March 2023 - 27

Mudsnails are successful invaders because
they have many advantages over native species.
They feed on algae and decomposing
organisms, so they can find a food source in
most aquatic habitats. In their native range,
mudsnails have natural predators and parasites
that limit their population growth and cause
them to employ different reproductive strategies
where both sexual and asexual reproduction
occur. However, mudsnails found in the
U.S. are all female and reproduce asexually.
Therefore, only one snail is required to start
a new population and the number of snails
in a population can quickly grow.
These snails can be elusive, even when
there are a lot of them. They're small, only up
to a quarter-inch long as adults and smaller
as juveniles. They can hide in aquatic plants
or floating debris that can be moved from
water to water, which expands their range.
People can easily move these snails without
even knowing they're there, making humans
the primary vector of spread in the U.S.
Mudsnails are commonly found at wading
access points and boat launches. Wading
anglers often spread populations from these
sites unknowingly. Mud and plants concealing
mudsnails can be easily transported
within and between waters, especially on gear
and equipment such as waders, watercraft
and anchors. Wading boots, especially those
with felt soles, can be difficult to clean and
are effective at concealing and transporting
mudsnails. Mud from a river bottom brought
into drift boats from waders or anchors can
contain hundreds of snails. Their small size
and dark coloration help them avoid detection
during gear inspection.
Using their opercula, mudsnails seal themselves
off from the environment and can live
outside water for extended periods if they
have moisture around them. Studies have
shown mudsnails can survive for more than
a month on a damp surface. If equipment is
not cleaned and allowed adequate time to
dry, there is ample opportunity for snails to
be moved long distances and remain alive
once they enter a new water.
BEATING THE COMPETITION
Mudsnails can quickly become prolific
outside their native range. Mudsnail populations
have a pattern of booming and busting
in these environments. Densities reach
extremely high levels, with mudsnails dominating
an ecosystem, then sharply decrease.
Researchers have observed this pattern in
mudsnail populations in Wyoming. Leslie
Riley, professor of biology at Ohio Northern
University, conducted studies on the effects
of mudsnails near Yellowstone National Park
in the early 2000s and saw these population
dynamics firsthand.
" In Polecat Creek, that population was
500,000 snails per meter squared at one point,
and it crashed, " Riley said. However, a crash or
bust for mudsnails does not indicate a collapse
of the population. In subsequent sampling,
researchers found fewer mudsnails but similar
issues within the community.
When snail densities are high, ripple
effects can be seen throughout the aquatic
ecosystem. Having hundreds of thousands of
mudsnails in a water body can cause increased
competition for food, and a system may not
have the capacity to support this population
in addition to the preexisting invertebrate
community. The food source for mudsnails
overlaps with native snails and invertebrates,
often to the detriment of those species.
Mudsnails are successful
invaders because they have
many advantages over native
species. They feed on algae
and decomposing organisms,
so they can find a food source
in most aquatic habitats.
Although small, New Zealand mudsnails outcompete other native species
for food and can damage fisheries. (Photo by Tracie Binkerd/WGFD)
Wyoming Wildlife | 27
March 2023

Table of Contents for the Digital Edition of March 2023
