Erica's Original Notes When one is in the Garden, it is hard not to notice some of the other 'visitors' exploring the plant displays! Here you will find a few brief notes on the most interesting ones we meet:
Slugs and snails: These are our nearsighted, ever-present visitors in the garden; they have two eye-bearing tentacles which cannot form images but are sensitive to light. However, they have a strong sense of smell and touch and a unique tongue equipped with microscopic teeth that do such a great job on tender seedlings! They glide on a large ventral muscular foot aided by a secretion of slime; this coagulates like glue if you try to wash it off your hands, presuming you've picked one up in the first place! This slime serves the useful purpose of protecting them against predators and keeps them from dehydrating. They have a hole near their head, called a land lung, which traps the air. The blood then carries the oxygen to the body; the lung opens again to release carbon dioxide. They also excrete calcium carbonate which repairs their teeth and helps to enlarge the snail's shell. They are bisexual, which adds a certain variety to their love life, although this occupation does occur at 'a snail's pace'! And everyone can lay eggs, which may explain why there are SO MANY! Unfortunately those that are serious garden pests are imported from the Old World, especially the Black slug (Arion ater). The gross Banana slug (Ariolimax) is a native to North America and is relatively harmless.
Frogs are amphibians which remind us of life's early existence when we notice the gill clefts in the tadpoles; these gills can also be seen in the embryos of reptiles and birds. The frog stays in the muddy bottom of the pond during the winter months, as there is adequate oxygen for it, but, when the pond temperature rises in the spring, the frog's pulse quickens, and the need for extra oxygen makes it emerge from his winter environment. Its lungs are inadequate to meet its need for oxygen, so they are supplemented by its skin which absorbs oxygen as well; the skin must, however, be moist to do this; also the skin contains an extra supply of blood vessels for the exchange of gases. As well, the frog breathes with the floor of its mouth by closing the glottis, looking as though it is panting; to complete the procedure, it ventilates the lungs by opening the glottis and closing the nostrils, and, with a great GULP, exchanges the stale lung air with a fresh supply. The mucous membrane of the mouth is also used for exchange of gases.
The frog's temperature is controlled by evaporation from its skin, so the greater the heat, the more it transpires, and the colder it feels. The reverse is true on cold wet days. An aid to temperature control is the contraction of skin pigmentation, so it becomes much paler in hot weather. As to eating, the frog is not able to chew; its legs rake the food of any debris before being taken in by the tongue, with extra mucus being secreted and with blinking eyes! There is no bony base to the eye sockets, and an extra skinfold at the sternum allows room for extra large prey! Stay a while by one of the ponds and watch a frog; see how it pants and then gulps in fresh air; and, on a hot day, it will be in and out of the water to keep its skin moist and enable it to absorb more oxygen. If you have the opportunity to pick one up, gently turn it on its back and stroke its tummy with your forefinger; this will amazingly put the frong in a trance, and it will stay thus when replaced for quite a while - but don't let it get dehydrated!
Toads: These landlubbers have 'warts' on their skin, which are glands containing poison as a defense mechanism. In the seventeenth century, a Dr. Etmuller of Leipzig prescribed dried toad skin for heart diseases; it has since been discovered that toad skin contains a digitalis-like drug.
Sowbugs: They go by many names, each being slightly different; the woodlouse or pillbug is able to roll up in a tight little protective ball. They are terrestrial relatives of the lobster, feeding on decaying vegetation, but quite happy to have the odd meal of fresh plant growth. They are happiest living under anything that fits snugly against the soil, giving them a cozy, moist environment.
Earthworms: Below the surface of moist, fertile land live millions of earthworms, moving about in miniature tunnels which they have formed by pushing through moist soil and eating their way through when it is hardpacked. Much of the faint rustling noise heard in woods and fields at night is due to night-crawling worms foraging for fallen leaves. They pull them down into their tunnels, pointed end first; then, because they have no teeth for chewing, cover them with saliva to make them soft enough to eat. The moister the soil, the nearer the worms will be to the surface. They are sensitive to vibrations and to bright light; their sense of touch is concentrated near the head. Rough bristles, 'setae', grow along their body and give them traction. They start to aestivate, the opposite of hibernate, towards the end of June.
Moles: Although we're unlikely to meet these tireless diggers, we are certainly made aware of their work by the hills that appear, usually across an immaculate lawn. They spend their nights searching for worms and grubs, eating their own body weight daily; if they have no food for 12 hours, they will die. They tunnel up to 300 feet a night; their wedge-shaped head and enlarged forelegs with broad nails are a great asset in this endeavour. They are aided by short, powerful hind legs; their fur lies flat in both directions!
Coyotes: They are in the dog family, with light yellow fur tipped with black; a basically wild animal who seems to have become happily urbanized to the detriment of the local cats!
Raccoon: Another urban dweller, mostly nocturnal, lives during the day up in the trees hidden from sight, descending for any available handouts at dusk. Water is usually nearby for them to 'wash their hands' which are fantastically versatile and used in searching ponds for fish or opening garbage cans! [Hyperlinks added 2013]
Updates 2013 (MG) When Erica wrote her notes, she discussed painted turtles, but the current turtle population has been identified as red-eared slider turtles which are descended from abandoned pets. Erica's notes have been slightly amended to take this change into account:These cold-blooded, toothless reptiles can be found sunning themselves on rocks and banks of the lower lakes, after hibernating in the muddy bottoms. Their olive-black shell is protection against predators: the upper body, or carapace, is made up of the backbone and ribs joined by bony plates into a solid mass, the front border having a characteristic yellow margin; the bottom part, or plastron, is made up around the breastbone. We enjoy seeing these quiet visitors peacefully enjoying the garden, noticing the stripes on their heads sticking out of the water. It's a mystery just where they lay their eggs, especially when the surrounding area to the ponds are kept in such good order!
Later Note-2012: The mystery of where the turtles lay their eggs was partially solved in the summer of 2012 when they were seen digging nests in the Perennial Garden!