Guarding the Garden Toad from HarmBy Lois Tilton (LTilton)
April 11, 2008
Every spring, as the ground begins to warm up, I wait for the toads to begin singing down at the pond. Sometimes, when they are late emerging from hibernation, I worry. Existence is perilous for a toad. Environmental degradation has caused amphibian populations worldwide to decline. Closer at hand, the toads must face the effects of drought in the dwindling pond, and predators, including a burgeoning population of voracious bullfrogs. The children's book notwithstanding, Bullfrog and Toad are not really friends!
The toads that sing in the pond at the edge of my property are the American toad, Bufo americanus. The details in this article refer to this species, but they may apply to any member of the genus Bufo. The American toad's skin is mottled, usually brown with darker spots, and quite warty. A large female may grow to as much as 4 inches in length. Like many other members of this genus, it exudes a bufotoxin that coats its skin and makes it unpalatable to many predators [although not bullfrogs]. It is by any measure a common toad, the most widespread species in North America. While B americanus is not threatened or endangered in its range, individual populations can be put at risk by many local factors.
Most threatening are the effects of human activity. The gardener, who stands to benefit so much from the industry of the toad, can inadvertently do it more harm than any other agency. The toad's usefulness in the garden is measured by its diet. It exists primarily on common garden pests, such as slugs, grubs, snails, sowbugs, earwigs, cutworms, and destructive caterpillars. With its long, sticky tongue, B americanus is a successful predator that can eliminate as many as ten thousand of these undesirables in a growing season.
To safeguard the toad, it is important to understand its life cycle. Many people mistakenly believe the toad is an aquatic or semi-aquatic animal, like the frog, but for most of its life the toad is terrestrial. Only in spring, emerging from hibernation, does it make its way to the shallow edge of the pond to spawn. Toads prefer to return to the same body of water where they themselves were spawned, and may travel up to a mile to reach it. There, at night and sometimes during warm rainy days, the males begin their chorus of song to attract females. The male tightly grasps the female, who then releases her long strings of gelatinous black eggs into the water to be fertilized by the male. Each female can lay several thousand eggs that hatch into tadpoles within ten days or less, depending on the temperature of the water. It can take one to two months for the tadpoles to develop into toads; during this phase, they are entirely aquatic and highly vulnerable to contamination of the water, as well as predation by such creatures as bullfrogs. It is a profligate survival strategy; out of the thousands of eggs laid, less than a dozen will survive to maturity.
In summer, the toadlets complete their metamorphosis and hop out of the pond to begin their lives on land. In this phase, it can be hard to tell them from crickets, and they are now vulnerable to predation from birds instead of bullfrogs. Fortunately, even at this stage they secrete sufficient bufotoxin to repel many predators.
Except in the breeding season, toads are mainly concerned with finding food and shelter. They do not like the drying heat of the sun, which is why they are nocturnal and why they look for a damp, cool place to make their home. Since gardens tend to be watered or irrigated, they naturally attract toads, who usually find a plentiful supply of slugs and other toad-appropriate prey. If a toad settles into a spot and is undisturbed, it will not only remain but return, year after year, to the same location.
Toads are excellent diggers and often excavate dens in soft soil or mulch – toads love mulch. They dig out a cavity with their rear feet, appearing to sink backwards into the hole. There they will rest during the day and emerge at night to hunt for food. When the weather turns colder, the toads prepare to hibernate, either by digging out their den to a deeper level or by finding a more protected location. There they remain until the warm weather of spring brings them out again to spawn. It takes two or three years for a toad to reach breeding maturity, and if fortunate it may have another three seasons to live and reproduce.
So the toad lived in harmony and mutual benefit with the gardener for hundreds of years. Unfortunately, changes in gardening technology have been at the expense of the toads. While tilling and cultivating were carried on by hand, with spade and hoe or horse-drawn plow, these activities did not greatly endanger the toad. However, a riding mower at full throttle with a speed-crazed teenager at the helm is another matter. Lawnmowers, rototillers and weed-wackers all wreak carnage on the toad population. In the garden, a toad's natural camouflage can work against it, making it all too hard to distinguish from a clod of dirt.
What to do? Besides hiring a horse and plow? First of all, simply taking care will save a great number of toads.. These creatures are alert to danger, with acute hearing. They can tell when a weed-wacker is approaching the border where they are concealed in the overgrown grass or weeds. So when you are using machinery, be aware where toads are likely to be hiding, be alert to spot them, and give them a chance to hop out of danger. Don't be in such a hurry to get the job done that you run over the toads in your way.
Another effective way to protect your toads is to provide them a shelter. The classic method of making a toad house is to cut a toad-sized opening in the rim of a terra-cotta pot and set it upside down in the soil, preferably in a shady spot. The unglazed terra-cotta absorbs water and keeps the toad house nice and moist and cool in the heat of the day. It can be difficult to cut the opening without cracking the pot, however; some people claim to have success with drilling pilot holes or using a tile saw. I take the easy way out and simply prop up one edge of the pot with a couple of flat stones. The toads haven't complained.
Some people enjoy providing more elaborate houses for their toads. But many kinds of garden decorations and building materials can serve just as well as toad sanctuaries – flagstones, retaining walls, statuary. Toads are not demanding. A compost heap, a couple of rocks, a woodpile – any of these are likely to harbor a happy toad. Last year, I found a small colony of them living contentedly in the deep, damp straw covering my potato patch. They were not so pleased, however, when I raked away the straw and started to dig up the tubers.
The other great danger to toads is through the use of pesticides and other garden chemicals. Look on the label of these products, and you are likely to see an environmental warning that they are toxic to aquatic organisms such as tadpoles. Pesticides, herbicides, fungicides, even nitrogen-based fertilizers – any of these may be poisonous or harmful to amphibians if they contaminate the water in which they breed. This includes chemicals applied anywhere that runoff can carry them into the pond.
But adults are almost as vulnerable as the tadpoles, even after they have left the water. The skin of a toad is permeable; rather than drinking, it absorbs water by osmosis through the skin of its belly. In doing so, it also absorbs any chemicals it comes into contact with. While a toad shelter may provide some protection against direct application, these chemicals can still be deadly when the spray drifts onto the ground. There is simply no doubt: the more organic your garden practices, the safer it will be for toads.
There is one more thing you can do for toads: make them a pond. Without a body of water in which to spawn, toads can not breed. The pond need not be overly large or even permanent, as long as it does not dry out during the spring and early summer, while the tadpoles are growing. The ideal pond should have shallow sloping sides where the toads can enter the water. Besides the toad pond here, I have a smaller ornamental pond elsewhere on my property, where for years I tried to attract toads until I realized that they did not care for its steep, straight sides. [Small bullfrogs, unfortunately, had no such problem with it, leaping to and from the lily pads.] There should be vegetation growing both in the water and along the margins of the pond to provide cover for the tadpoles and shelter for the mating toads, as well as attracting insects for them to eat.
If you build it for them, the toads will come. And if you keep the water safe from contamination, they will reward you in the spring with delightful song.
Photo Credits: Toad spawn - bonitin