Invasive Species Awareness Spotlight – the American Bullfrog

The last week in February marks National Invasive Species Awareness Week, a week that highlights the non-native flora and fauna that wreak havoc on our ecosystems.

The Montana Invasive Species Council (MISC) published a list of nine ‘invasive species to watch’ for the State of Montana, each containing a marker of how likely prevention and eradication is for the species. One species mentioned to have remarkably widespread consequences is the American Bullfrog.

This hoppy, unsuspecting critter is native to the central and eastern United States; however, it is invasive in Montana. The threat of the bullfrog mainly lies in their ability to eat just about anything they can fit in their mouth, including birds, rodents, frogs, snakes, turtles, and bats. Unlike our native frogs (the northern leopard frog and the Columbia spotted frog), adult bullfrogs grow to be significantly large, weighing up to 2 pounds and measuring more than 8 inches in length. Their large size may supply their voracious appetite, but it also likely aids in their ability to migrate easily over land to find more suitable habitats. Research has shown that adult bullfrogs can travel distances exceeding 1 kilometer depending on conditions.

The bullfrog also has the potential to carry amphibious diseases, such as the chytrid fungus that has been cited as one of the biggest threats to amphibians worldwide, although it seems to have the most severe impact on frog populations.

Like other invasive species, bullfrogs can reproduce rapidly, as well. Females can produce anywhere from 10,000 to 20,000 eggs a day and these eggs only take 4-5 days to hatch. Depending on the conditions of the waterbody the tadpoles are in, it may take from 4 months to 3 years, to mature. Studies on bullfrog populations in the Yellowstone and Bitterroot Rivers suggest that the tadpole stage may last 2-3 years in Montana.

Currently, the bullfrog has only been found in the Bitterroot, Flathead, and Yellowstone River basins in Montana. It is assumed that they established in the Bitterroot and Flathead basin in the 1960’s, however the Yellowstone population is more recent. Bullfrogs were found in wetland/pool complex of the Yellowstone River in 1999, just outside of Billings, Montana. It is believed that these frogs ended up in the rivers of Montana after someone illegally released their pet bullfrog or a frog being used as bait.

To help protect our wildlife and waters from bullfrogs or other potentially invasive species, there are several things you can do:

1. Never move or dump a bullfrog into a pond or river in Montana. If you are ever unable to care for a bullfrog pet or other animal please re-home it. The “Don’t Let it Loose” webpage has resources for rehoming pets organized by state and city.
2. Report bullfrogs if you see one on the water to Montana FWP.

Groups, such as the Montana Conservation Corps (MCC), have taken more creative approaches to eradicating bullfrogs. Once every Fall, MCC, in partnership with Montana FWP, and the Confederated Salish and Kootenai Tribes, host a Bullfrog Removal Volunteer Night. Volunteers have the opportunity to gig (spear) the frogs, with the option to roast the frogs later, and enjoy the fruits of their labor.

Promoting eating invasive species is nothing new or unheard of. This year, the US Fish & and Wildlife Service launched a campaign, encouraging people to eat certain invasive species as a means to diminish their population. The campaign focused on five invasive species causing trouble within the US: nutria, northern snakehead, green iguana, invasive carp (bighead, silver, black, and grass carp), and feral hogs; stating they are “downright delicious.” An article written to promote eating the invaders, encourages people to check their state’s regulations and restrictions before grabbing a fishing pole or hunting rifle.

While Invasive Species Awareness Week has ended, monitoring for and preventing invasive species is something that can happen year-round. For more information on Montana’s Species of Interest, visit FWP’s website at: https://fwp.mt.gov/conservation/species-of-interest.