Recent
PUBLICATIONS
Research
PUBLICATIONS
The following is a list of many of the CWR publications. New articles are added once available.
RECENT RESEARCH
Costly lifetime maternal investment in killer whales
Weiss, M. N., Ellis, S., Franks, D. W., Nielsen, M. L. K., Cant, M. A., Johnstone, R. A., Ellifrit, D. K.,
Balcomb, K. C., and Croft, D. P. (2023).
Costly lifetime maternal investment in killer whales. Current Biology 33, 1–5.
Summary
Parents often sacrifice their own future reproductive success to boost the survival of their offspring, a phenomenon referred to as parental investment. In several social mammals, mothers continue to improve the survival of their offspring well into adulthood; however, whether this extended care comes at a reproductive costs to mothers, and therefore represents maternal investment, is not well understood. We tested whether lifetime maternal care is a form of parental investment in fish-eating ‘‘resident’’ killer whales. Adult killer whales, particularly males, are known to receive survival benefits from their mothers; however, whether this comes at a cost to mothers’ reproductive success is not known. Using multiple decades of complete census data from the ‘‘southern resident’’ population, we found a strong negative correlation between females’ number of surviving weaned sons and their annual probability of producing a viable calf. This negative effect did not attenuate as sons grew older, and the cost of sons could not be explained by long-term costs of lactation or group composition effects, supporting the hypothesis that caring for adult sons is reproductively costly. This is the first direct evidence of lifetime maternal investment in an iteroparous animal, revealing a previously unknown life history strategy.
The effect of age, sex, and resource abundance on patterns of rake markings in resident killer whales (Orcinus orca). Marine Mammal Science, 2022; 1–18.
Abstract
Fluctuations in aggressive behavior of group-living species can reflect social conflict and competition for resources faced by individuals throughout their lifespan and can negatively impact survival and reproduction. In marine mammals, where social interactions are difficult to observe, tooth rake marks can be used as an indicator of received aggression. Using 38 years of photographic data, we quantified the occurrence of tooth rake marks on wild resident killer whales (Orcinus orca), examining the effects of age, sex, and prey abundance on rake density. Our analysis revealed sex and age effects, with males exhibiting higher rake density than females and rake density declining significantly with age. Contrary to predictions, we observed an increase in rake density across the population as the abundance of their primary food resource, Chinook salmon (Oncorhynchus tshawytscha), increased. These results provide indirect evidence of fluctuations in received aggression from conspecifics across the lifespan of an individual, possibly reflecting changes in patterns of social conflict which may be mediated by resource abundance. Our findings highlight the need for further research to examine the fitness consequences of aggression in killer whales and to understand the proximate mechanisms by which resource abundance influences rates of aggression in the population.
A long postreproductive life span is a shared trait among genetically distinct killer whale populations
Nielsen, M. L. K., Ellis, S., Towers, J. R., Doniol-Valcroze, T., Franks, D. W., Cant, M. A., Weiss, M. N., Johnstone, R. A., Balcomb, K. C., Ellifrit, D. K., and Croft, D. P. (2021). A long postreproductive life span is a shared trait among genetically distinct killer whale populations. Ecology and Evolution 11(13): 9123-9136.
Abstract
The extended female postreproductive life span found in humans and some toothed whales remains an evolutionary puzzle. Theory predicts demographic patterns resulting in increased female relatedness with age (kinship dynamics) can select for a prolonged postreproductive life span due to the combined costs of intergenerational reproductive conflict and benefits of late-life helping. Here, we test this prediction using >40 years of longitudinal demographic data from the sympatric yet genetically distinct killer whale ecotypes: resident and Bigg's killer whales. The female relatedness with age is predicted to increase in both ecotypes, but with a less steep increase in Bigg's due to their different social structure. Here, we show that there is a significant postreproductive life span in both ecotypes with >30% of adult female years being lived as postreproductive, supporting the general prediction that an increase in local relatedness with age predisposes the evolution of a postreproductive life span. Differences in the magnitude of kinship dynamics however did not influence the timing or duration of the postreproductive life span with females in both ecotypes terminating reproduction before their mid-40s followed by an expected postreproductive period of about 20 years. Our results highlight the important role of kinship dynamics in the evolution of a long postreproductive life span in long-lived mammals, while further implying that the timing of menopause may be a robust trait that is persistent despite substantial variation in demographic patterns among populations.
Killer Whales
Weiss, M. N., Ellis, S., Franks, D. W., Nielsen, M. L. K., Cant, M. A., Johnstone, R. A., Ellifrit, D. K., Balcomb, K. C., and Croft, D. P. (2023). Costly lifetime maternal investment in killer whales. Current Biology 33, 1–5. Full Text.
Grimes, C., Brent, L. J. N., Weiss, M. N., Franks, D. W., Balcomb, K. C., Ellifrit, D. K., Ellis, S., and Croft, D. P. (2022). The effect of age, sex, and resource abundance on patterns of rake markings in resident killer whales (Orcinus orca). Marine Mammal Science, 2022;1–18. Full Text.
Nielsen, M. L. K., Ellis, S., Towers, J. R., Doniol-Valcroze, T., Franks, D. W., Cant, M. A., Weiss, M. N., Johnstone, R. A., Balcomb, K. C., Ellifrit, D. K., and Croft, D. P. (2021). A long postreproductive life span is a shared trait among genetically distinct killer whale populations. Ecology and Evolution 11(13): 9123-9136. Full Text.
Weiss, M. N., Franks, D. W., Giles, D. A., Youngstrom, S., Wasser, S. K., Balcomb, K. C., Ellifrit, D. K., Domenici, P., Cant, M. A., Ellis, S., Nielsen, M. L. K., Grimes, C., and Croft, D. P. (2021). Age and sex influence social interactions, but not associations, within a killer whale pod. Proceedings of the Royal Society B, Volume 288 Issue 1953. Full Text.
Ellis, S., Franks, D. W., Weiss, M. N., Cant, M. A., Domenici, P., Balcomb, K. C., Ellifrit, D. K. and Croft, D. P. (2021) Mixture models as a method for comparative sociality: social networks and demographic change in resident killer whales. Behavioral Ecology and Sociobiology 75,
Article number: 75. Full Text.
Weiss, M. N., Franks, D. W., Balcomb, K. C., Ellifrit, D. K., Silk, M. J., Cant, M. A., and Croft, D. P. (2020). Modelling cetacean morbillivirus outbreaks in an endangered killer whale population. Biological Conservation 242: 108398. Full Text.
Nattrass, S., Croft, D. P., Ellis, S., Cant, M. A., Weiss, M. N., Wright, B, M., Stredulinsky, E., Doniol-Valcrozef, T., Ford, J. K. B., Balcomb, K. C., & Franks, D. W. (2019). Postreproductive killer whale grandmothers improve the survival of their grandoffspring. PNAS. Full Text.
Ellis, S., Franks, D. W., Nattrass, S., Currie, T. E., Cant, M. A., Giles, D., Balcomb, K. C., & Croft, D. P. (2018). Analyses of ovarian activity reveal repeated evolution of post-reproductive lifespans in toothed whales. Scientific Reports, 8(1). Full Text.
Ford, M. J., Parsons, K. M., Ward, E. J., Hempelmann, J. A., Emmons, C. K., Hanson, M. B., Balcomb, K. C., & Park, L. K. (2018). Inbreeding in an endangered killer whale population. Animal Conservation 21(5): 423-432. Full Text.
Ellis, S., Franks, D. W., Nattrass, S., Cant, M. A., Bradley, D. L., Giles, D., Balcomb, K. C., & Croft D. P. (2018). Postreproductive lifespans are rare in mammals. Ecology and Evolution 8(5): 2482-2494. Full Text.
Fearnbach, H., Durban, J. W., Ellifrit, D. K., & Balcomb, K. C. (2018). "Using aerial photogrammetry to detect changes in body condition of endangered southern resident killer whales." Endangered Species Research 35: 175-180. Full Text.
Ellis, S., Franks, D.W., Nattrass, S., Cant, M.A., Weiss, M.N., Giles, D., Balcomb, K.C., & Croft, D.P. (2017). Mortality risk and social network position in resident killer whales: sex differences and the importance of resource abundance. Proceedings of the Royal Society B: Biological Sciences, 284(1865), 20171313-20171313. Full Text.
Wasser, S. K., Lundin, J. I., Ayres, K., Seely, E., Giles, D., Balcomb, K., Hempelmann, J., Parsons, K., & Booth, R. (2017). Population growth is limited by nutritional impacts on pregnancy success in endangered Southern Resident killer whales (Orcinus orca). PloS One, 12(6), p.e0179824. Full Text.
Croft, D. P., Johnstone, R. A., Ellis, S., Nattrass, S., Franks, D. W., Brent, L. J. N., Mazzi, S., Balcomb, K. C., Ford, J. K. B., & Cant, M. A. (2017). Reproductive conflict and the evolution of menopause in killer whales. Current Biology, 27(2), 298–304. Full Text.
Lacy, R. C., Balcomb, K. C., Brent, L. J. N., Croft, D. P., Clark, C. W., & Paquet, P. C. (2016). Report on Population Viability Analysis model investigations of threats to the Southern Resident Killer Whale population from Trans-Mountain Expansion Project. Full Text.
Ward, E. J., Dahlheim, M. E., Waite, J. M., Emmons, C. K., Marshall, K. N., Chasco, B. E., & Balcomb, K. C. (2016). Long-distance migration of prey synchronizes demographic rates of top predators across broad spatial scales. Ecosphere, 7(2), e01276. Full Text.
Brent, L. J. N., Franks, D. W., Foster, E. A., Balcomb, K. C., Cant, M. A., & Croft, D. P. (2015). Ecological knowledge, leadership, and the evolution of menopause in killer whales. Current Biology, 25(6), 746–750. Full Text.
Cogan, J. (2015). 2015 Whale Sightings in the Salish Sea Central Salish Sea and Puget Sound. Center for Whale Research. Full Document.
Croft, D. P., Brent, L. J. N., Franks, D. W., & Cant, M. A. (2015). The evolution of prolonged life after reproduction. Trends in Ecology and Evolution, 30(7), 407–416. Full Text.
Foster, E. A., Franks, D. W., Mazzi, S., Darden, S. K., Balcomb, K. C., Ford, J. K. B., & Croft, D. P. (2012). Adaptive prolonged postreproductive life span in killer whales. Science, 337(6100), 1313–1313. Full Text.
Foster, E. A., Franks, D. W., Morrell, L. J., Balcomb, K. C., Parsons, K. M., van Ginneken, A., & Croft, D. P. (2012). Social network correlates of food availability in an endangered population of killer whales, Orcinus orca. Animal Behaviour, 83, 731–736. Full Text.
Fearnbach, H., Durban, J. W., Ellifrit, D. K., & Balcomb, K. C. (2011). Size and long-term growth trends of endangered fish-eating killer whales. Endangered Species Research, 13, 173–180. Full Text.
Ford, M. J., Hanson, M. B., Hempelmann, J. A., Ayres, K. L., Emmons, C. K., Schorr, G. S., Baird, R. W., Balcomb, K. C., Wasser, S. K., Parsons, K. M., Balcomb-Bartok, K. (2011). Inferred paternity and male reproductive success in a killer whale (Orcinus orca) population. Journal of Heredity, 102(5), 537–553. Full Text.
Ford, J. K. B., Ellis, G. M., Olesiuk, P. F., & Balcomb, K. C. (2010). Linking killer whale survival and prey abundance: food limitation in the oceans’ apex predator? Biology Letters, 6(1), 139–142. Full Text.
Parsons, K. M., Balcomb, K. C., Ford, J. K. B., & Durban, J. W. (2009). The social dynamics of southern resident killer whales and conservation implications for this endangered population. Animal Behaviour, 77(4), 963–971. Full Text.
Ward, E. J., Holmes, E. E., & Balcomb, K. C. (2009). Quantifying the effects of prey abundance on killer whale reproduction. Journal of Applied Ecology, 46(632–640). Full Text.
Ward, E. J., Parsons, K., Holmes, E. E., Balcomb Iii, K. C., & Ford, J. K. (2009). The role of menopause and reproductive senescence in a long-lived social mammal. Frontiers in Zoology, 6(4). Full Text.
Dahlheim, M. E., Schulman-Janiger, A., Black, N., Ternullo, R., Ellifrit, D., & Balcomb, K. C. (2008). Eastern temperate North Pacific offshore killer whales (Orcinus orca): Occurrence, movements, and insights into feeding ecology. Marine Mammal Science, 24(3), 719–729. Full Text.
Durban, J. W., & Parsons, K. M. (2006). Laser-metrics of free-ranging killer whales. Marine Mammal Science, 22(3), 732–743. Full Text.
Ford, J. K. B., & Ellis, G. M. (2005). Prey selection and food sharing by fish-eating “resident” killer whales (Orcinus orca) in British Columbia. Report to Fisheries and Oceans Canada. Full Text.
Ford, J. K. B., Ellis, G. M., Matkin, D. R., Balcomb, K. C., Briggs, D., & Morton, A. B. (2005). Killer whale attacks on minke whales: Prey capture and antipredator tactics. Marine Mammal Science, 21(4), 603–618. Full Text.
Ford, J. K. B., Ellis, G. M., & Olesiuk, P. F. (2005). Linking prey and population dynamics: did food limitation cause recent declines of “resident” killer whales (Orcinus orca) in British Columbia? Report to Fisheries and Oceans Canada. Full Text.
Gaydos, J. K., Balcomb, K. C., Osborne, R. W., & Dierauf, L. (2004). Evaluating potential infectious disease threats for southern resident killer whales, Orcinus orca: A model for endangered species. Biological Conservation, 117, 253–262. Full Text.
Krahn, M. M., Wade, P. R., Kalinowski, S. T., Dahlheim, M. E., Taylor, B. L., Hanson, M. B., Ylitalo, G. M., Angliss, R. P., Stein, J. E., & Waples, R. S. (2002). Status Review of Southern Resident Killer Whales (Orcinus orca) under the Endangered Species Act. NOAA Technical Memorandum NMFS Series. Full Text.
Ford, J. K. B., Ellis, G. M., & Balcomb, K. C. (2000). Killer Whales: The natural history and genealogy of Orcinus orca in British Columbia and Washington State, Second Edition. Vancouver, BC: UBC Press.
Ford, J. K. B., Ellis, G. M., Barrett-Lennard, L. G., Morton, A. B., Palm, R. S., & Balcomb, K. C. (1998). Dietary specialization in two sympatric populations of killer whales (Orcinus orca) in coastal British Columbia and adjacent waters. Canadian Journal of Zoology, 76, 1456–1471. Full Text.
Dahlheim, M. E., Ellifrit, D. K., & J. D. Swenson. (1997). Killer whales of southeast Alaska: A catalogue of photo-identified individuals. Full Text.
Brault, S., & Caswell, H. (1993). Pod-specific demography of killer whales (Orcinus orca). Ecology, 74(745), 1444–1454. Full Text.
Bigg, M. A. (1990). Social organization and genealogy of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. In P. Hammond, S. Mizroch, & G. Donovan (Eds.), Individual Recognition of Cetaceans: Use of Photo-Identification and Other Techniques to Estimate Population Parameters (pp. 383–405). Cambridge. Full Text.
Olesiuk, P. F., Bigg, M. A., & Ellis, G. M. (1990). Life history and population dynamics of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. In P. S. Hammond, S. A. Mizroch, & G. P. Donovan (Eds.), Individual Recognition of Cetaceans: Use of Photo-Identification and Other Techniques to Estimate Population Parameters (pp. 209–243). Cambridge. Full Text.
Bigg, M. A. (1987). Killer Whales: A Study of Their Identification, Genealogy and Natural History in British Columbia and Washington State. Nanaimo: Phantom Press.
Balcomb, K. C., & Bigg, M. A. (1986). Population biology of three resident killer whale pods in Puget Sound and off southern Vancouver Island. In B. C. Kirkevold & J. S. Lockard (Eds.), Behavioral Biology of Killer Whales (pp. 85–95). Alan R. Liss, Inc.
Heimlich-Boran, J. R. (1986). Behavioral ecology of killer whales (Orcinus orca) in the Pacific Northwest. Canadian Journal of Zoology, 66, 565–578. Full Text.
Dolphins
Fearnbach, H., Durban, J., Parsons, K., & Claridge, A. D. (2012). Photographic mark–recapture analysis of local dynamics within an open population of dolphins. Ecological Applications, 22(5), 1689–1700. Full Text.
Fearnbach, H., Durban, J., Parsons, K., & Claridge, D. (2012). Seasonality of calving and predation risk in bottlenose dolphins on Little Bahama Bank. Marine Mammal Science, 28(2), 402–411.
Parsons, K. M., Durban, J. W., Claridge, D. E., Herzing, D. L., Balcomb, K. C., & Noble, L. R. (2006). Population genetic structure of coastal bottlenose dolphins (Tursiops truncatus) in the northern Bahamas. Marine Mammal Science, 22(2), 276–298. Full Text.
Parsons, K. M., Durban, J. W., Claridge, D. E., Balcomb, K. C., Noble, L. R., & Thompson, P. M. (2003). Kinship as a basis for alliance formation between male bottlenose dolphins, Tursiops truncatus, in the Bahamas. Animal Behavior, 66, 185–194.
Parsons, K. M. (2001). Reliable microsatellite genotyping of dolphin DNA from faeces. Molecular Ecology Notes, 1, 341–344.
Durban, J. W., Parsons, K. M., Claridge, D. E., & Balcomb, K. C. (2000). Quantifying Dolphin Occupancy Patterns. Marine Mammal Science, 16(4), 825–828.
Parsons, K. M., Dallas, J. F., Claridge, D. E., Durban, J. W., Balcomb, K. C., Thompson, P. M., & Noble, L. R. (1999). Amplifying dolphin mitochondrial DNA from faecal plumes. Molecular Ecology, 8, 1753–1768.
Claridge, D. E. (1994). Photo-identification study to assess the population size of Atlantic bottlenose dolphins in central Abaco. Bahamas. Journal of Science, 1, 12–16.
Humpback Whales
Calambokidis, J., Steiger, G., Straley, J., Herman, L., Cerchio, S., Salden, D., Urban R., J., Jacobsen, J., von Ziegesar, O., Balcomb, K. C., Gabriele, C., Dahlheim, M., Uchida, S., Ellis, G., Miyamura, Y., de Guevara P., P. L., Yamaguchi, M., Sato, F., Mizroch, S., Schlender, L., Barlow, J., & Quinn II, T. (2001). Movements and population structure of humpback whales in the North Pacific. Marine Mammal Science, 17(4), 769–794.
Calambokidis, J., Steigerl, G. H., Rasmussenl, K., Urban, J. R., Ladron de Guevara, P. P., Salinas, M., Jacobsen, J. K., Scott Baker, C., & Herman, L. M. (2000). Migratory destinations of humpback whales that feed off California, Oregon and Washington. Marine Ecology Progress Series, 192, 295–304.
Urban, J., Alvarez, C., Salinas, M., Jacobsen, J., Balcomb, K. C., Jaramillo, A., de Guevara, P. L., & Aguayo, A. (1999). Population size of humpback whale, Megaptera novaeangliae, in waters off the Pacific coast of Mexico. Fishery Bulletin, 97, 1017–1024.
Calambokidis, J., Steiger, G. H., Evenson, J. R., Flynn, K. R., Balcomb, K. C., Claridge, D. E., Bloedel, P., Straley, J.M., Baker, C.S., von Ziegesar, O., Dahlheim, M. E., Waite, J. M., Darling, J. D., Ellis, G., & Green, G. (1996). Interchange and isolation of humpback whales off California and other North Pacific feeding grounds. Marine Mammal Science, 12(2), 215–226.
Darling, J. D., Calambokidis, J., Balcomb, K. C., Bloedel, P., Flynn, K., Mochizuki, A., Mori, K., Sato, F., Suganuma, H., & Yamaguchi, M. (1996). Movement of a humpback whale (Megaptera novaeangliae) from Japan to British Columbia and return. Marine Mammal Science, 12(2), 281–287.
Steiger, G., Calambokidis, J., Sears, R., Balcomb, K. C., & Cubbage, J. (1991). Movement of humpback whales between California and Costa Rica. Marine Mammal Science,7(3), 306–310.
Calambokidis, J., Cubbage, J. C., Steiger, G. H., Balcomb, K. C., & Bloedel, P. (1990). Population estimates of humpback whales in the Gulf of the Farralones, California. In P. S. Hammond, S. A. Mizroch, & G. P. Donovan (Eds.), Individual Recognition of Cetaceans: Use of Photo-Identification and Other Techniques to Estimate Population Parameters (pp. 325–328). Cambridge.
Blue Whales
Calambokidis, J., Steiger, G. H., Cubbage, J. C., Balcomb, K. C., Ewald, C., Kruse, S., Wells, R., & Sears, R. (1990). Sightings and movements of blue whales off central California 1986-1988 from photo-identification of individuals. In P. S. Hammond, S. A. Mizroch, & G. P. Donovan (Eds.), Individual Recognition of Cetaceans: Use of Photo-Identification and Other Techniques to Estimate Population Parameters (pp. 343–349). Cambridge
Beaked Whales
Cox, T. M., Ragen, T. J., Read, A. J., Vos, E., Baird, R. W., Balcomb, K. C., Barlow, J., Caldwell, J., Cranford, T., Crum, L., D’amico, A., D’Spain, G., Fernandez, A., Finneran, J., Gentry, R., Gerth, W., Gullands, F., Hilderbrand, J., Houserp, D., Hullar, T., Jepson, P. D., Ketten, D., Macleod, C. D., Miller, P., Moore, S., Mountain, D. C., Palka, D., Ponganis, P., Rommel, S., Rowles, T., Taylor, B., Tyack, P., Wartzok, D., Gisiner, R., Meads, J., & Benner, L. (2006). Understanding the impacts of anthropogenic sound on beaked whales. Journal of Cetacean Resource Management, 7(3), 177–187.
General Cetaceans
Durban, J. W., Elston, D. A., Ellifrit, D. K., Dickson, E., Hammond, P. S., & Thompson, P. M. (2005). Multi-site mark-recapture for cetaceans: population estimates with Bayesian model averaging. Marine Mammal Science, 2(1), 80–92.
Durban, J. W., & Elston, D. A. (2005). Mark–recapture with occasion and individual effects: abundance estimation through bayesian model selection in a fixed dimensional parameter space. Journal of Agricultural, Biological and Environmental Statistics,10(3), 291–305. Full Text.
Parsons, K. M., & Durban, J. W. (2003). Comparing two alternative methods for sampling small cetaceans for molecular analysis. Marine Mammal Science, 19(1), 224–231.