Figure 2:

Baleen nitrogen (δ¹⁵N) stable isotope records for North Atlantic right whales. (A) Female 1 (Eg #1004 ‘Stumpy’, n = 115). (B) Female 2 (Eg#1014 ‘Staccato’, n = 105). Yellow bars indicate predicted high-progesterone regions based on calf sightings, post-mortem examination data and the estimated 12–13 month gestation length for this species. Circle in panel (A) is an example of a time period with multiple sightings of Female 1 in the same, isotopically distinct, geographical area (Bay of Fundy sightings in June, July, August and September 1997) corresponding to points on the baleen that had similar stable isotope ratios.