Tuesday, December 3, 2013: we saw sign of beaver activity in the form of several small trees (willows?) felled in the upper reach of the Creek near where the eastern rivulet empties from the Pond into the Creek.
Friday, March 7, 2014: we heard in the late evening the sound of a beaver slapping its tail on the waters of the Pond.
Saturday, March 8: we finally saw a beaver swimming in the waters on the east side of the Pond.
In what is a book on the subject of ancient burial practices in this Central Texas area (Hunter-gatherer Mortuary Practices During the Central Texas Archaic, by Leland C. Bement), we read as a series of side notes some interesting theories about the flora and fauna of our region before, during, and just following the most recent ice age.
Paleoenvironmentalists work to create a series of changing pictures of plant and animal life over periods of long ago by observing such data as can be found in the pollen record and in protected caves, for instance. And during the period known as the Wilconsin Fullglacial (22,500-14,000 B.P.), the giant beaver (Castoroides sp.) lived and felled trees within the forests that covered a much cooler and wetter Central Texas than the one we inhabit. This was the same period in which lived the mastodon, the tapir, the long-nosed peccary, and the bog lemming (this last species being found today only in the colder, wetter northern region of our continent).
Here are some of the recent periods, their years back from us, and the Central Texas ecology of the time:
Late Quaternary period — 33,500 B.P. to the present
Wisconsin Interpluvial — 33,500-22,500 B.P.
cooler, wetter grassland with herbaceous plants and a few scattered conifers. For our area, probably tall grass prairie with pine and aspen growing in canyons such as ours.
Wisconsin Fullglacial — 22,500-14,000 B.P.
“conifers and deciduous trees expanded their ranges, reducing the grasslands of central Texas. Pollen data from west and central Texas show a rapid increase in the percentages of spruce and pine pollen, as well as pollen from basswood, maple, poplar, and alder. Specifically from central Texas, pine and oak pollen percentages are low during the Fullglacial period. Support for a forested central Texas during the Fullglacial is provided by faunal species such as the giant beaver.”
Lateglacial — 14,00-10,000 B.P.
a drier and warmer climate with “reduced woodlands and parklands and increased scrub grasslands. . . . Certain tree species, including willow, birch, spruce, basswood, alder, tupelo, and ash, were gone from central Texas by the end of the Lateglacial period. This is also the period of extinction for many of the large mammals, including the Jeffersonian mammoth, American mastodon, saber-toothed cat, dire wolf, and Harlan’s ground sloth.
Postglacial — 10,000-0 B.P.
warmer and drier, with pollen analysis revealing a decrease in woodlands, except for the increase in oak pollen, suggesting a post oak savanna much more like what we have today, with greater variation in the climate than before.
Below is a good summary of glaciation on this continent. This is from the U.S. Environmental Protection Agency’s site (http://www.epa.gov/gmpo/edresources/pleistocene.html):
“Several times in the history of the earth huge sheets of ice, or glaciers, covered large portions of its continents. The most recent episode of glaciation, the Pleistocene epoch, is commonly referred to as the Ice Age and began approximately 1.6 million years ago. During that time there were a number of advances and retreats of the glaciers, which are termed glacial and interglacial stages, respectively. The glaciers of Greenland and Antarctica are remnants of the last glacial advance, and we presently live in an interglacial stage termed the Holocene epoch. With the end of the Pleistocene (and the beginning of the Holocene) about 11,000 years ago, the Ice Age ended in name only. It is very likely that the earth will experience another glacial advance, perhaps in the next 10,000 to 20,000 years, and that the glacial/interglacial cycles will continue. Geologic history shows, however, that ice ages eventually come to a complete end and do not occur again for several hundred million years.
"There is debate in the scientific community about what caused the glaciers to advance and retreat, but current theory attributes it to astronomical causes. Because of variations in the earth's orbit, average summer and winter temperatures change with time. There are periods when winters are colder and summers hotter, followed by periods when winters are warmer and summers cooler. The latter are thought to produce glacial advances, because the cooler summers are not adequate to melt all of the previous winter's snow. The result is that snow and ice begin to accumulate from one winter to the next. During periods when summers were warmer, and winters cooler, the glaciers are thought to have retreated. During the Pleistocene epoch, two or more centers of glaciation in Canada probably joined to form one large sheet of ice. . . .
"The southern limit all of the glacial advances, not including the Rocky Mountains, is approximately the present day location of the Ohio and Missouri Rivers, although the last (Wisconsin) advance did not reach as far south as some of the previous advances. The glacial advances and retreats also had a dramatic effect upon the geology and ecology of areas south of the glaciers. It took so much water to form the glaciers that the world sea level fell approximately 140 meters (425 feet). This exposed the flat continental shelves, now covered with water, as dry land. This lowering of sea level has the same effect as raising the land, which caused rivers to begin eroding deep valleys. . . .
"The leading edge of the glaciers was an ice cliff, sometimes hundreds of feet high, and cold dry winds swept down from the glaciers. As the glaciers slowly spread south, they pushed the climatic zones Exit EPA Disclaimer farther south. Just south of the glaciers was a zone of tundra, next was a zone of shrub tundra, then scrub birch forests, then boreal forests, and finally mixed deciduous forests. Approximately 18,000 years ago, when the Wisconsin stage glaciers were at their maximum southern extent, the Gulf Coast climate was colder and drier. The mean annual rainfall in southern Louisiana was possibly as much as 40 inches less than it is today. Boreal forest Exit EPA Disclaimer, similar to those now found in Canada and the northern U.S., extended as far south as northern Louisiana, Mississippi, and Alabama. The north central Gulf Coast was probably covered by sparse forests of northern pine, similar to portions of southern Wisconsin or New England. Oak and hickory forests, similar to those now found in Kentucky or Missouri, probably covered the river bottoms. Florida was drier and its mean annual temperature may have been as much as 10 F colder. It was covered with sparse, scrubby vegetation, sand dunes, and steppe-like open grasslands. There were some scattered pines and broadleaf trees. Central Texas was probably covered by tall grass prairie, Exit EPA Disclaimer with pine and aspen growing in the river bottoms. The high plains of west Texas were most likely covered by short grass prairie Exit EPA Disclaimer and semidesert. These prairies were probably similar to those of the present day Canadian Provinces of Saskatchewan and eastern Alberta.”
All this is to say that our beaver’s lineage goes way back into a time that was much more hospitable than the present.
This about their burrows is interesting:
“In cold regions, beavers live in houses constructed of sticks and mud and enter and leave them by means of underwater tunnels or "plunge holes"; in Texas they may burrow into cut banks of streams or lakes. Burrows examined in the Rio Grande in the Big Bend section of Texas were large enough to admit a man and were 10 m or more in length. Burrows as long as 50 m have been reported. Burrows, or houses, are used for loafing, sleeping, and rearing the young.
“Beavers feed on a variety of vegetation, but the inner bark of willows and cottonwood seems to be their mainstay. In summer a number of herbaceous aquatic plants and sedges are eaten. In central Texas, where willows are absent, beavers in winter utilize as first choice such trees as button willow, juniper, and pecan and rely heavily on Bermuda grass, beard grass, ragweed, and yellow water lily in summer. Thus, the plants eaten and their order of preference depend in large measure on availability.
“Breeding begins in January or February, and the young are normally born in May or June after a gestation period of about 107 days. Beavers are usually monogamous, and normally only one litter of three to four young is produced each year, but some females produce a second litter in August or September." ( http://www.nsrl.ttu.edu/tmot1/castcana.htm)
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| Newest remains found on the west side of the Pond this evening, along the narrow trail directly across the water from where we saw the beaver. |
Just got word that this winter has been the third driest one in our regions's history. The flow in the creek doesn't indicate any such fact, nicely enough.
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