I have received a version of the following question from people in several states, most recently Alabama, South Carolina and Tennessee.
Q. We see or hear various frogs and toads in our neighborhood almost year round. This summer, our dog has managed to lick a couple and immediately started foaming at the mouth and shaking his head. The next day he did the same thing, as if he had not learned a lesson. Are there any particular species we need to be vigilant about avoiding for our dog’s health? I have heard of a toad in Florida that can kill a dog.
A. The most likely culprit in your case is one of the common brown garden toads native throughout most of the country east of the Rockies, from Canada to Mexico. Several different species occur, depending on geographic region. Dogs are most likely to encounter and catch a toad rather than a frog because toads are strictly terrestrial. They lay their eggs in an aquatic habitat, including puddles after heavy rains, but spend the majority of their life on land. Plus, toads hop slowly, cannot climb trees like treefrogs nor escape by jumping long distances and into water like bullfrogs.
Toads produce a toxic product called bufotoxin in glands on their heads, although the chemical makeup of the poison is complex and varies among species. Two large parotoid glands serve as a protective measure against most predators. When a dog bites a toad and squeezes the glands, a milky substance is secreted. The dog foams at the mouth almost immediately and usually releases the toad. I have not heard of a dog that died or got seriously ill from biting one of the native U.S. toads. But it may have happened.
The Florida toad you mention is actually the South American cane toad, sometimes called the marine toad. Both names are misnomers. Cane toads occur from Brazil through Central America to Texas. And these giant toads breed in freshwater habitats like other toads. They can be monstrous, nearly as wide as a dinner plate. Their parotoid glands can be the size of a bar of soap, produce large quantities of poison and be extremely toxic to other animals. Unfortunately, cane toads have been introduced into Florida and documented as the cause of death for dogs and cats that tussle with them. As for why a dog would keep biting toads, the toxin in certain toad species has a hallucinogenic component. Maybe some dogs, like some people, enjoy the high.
Like many other animals, toads have an arsenal of defenses against predators. In addition to having poisonous skin glands, a toad can fill its lungs with air if it is attacked. This ballooning strategy can be quite effective. A small snake, bird or mammal that tries to eat the toad will find the prey is now too large to swallow. Poison skin glands are widespread globally among frogs as well as toads. A few South American frogs known as the poison dart or poison arrow frogs produce alkaloid toxins all over their bodies and legs, providing protection no matter where a predator grabs it. These are among the deadliest poisons known. I have a friend who picked up one of these frogs in Colombia, South America. The skin secretions got into a minor cut on his arm and within seconds he was comatose and had to be transported to a hospital. He almost died.
Common garden toads, on the other hand, perform a great service in a backyard garden: They eat the insects that might otherwise eat your flowers, shrubs or vegetables. Although our native toads carry around a supply of poison for protection, they are completely harmless creatures when left alone and should be welcome in any yard.
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