Hi Rob and Angi,

Thank you for contacting OSU Extension Service and for your terrific questions!

The photo that you shared is indeed of an American Bullfrog - https://www.dfw.state.or.us/conservationstrategy/invasive_species/docs/bullfrog_fact_sheet.pdf. Here are some responses to each of your questions:

• Should we try to eradicate them or is it a lost cause?

Yes! Working toward eradication is the preferred goal. The American Bullfrog is a non-native frog species in Oregon, and causes ecological harm to native wildlife species and their habitat. While we are not likely to eradicate this species entirely from Oregon, removing their egg masses early (or tadpoles and adults if spotted later) will help reduce their negative impacts on the other desirable species, such as the native Pacific Treefrog (likely the species of tiny green frog you mentioned), that use your water feature and our wild lakes, ponds, marshes and rivers and surrounding habitats. Doing your small part to reduce the population of American Bullfrogs will have positive benefits!

(see this terrific slideshow for information on bullfrog (and other amphibians) identification, including eggs, tadpoles and adults: https://wdfw.wa.gov/sites/default/files/2020-05/amphibian__eggmass_lesson.pdf).

• If we do nothing will the biggest one eat the others and thus control their own population? 

Adult bullfrogs are known to eat the young of their own species, but not enough to be a control on its own population. Bullfrogs lay between 8000 - 120,000 eggs (source: WDFW slideshow above), but typically an average of 20,000 eggs, while native frogs tend to lay many less eggs (e.g., the native red-legged frog lays an average of 5000). The egg masses of the bullfrog take the form of a floating mat. While many of those eggs will not survive to adulthood, that's still a lot of potential adult bullfrogs making it!

• If eradication is the answer, should we just "shoot 'em when we see 'em"?

Yes, that is really the only answer. The benefits of having water on your land outweighs the negatives of attracting bullfrogs, and so short of removing the water entirely, lethal means are the only option if you wish to get ahead of the issue. The linked ODFW fact sheet above describes methods of killing the adults (Bullfrogs take 2-4 years to become fully adult), which includes "stunning the frog with a sharp blow to the head, followed by decapitation." Adults are not easy to approach, so my recommendation is to scan for egg masses early in the season (eggs are laid typically June). The eggs can be hard to see, because as they begin to develop, they tend to stick to vegetation and get covered in algae. Best to search early and remove and discard as soon as you see them. Also, if you see tadpoles, try to get them out early too - I'm thinking maybe something like a long handled net used to skim leaves and other debris from a swimming pool may be an effective tool.

• Are the birds mentioned above likely to be adversely affected by bullfrogs?

Bullfrogs have been known to eat ducklings and other small aquatic birds - if it can fit into its mouth, they will eat it. Songbirds are less likely to be consumed by bullfrogs because they aren't generally on the water, but if they happen to be foraging near the edge of water where bullfrogs hang out, they can be at risk of being eaten. What is probably more detrimental to birds is that bullfrogs eat aquatic insect larvae that songbirds will eventually eat (such as aquatic insects that become flying adults, e.g., mayflies, caddisflies, stoneflies). Bullfrogs are very detrimental to other aquatic amphibians and reptiles, like our native and rare red-legged frog and western pond turtle. 

• If the birds will still stop by every year and the population doesn't become obnoxious we can share our little pond with the new frog.

The answer to this is more complicated. Having the water feature attracts the adult bullfrogs to lay eggs that hatch and develop into tadpoles and eventually adults. It also attracts the desirable native species, such as songbirds, treefrogs, dragonflies, etc. Water is a vital part of the habitat for migrating and nesting birds. As mentioned earlier, it is next to impossible to completely eradicate the bullfrog now that it has gotten a foothold in Oregon. That said, getting the population down to a manageable number is the goal, and you may even find that you can eliminate the species over time and maintain that condition with regular monitoring and intervention. If you happen to completely eliminate the bullfrog, that's a huge win for native species, especially other frog species like the Pacific Treefrog that already uses your pond. Song birds are likely to continue to visit the water feature whether or not it has bullfrogs, and they are probably going to do just fine. That doesn't mean there is NO risk to the birds, so the best option is to keep striving toward no bullfrogs in your pond. The good news is that it is small enough that monitoring it for eggs and adults is going to be a lot easier than if it were a large pond or lake.

A couple final thoughts: 

Bullfrogs thrive in warm water. If you can decrease the temperature of your pond, you may reduce the suitability of it to attract bullfrogs. If you can, plant trees, shrubs, native forbs (wildflowers), and maybe even sedges and rushes (grasslike plants) to increase the amount of shade that falls on the pond. Choosing wildlife friendly (and native) trees, shrubs and other plants will improve the habitat for more diversity of species of birds and pollinators, and improve water quality and decrease the suitability for bullfrogs. 

I hope this response helps.

Best of luck on removing bullfrogs from your pond!

You are quite welcome! Glad to know you can manage the bullfrogs.

Enjoy the little pond and best of luck!

Jason

There are thirteen fewer threats to native species today. Thank you again for your assistance. We will remain vigilant and continue to shoot on sight any confirmed bullfrogs. The native tree frogs are already chirping their approval at this new turn of events.

Hi Rob! Thanks for the update! Glad to know the eradication has gotten off to a successful start!

Jason