2024-25762. Marine Mammals; Incidental Take of Polar Bears During Specified Activities; North Slope, Alaska

Table 1—Probability of Simulated Exposures Resulting in Disturbance Response to Denning Polar Bears

[MMPA Level A and Level B harassment and lethal take]

Denning period	None (sow or cub(s))	Level B (sow)	Level B (cub(s))	Level A (cub(s))	Lethal cub(s)
Den establishment	0.750	0.250	0.000	0.000	0.000
Early denning	0.870	0.130	0.000	0.000	0.130
Late denning	0.510	0.490	0.000	0.490	0.000
Post emergence—previously undisturbed den	0.000	1.000	0.200	0.800	0.000
Post emergence—previously disturbed den	0.000	1.000	0.474	0.526	0.000

We also use newly described relationships between den emergence date, den departure time, and litter survival (Andersen et al. 2024) to assign litter survival rates to simulated dens that experienced Level A harassment, a method used in recent polar bear take authorizations (88 FR 88943, December 26, 2023). If an exposure resulted in a disturbance response during the late denning period, we first assigned that den a new random earlier emergence date. We then simulated whether that den was disturbed during the post-emergence period. Dens that were disturbed during the post-emergence period were also assigned a new random earlier den departure date. We relied on estimates of litter survival derived from empirical data from approximately 100 days post emergence (Andersen et al. 2024) to determine the fitness consequence of the Level A harassment, and we consider this information below when addressing the MMPA's negligible impact standard. This revised methodology provides a clearer and more in-depth understanding of the potential fitness consequence of polar bear disturbance.

As in the existing 2021-ITRs, some concepts and mitigation measures could potentially reduce impacts to polar bears, but they are not reflected in our take estimates because their mitigative benefit is not quantifiable. For example, LOA holders must train their staff to identify the characteristics of a polar bear den, and if a suspected den is identified, they must cease operations and notify the Service. However, the efficacy of this technique cannot be quantified and could not be accounted for in the model results. Consideration of the conservative nature of certain model assumptions along with qualitative factors suggests that if the actual number of Level A harassment events does not align with the median model output, the actual number of Level A harassment events would be fewer than modeled. However, we preliminarily find, based on best professional judgment, that Level A harassment is reasonably likely to occur, and is anticipated, during the 5-year period of the 2021-ITRs (table 2).

Table 2—Anticipated Level A Harassment Over the 5-Year Period of the 2021-ITRs

Type of take	Probability	Mean	Median	95% CI *
Level A harassment	0.93	5.04	5	0-13
* Confidence interval (CI).

We base this conclusion on the strength of the modeled probability of Level A harassment (0.93), the estimated median number of harassments (5), and denning observations that have occurred within the area of the 2021-ITRs subsequent to the promulgation of the regulations in 2021. Of the four dens that have been observed within 1 mile of the human activity since 2021, two polar bear family groups appear to have spent less time at the den site during the post emergence period than average. Following the relationship between den emergence date and den departure date described by Andersen et al. (2024), the cubs in the early departing family groups may have experienced a reduction in fitness and, as a result, a temporary decrease in their probability of survival. The Service considers such reductions in fitness as “injuries” for the purposes of interpreting the MMPA's definition of Level A harassment.

Updated and Revised Findings

Our reanalysis has led to the conclusion that Level A harassment of polar bears is reasonably likely to occur during the 5-year effective period of the 2021-ITRs. Due to this conclusion, and in light of the Court's remand, we propose to revise aspects of the 2021-ITRs that pertain to polar bears (but not Pacific walruses).

Updated “Small Numbers” and “Negligible Impact” Determinations

In conducting analysis for this proposed revision to the 2021-ITRs, we began by focusing on the impact of AOGA's specified activities that may occur during the 2 remaining years of the 2021-ITRs (which expire August 5, 2026), i.e., the activities to which revised regulations would apply. Using the updated information and denning model methodology described above, we estimated the potential Level B harassment, Level A harassment, and lethal take of denning polar bears that may occur as a result of these specified activities (table 3). ( print page 88220)

Table 3—Annual and Aggregate Estimates of MMPA Take of Denning Polar Bears Under the 2021-ITRs August 6, 2024, Through August 5, 2026

Type of take	Probability	Mean	Median	95% CI
Level B harassment: 2-year	0.97	4.27	4	0-10
Level B harassment: 1-year	0.86	2.45	2	0-7
Level A harassment: 2-year	0.71	2.31	2	0-8
Level A harassment: 1-year	0.49	1.27	0	0-6
Lethal take: 2-year	0.45	1.05	0	0-5
Lethal take: 1-year	0.31	0.65	0	0-4