American Toad, American Lawns

Deborah and I were out in our garden (or, more accurately, “weed patch”) this past Saturday taking advantage of the warm, sunny weather to get ready for our spring plantings. In the asparagus patch, as she was clipping off the old, standing stems, Deborah reached down to dislodge a fist-sized stone only to be surprised by its softness and mobility! It was an American toad, Bufo americanus, still a bit torpid, half-buried in its hibernation hole. The toad was caked with soil and slowly hopped about until we covered it up back in its hibernaculum. Given the cool weather of this year’s April, it was probably still a little too early for its emergence. Bufo americanus can be active, though, from April to November depending upon the local climate and weather conditions. During their active seasons, they typically spend the day-light hours in shallow soil burrows, or under logs, or within leaf piles and then emerge at night to feed on a wide variety of insects. Their inactive seasons are spent in the deeper, hibernation burrows that they dig into the soil. We have been fortunate to have American toads in and around our garden for many years now.
In their natural habitats most American toads live for a year or significantly less. Successful (or lucky!) individuals, though, may live for 5 to 10 years in natural ecosystems and are, thus able to reproduce (sexually maturity occurs after 2 to 3 years). In captivity, American toads are known to live much longer. One captive individual, for example, lived for 35 years before its unfortunate, accidental death.

Bufo americanus’s main tool for food gathering is its tongue which is long, sticky, and rapidly extensible. The attachment of the tongue inside of the lower jaw facilitates its rapid extension toward prey. The toad’s visual acuity, total visual fields, and large, binocular visual fields (for 3-D vision) contribute to the efficiency of prey detection and capture. Prey items readily taken include flies, crickets, locusts, grasshoppers, bees, wasps, beetles, spiders, caterpillars, earthworms, slugs, and snails. It is estimated that 88% of their prey are invertebrates that are classified as agricultural pests. In a three month season, a single toad will consume nearly 10,000 insects and, thus, has a significant economic value for farmers and gardeners.

Many predators would be expected to find B. americanus an ideally sized prey choice. Relatively few predators, though, readily take American toads for food. Its cryptic coloration, its ability to change its coloring to match substrate, and its avoidance of daylight and even moonlit nights all contribute to the effectiveness of its camouflage. Toads are also able to “play dead” upon encountering a predator thus confusing the predator’s instinctive behaviors. Also, the production of toxic cutaneous secretions and parotoid gland (two glands located on the head just behind the eyes) poisons make the American toad a less attractive food item than might have been originally suspected. Garter snakes (which may have a resistance to the toad toxins), hognose snakes, hawks, herons, and raccoons are predators of adult toads. Eggs and tadpoles are eaten by a variety of fish, diving beetles, and predaceous diving bugs.  It is interesting that toads raised in captivity do not, apparently, produce the parotoid and cutaneous poisons.  The chemically complex arthropod diet of naturally raised toads is thought to be the source of the toad’s protective toxins.

As many of you know, last June 21 three massive thunderstorm fronts blasted through southern Armstrong County. Many trees were knocked down by the strong wind gusts including eight of our, fifty foot tall Norway spruces. The loss of these trees changed the appearance of our property considerably and also exposed a large area of soil that had been sheltered by these trees for the past sixty years. The thick accumulation of spruce needles along with the dense shading of the standing trees had generated an area almost totally free of any understory vegetation. Coming into this area now, though, are the first waves of pioneering plants that are able to tolerate the dry, acidic conditions of the thick spruce mulch.  European generalist species like broad leafed dock, common chickweed, garlic mustard, dandelions, money plant, and red clover are growing in isolated patches along with a few native plants like yellow corydalis and wild mustard. There are also clumps of various grasses (including bluegrass, rye grass, and fescue) which are also, like most of the other “pioneers,” introduced, European species. These plants are forming the first stages of a successional sequence that will, if left on their own, re-vegetate the entire disturbed area. Last summer, in a small (about 30 by 30 foot) portion of this area, I spread topsoil and seeded in some grasses (a mix of fescue and bluegrass). I then was forced to water the area extensively in order to get the grasses to germinate, root, and grow. The impact on my water bill was phenomenal! This experience reinforced some very simple lessons about lawns: they are both economically and ecological very expensive entities.

The American Water Works Association Research Foundation (1999) estimates that 57% of all residential water is used to water lawns! Martin Quigley of Ohio State University (Research Extension Bulletin 177-01) states that lawns cover more land in the United States than any agricultural crop (over 50,000 square miles!) and that more chemicals (herbicides, pesticides) are applied to lawns than are used to raise any single agricultural crop. The Garden Club of America estimates that three million tons of fertilizers are applied to American lawns each year. They also indicate that much of this fertilizer is applied so inappropriately that it causes extensive surface and ground water pollution. And, the EPA (2003) estimates eight hundred million gallons of gasoline are used each year in the United States just to run lawn care equipment and that seventeen million of these gallons are spilled leading to air, soil, and water pollution. This use of gas powered machinery, again according to the EPA, generates 5 % of nation’s total air pollution including a substantial percentage of the lower atmospheric ozone and smog in the summer.  Lawns are beautiful things, but we have to be careful how we manage them!

Faced with a water bill last summer that was 50% higher than usual, and with the recognition of the ecological realities of lawns, Deborah and I have decided to do something different in our spruce area. Xeriscaping (“dry landscaping”) involves many of the principles and plants used in Green Roofs (a topic that was developed by a group of my students four years ago and presented at the 2004 Undergraduate Research Fair). We are going to transplant some myrtle that has taken over one of our perennial gardens and add some sedum and a number of drought tolerant herbs (like lavender and juniper) right on top of the spruce mulch to try to generate a green cover of these plants. These plants will compete with the current “weeds” and, hopefully, generate a rich, self-sustaining plant community. This “lawn” will not require mowing, fertilizer, or water and should result in an aesthetically pleasing and ecologically “friendly” system. I will keep you posted!

What else? Trillium is blooming on the Rock Furnace Trail. Turkey vultures are perching on my silver maple tree (more on them next week!), and great blue herons are flying overhead. Spring is really here!

More next week! Remember, this Tuesday is Earth Day.  To help mark the day, a map and reference guide to the arboretum trees of the Campus Nature Trail will be posted on the Virtual Nature Trail web site ( www.nk.psu.edu/naturetrail). Get out and see the rich array of trees that we have growing along this wonderful trail!

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