Ben Colteaux, Ph.D., in the
Integrative Life Sciences program holds a snapping turtle in the field. (Photo
credit: Courtesy of Team Snapper)
By Leah Small
University Public Affairs
804-828-8355
Wednesday, Oct. 25, 2017
Crawling through neck-high mud on
riverbanks is a dirty job, but someone has to do it for the sake of Virginia’s
snapping turtles.
For four years, the researchers
spent several weeks at a time trekking through muddy turtle turf to catch and
tag the animals, and record indices of health and growth for multiple studies
on the impacts of wild turtle harvesting.
“Some would say it’s disgusting
and messy, but for my team and me it’s been a blast!” Colteaux said.
Team Snapper has documented the
extent of snapping turtle population decline due to skyrocketing rates of
harvesting in Virginia — a trend also occurring in other states. Three
tributaries of the Mattaponi, Chickahominy and Rappahannock rivers served as
study sites with harvest levels ranging from zero to almost 50 percent of the
snapping turtle population.
More than 200,000 wild snapping
turtles were harvested across the United States in 2012 and 2014, Colteaux
said, a dramatic increase from the nearly 50,000 harvested cumulatively from
1999 to 2011.
Colteaux said increased
harvesting of wild snapping turtles may indicate growing pressure on domestic
snapping turtle farms, which may not be meeting demand. The vast majority of
wild snapping turtles harvested throughout the country are exported to Asian
markets, mainly China, where animal populations have been decimated and farming
efforts are nascent, he added.
Colteaux, who heads the snapping
turtle project, is partnering with Johnson on four scientific papers that will
show the impacts of harvesting on wild snapping turtle populations. During his
dissertation defense in November, Colteaux will present data gathered in the
field from 2012 to 2015.
The pair published a paper last
year in the Journal
for Nature Conservation on the efficacy of size limits for
harvest reduction. In addition, one of Colteaux’s field technicians went on to
earn her master’s degree in environmental studies from VCU based on data from
this project.
“Low hatchling survival, combined
with late maturation and prolonged harvest, has the potential to decimate
populations in a very short period of time,” Colteaux said. “Even if harvest is
reduced or eliminated, it will take decades for populations to rebound.”
In Virginia, the population
decline has led to consideration of regulatory changes that would further
protect the turtles. The Virginia Department of Game and Inland Fisheries, the
state’s primary wildlife regulatory agency, has funded most of Team Snapper’s
work to learn more about snapping turtle population stress. The researchers
have also received substantial contributions from the VCU Rice Rivers Center.
“It’s one thing to say we need to
preserve wild snapping turtle populations, but protective legislation is made
more effective when it’s informed by solid research,” Colteaux said.
Saving the turtles
The data to back up stronger
regulations to protect turtles was difficult to collect, considering the
aquatic creatures’ habit of submerging to dine on fish and the detritus on
river bottoms. Team Snapper spent months traipsing through muck to set 20
netted traps daily in each of the three study sites. Armed with protective
gauntlets that guard against the animal’s claws and powerful legs, the
researchers checked the traps the morning after setting them. They recorded
weight, size, sex and other demographic measurements for any turtles that
wandered into the nets.
Team Snapper measures a turtle's
shell and fits it with a tracking device. Trackers help scientists determine
the animal's territorial boundaries. (Photo credit: Courtesy of Team Snapper)
“Each one is then fitted with a
numbered tag, in the hope of recapturing them at some later date,” Colteaux
said. “It’s incredibly hard work and a lot of trudging through mud and hauling
back nets and turtles.”
When turtles are recaptured over
subsequent seasons, the researchers are able to record growth rates and
estimate population sizes. Many of the turtles are fitted with tracking devices
that are painlessly bolted onto their shells, allowing the team to track range
boundaries, assess whether animals are territorial and identify variations in
range size between the sexes and across seasons.
“We use a handheld receiver to
track their positions. Frequently, we were up to our necks in mud or water with
the receiver overhead following the beeps,” Colteaux said.
This work is the first of its
kind, Colteaux said. Previous studies on these animals have focused on lakes
and other still bodies of water. Team Snapper has collected a wealth of new
information on turtle life in river systems that can be used to launch more
studies by researchers at any institution.
“Studying these animals in an
open water system is critical to understanding the potential effects prolonged
harvest has had on populations, as the majority of wild turtles harvested come
from rivers and not lakes or ponds,” Colteaux said.
Field technician Eric Burke uses
a radio receiver to track snapping turtles. (Photo credit: Courtesy of Team
Snapper)
Changing regulations
Virginia is one of many states
that have regulations on the size snapping turtles must reach before harvest.
In 2012, size limits were increased from a curved carapace length of nine
inches (which is a measurement of a shell from front to back over its peak) to
a length of 11 inches.
While that is an improvement, it
is not enough to protect the turtles, Colteaux said. Totuskey Creek, located
off the Rappahannock River, had an estimated harvest rate as high as 46 percent
annually from 2012-2015. The rate was the highest of the three sites studied.
Meanwhile, in areas untouched by harvesting, turtle populations are thriving.
One such site is Morris Creek, a tributary of the Chickahominy River, which had
an estimated annual population increase of 4 percent over the same time frame.
VDGIF staffing constraints have also hampered regulation enforcement and public
attention has focused more on the protection of big game, Colteaux added.
But as concern for snapping
turtles grows, so does self-policing by the watermen who harvest the animals.
Many harvesters frequently report to authorities incidences of overharvesting
by watermen from neighboring states working under Virginia licenses. The majority
of commercial snapping turtle harvest in Virginia is driven by out-of-state
harvesters, Colteaux said.
“The VDGIF receives many calls
that are from lifetime harvesters who say their fathers taught them and it’s a
family tradition. They are complaining there are too many out-of-state
harvesters taking too much,” he said. “They are at least letting us know where
there might be a problem and allowing us to get some eyes on the issue.”
The researchers also work with
domestic turtle processing plants to ensure the facilities are not purchasing
from harvesters animals that do not meet the size limit. One of the largest of
these plants is located in Maryland. From there, live females are shipped to
China to augment aquaculture operations. Males are mostly butchered, and the
meat sold to a variety of domestic and foreign markets. A small turtle plant
that serves local markets is located in Virginia Beach.
Armed with gauntlets, or
protective gloves, Colteaux holds a snapping turtle. (Photo credit: Courtesy of
Team Snapper)
To better inform VDGIF regulators
on turtle harvesting, the researchers are calculating the impact that
Virginia’s previous and current harvest size limits have on population decline.
They are also analyzing a plethora of potential harvest regulations to find the
best method to ensure viability of the populations. Two scenarios include
increases to the minimum size limit and the establishment of a maximum size
limit.
As Colteaux’s mentor and
co-author, Johnson taught the wildlife conservationist much of the analysis and
data interpretation required to draw conclusions from the scenarios.
Johnson helped Colteaux use data
on growth rates gathered from his recapture of snapping turtles, and other
indicators of population health, to determine the impacts of
overharvesting.
“When we combine Ben’s data with
other information on snapping turtles like harvest rates, survival probability
and reproductive output, we can model population growth under various harvest
pressure scenarios,” Johnson said.
According to the researchers’
models, if the stress on the population is reduced, snapping turtles could have
a fighting chance because they are naturally hardy creatures.
“Once they get to the adult
stage, they are bullet proof,” Colteaux said. “Their estimated rate of survival
at that point is about 94 percent and they can live upwards of 50 years. But
getting them to that point is really tough under current harvest conditions.”
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