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Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations
expected i.e., undisturbed dates. Thus, we do account for the suite of activities that can disturb a den. We agree with the commenter that no studies exist looking at how denning bears respond to specific activities. We agree that it would be ideal to know the probability of different levels of response to different types of activity.
Unfortunately, those data do not currently exist. While Owen et al. 2020
shows varied distances that denning bears can detect different types of activities, there are no associated data with the distances at which bears will display a disturbance response once a stimulus is detected. So, we had to take the average approach across activity types. This likely leads to overestimate of take for more limited activities and underestimate of take for more significant activities. But on average, the results would be accurate.
Comment 84: One commenter suggested that the Service should consider individual variability and local weather conditions when determining the time period in which polar bears emerge and depart from their dens.
Response: We agree that local conditions may influence when bears choose to depart their den sites.
Unfortunately those relationships have not been established so are currently just conjecture. We use the best available data to establish the range of emergence and departure dates so they capture the natural range of variability in when bears decide to emerge from and depart their dens. We simulate each individual den with specific dates when key activities occur e.g., emergence, departure, so we incorporate the individual decision on what constitutes early and do not base it on an overall population-level mean.
Comment 85: One commenter suggested that the Service should consider Industry impacts on mother polar bears and cubs as they are traveling from den sites to the sea ice.
Response: The encounter rates used by the Service were generated using records of polar bear encounters that encompass the dates when sows and cubs are likely moving from den sites to the sea ice i.e., the best available information. Thus, these individuals are currently incorporated in the take estimates presented in the ITR. While we agree that the type of encounter described by the commenter is possible, we found no evidence in the encounter data used that shows instances of females abandoning cubs while after departing the den site as a result of disturbance from industrial activities.
This indicates these types of impacts are likely very rare. The research operation
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flights referenced by the commenter are typically at a much lower elevation than industrial flights, and the potential take of these flights has been discussed in Aircraft Impact to Surface Bears.
Comment 86: Two commenters suggested that the Service should clarify the operational constraints of Industry vehicles in polar bear denning habitat and whether vehicle activity was evaluated as an impact factor in the denning analysis.
Response: We disagree with the commenter that an attempt would be made to identify denning habitat in the winter once snow fell. Instead, we rely on studies that have already occurred to identify areas with suitable conditions for capturing snow. The commenter cites the comments from Steve Amstrup, yet he is a co-author on most of the studies that have identified these areas in advance of activities. The overall probability of running over a den is exceptionally small. First, two to three AIR surveys must occur before activity commences in an area. Given the detection probability of AIR, this leads to 6580% on average of dens being detected. Then, given the overall avoidance by Industry of crossing areas suitable for denning and the relatively small footprint of off-road travel in the project area, and the likelihood of bears abandoning a den before vehicles physically run over it leads to a very low risk of this occurring. Operators will be required to have and use the USGS denning habitat layer to avoid denning habitat whenever possible. See also Analysis and Assumptions Regarding Den Collapse, above.
Comment 87: One commenter suggested that there is insufficient information regarding the vulnerability of denning habitat to vehicle travel, and that the Service should restrict Industry vehicle activities in all potential polar bear denning habitat defined by USGS
in order to reduce impacts to denning polar bears.
Response: We disagree that there is insufficient information in the ITR to ascertain how much denning habitat will be vulnerable to vehicle travel. We provided all of the tundra travel, ice road, and seismic survey region spatial data that are part of this ITR. One could easily use those files and calculate how much denning habitat might be exposed to activities. We note, however, that just because there is sufficient topographic relief to capture snow doesnt mean that bears will use it for denning. Thus, its inappropriate to consider any area with sufficient slope to be off limits. That requires some additional assessment of the probability of a bear using that area.
We also provided the layer on relative
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probability of denning. We account for the number of dens that go undetected and are likely to be disturbed by activities. See also comments and responses above.
Comment 88: Two commenters suggested that the Service should evaluate the limitations of ground-based den detection, such as difficulty visibly distinguishing dens and suitable denning habitat in winter and low efficacy of hand-held infrared detectors, as part of the Services risk assessment for industry vehicles causing den disturbance.
Response: We disagree. The applicant stated that they would avoid steep banks so we also considered this in our analysis, which, along with the other mitigation measures in place i.e., aerial infrared surveys, trained observers, etc.
reduced the probability of running over a den to such a small level that it could be dismissed and not considered in the analysis. See also the comments and responses above.
Comment 89: One commenter suggested that the Service should clarify how the multiple disturbance events during seismic surveys are evaluated in order to determine impacts to denning polar bears and whether the Services assumption for seismic survey impacts accurately represents realistic impacts.
Response: The proposed ITR does account for the activity associated with advance crews during seismic surveys.
The start date for seismic activities is when the advance crews first enter the seismic areas, so those are the first dates that dens are exposed to disturbance and a determination is made in the model framework whether a den is disturbed or not. The response probabilities we used for seismic were derived from case studies where the activities occurred repeatedly, similar to activities related to seismic surveys.
Thus, the repeated activities associated with seismic were accounted for based on the set of response probabilities we used.
Comment 90: One commenter suggests that the Service should account for take of polar bears during AIR
calibration flights, in which aircraft calibrate their infrared instruments over known polar bear dens.
Response: The AOGA did not include flights over known dens on barrier islands in their Request for an ITR.
Thus, potential take from this practice was not analyzed, and any potential take that may occur as a result of these calibration flights would not be covered by the ITR.
Comment 91: One commenter suggested that the Service should more thoroughly evaluate the distance at
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