Showing posts sorted by relevance for query beaver dam. Sort by date Show all posts
Showing posts sorted by relevance for query beaver dam. Sort by date Show all posts

Friday, October 01, 2010

Students Study Beaver Engineers

Today, 4th grade students from Harleyville-Ridgeville Elementary School visited the Audubon Center at the Francis Beidler Forest.

As noted previously in this blog, beavers (Castor canadensishave constructed a dam in the swamp. Unfortunately, the dam cannot be seen from the boardwalk and it is not feasible to take 70 students off the boardwalk along the rain-soaked swamp edge to see it.  However, the recent rains have created drainage channels along the low, educational boardwalk next to the nature center.  Using the natural terrain and drainage pattern along the low boardwalk, students were given the opportunity to direct their guide in constructing dams of sticks and leaves.  Two sites, one with a single channel and one with a broad flood plain, were used to demonstrate how a beaver dam can change the habitat.

The South Carolina science standard addressed was:
4-2.6            Explain how organisms cause changes in their environment.

Once at the first site, students were asked to discuss the following within their small groups:

  1. What do beavers eat? (plant material, especially cambium)
  2. What do beavers build? (dams, lodges)
  3. How do beavers build their structures? (using logs, branches, mud, leaves)
  4. Where do beavers build their structures? (dams in channels of flowing water, lodges in pooled water)
Once students shared their answers, each group had the opportunity to suggest where a beaver might construct a dam at the site.  Though most would have preferred to jump off the boardwalk and into the water and mud, we were certain that those responsible for the laundry would want to have a word or two with us.  Therefore, we opted for the next best thing.  With great excitement, students/beaver engineers directed their guide on how and where to construct the dams using nearby sticks and leaves. Who knew there were so many expert dam makers in our community?

After observing the results, the group moved to the second site and repeat dam construction procedures.  The second site was a better representation of what the beavers have accomplished in the swamp.  There was not one obvious channel to block and natural features (trees, logs, and high ground) were incorporated into the dam's construction.  After observing the results of the second dam, students discussed the following questions within their small groups:

  1. How did the dams immediately affect the habitat upstream from the dam? (water pooled; deeper, more-consistent levels of water behind the dam; some plants may be in the water more often than before)
  2. What species might benefit from the change in habitat? (trees or aquatic plants that need or can tolerate constant flooding; fish; frogs; water snakes; wading birds that eat those species; dabbling ducks and geese; bitterns that like thicker, marsh-like habitat)
  3. How do dams immediately affect the habitat downstream from the dam? (less water, other plant species may be able to grow in the drier conditions)
  4. Over time, how will the habitat behind the dam change? (sedimentation will fill the pool and create higher ground and meadow-like conditions and eventually habitat as seen along the swamp’s edge; or the habitat may attract the attention of an alligator, which may eat the beavers allowing the dams to fall into disrepair and the swamp to reclaim the area)
Since the actual beaver dam would remain out-of-sight, students used the iPod Touches to view the beaver dam video and peruse the beaver-related images.  Students could also look in the other image folders for species that they previously identified as having benefited from the beavers’ damming activity.

By the end of the activity and boardwalk tour, the students were expert dam engineers and had no problems writing a letter to the editor for or against the presence of beavers and their construction work in the swamp.

Wednesday, November 19, 2008

Damming Beavers!

According to the South Carolina Department of Natural Resources (SCDNR) webpage, The beaver, the largest rodent found in North America, was once abundant in South Carolina, and was found commonly in all areas with the exception of a narrow strip of sandy soil along the coast. These animals were trapped extensively by early trappers and by the late 1800s or early 1900s had disappeared from most of the state. Many feel the beaver was eradicated; however, some remnant populations may have persisted in remote areas.

During the winter of 1940 to 1941, United States Fish and Wildlife Service personnel released six beavers, which were captured in Georgia, on the Sandhills Wildlife Refuge in Chesterfield County, South Carolina. During the same period, beavers from Georgia began to invade the Savannah River drainage system. These animals established populations in counties which border the Savannah River.

The beavers in these two areas and existing remnant populations have increased their range significantly and presently occur in portions of all 46 counties in the state.


Several years ago, beavers returned to area near the boardwalk at Beidler Forest and we've since noted their activity in previous entries (1, 2). However, except for a pathetic attempt at a lodge off of Mallard Lake, we have not seen any damming within our 1.5-mile wide swamp. Damming within the swamp is certainly possible (although we thought improbable) as South Carolinians named an entire swamp for that activity. Beaver Dam Swamp is located east of Lake Moultrie near the intersection of SC 45 and US 17-A (Decimal Degrees: Latitude: 33.29833 Longitude: -79.78528). Maybe the beavers we discovered during our off-boardwalk exploration received their training in Beaver Dam Swamp.


As we walked back to the nature center on a path between the boardwalk and the cross-swamp powerline, we discovered a beaver dam across one of the many channels in the swamp. This particular channel flows under the boardwalk at #5. In the satellite image, you can see the channel of water as it crosses the clearing under the powerline. The dam is built along the southern edge of the powerline clearing and is stitched between the buttresses of trees, root masses, fallen logs, stumps, and finally to higher 100 meters to the east. The lodge is located in the deep water near the center of the powerline clearing (it appeared as if it would top our hip waders on a day that didn't top 40F, so we didn't obtain a more accurate depth reading).



Although rising water will likely overtop the dam or simply spill around the current east and west anchor points, the water currently pooled behind the dam will be irresistible to wintering waterfowl! Besides humans, no animal has the power to so dramatically alter its environment. Beavers may abandon the site when rising water circumvents their engineering project, but they will undoubtedly attempt to first modify their dam to contain the water in its new configuration.




Images by Mark Musselman

Friday, March 18, 2011

Yellow-crowned Night Heron

Yellow-crowned Night Herons (Nyctanassa violacea) have returned to the swamp around the boardwalk at the Audubon Center at the Francis Beidler Forest.  They winter south to Panama and throughout the Caribbean islands. The heron gets its name from its habit of foraging mainly at night.  In the swamp, these herons can be seen in the dim light slowly wading through the shallow water looking with their large eyes for crayfish moving in the detritus.


In past years, the Yellow-crowned Night Herons have been conspicuous in all wet areas touched by the boardwalk.  However, last year the birds were mainly absent from view.  As the swamp itself appeared not to have changed along the boardwalk, the lack of heron sightings was puzzling.  The mystery was solved during a reconnaissance for cover board sites during planning for the herp-themed summer camp.  As we walked along the edge of the swamp near #112 on the boardwalk, we came upon the beaver dam and the knee-deep water being pooled on the upstream side of the dam.  We already knew about the beaver dam and reported its presence in this blog.  However, we had not realized how the consistent water level behind the dam had changed animal behaviors.

Canada Geese (Branta canadensis) are not denizens of the swamp, but we had begun to hear their familiar honk-like calls coming from the treeless power line right-of-way north of the center where open water pooled like pond.  The chattering call of Belted Kingfishers (Ceryle alcyon) became more frequent within the same power line corridor.  Although Yellow-crowned Night Herons did not seek the open water and sunny environs of the power line corridor, they were actively hunting in the water behind the dam and beneath the tree canopy.  We found a half dozen Yellow-crowned Night Herons in the narrow band of trees between the dam and the power line corridor (see map).  Turtles, snakes, and big fish also found the consistent water depth more to their liking.

If you visit the Francis Beidler Forest and see a Yellow-crowned Night Heron stalking a crayfish, you'll know by the waggle of the bird's tail end that it is prepared to strike with its large bill.  We all tend to waggle in anticipation of good eats!

Image by Mark Musselman

Wednesday, March 10, 2010

Busy Beavers

There have been busy beavers at the Audubon Center at Francis Beidler Forest...figuratively and literally!

First, after much gnashing of teeth and secret Apple computer handshakes, the Beidler Forest boardwalk-specific app has finally made it through the approval uploading process. If Apple doesn't have any issues with the "tight" coding, the app should be approved by next week for free downloading at the iTunes App Store.

Boardwalk-specific app for Audubon at Francis Beidler Forest by Mark Musselman

Second, the actual beavers have been busy. We have previously reported on the return of beavers to the swamp, the dangers they faced in the open water, the dam and lodge they built to avoid the open water, how other animals benefited from the beavers' environmental changes, and how they had begun gnawing on trees near the swamp's edge. We now know why the beavers have been so busy near #114 along the boardwalk.

Beaver dam at Audubon's Francis Beidler Forest by Mark Musselman
Beaver sign at Audubon's Francis Beidler Forest by Mark Musselman


















While scouting sites to place cover boards for our herp-themed summer camp, we discovered additional beaver damming. Beavers have gnawed on numerous cypress knees, gnawed on a variety of other trees, and girdled a spruce pine tree. Once again, the dam is less than two feet tall, but it is pooling water behind it. Although the dam is far enough from the boardwalk to make it difficult to see even with binoculars, we'll continue to monitoring the beaver activity to see how the swamp will be affected in that area.

Beaver sign at Audubon's Francis Beidler Forest by Mark Musselman
Beaver sign at Audubon's Francis Beidler Forest by Mark Musselman

Images by Mark Musselman

Wednesday, June 02, 2010

Beaver Engineers

The staff at the Audubon Center at Francis Beidler Forest continues to monitor the changes in the swamp that beavers (Castor canadensis) are creating via their water-management engineering.



As many of the animals in the swamp are adapted to the wetland ecosystem, water is a critical component of their life cycles. Though the dam is not tall it is effectively slowing the flow of water.  The upstream side of the dam appears bright green in the video as duckweed has taken hold in the non-flowing water.  The downstream side of the dam is brown exposed swamp bottom with little water outside of the deepest channels.  Obviously, animals that live in water (fish, crayfish, mussels) will continue to thrive in the pool of water created by the beaver dam.  These same prey items will be fewer in number on the downstream side of the dam, so predators will move their hunting efforts to the upstream side of the dam.  The numerous crayfish parts indicate that hunting is good for the Raccoons (Procyon lotor) and Barred Owls (Strix varia), while tracks from Yellow-crowned Night Herons (Nyctanassa violacea) and scat from River Otters (Lutra canadensis) show that they too have discovered the bounty sustained by the beavers' water-management project.

While we were exploring the area around the dam, we flushed eight Wood Ducks (Aix sponsa) that were resting in the quiet backwater and spotted a Greenish Rat Snake (Elaphe obsoleta x quadrivittata) moving rapidly across the weed-covered water.



We will definitely be making this one of the stops during summer camp, which begins next week!

Images and video by Mark Musselman

Monday, July 16, 2012

2012 Advanced Camp

The advanced camp at the Audubon Center at Francis Beidler  Forest has begun!  Day 1 involved a walk around the boardwalk (virtual tour here) before lunch and then a stomp through the swamp in the afternoon.  Here is some of what we saw:

Young raccoon out foraging in shallow water - Mark Musselman

Young raccoon climbing tree for safety - Mark Musselman

Banded Water Snake - Mark Musselman

Eastern Mud Turtle - Mark Musselman

Eastern Cottonmouth - Mark Musselman

Eastern Cottonmouth - Mark Musselman

Bowfin - Mark Musselman

Barred Owl - Mark Musselman

Barred Owl - Mark Musselman

Yellow-crowned Night Heron - Mark Musselman

Eastern Box Turtle - Mark Musselman

Banded Water Snake - Mark Musselman

Great Egret - Mark Musselman

Carolina Wren nest under construction - Mark Musselman
 See images and video here of a previous attempt for this site.
Carolina Wren building nest in cigarette disposal container - Mark Musselman

Orbweaver capturing yellow jacket - Ricky Covey

Unidentified insect - Ricky Covey

Dark Fishing Spider - Ricky Covey

Swamp stomp behind beaver dam - Ricky Covey

Beaver dam - Ricky Covey
Although we did not get any pictures, we also saw White Ibis, Little Blue Herons, a male Common Yellowthroat, Northern Cardinals, Musk Turtles, Yellow-bellied Sliders, a female Prothonotary Warbler, a Red-shouldered Hawk, Northern Parulas, Tufted Titmouse, and several fawns.

Tomorrow, we will post a Geographic Information System (GIS) map showing the boardwalk, the beaver dam, our morning and afternoon tracks, and points for the various wildlife sightings.

Thursday, September 16, 2010

New Bird for Beidler Forest

Since its purchase in 1969, the Francis Beidler Forest has been studied and lists have been compiled cataloging the plants and animals within its boundaries.  Some groups of animals have been studied more thoroughly than others.  Insects remain a critical component of the swamp ecosystem, but have received little direct attention.  We continue to add species to the list as we discover them in the process of completing our regular duties.  Birds are another story.

Being that the National Audubon Society formed from grassroots efforts to end the killing of birds for the fashion industry and continues to work for the protection of birds and their habitat, it is no surprise that the bird list for the Francis Beidler Forest is extensive.  Additionally, thousands of people a year have been looking at birds after the completion of the boardwalk in 1977.  There are very few surprises when in comes to birds at the Francis Beidler Forest.  That's part of what makes yesterday's bird sighting interesting.

Previously in this blog (MayJune), we have covered beavers (Castor canadensis) and their return to the Francis Beidler Forest.  Yesterday, we wanted to take the Global Positioning System (GPS) unit and capture coordinates for the beaver dam (shown in blue) in order to show its location on maps of the boardwalk area.  The water level is quite low, so walking along the low dam was not difficult and we were out of the office.  A short dam near the nature center keeps water from leaking up a low draw, while the 1/4-mile section of dam ties the lodge under the powerline to the high ground near the fork of the boardwalk.  There is another 1/4 mile of dam that runs north from the lodge to the swamp across the powerline right-of-way, but we ran out of time and did not gather its coordinates.  Good excuse for another day out in the swamp.


Along the way, we saw or heard a Belted Kingfisher (Ceryle alcyon), Red-shouldered Hawks (Buteo lineatus), a Common Yellowthroat (Geothlypis trichas), a Wood Duck (Aix sponsa), an Anhinga (Anhinga anhinga), and a juvenile White Ibis (Eudocimus albus).  All of these birds were taking advantage of the pooled water and altered habitat created by the beavers' dam.  We were certain that we had not detected all of the animals benefitting from the beaver activity, but we were surprised when an American Bittern (Botaurus lentiginosus) lifted from the tall grass on one side of a swollen creek channel and quickly dropped into the vegetation cover on the other side of the channel before we could take a picture.  Bitterns of any sort have not been seen within the boundaries of the Francis Beidler Forest due mainly to the lack of suitable habitat.  However, with the powerline right-of-way being kept clear of trees and the beavers pooling water that normally would have quickly drained to the Edisto River, the habitat in that small portion of the swamp now has the feel of a marsh...and bitterns feel comfortable in its dense cover.


It was another day in the swamp, but as always, it was something new and exciting!

Images by Mark Musselman

Wednesday, February 03, 2010

Beaver Chews

Today, the sun came out at the Audubon Center at Francis Beidler Forest and lured us out onto the boardwalk. The swamp is full from the recent rain, including yesterday's day-long soaking, and the higher water has allowed beavers (Castor canadensis) to explore territory that was previously farther from the water's edge.


Beaver sign at Audubon's Francis Beidler Forest by Mark Musselman Beaver sign at Audubon's Francis Beidler Forest by Mark Musselman












When a beaver gnaws on a tree or a branch, it is not eating everything. The large branch may eventually make it to the dam/lodge complex in the powerline right-of-way as it is an appropriate size, but the bark has been removed (not eaten) and the cambium has been consumed. The same fate befell the smaller branch. All the wounds on the trunks of various tree species have bark shavings below, the cambium consumed, and the interior portion of the tree untouched. Only the cambium, the living cells connecting the leaves with the roots and serving as the avenue for the transportation of water and nutrients throughout the tree. This is the delicious, nutritious part of the tree sought after by the beavers. If a beaver gnaws completely around the tree, it will girdle the tree and cut the connection between the leaves and the roots. A girdled tree will inevitably die. We're guessing that an inexperienced beaver began gnawing on the Loblolly Pine and that its gummed up mouth caused it to stop!


Beaver sign at Audubon's Francis Beidler Forest by Mark Musselman
Beaver sign at Audubon's Francis Beidler Forest by Mark Musselman



Beaver sign at Audubon's Francis Beidler Forest by Mark Musselman








The beavers were not the only animals becoming active with the warmer, sunnier weather. Right out the nature center, Spotted Turtles (Clemmys guttata) were basking on logs in the shallow water outside of the main flow of the swamp. Where the boardwalk forks at the swamp's edge, an Eastern Cottonmouth (Agkistrodon piscivorus piscivorus) was partially out of the water and on a log. At Goodson Lake, a Yellow-bellied Slider (Trachemys scripta scripta) was warming in the sun and possibly causing leeches to disembark. Finally, rounding the last curve in the boardwalk before the fork, a male Hooded Merganser (Lophodytes cucullatus) was busy taking a bath in the shallow water at the swamp's edge.



Spotted Turtles at Audubon's Francis Beidler Forest by Mark Musselman
Yellow-bellied Slider at Audubon's Francis Beidler Forest by Mark Musselman









Eastern Cottonmouth at Audubon's Francis Beidler Forest by Mark Musselman
Eastern Cottonmouth at Audubon's Francis Beidler Forest by Mark Musselman



Male Hooded Merganser at Audubon's Francis Beidler Forest by Mark Musselman


















Along with the wildlife, we enjoyed the sun while we could. Tomorrow, rain is scheduled to return!


Images by Mark Musselman

Wednesday, October 17, 2012

Busy Beavers Expand Operation

The beavers (Castor canadensis) at Audubon's Francis Beidler Forest have been busy again!  Previously, none of the beaver construction (shown in orange) could be easily seen from the boardwalk.


However, beavers have recently constructed a 20+-foot section damming the creek channel that runs under the boardwalk at #5.


The image below shows the view back toward the boardwalk (look closely).


Only a portion of this short dam can be seen from the boardwalk, but it slows water that has found its way through or under the main dam, which is another 50 meters north at the power line right-of-way/tree line interface.  A few meters behind the main dam and hidden by a thick screen of cattails, is the beaver's lodge.


Although some trees may not survive the gnawing of the beavers or the near-permanent presence of water behind the dam, other species are benefiting from the beavers' work.  As noted above, cattails are growing in a dense block from tree line to tree line in the sunny, pond-like conditions in the power line right-of-way.  A small Banded Water Snake (Nerodia fasciata fasciata) sought refuge the dam shown above and an Eastern Mud Turtle (Kinosternon subrubrum subrubrum) was foraging in the shallow water on the downstream side.  Wood Ducks (Aix sponsa) and Belted Kingfishers (Ceryle alcyon) can be heard calling behind the dam and big fish can be heard pursuing smaller prey through the deeper water.

While beavers may be providing improved habitat and a bounty for other species, they may have improved the habitat sufficiently to entice an American Alligator (Alligator mississippiensis) to take up residence in the deeper water and sunshine within the power line corridor.  If that occurs, beavers will likely become meals and the maintenance-intensive dam system will fall into disrepair.