The Nature Writers of Texas

The best nature writing from the newspaper, magazine, blog and book authors of the Lone Star State . . .

Sunday, August 15, 2004

Slugs are not the Loveliest of Creatures
Ro Wauer, August 15, 2004, The Victoria Advocate, © 2004

Most non-biologists or gardeners think of a slug as the guy next door who spends most of his time drinking beer and watching TV, and rarely if ever has anything nice to say. We all know some slugs, and none are very pleasant. And what is fascinating is that the slow moving creature that crawls across the roadway, invades gardens, and is a beer-lover - also known as a slug - fits the human profile pretty well.

The outdoor slug is closely related to snails, even possessing a shell. Those of snails are obvious, but slug shells are much smaller and rarely visible as they are located underneath the flesh on their back. Their mouthparts are located in front of the head and contain a sharp rasping strap, called the radula. It is used to tear food into small pieces, which are then passed back through a cavity to be digested.

Slugs move across the terrain by gliding on a ribbon of mucous secreted by their own bodies. They are able to follow slime trails secreted earlier by themselves or other slugs. In this manner they are able to utilize a network of host plants. Dee Kennedy, in "Nature's Outcasts," wrote that "slugs aren't just slimy - they're connoisseurs of slime. They secrete and employ different kinds of mucous for use in locomotion, self-defense, temperature regulation, and mating."

But what is the strangest slug characteristic is that it is a hermaphrodite, having both male and females reproductive organs. They go through male and female stages at different time. In a sense, they can mate with themselves. Eggs are laid in the soil in clusters of two dozen or more. Adults usually overwinter in the soil and can live for several years. When warm weather arrives, they soon are gliding about in search for food.

There are about 40 species of slugs in the United States. Three of the more common types include grey field, black, and common garden slugs. In the Northwest there is a huge yellow slug known as a banana slug because of its banana-like appearance. The slug in the Mission Valley area where I live is the common garden slug. I believe that it has only moved into the area during the last couple years; I never saw one until about two years ago. And now it seems to be on the increase; it is most abundant during rainy periods. During dry periods, like what we have experienced the last few weeks, slugs remain burrowed in the soil or in other moist sites. Since slugs are composed mostly of water, dehydration is dangerous. The common garden slug is one to two inches in length with a lighter side-stripe. Like all slugs, it has two pairs of tentacles, a longer upper pair that has eyes on the end and a shorter lower pair that is utilized for smell.

Most slugs are vegetarians and can cause serious damage to garden plants, but a few are carnivorous and prey on snails and earthworms. The latter group may have little effect on gardens, but the vegetarians can be a real pest. Those species feed on many kinds of leaves, stems, bulbs, and even tubers, often digging deep into the soil for a choice meal. They are able to detect food at a distance, and Kennedy points out that "if you change the location of the food while they're en route, they'll reorient and set off in a new direction."

Does this suggest that our gardens are doomed once slugs invade? Although many unattended gardens can be impacted, slug control is possible. Controls can range from direct elimination, which takes a concerted effort once the slugs have invaded, to a number of ideas from maintaining soil free from decaying materials, establishing a barrier, to various chemical controls. I once attracted slugs to beer bait and physically killed those that I found in the saucer of beer. C. Malcolm Beck and John Howard Garrett, in the "Texas Big Book," suggest dusting "dry hot pepper in problem areas," or using citrus oil spray or coffee grounds "sprinkled on top of mulch." They also suggest some natural controls like planting "stands of clover and mulches to favor ground beetles and rover beetles (which eat slugs). Centipedes also eat slug eggs." And they point out that "in the insect world their biggest enemy in the larva of the lightening bug." The abundance of lightening bugs in our area is on the side of our gardens.

Sunday, August 08, 2004

Fall Migrants Already
Ro Wauer, August 8, 2004, The Victoria Advocate, © 2004

The appearance of a female black-and-white warbler in my yard on July 27 suggested an earlier than normal southbound migration this year. Although this warbler species nests in woodland areas not far to the north of the Golden Crescent, any warblers that enter our area after mid-July can be considered a migrant. This is especially true for females, because females of most bird species usually remain on their breeding grounds longer than the males. Males of many species are well known for their habit of departing early, leaving the ladies to finish raising the babies.

Hummingbird males always leave early. They are considered little more than "promiscuous rakes," departing their breeding grounds almost immediately after breeding. Even male rufous hummingbirds, a species that is little more than an uncommon migrant and winter resident in South Texas, can be found in mountain meadows of Mexico by early July. Rufous hummingbirds nest only in the extreme northwestern United States and north into Alaska.

There are numerous other bird species considered "early" migrants. Examples include most shorebirds and many ducks, especially those that nest on the northern tundra. These birds usually arrive on their nesting grounds in early spring, raise a precocial family, and must leave before winter weather sets in. Sometimes circumstances, such as nest destruction in the far north where time does not permit a second try, can lead to an earlier than normal movement toward the south.

Some of the earliest of the southbound migrants reaching the central Texas Coast area include species that nest just north of our area. A few examples include broad-winged hawk, eastern wood-pewee, northern rough-winged swallow, yellow-throated and black-and-white warblers, Louisiana waterthrush, and field sparrow. Some usually late southbound migrants to reach South Texas include house and winter wrens, hermit thrush, orange-crowned and yellow-rumped warblers, scarlet tanager, and white-crowned sparrow.

One of the very best references to our local bird's status and their movements through our area is Mark Elwonger's little book, "Finding Birds on the Central Texas Coast," subtitled "What to look for, how, when, and where to look," is available from the author at greenowl@vicec.org. The bird distribution list included with this book can also be obtained from ornifolks.org. Elwonger's book also includes 19 of the best bird-finding sites in the Central Texas Coast area.

Is there any significance to an earlier than normal migration period? Any response to that question would be analogous to a meteorologist explaining why Hurricane Claudette hit our area earlier than predicted in July 2003. However, everything about nature has an explanation. And most explanations regarding bird migration relates one way or another to weather conditions. But one explanation is that an earlier or more severe than normal stormy period in the Arctic or elsewhere in northern North America could speed the departure of many species, resulting in their arrival into Texas earlier than normal.

Whether that occurrence suggests weather patterns to the south, such as whether or not we can expect a colder or warmer winter than normal, does not relate.

What does relate, however, is the greater than normal number of waterfowl, sandhill cranes, and some of the more northern songbirds in South Texas when wintertime weather patterns just north of our area are extremely cold. For instance, ducks and geese can occur in huge numbers in South Texas when weather conditions in northern Texas and further north produce heavy snows and frozen lakes and bays. It is far too early to predict winter bird numbers.

Sunday, August 01, 2004

Water Snakes in South Texas
Ro Wauer, August 1, 2004, The Victoria Advocate, © 2004

Water snakes, those that live primarily in and adjecent water, are not often seen in most of South Texas. So, when I recently encountered two individuals of a species I had not previously seen, it awakened my interest in these water-loving creatures. This new find was especially well marked with broad yellow-orange bands across its black body and an orange head pattern. Both individuals were about three feet in length. It took me only a few minutes to identify it as a broad-banded water snake once I got home and looked through my various reptile books.

The location, Palmetto State Park in Gonzales County, where I found these serpents represents the western edge of its range, according to my three reference books: Roger Conant's "A Field Guide to Reptiles and Amphibians of Eastern and Central North America," Werler and Dixon's "Texas Snakes," and Alan Tennant's "A Field Guide to Texas Snakes." The latter two contain excellent photographs of this colorful snake, and all three describe its normal range extending eastward along the Gulf Coast and within the lower reaches of the Mississippi River Valley. They also point out that broad-banded water snakes prefer fresh water sites, although the species also occurs in marshes of Chambers and Jefferson counties, some of which lie along salt water margins.

There seems to be a difference in this water snake's taxonomy. Werler and Tennant (published in 2000 and 1999, respectively) refer to the broad-banded species as Nerodia fasciata confluens, while Conant (1975) uses the genus Natrix. But to most of us it matters little whether it is Nerodia or Natrix; the common name remains the same in this case. They all agree it is live bearing, broods number about 15 young, and it preys primarily on fish, frogs, toads, salamanders, and crayfish. It feeds both at night and during the daylights hours, foraging mainly along the shoreline.

At least four additional species of water snakes occur in South Texas: diamondback, blotched, gulf salt marsh, and Mississippi green. Diamondback water snake (N. rhombifer) inhabits much of Texas, including the coastal plain where it can be abundant. It has blackish-brown lines that form a diamond-shaped network across its dark olive to grayish-brown back. Blotched water snake (N. erythrograster) also occurs throughout most of Texas. It is gray-brown with a hint of olive color with pale dorsal lines bordered with black. Gulf salt marsh water snake (N. clarkii) is restricted in Texas to a coastal fringe south to about Corpus Christi. It has a pair of dark brown stripes against a paler, grayish ground color. Mississippi green water snake (N. cyclopion) is also restricted to the coastal plain, but it does occur further inland than the gulf salt marsh species. It is poorly marked, but is blackish with faint paler markings.

None of the Nerodia/Natrix water snakes are poisonous. All will attempt to escape when cornered, and will bite only as a last resort. There are several more snake species that spend considerable time in and around water areas, in both fresh and salt water. Several of the garter snakes (genus Thamnophis), a few occur in South Texas, are good examples. And several of the poisonous snakes also frequent water areas. The best known of these includes the western cottonmouth and a number of the rattlesnakes.
Snakes are fascinating creatures, and the encounter of one not previously seen was something special!