Abstract
Sex-biased predation, a predator’s bias for one prey sex over the other, can have important demographic impacts on prey species of conservation concern. Yet, it is difficult to measure in the wild. Molecular scatology has been used to indirectly determine the proportion of prey items consumed in the diet, and it may be possible to apply similar approaches to determine the sex-biased consumption of prey items. We developed a molecular method to indirectly examine sex-specific predation employing scat, focusing on predator–prey interactions between Chinook salmon (Oncorhynchus tshawytscha) and harbor seals (Phoca vitulina richardii). We established that the proportions of male and female Chinook DNA can be determined in a controlled sample by measuring a Y-linked marker, growth hormone pseudogene, using qPCR. We then applied the assay to harbor seal scat samples. Although the assay amplified in 83% of scat samples, 27% of samples quantified had an estimated male proportion > 1, which may have been due to a lack of robustness of the PCR assay in samples. Lastly, we constructed a biomass calibration curve to determine whether DNA measurements could estimate the proportions of male and female biomass consumed. The calibration curve was skewed by high male DNA density precluding our ability to quantify the relative amounts. We demonstrated that nuclear prey markers can be amplified in predator scat, however, contamination and extreme DNA density differences between the prey sexes may pose practical difficulties to estimate the relative amounts of male to female biomass consumed.
Similar content being viewed by others
References
Bigg MA, Ellis GM, Cottrell P, Milette L (1990) Predation by harbour seals and sea lions on adult salmon in Comox and Cowichan bay, British Columbia. Can Tech Rep Fish Aquat Sci 1769:31
Boukal DS, Berec L, Křivan V (2008) Does sex-selective predation stabilize or destabilize predator-prey dynamics? PLoS ONE 3:e2687
Bowles E, Schulte PM, Tollit DJ, Deagle BE, Trites AW (2011) Proportion of prey consumed can be determined from faecal DNA using real-time PCR. Mol Ecol Resour 11:530–540
Brankatschk R, Bodenhausen N, Zeyer J, Bürgmann H (2012) Simple absolute quantification method correcting for quantitative PCR efficiency variations for microbial community samples. Appl Environ Microbiol 78:4481–4489
Čikoš Š, Bukovská A, Koppel J (2007) Relative quantification of mRNA: comparison of methods currently used for real-time PCR data analysis. BMC Mol Biol 8:113
Deagle BE, Tollit DJ (2006) Quantitative analysis of prey DNA in pinniped faeces: potential to estimate diet composition? Conserv Genet 8:743–747
Deagle BE, Tollit DJ, Jarman SN, Hindell MA, Trites AW, Gales NJ (2005) Molecular scatology as a tool to study diet: analysis of prey DNA in scats from captive Steller sea lions. Mol Ecol 14:1831–1842
Deagle BE, Eveson JP, Jarman SN (2006) Quantification of damage in DNA recovered from highly degraded samples—a case study on DNA in faeces. Front Zool 3:11
Deagle BE, Kirkwood R, Jarman SN (2009) Analysis of Australian fur seal diet by pyrosequencing prey DNA in faeces. Mol Ecol 18:2022–2038
Deagle BE, Chiaradia A, McInnes J, Jarman SN (2010) Pyrosequencing faecal DNA to determine diet of little penguins: is what goes in what comes out? Conserv Genet 11:2039–2048
Devlin RH, Biagi CA, Smailus DE (2001) Genetic mapping of Y-chromosomal DNA markers in Pacific salmon. Genetica 111:43–58
Devlin RH, Park L, Sakhrani DM, Baker JD, Marshall AR, LaHood E, Kolesar SE, Mayo MR, Biagi CA, Uh M (2005) Variation of Y-chromosome DNA markers in Chinook salmon (Oncorhynchus tshawytscha) populations. Can Tech Rep Fish Aquat Sci 62:1386–1399
Du SJ, Devlin RH, Hew CL (1993) Genomic structure of growth hormone genes in Chinook salmon (Oncorhynchus tshawytscha): presence of two functional genes, GH-I and GH-II, and a male-specific pseudogene, GH-ψ. DNA Cell Biol 12:739–751
Garner SR, Bortoluzzi RN, Heath DD, Neff BD (2010) Sexual conflict inhibits female mate choice for major histocompatibility complex dissimilarity in Chinook salmon. Proc Biol Sci 277:885–894
Gentry-Shields J, Wang A, Cory RM, Stewart JR (2013) Determination of specific types and relative levels of QPCR inhibitors in environmental water samples using excitation–emission matrix spectroscopy and PARAFAC. Water Res 47:3467–3476
Gervasi V, Nilsen EB, Sand H, Panzacchi M, Rauset GR, Pedersen HC, Kindberg J, Wabakken P, Zimmermann B, Odden J, Liberg O, Swenson JE, Linnell JDC (2012) Predicting the potential demographic impact of predators on their prey: a comparative analysis of two carnivore–ungulate systems in Scandinavia. J Anim Ecol 81:443–454
Götmark F, Post P, Olsson J, Himmelmann D (1997) Natural selection and sexual dimorphism: sex-biased sparrowhawk predation favours crypsis in female chaffinches. Oikos 80:540–548
Healey MC (1991) Life history of Chinook salmon (Oncorhynchus tshawytscha). In: Groot C, Margolis L (eds) Pacific salmon life histories. UBC Press, Vancouver, pp 311–394
Hendry AP, Dittman AH, Hardy RW (2000) Proximate composition, reproductive development, and a test for trade-offs in captive sockeye salmon. Trans Am Fish Soc 129:1082–1095
Horsman KM, Hickey JA, Cotton RW, Landers JP, Maddox LO (2006) Development of a human- specific real-time PCR assay for the simultaneous quantitation of total genomic and male DNA. J Forensic Sci 51:758–765
Hoy SR, Petty SJ, Millon A, Whitfield DP, Marquiss M, Davison M, Lambin X (2015) Age and sex- selective predation moderate the overall impact of predators. J Anim Ecol 84:692–701
King RA, Read DS, Traugott M, Symondson WOC (2008) Invited review: molecular analysis of predation: a review of best practice for DNA-based approaches. Mol Ecol 17:947–963
Kohn MH, Wayne RK (1997) Facts from feces revisited. Trends Ecol Evol 12:223–227
Maddison DR, Schulz KS (2007) The tree of life web project. http://tolweb.org. Accessed 13 August 2014
Mann RD, Peery CA, Pinson AM, Anderson CR (2009) Energy use, migration times, and spawning success of adult spring–summer Chinook salmon returning to spawning areas in the South Fork Salmon River in Central Idaho: 2002–2007. Technical Report 2009-4, Cooperative Fish and Wildlife Research Unit, University of Idaho, Moscow, Idaho, USA
Matejusová I, Doig F, Middlemas SJ, Mackay S, Douglas A, Armstrong JD, Cunningham CO, Snow M (2008) Using quantitative real-time PCR to detect salmonid prey in scats of grey Halichoerus grypus and harbour Phoca vitulina seals in Scotland—an experimental and field study. J Appl Ecol 45:632–640
Murphy MA, Waits LP, Kendall KC (2003) The influence of diet on faecal DNA amplification and sex identification in brown bears (Ursus arctos). Mol Ecol 12:2261–2265
Muttray AF, Sakhrani D, Withler RE, Devlin RH (2015) Low variation in a Y-chromosomal growth hormone pseudogene relative to its functional autosomal progenitor gene in Chinook salmon. Trans Am Fish Soc 144:1029–1039
Nagler JJ, Cavileer T, Steinhorst K, Devlin RH (2004) Determination of genetic sex in Chinook salmon (Oncorhynchus tshawytscha) using the male-linked growth hormone pseudogene by real-time PCR. Mar Biotechnol 6:186–191
NMFS (1997) Investigation of scientific information on the impacts of California sea lions and Pacific harbor seals on salmonids and on the coastal ecosystems of Washington, Oregon, and California. Technical Memorandum NMFS-NWFSC-28. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Seattle, Washington
Olsen JB, Miller SJ, Harper K, Nagler JJ, Wenburg JK (2006) Contrasting sex ratios in juvenile and adult Chinook salmon Oncorhynchus tshawytscha (Walbaum) from south-west Alaska: sex reversal or differential survival? J Fish Biol 69:140–144
Opel KL, Chung D, McCord BR (2009) A study of PCR inhibition mechanisms using real-time PCR. J Forensic Sci 55:25–33
Peirson SN, Butler JN, Foster RG (2003) Experimental validation of novel and conventional approaches to quantitative real-time PCR data analysis. Nucleic Acids Res 31:e73
Pfaffl MW (2001) A new mathematical model for relative quantification in real-time RT–PCR. Nucleic Acids Res 29:e45
Ramakers C, Ruijter JM, Deprez RHL, Moorman AFM (2003) Assumption-free analysis of quantitative real-time polymerase chain reaction (PCR) data. Neurosci Lett 339:62–66
Scordino J (2010) West coast pinniped program investigations on California sea lion and Pacific harbor seal impacts on salmonids and other fishery resources. Pacific States Marine Fisheries Commission, Portland
Shipley GL (2013) Assay design for real-Time PCR. In: Nolan T, Bustin SA (eds) PCR technology: current innovations, 3rd edn. Taylor & Francis, New York, pp 177–198
Spidle AP, Puinn TP, Bentzen P (1998) Sex-biased marine survival and growth in a population of Coho salmon. J Fish Biol 52:907–915
Thomas AC, Jarman SN, Haman KH, Trites AW, Deagle BE (2014) Improving accuracy of DNA diet estimates using food tissue control materials and an evaluation of proxies for digestion bias. Mol Ecol 23:3706–3718
Thomas AC, Nelson BW, Lance MM, Deagle BE, Trites AW (2016) Harbour seals target juvenile salmon of conservation concern. Can J Fish Aquat Sci. https://doi.org/10.1139/cjfas-2015-0558
Thorgaard GH (1977) Heteromorphic sex chromosomes in male rainbow trout. Science 196:900–902
Trites AW, Beggs CW, Riddell B (1996) Status review of the Puntledge river summer Chinook. Department of Fisheries and Oceans, Pacific Region, PSARC Document S96–16, Namaino
Wang LJ, Chen YM, George D, Smets F, Sokal EM, Bremer EG, Soriano HE (2002) Engraftment assessment in human and mouse liver tissue after sex-mismatched liver cell transplantation by real-time quantitative PCR for Y chromosome sequences. Liver Transpl 8:822–828
Waples RS (2002) Effective size of fluctuating salmon populations. Genetics 161:783–791
Wedekind C (2012) Managing population sex ratios in conservation practice: how and why? In: Povilitis T (ed) Topics in conservation biology. Intech, Croatia, pp 81–96
Werner EE, Hall DJ (1974) Optimal foraging and the size selection of prey by the bluegill sunfish (Lepomis macrochirus). Ecology 55:1042–1052
Wilson IG (1997) Inhibition and facilitation of nucleic acid amplification. Appl Environ Microbiol 63:3741–3751
Zuk M, Kolluru GR (1998) Exploitation of sexual signals by predators and parasitoids. Q Rev Biol 73:415–438
Acknowledgements
We would like to thank Dr. Craig Moyer and Dr. Alejandro Acevedo for their feedback on experimental design and helpful comments on the manuscript. Thanks to Dionne Sakhrani and Krista Woodward at Fisheries and Oceans Canada for assistance with the sex-determining assay. Special thanks to the Cowlitz Fish Hatchery (WDFW) and Dr. Katherine Haman who provided Coho salmon. Thanks to Allegra La Ferr, Ashlyn Teather, Jenna Brooks, and Ryan Mclaughlin who assisted in fish homogenization. This project was funded by the Coastal Fish and Wildlife Compensation Program, the Pacific Salmon Foundation, WWU Biology Graduate Summer Scholarship, and the WWU Research and Sponsored Programs.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Ethical approval
The harbour seal scats were collected under Fisheries and Oceans Canada Marine Mammal Research License (MML 2011-10) and a University of British Columbia Animal Care Permit (A11-0072).
Rights and permissions
About this article
Cite this article
Balbag, B.S., Thomas, A.C., Devlin, R.H. et al. Can sex-specific consumption of prey be determined from DNA in predator scat?. Conservation Genet Resour 11, 447–455 (2019). https://doi.org/10.1007/s12686-018-1037-9
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12686-018-1037-9