Beavers and Brackish Waters
Thinking about beavers does not conjure up images of urban areas. Quite to the contrary, as a matter of fact, and people do not often associate the Bronx with beavers, but we do have one: at least one.
Since the first bite marks were noticed over two years ago, the now named Jose the Beaver has been little seen but his presence has been noticed. In the section of the Bronx River that stretches between the New York Botanical Garden and the Bronx Zoo, trees ave been gnawed and felled, and two lodges and a burrow have been identified has beaver housing. Being largely nocturnal, Jose works while the two establishments are closed and he (she?) is out of sight of the casual passersby. Photographs were taken with trip cameras by WCS, and a writer for Outdoor Magazine claims to have infrared photos but nobody has seen them. A staffer at the Bronx Zoo did see Jose one morning and placed Jose among the biggest beavers he had ever seen. Running between 30 and 70 lbs, the guesstimate weighs him in around 50 lbs.
If you put yourself on the list of those who have not seen Jose The Bronx River Beaver, you may now remove yourself from that list. On the morning of June 12, 2009 Jose put in an appearance at Drew Gardens as the participants in Bronx River Crossing made preparations to launch their watershed representation. Chris Kannon was able 
to take a series of shots as Jose swam leisurely upstream before lumbering out of the water to walk under East Tremont Ave. Some of us noted that he seemed sluggish or even disoriented. Of course, having never seen a beaver, maybe they always look that way. On more than one occasion the same has been said about me. Maybe it was the salty water where he was swimming? Drew gardens is at the top of the estuary and has been found to have levels of salinity up to 8 parts per thousand (oceans are 30-35 ppt and freshwater is usually < 0.5 ppt) When the dying beaver was found last year in the East River on the day of the pope’s visit, it was reported that, while that beaver had already been sick, it was probably the brackish waters of the East River that finally did him in. Could Jose be on his way to a similar fate? Could the stresses of life in the zoo and the garden be such that he is being chased down stream and into a perilous situation?
Jose came up again in a discussion that our Executive Director had with a local fisherman on Saturday in River Park, just south of the last dam on the river and the zoo. When she mentioned the beaver having been seen just to the south, the fisherman nonchalantly replied, “Oh yeah, I see that beaver all the time down here.” Could it be that Jose is putting himself in danger on a regular basis? Why would he chance forays into brackish water unless he has a death wish or is suffering from dementia?
In May of this year, W. Gregory Hood, Ph.D. of the Skagit System Cooperative published a research paper entitled The Overlooked Ecosystem. Dr. Hood had set out to study the distribution of Sweetgale (myrica gale) in the estuarine section of the Skagit River in Seattle. While he did find the sweetgale, he also found that the estuary was frequented by beaver from the fresh water section of the river. Dr. Hood explains that beavers are known to make use of estuarine areas with salinity levels as high as 10 ppt. Being true vegetarians, they are in search of those trees that will fulfill their appetite while providing the needed nutrients. If the trees in question are along the banks of brackish water, the beaver is prepared to go there. Beavers rarely forage more than 100 yards from the stream they call home which makes upstream and downstream travelling the normal event. Jose is probably in search of food and a quiet place. In most land conflict events, beaver will look for new foraging areas. This explains Jose’s “bizarre” behavior. It was our lack of understanding of normal behavior that made his acts seem bizarre.
But Dr. Hood also raises some questions that are pertinent to our river. Hood makes the connection between the salmon that use the river for spawning and the beaver that rework the habitat in the estuary and beyond. Being tidal, some estuary sections can become quite shallow at low tide. While the beaver may be in the area to forage, an effort may also be made to dam up small areas, causing tidal pools that will provide safe harbor when the tide runs out. Perhaps coincidentally, these tidal pools also provide a safe zone for salmonids in the area. Being that the beavers prefer somewhat deeper water, the pools are deeper than the areas where wading birds generally will hunt. By providing for personal needs, the beaver helps a multitude of other organisms. While we do not have salmon on the Bronx River, the return of the alewife herring and the catadromous eels fill a similar niche. Both would benefit from a tidal hideout at low tide.
And just what is Jose feeding on in the estuary? It will mean some kicking about in the area, but while beavers preference is for aspen and poplar, they will go for whatever is available when necessary. In that area there are willow trees which are always a part of the diet, but perhaps this new understanding of the range of the beaver and its possible utility can become a part of th present converstation about the soon-to-begin construction in Starlight Park, just south of the Cross Bronx Expressway. From drew Gardens south, the river is armored on both sides with rip rap, leaving the banks barren and lifeless. Dr. Hoods research found that trees growing along the banks of the river did so above the tidal zone, though they did not grow in soil. Instead the trees were able to take root in the woody debris that washed down from upstream and became lodged on the bank at high tide. Perhaps a consideration in the lower Bronx River would be to provide such woody debris. At the present time most woody debris cannot make it down stream due to the dams that block the river at certain point. In some upstream areas, logs have been cabled to the banks as a form of bank stabilization. The Section of the river between Drew Gardens and the south end of Starlight Park needs little bank stabilization due to the rip rap, but taking the same simple idea may provide a landing zone for seeds that can then provide a food source for beaver and create habitats for other unexpected guests.
DG
Cool links:
http://books.google.com/books?id=-xQalfqP7BcC&pg=PA295&lpg=PA295&dq=beaver+favored+diet&source=bl&ots=XOlaFu5796&sig=kBq_s3ePD5K2dJ2eg1exkObBNUE&h
l=es&ei=IdRKSufeIofCNu7v4KoB&sa=X&oi=book_result&ct=result&resnum=1
http://www.wildlife.state.nh.us/Wildlife/Wildlife_PDFs/Beaver_control.pdf
http://www.skagitwatershed.org/rpapers_overlooked.html
Add comment July 6th, 2009
