Chapters 1 - U.S. Fish and Wildlife Service

Environmental Consequences
USEPA ecotoxicity criteria, imazapyr is practically non-toxic to insects; however, little data is
available regarding the toxicity effects of imazapyr to reptiles and amphibians. Adherence to the
label requirements of these products and implementation of BMPs related to herbicide application
will ensure that the use of these products on the Refuge will not adversely affect invertebrates or
any reptiles and/or amphibians present on the Refuge.
Mosquito control involving the use of Bti and Bs are also not expected to significantly impact these
organisms. The USEPA, after considering the available studies, has concluded that methoprene
applied at levels recommended on the label is of low toxicity and poses very little hazard to nontarget
species (USEPA 2001). However, earlier studies of some species in the order Coleoptera
did show some sensitivity to methoprene (Marten et al. 1993). This is of concern on the Refuge
because at least two of the areas currently being treated for mosquitoes are believed to support
one or more species of tiger beetles (in the order Coleoptera). A search of the existing literature
did not find any studies that evaluated the effect of methoprene on tiger beetles; therefore, the risk
of using this product in areas where these organisms occur is unknown. To avoid potential impacts
to sensitive tiger beetle species, under this alternative, future SUPs for mosquito control will
restrict the use of methoprene to those areas of the Refuge that are not known or expected to
support high numbers of tiger beetles.
Public Use
Public use activities are primarily limited to existing roads and pathways, therefore, no adverse
effects to terrestrial invertebrates, amphibians and reptiles would result from the continuation of
the existing public use program on the Refuge.
5.4.1.5 Effects to Mammals
Wildlife and Habitat Management
The management activities proposed under Alternative A would have minimal effect on the
mammal populations that occur on the Refuge. The activity with the greatest potential for impact
to mammals is predator management, which is implemented as part of the Endangered Species
Management and Protection Plan (USFWS and Navy 1990). Additional information about this
plan is provided in Section 3.4.3.1.
Implementation of the predator management plan between 2007 and 2009 has only resulted in the
lethal control of one mammal, a coyote (Canis latrans) in 2007. This individual was responsible for
predating approximately 160 least tern nests before it was removed from the site (Ross 2007). In
2008, a small barrier fence was installed on each side of the site near the entrance to nesting area,
to further discourage coyote activity in the vicinity of the nesting site. This management action
proved effective. No evidence of coyote activity was observed near the site; therefore, no direct
control of coyotes was required in 2008 or 2009. Based on past actions, continuing the existing
predator management plan would not adversely affect the mammal populations on the Refuge.
Pest Management
The active ingredients glyphosate, oryzalin, and imazapyr are all considered to be practically
nontoxic to mammals by the USEPA (USEPA 1993, 1994, and 2006b); therefore, no adverse affects
to mammal present on the Refuge are anticipated as a result of the continued use of these products
in accordance with label requirements and the implementation of appropriate BMPs.
According to the USEPA, various tests conducted for Bti and Bs revealed no expected harm to
non-target organisms, therefore, when applied in accordance with label directions, microbial
larvicides (Bti and Bs) are not expected to pose a risk to mammals. Studies also demonstrate that
Draft Comprehensive Conservation Plan 5-43