One of the most important (but least appreciated) aspects of a good three-dimensional yard wildlife habitat is the ground surface. Most people would consider this the proper place for a lawn, which should be kept clean of debris. However, to have healthy wildlife habitat in your yard, you must have a substantial and natural litter layer.
A litter layer provides habitat for a community of critters, both invertebrate and vertebrate, that add biodiversity and interest to your yard. Whereas the average yard would be kept clean of leaves with chipped mulch just around flower beds, our yard includes many areas of leaf litter around shrubs, trees and flowers.
Leaves have substantial advantages over commercial mulch, especially the much-touted melaleuca variety. They provide natural food and cover for a wide variety of creatures. By contrast, exotic wood mulch may be rather sterile because it is too densely packed and can contain toxins.
Let’s look at some critters found in our Florida yard leaf litter. My favorite is the giant whip scorpion or vinegaroon, which is not uncommon on Manasota Key. It lives in shallow burrows under debris. While scary looking, it’s harmless unless you’re a small roach or cricket. It catches prey with a downward movement of its two fearsome pincers, but unlike its arachnid relative the true scorpion, has no venom — only a gland that sprays vinegar or acetic acid from the base of its whip-like “tail.”
Some common invertebrate consumers of leaf detritus are sow bugs and millipedes. This red millipede, one of the more attractive of the “thousand-legged” clan, actually has only two legs on each side per segment. They can secrete cyanide from glands if disturbed, but pose no threat to humans.
Some lizard predators of insects in the litter layer are the glass lizard and the five-lined or blue-tailed skink. The glass lizard resembles a snake since it has no legs and has a very long tail. This tail will autotomize (break off) when a predator attacks. But you can see that it is a lizard since it has tiny external ears, eyelids, a rigid body and a thick tongue — all characteristic of lizards. This predator “swims” in the litter and hunts its invertebrate prey.
The skink, shown here with a clutch of incubating eggs, is protected from larger predators by a toxin. This toxicity is advertised by the blue tail which will also break off if grasped by a predator. These blue-tailed skinks apparently have such an advertisement for two purposes: First, to direct the attack of a color vision predator (birds) towards the tail, which can be broken off to allow the lizard to escape; and second, to warn predators of the toxin.
Although the toxic nature of such skinks has long been known in woods folklore (large skinks are called scorpions in many areas of the South), it is only recently that herpetologists have known that these skinks are toxic to predators and cats have been known to become paralyzed after eating one. But blue is an unusual color to have been selected for this purpose, since red is the typical warning coloration for toxicity (for example, the red eft stage of the eastern newt).
Two small snake predators that live in the litter layer are the so-called blind snake, which has vestigial eyes and feeds on ants and termites, and the ring-necked snake. The non-native Brahminy blind snake, which few people are aware of, has made its entry to Florida in the dirt of imported potted plants. It resembles a dark-colored worm, and only upon very close inspection can you see that it has scales and a snake-like forked tongue. All individuals are females and reproduce without males, which facilitates their spread around the world.
The ring-necked snake is mildly venomous to small prey animals, and advertises this to potential predators with a bright yellow to red color of the abdomen — which is sometimes revealed by the uplifted coiled tail. The iridescent color of the skins of these burrowing snakes is due to a special surface layer that repels dirt particles.
Birds of the thrush family utilize the litter layer as a place to hunt by scratching with their feet. We had a hermit thrush that spent the whole winter in our yard, and this gray cheeked thrush stopped in our yard for several weeks while migrating north.
These are just a few of the marvelous inhabitants of the mostly unseen world of the litter. They are all beneficial in maintaining a balance among the sometimes obnoxious ground-living invertebrates that enter our houses and make themselves unwelcome. I find that the best defense against roaches is a twin strategy: Keep mulch and plants away from the house foundation, and encourage invertebrate and vertebrate predators which act as bio-control agents and add to the biodiversity of wildlife in our yards.
Bill Dunson is Professor Emeritus of Pennsylvania State University, thanks to a career spent entirely at that institution, teaching and doing research. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. Contact him at WDunson@comcast.net.