Sunday, October 12, 2008

Bullfrogs "Tastes Like Chicken"


What tastes like chicken, is as large as a (small Bantam) chicken and eats ducklings?
Metchosin’s newest unwanted residents are giant bullfrogs that can be eight inches in length, weigh a pound and a half, have a loud, deep, sonorous call that is somewhat like a stuttering foghorn and ravenous appetites which are only controlled by what will fit in their ample mouths. Insects, snakes, birds, salamanders, fish, native frogs, even their own young are fair game for these frog leviathans.
Unfortunately, sometime in the 1930’s bullfrogs were introduced to Vancouver Island by entrepreneurial spirits who hoped to farm them for their small, chicken-like drumsticks (why not chickens you might ask). However the reality is that it takes a minimum of three years (usually more), under ideal circumstances, to grow a marketable frog and they are difficult to feed. Although they will eat almost anything, it must be moving prey and supplying sufficient quantities of live feed is expensive. So, plans that started out with high expectations were not realized and many frogs were dumped into our local lakes and ponds to fend for themselves.
It took awhile (apparently many invasive species spend 40-80 years slowly enlarging their range before they exhibit exploding populations) but bullfrogs have become the newest in a long line of introduced, invasive species to call Metchosin home.
And what is so bad about that?
They eat too many of our native species that have not evolved methods to evade them. Our red-legged frogs are in decline and are included in the province’s blue list; they don't need this extra burden on their chances for survival. Bullfrogs are also thought to transmit but not be affected by the potentially fatal frog disease Bd or chytrid fungus that has caused mass mortalities of some amphibians species around the world, the impact on amphibians on Vancouver Island is not known yet. Bd is amphibian specific and will not harm humans, ducks or fish.
They have few predators here because our native species that could hunt them have not evolved to eat them and just don’t recognize the food opportunity that bullfrogs present. Bullfrogs are cannibalistic and they are their own most fearsome predators As well, bullfrogs have protected themselves for eons by producing eggs and tadpoles that are considered distasteful to many would-be predators.
Bullfrogs adapt easily to disturbed habitats. Because they need 20-25ºc water temperatures before they can breed in June/July, they like the increase in water temperature that comes when riparian vegetation is removed and the sun can beat down on open water. Because their tadpoles take one to two years until they transform into frogs, they need bodies of permanent water. When we change a temporary wetland into a year round pond or even construct ponds, we are sending out an invitation to bullfrogs that reads, “Highly desirable accommodations with excellent food supply available for newcomers!”
Our native red-legged frogs and Pacific treefrogs breed in early spring in temporary (and permanent) wetlands that can dry up by mid-summer. However this type of habitat is increasingly scarce as development and ignorance of their importance cause them to be bulldozed and paved or converted into year round ponds. This in turns leads to increased proximity with these new arrivals as bullfrogs and our native amphibians use the remaining lakes and ponds.
Adult bullfrogs are easy to recognize because of their large size, smooth skin (not warty like our toads), round disk on the side of their heads (set near their eyes), and their guttural vocal displays. They are somewhat more problematic to recognize in their younger stages. A young bullfrog might be confused with an adult red-legged frog but a bullfrog has the large ear drums and a red-legged frog has reddish colouring on the inside of its thigh.
Our native frogs breed in early spring and the raucous two-note chorus you hear early in the year is from our treefrogs. Red-legged frogs only call underwater and western toads have a quiet twittering bird-like vocalization. Bullfrogs remain hibernating on lake bottoms until late April or early May and their mating calls happen from May through August. One story has it that they are named bullfrogs because their calls “sound like a bull a quarter mile off”!
Bullfrog egg masses can be found for only a few days after mating, during the summer, and they look like poppy seeds scattered in a large (1 m x 1 m) patch of frothy slime which may be covered in algae. No wonder they are proliferating, they can contain up to 20,000 eggs! If you find an egg mass like this, often surrounded by vegetation, try to gently lift it out of the water (it breaks apart easily) or suck it out with your shop vac or bilge pump! However do not attempt this unless you are have a positive identification that you are looking at bullfrog spawn. Get expert advice.
Our other aquatic amphibians have dissimilar egg masses that you should be able to differentiate. Treefrog and red-legged frog egg masses are found earlier in the year; treefrogs are only about 4 cm in size and round with 12-60 eggs while red-legged frog egg masses are cantaloupe sized. In mid-spring, western toads lay long single strands of eggs, although many strands may be laid on top of one another.
Our aquatic salamanders all have distinctive eggs that cannot be confused with the bullfrogs. Northwest salamanders eggs are massed into a firm orange to grapefruit sized ball of jelly, long-toed salamanders are laid singly or in small plum sized masses that are attached to rocks or vegetation and roughskin newts hide their single eggs so they are difficult to find.
The best way to protect our native species and to prevent the influx of bullfrogs is to refrain from moving frogs, their eggs or tadpoles. If you have a new pond that you would like populated by our native frogs and salamanders, supply conditions they can use and they will find you, they are always on the hunt for new habitat. There is a provincial law which prohibits the release or transport of non-native species except by permit and in 1992 the federal government signed onto the Convention on Biological Diversity which reads “as far as possible and as appropriate, prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitat or species”. It seems highly unlikely anyone will get even a token fine for being in contravention of these laws but your good conscience might dissuade you.
Additional ways to prevent bullfrog infestations include retaining your seasonal wetlands and resisting the temptation to turn them into permanent waterbodies. Try to leave the shoreline vegetation intact or replant with native species, which helps to keep water temperatures cooler and undesirable to bullfrogs. Even where bullfrogs are numerous some native species can survive if there is enough vegetation that can provide protected areas in which to hide and feed.
Bullfrog tadpoles start small but can reach up to six inches in length and have been used as fish bait. Sometimes the bait swims away and starts to colonise new areas so please resist using them as bait.
If you would like to capture the adults, they are most easily approached at night, quietly and slowly, using a bright light which will immobilize them for a while. There are many methods of capture including using nets, spears, bows and arrows and angling. Use weapons only for adult bullfrogs so that there is no confusion between the juvenile bullfrogs and red-legged frogs. The animal care community has approved any method which rapidly severs brain function, such as decapitation. According to an article I recently read “the most humane way to kill the cold-blooded bullfrogs is to place them in a sealed container in the refrigerator for about 6-12 hours to kick in their hibernation instincts, and then place them in a freezer for one-two days.”. I’m not sure how the rest of the family will react to a fridge full of frogs however! Cajun frog legs?
Broom, gorse, tansy ragwort, rabbits, starlings and now bullfrogs; all these invasive species are having a huge impact on our natural ecosystems. However bullfrogs have just arrived in Metchosin and perhaps with a little knowledge and persistence we can contain or eradicate them before they cause irreparable damage. For more information, contact the Bullfrog Project or Bullfrog Control, listed below.

Amphibians of Oregon, Washington and British Columbia by Corkran and Thoms
The Bullfrog Project:
Bullfrog Control:

Cajun Frog Legs Recipe from the Internet:
16 good sized frog legs,
1 cup shortening,
1/2 cup flour,
3 cups milk,
1 tsp paprika.
1/2 tsp onion powder,
1/2 tsp garlic juice,
1/2 tsp ground cayenne pepper,
1/4 tsp black pepper,
1 dash white pepper,
1 dash oregano,
1 dash rosemary, salt to taste
Directions: Skin, clean and rinse frog legs well. Cover with whole milk and garlic juice in a plastic mixing bowl, refrigerate overnight. Pat dry, season with paprika, onion powder, cayenne, black pepper and desired amount of salt. Add white pepper, oregano and rosemary to the flour. Heat shortening in a skillet. Lightly flour the frog legs and fry until golden brown.

1 comment:

Richard Powell said...

Great article, good information and well written. Thanks!