Beware of Beaver Extinction

ESA Assignment: Cory Kent

(drakehs.org)

Recovery Plan for Point Arena Beaver:

This is a mountain beaver that is listed on the endangered species list.  The particular subspecies is only located in a small coastal area in Mendocino County, CA.  There are about twenty-six populations that have been found in this area, so the total number of beavers is estimated to be somewhere between 200 and 500 (US Fish and Wildlife Service 27).  Beavers are very hard to observe because they build such intensive burrows to protect themselves.  These animals are also not colonial and they have very little social interaction.  They are for the most part solitary animals until a small breeding window.  They are a keystone species to several vertebrates and other animals thanks to their burrowing system.  Their presence creates a suitable habitat for salamanders, skunks, moles, mink, and many others.    
The population density for this subspecies is hard to determine but it is somewhere between .61 to .81 individuals per hectare (US Fish and Wildlife Service 33).  This species' population is so hard to determine because it is difficult to count how many beavers are in one burrow.  The reasons that this species has become endangered are habitat degradation and predation.  Their habitat has either been eliminated or degraded due to land development, grazing, timber harvest, and invasion of alien plants species.  Direct threats include predation from household pets and feral animals, poisoning, genetic isolation, and human caused disturbances.  Another handicap for beavers and their need for a specific environment is the fact that they are unable to thermoregulate.  They can handle colder temperatures better than hotter.  Beavers have an unusually low reproductive rate.  Females do not mature until their second year, only have gestation once a year, and usually only produce two or three offspring in the once a year litter (US Fish and Wildlife Service 35)

(Rue)

 
These beavers require a cool, moist area for an ideal environment.  In the Point Arena area that these beavers reside, the environment has been heavily forested due to agriculture, including cattle grazing, which has resulted in the distribution of this beaver population being altered (US Fish and Wildlife Service 5).  

(Wikipedia)

The name of the recovery plan is Point Arena Mountain Beaver Aplodontia rufa nigra (Rafinesque).  The date of the listing was June 2, 1992 in the California/ Nevada region, it was listed as endangered and the plan has been finalized.  The species will be considered for down listing when sixteen populations are protected from human caused disturbance in perpetuity, when they are stable or increasing over ten years, and if they have a mean density of at least four beavers per hectare.  In order to do this, the recovery plan states that we must protect known populations, protect suitable habitats, buffers, and corridors, and develop management plans and guidelines.  Another danger for these beavers is residential neighborhoods setting out rodent traps that sometimes these beavers succumb to.  It is also important to rope off areas where these beavers have their burrows so that humans do not stomp on them, or their surrounding habitat.  Downlisting could be initiated in 2015 and delisting by 2025 (US Fish and Wildlife Service 7).

Other Sources:

http://www.enature.com/fieldguides/detail.asp?recnum=MA0073

http://www.iucnredlist.org/details/1869/0