A great grandmother, T059, swims with her great granddaughter, T059A1A, by Pender Island.
A great grandmother, T059, swims with a great granddaughter, T059A1A, off of Pender Island. Photo taken from land by Janine McNeilly.

Guided by mom: The matriarchal world of killer whales

Like us, motherhood is a lifetime commitment for these mammals.

By Amy Rowley and Janine McNeilly 5 min. read

Mothers are at the centre of all killer whale families.

In resident killer whale societies, sons and daughters typically remain with their mother for life, forming tight-knit family groups led by older, experienced females.1 These matriarchs hold critical knowledge, like where to find food and when to travel to different parts of their habitat. Their leadership is not just social; it is essential for the pods’ survival. 

Killer whale mothers invest heavily in caring for their offspring: after an approximately 18-month pregnancy, they give birth to a single calf, which they will then feed with nutrient-rich milk for up to three years.2 This comes at a cost to the mothers, who experience a significant decline in body condition while nursing their calves.3 

Parental care doesn’t end after calves are weaned – killer whale mothers engage in prey-sharing throughout their offspring’s life. From the day their calf starts trying solid food, mothers will find and catch a fish, bring it to the surface, and break it apart to share with their kids. 

This behaviour doesn’t stop once the kids grow up; fully grown males still go to their moms for an extra salmon snack.4 One study of Northern Resident killer whales observed adult females sharing 91% of prey captured, the vast majority of which was shared with offspring and grandoffspring.5 This generosity appears to affect their own health, with mothers that have more offspring exhibiting worse body condition for their age than mothers with fewer offspring.6

The impact of a strong matriarch has quantifiable effects. Calves are more likely to survive if their grandmother is still alive.7 

Females separating from their mothers to start a pod of their own is more common in Bigg’s (transient) killer whales than in residents. A new mom might form her own pod with the birth of her first calf.8 Adult male Bigg’s are known to travel alone or with their brothers, but they always end up coming home to their moms.9 Having smaller family groups may be beneficial to the Bigg’s, who need to remain as quiet as possible when hunting for marine mammals.10 

Sound is survival for these marine mammals – mothers and calves rely on vocalizations to bond and communicate with each other. Ensuring they have an acoustic habitat that can support their growth and development, where these families can thrive, is a long-term goal of Raincoast’s work.11 12

Give killer whales a voice

Raincoast’s Give Killer Whales a Voice initiative aims to protect killer whales from an ocean growing louder every year. We are currently preparing for an ambitious upcoming field season, and we need your help to safeguard these vulnerable animals.

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Notes and references

  1. Wright BM, Stredulinsky EH, Ellis GM, Ford JKB. 2016. Kin-directed food sharing promotes lifetime natal philopatry of both sexes in a population of fish-eating killer whales, Orcinus orca. Anim Behav; 115:81-95. https://doi.org/10.1016/j.anbehav.2016.02.025.
  2. Newsome SD, Etnier MA, Monson DH, Fogel ML. 2009. Retrospective characterization of ontogenetic shifts in killer whale diets via δ13C and δ15N analysis of teeth. Marine Ecology Progress Series. 374:229–242. doi:https://doi.org/10.3354/meps07747.
  3. Kay SWC, Rowley AG, Visona-Kelly BC, Barrett-Lennard LG, Thompson PR, Sutton GJ, Fearnbach H, Durban JW, Darimont CT. 2026. Costs of maternal care revealed through body conditionin Northern Resident killer whales (Orcinus orca). Scientific Reports. 16(1). https://doi.org/10.1038/s41598-026-38696-0.
  4. Wright et al. 2016.
  5. Wright et al. 2016.
  6. Kay et al. 2026.
  7. Nattrass S, Croft DP, Ellis S, Cant MA, Weiss MN, Wright BM, Stredulinsky E, Doniol-Valcroze T, Ford JKB, Balcomb KC, & Franks DW. 2019. Postreproductive killer whale grandmothers improve the survival of their grandoffspring. Proc. Natl. Acad. Sci. 116(52):26669-26673, https://doi.org/10.1073/pnas.1903844116.
  8. Nielsen MLK, Ellis S, Weiss MN, Towers JR, Doniol-Valcroze T, Franks DW, Cant MA, Ellis GM, Ford JKB, Malleson M, Sutton GJ, Shaw TJH, Balcomb KC 3rd, Ellifrit DK, Croft DP. 2023. Temporal dynamics of mother-offspring relationships in Bigg’s killer whales: opportunities for kin-directed help by post-reproductive females. Proc Biol Sci. doi: https://doi.org/10.1098/rspb.2023.0139.
  9. Nielsen MLK, Ellis S, Weiss MN, Towers JR, Doniol-Valcroze T, Franks DW, Cant MA, Ellis GM, Ford JKB, Malleson M, Sutton GJ, Shaw TJH, Balcomb KC 3rd, Ellifrit DK, Croft DP. (2023). Temporal dynamics of mother-offspring relationships in Bigg’s killer whales: opportunities for kin-directed help by post-reproductive females. Proc Biol Sci. 290(2000):20230139. doi: https://doi.org/10.1098/rspb.2023.0139.
  10. Nielson et al. 2023.
  11. McNeilly J, Hendricks B, and Vergara V. 2026. NoiseTracker: Tracking vessel noise and its implications for Southern Resident killer whales in the Salish Sea. Raincoast Conservation Foundation. DOI: 10.70766/8.76355
  12. Independent Science Panel on SRKW Recovery. 2025. Strengthening recovery actions for Southern Resident killer whales. https://doi.org/10.70766/32.7300

Cetacean Conservation Research ProgramKiller whalesMatriarchsParental care