Bullfrogs are the largest frog in North America. Their size ranges from 8 to 20 cm when measured from the tip of the nose to the end of the body (not including the legs). A big female Bullfrog can weigh up to three quarters of a kilogram.

Habits: Bullfrogs prefer warm, weedy, permanent ponds and lakes. However, they are sometimes found in small ditches and along slow moving streams. Bullfrogs emerge from winter torpor in April. Adults bask on the surface of the water or on the shore but always remain close to the water. They are very wary during the day and may disappear quickly if approached closely. When startled, young Bullfrogs jump into the water with a distinctive "eeep" call.
      Adult Bullfrogs are voracious generalist predators which means that they have a very varied diet. On the menu are insects, tadpoles, frogs, salamanders, snakes, and occasionally fish, small mammals and birds. They can easily eat our native frogs but they often eat large numbers of smaller Bullfrogs.

Photograph by D. Purcell-Chung

Predators of small Bullfrogs include larger Bullfrogs herons snakes otters mink ospreys kingfishers

Larger individuals are beyond the grasp of most of the predators in our region. Bullfrog populations are mainly controlled through cannibalism.

Photograph by S. Price

Breeding: In late spring, male bullfrogs establish breeding territories which they aggressively defend from other males. They attract females with their snorous bass serenade while they lie inflated on the surface of the water exhibiting their bright yellow throats. It is this mating call that gives them their common name in French - auoauaron. The call has somtimes been described as sounding like jug o'rum but it is unclear how many jugs o'rum have to be consumed before this resemblance becomes evident.
      In the frenzy of mating a male bullfrog may sometimes grab another male by mistake. The unwilling suitor immediately gives a release call that sounds like someone with a bad cold blowing their nose, and the mistake is rectified. When a female enters the territory she is grabbed from behind in a loving embrace known as amplexus in frogs. If she is willing, she releases her eggs, which are then fertilized externally by the male.

Photograph by S. Price

Bullfrog egg-masses are laid in mainly in June and July, although they can be found as early as May and as late as August. Bullfrog egg-masses can contain up to 20000 eggs. The whole egg-mass is large (up to 1 m x 1 m), flat and floats close to surface of the water or is draped on submerged vegetation. The individual eggs are jet black, the size of mustard seeds, and are scattered in the transparent frothy jelly mass. Eggs hatch within 3 to 5 days of being laid.

Newly hatched tadpoles are tiny and sink to the mud and feed off their yolk sacs for the first week. Once they become active, tadpoles feed by scraping algae, bacteria and small organisms that grow on the surface of underwater objects. They also feed on decaying organic matter and even on dead tadpoles. By late summer they are about 3 to 10 cm long and spend the winter buried in the muddy bottom of the pond. They become active again in spring and spend the following summer as tadpoles and transform into froglets late in the summer. Some tadpoles may spend another year in the pond before metamorphosis. Newly metamorphosed frogs are about four centimetres long and will be ready to breed in three to four years.

Photograph by S. Price