Social survival: Humpback whales (Megaptera novaeangliae) use social structure to partition ecological niches within proposed critical habitat

Abstract

Animal culture and social bonds are relevant to wildlife conservation because they influence patterns of geography, behavior, and strategies of survival. Numerous examples of socially-driven habitat partitioning and ecological-niche specialization can be found among vertebrates, including toothed whales. But such social-ecological dynamics, described here as ‘social niche partitioning’, are not known among baleen whales, whose societies—particularly on foraging grounds—are largely perceived as unstructured and incidental to matters of habitat use and conservation. However, through 16 years of behavioral observations and photo-identifications of humpback whales (Megaptera novaeangliae) feeding within a fjord system in the Canadian Pacific (primarily within Gitga’at First Nation waters), we have documented long-term pair bonds (up to 12 years) as well as a complex societal structure, which corresponds closely to persistent patterns in feeding strategy, long-term site fidelity (extended occupancy and annual rate of return up to 75%), specific geographic preferences within the fjord system, and other forms of habitat use. Randomization tests of network congruency and clustering algorithms were used to test for overlap in patterns of social structure and habitat use, which confirmed the occurrence of social niche partitioning on the feeding grounds of this baleen whale species. In addition, we document the extensive practice of group bubble net feeding in Pacific Canada. This coordinated feeding behavior was found to strongly mediate the social structure and habitat use within this humpback whale society. Additionally, during our 2004–2019 study, we observed a shift in social network structure in 2010–2012, which corresponded with environmental and demographic shifts including a sudden decline in the population’s calving rate. Our findings indicate that the social lives of humpback whales, and perhaps baleen whales generally, are more complex than previously supposed and should be a primary consideration in the assessment of potential impacts to important habitat.

Fin whales of the Great Bear Rainforest: Balaenoptera physalus velifera in a Canadian Pacific fjord system

“…Recovery ecology. The non-exclusive form of seasonal residency exhibited by KFS fin whales, in which individuals rely on the KFS as a regular destination within a larger spatial pattern of habitat use, differs from the strategy of sustained occupancy practiced by the resident humpback whales of this area [111]. This is just one of many site use differences found in these two sympatric populations within the KFS [48][49][50].…”

“…These two populations also differ starkly in size. Humpback whales here are much more numerous [48,111], which is curious considering that relatively few humpback whales were taken or even recorded in sighting logs during the whaling era (S1 Appendix). This discrepancy could simply be due to the whaler's preferential attention to the larger and more lucrative species, or to the inaccuracy of the logs.…”

DNA from dives: Species detection of humpback whales (Megaptera novaeangliae) from flukeprint eDNA

“…Monitoring programs for humpback whales in the Canadian Pacific consist of citizen science reporting (e.g., Ocean Wise's Cetacean Sightings Network), boat‐ and land‐based visual surveys (Ashe et al., 2013; McMillan et al., 2022; Wray et al., 2021), acoustic monitoring (Ford et al., 2010; Kyhn et al., 2013), and genetic monitoring (Baker et al., 2013; Reidy et al., 2022). Photo‐identification surveys are commonplace for humpback whales, but it remains difficult to obtain genetic data from humpback populations (Cheney et al., 2022).…”