Voglio sapere a riguardo di…

57780

Federal Register / Vol. 86, No. 199 / Tuesday, October 19, 2021 / Proposed Rules
jspears on DSK121TN23PROD with PROPOSALS1

that require some form of protection to achieve recovery, and they contribute to the DPSs resiliency, redundancy, and representation across its range.
Habitat Analysis We used several habitat models developed by CBI to better understand the broad-scale spatial extent of denning habitat. Our analysis was largely focused on denning habitat because this habitat type is essential for female survival and reproduction, and denning structures are considered the most limiting habitat element for fishers Spencer et al. 2015, p. 33. Denning habitat also supports other life-history activities necessary for female and male survival, such as foraging, resting, and dispersal. The models used for our analysis may overestimate current denning habitat quality in certain finescale areas, but these fine-scale areas are expected to support foraging and dispersal and would be included in established and potential fisher home ranges. Therefore, protecting and enhancing the broad-scale spatial extent of denning habitat, including the finescale foraging and dispersal areas, is vital to conservation and recovery of the species.
We used a combined output from CBIs Pre-Drought Fisher Denning Habitat Suitability Model Spencer et al.
2015, pp. A8A12 and the PostDrought Fisher Denning Habitat Suitability Model Thompson et al.
2020, p. 6 to identify the broad-scale spatial extent of denning habitat. The pre-drought denning model used den locations and an array of environmental predictors from 2013 or earlier but did not account for recent drought, tree mortality, and wildfires that have significantly altered the landscape within the DPS. Fishers response to these landscape-scale changes is not yet fully understood, but preliminary findings indicate that females are still denning in many areas that previously supported breeding fishers, despite the changes to the landscape Green 2020a, pers. comm.. The availability of live forest has decreased across the landscape, but these data suggest that areas that previously supported denning fishers still support the best available habitat, even in an altered state Green 2020b, pp. 1718. Experts believe that this pattern may justify continued use of pre-drought data for modeling and analyses Green 2020b, p. 18. The postdrought denning model includes more recent canopy cover data i.e., this model may reflect current habitat conditions more accurately, but recent den location data were not available to be incorporated into the updated model.

VerDate Sep<11>2014

17:18 Oct 18, 2021

Jkt 256001

Therefore, we determined that a combined output from these two denning models captures areas that previously supported, and likely still support, denning fishers and areas that currently provide the best available habitat. In other words, the combined output represents the best prediction of suitable denning habitat currently available.
The Kern Plateau, which contains a known breeding population of fishers, has unique environmental conditions due to differences in climate, geology, and vegetation compared to the westslope of the Sierra Nevada Spencer et al. 2015, p. 44. These unique conditions result in true differences in denning habitat value on the Kern Plateau compared to the rest of the fishers range Spencer et al. 2015, p.
35. For this reason, the denning models fail to accurately predict denning habitat in this part of the range. To ensure that essential areas of suitable habitat on the Kern Plateau are considered for inclusion in critical habitat, we used CBIs Post-Drought Fisher Landscape-Scale Habitat Suitability Model, which predicts the probability of fisher occurrence also interpreted as a measure of habitat quality Spencer et al. 2015, pp. A1
A4. Areas that are strongly selected for by fishers have a predicted probability of fisher occupancy i.e., habitat suitability of 0.41 and higher Spencer et al. 2015, p. 42. For the purposes of our analysis, we consider habitat above this threshold to be high-quality habitat. Using the post-drought habitat suitability model, we identified all highquality habitat on the Kern Plateau. We compared this high-quality habitat with fisher detection data and determined that this output is an appropriate surrogate for denning habitat on the Kern Plateau.
To determine if a patch of denning habitat, or high-quality habitat in the case of the Kern Plateau, is essential to the conservation of the species, we considered the size of the patch in relation to fisher ecology. We compared patch size with female territory size to determine the minimum size patch necessary to aid in the conservation of the species. Based on an analysis of female home ranges, species experts identified an average female breeding territory size of 2,471 acres as the appropriate scale to assess fisher habitat Spencer et al. 2016, p. 27. This average territory size takes into account overlap between neighboring female home ranges and variation in habitat quality.
This territory size is also similar to the average size of a female fishers core use area, which is the portion of the home
PO 00000

Frm 00017

Fmt 4702

Sfmt 4702

range where an animal spends a majority of its time Spencer et al. 2015, pp. 1718. For the purposes of our analysis, we rounded this territory size up and consider a female home range size to be 2,500 acres. We determined patches of denning habitat that are of an appropriate size to support a subpopulation i.e., at least five female fishers based on analyses conducted by Spencer et al. 2015, pp. 4142 as essential to the conservation of the species. Therefore, patches of denning habitat 12,500 ac 5,059 ha or larger are included in the proposed critical habitat designation. We also included one additional patch that plays an important role for the DPS despite being smaller than the area we determined was necessary to directly support a subpopulation. While this patch is only able to support three females, it is located within the average juvenile female dispersal distance 3.04 miles Spencer et al. 2015, p. 20 of two subpopulations with high occupancy rates. The location and significant amount of contiguous denning habitat provides important connectivity between the two robust subpopulations, highlighting its importance for the conservation of the DPS.
The models used for our analysis resulted in outputs with several holes where modeled denning habitat quality dropped below a threshold set by the modelers based on their understanding of denning habitat selection by fishers.
Based on our review of aerial imagery, canopy cover, and other data, the habitat within these holes is still expected to support fisher foraging or dispersal. Due to their proximity to denning habitat and their utility to support other fisher life-history needs, we determined that the habitat within these holes can play an essential role in an established home range or for a dispersing female or male fisher.
Therefore, we determined that these areas contain the physical and biological feature essential to the conservation of the SSN DPS of fisher and are included in the proposed critical habitat designation.
Within the areas modeled as denning habitat, and the additional areas that support foraging and dispersal, we identified and removed certain areas that do not contain the physical and biological feature or are not essential to the conservation of the species. First, we removed all lakes, reservoirs, and ponds from the proposed designation because these features do not contain fisher habitat. Next, we identified areas with high human activity i.e., areas with houses and buildings that, although they may support fishers and their
E:FRFM19OCP1.SGM

19OCP1