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Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations
accounted for in the Services take determinations.
Response: Table 8 shows the breakdown of estimated take by the level of take. We provided this table so readers could see the relative differences. As is discussed in the description of take by Level A
harassment within the proposed rule, Level A harassment either non-serious or serious to bears on the surface is extremely rare within the ITR region, and no Level A harassment to Pacific walruses has been reported in the Beaufort Sea ITR region. Thus, the best available information does not support Level A harassment to occur due to surface interactions for polar bears, or in general for walrus given the proposed activities.
Comment 75: One commenter suggested that the Service should consider the probability of take by Level A harassment for polar bear adult females during a den disturbance event.
Response: We disagree that there is a significant probability of an adult female experiencing Level A harassment due to disturbance at the den site.
During our review of case studies, we observed no examples where an adult female experienced any sort of harassment that had the potential to injure her. There are also no examples that we are aware of in the literature.
Whereas disruptions to the normal timing of den phenology have clearly published negative relationships to cub survival, no such relationships exist for adult females.
Comment 76: One commenter suggested that the Service should clarify their explanation for the impact sources assessed in the denning analysis and whether take by Level A harassment and lethal take are underestimated.
Response: We disagree that our use of disturbance probabilities from the repeated set of probabilities is inappropriate. During our review of case studies used to estimate these probabilities, the types of activity classified as repeated are analogous to those expected from seismic surveys.
The commenters assessment that any activity will experience the disturbance first as a discrete event is inaccurate. For the case studies we reviewed, the same inaccurate argument could be made, but as a result the probabilities in the repeated category inherently incorporate that first exposure and its potential to cause disturbance. Based on our definition of what constituted repeated exposure, and therefore whether a case study was classified as repeated/discrete, it would be inappropriate to apply the discrete probabilities to seismic given the
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unquestionable repeated nature of those activities. We should also note that depending on a simulated dens phenology and the proposed dates of seismic activity, dens could have disturbance applied multiple times if previous exposures did not result in lethal take or take by Level A
harassment response.
We also disagree with the commenter that our decisions on how case studies were classified was arbitrary. We developed clear rules based on a large body of scientific literature to help classify whether a response to an exposure was larger than expected under unexposed conditions. Similarly, we did not arbitrarily decide when to exclude case studies from consideration.
A significant amount of deliberation went into the assessment of each case study, and only two factors would disqualify a case study from being included in the final probability calculations: 1 There was insufficient information to identify when disturbance occurred or what the outcome was to the den under consideration, or 2 the type of activity was deemed to be outside of the activities proposed by AOGA e.g., physical capture of polar bears in dens.
We disagree with the commenters assessment that the Service was overly arbitrary in how the different case studies were summarized. They cite our assessment of case study 47 as an example of there being sufficient information but the Service classifying it as insufficient information. The reality is, this case study did not provide information on how far the crews were from the den, nor the date that the bears emerged from the den.
Given our published criteria, we couldnt reliably assign take to this case.
We agree that take was certainly possible, but insufficient information precluded us from coming to that conclusion.
The commenter highlights case study 7 as another example. Yet, there were clear reasons we didnt include this case study. First, it was unclear whether the hunter identified in the case study actually observed the same bear as Amstrup did given the time lapse between observations. That would be another explanation for why there were no cubs observed. Thus, there was incomplete information to fully assess this case study. We disagree with the commenter that it is inappropriate to assume that once a Level A harassment or lethal take occurs that subsequent harassment/take is not considered. This really applies to only one period, the late denning period, because lethal take/
take by Level A harassment is not
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possible in the den establishment period; the only disturbance outcome during the early denning period is lethal thus future take/harassment is not possible, and during the postemergence period, any additional take is accounted for in the surface analysis i.e., not the denning analysis. During the late denning period, we believe it is appropriate to not consider additional harassment/take if Level A harassment is simulated to occur. In the late denning period, Level A harassment is considered serious take by Level A
harassment, thus it already assumes a likely lethal outcome. Thus, applying additional lethal take when it has already been accounted for is not appropriate.
Comment 77: One commenter suggested that the Service should consider the size of cubs, which may indicate poor body condition and lower survival likelihood, as factors to determine take for den disturbance events.
Response: The commenter outlines some well-established ecological relationships e.g., cub size and survival, sea ice and body condition, but fails to understand the purpose of the case study analysis, the underlying assumptions, and how the results are utilized in the simulation model. The case study analysis was used to estimate the probability of a disturbance eliciting a specific response during each denning period; we then used those probabilities in the model to determine how simulated dens would respond to disturbances at specific times. For example, from the case study analysis, we found that dens exposed to a discrete exposure during the late denning period resulted in early emergences 90.9% of the time.
Consequently, in the simulation model, dens exposed to a discrete exposure between the time cubs were 60 day old and their intended emergence date had a 90.9% chance, on average, of emerging early. Because the best available science indicates that early emergences are associated with decreased cub survival e.g., Rode et al. 2018, we classified those dens as incurring serious take by Level A harassment. The commenter argues that cubs today are smaller than in the past because of environmental changes and are therefore more likely to be impacted negatively by early emergences and departures. Although that assertion may be correct, no studies have demonstrated that cub size influences when a disturbance elicits an early emergence, and no studies have evaluated the relationship between cub size at emergence and survival probability in a manner that would
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