began experimenting with them,
Keller said.
That's partly a function of how percepe
tive
off-the-shelf cameras are now. Keller
points to another Game Commission project
that involves putting cameras inside
upside-down buckets with small holes cut
into them. The goal is to capture images of
least weasels and things they might prey
on, like mice and voles.
" And those cameras are picking up
slugs and ants and things you would never
expect them to pick up, " Keller said. " But
that's the kind of sensitivity we have right
now with the newer technology, whereas
before you'd almost have to have a deer
walk by a camera to get it to go off.
" They offer a glimpse of species we
don't normally see because they're either
nocturnal or shy. I think all of that just
opens up a huge opportunity for other
species that we're interested in looking at. "
But, because using cameras as a pas
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