Appendix S1: Possible sources of bias in meta-analysis and a list of references used as data
sources for this study.
Sources of bias in meta-analysis
Meta-analyses can provide powerful summaries of ecological results, but should be used
rigorously to avoid biased conclusions (Kotiaho & Tomkins 2002). Bias may already occur
in the publication phase of papers, when published studies are not representative of all
studies conducted (Csada et al. 1996; Møller & Jennions 2001). Reasons for publication
bias may be, for example, the preference for publishing statistically significant results
(“file-drawer problem”; Rosenthal 1979) or results supporting currently fashionable
hypotheses (Simmons et al. 1999). Significant results are also more likely to be published
in English, which may lead to more citations through indexing in an electronic database
(Egger et al. 1997). Bias may also occur in the selection and data extraction phases of a
meta-analysis (Gates 2002). In our analyses we follow the recommendations of Gates
(2002) to increase confidence in the generality of our results.
References:
Csada, R. D., James, P. C. & Espie, R. H. M. 1996 The ''file drawer problem'' of nonsignificant results: does it apply to biological research? Oikos 76, 591-593.
1
Egger, M., Zellweger-Zahner, T., Schneider, M., Junker, C., Lengeler, C. & Antes, G. 1997
Language bias in randomised controlled trials published in English and German. Lancet
350, 326-329.
Gates, S. 2002 Review of methodology of quantitative reviews using meta-analysis in
ecology. Anim. Ecol. 71, 547-557.
Kotiaho, J. S. & Tomkins, J. L. 2002 Meta-analysis, can it ever fail? Oikos 96, 551-553.
Møller, A. P. & Jennions, M. D. 2001 Testing and adjusting for publication bias. Trends
Ecol. Evol. 16, 580-586.
Rosenthal, R. 1979 The "File Drawer Problem" and tolerance for null results. Psychol. Bull.
86, 638-641.
Simmons, L. W., Tomkins, J. L., Kotiaho, J. S. & Hunt, J. 1999 Fluctuating paradigm.
Proc. R. Soc. B. 266, 593-595.
Below we list the sources of data for the meta-analysis: 45 replicated studies and 30
unreplicated studies. Numbers refer to respective rows in the dataset tables Table S1 for
replicated experiments and S2 for unreplicated experiments.
Replicated studies
2
1.
Balser, D. S., Dill, H. H. & Nelson, H. K. 1968 Effect of predator reduction on
waterfowl nesting success. J. Wildl. Manage. 32, 669-682.
2.
Banks, P. B. 1999 Predation by introduced foxes on native bush rats in Australia: do
foxes take the doomed surplus? J. Appl. Ecol. 36, 1063-1071.
3.
Banks, P. B., Newsome, A. E. & Dickman, C. R. 2000 Predation by red foxes limits
recruitment in populations of eastern grey kangaroos. Austral Ecol. 25, 283-291.
4.
Banks, P. B., Norrdahl, K., Nordström, M. & Korpimäki, E. 2004 Dynamic impacts
of feral mink predation on vole metapopulations in the outer archipelago of the Baltic
Sea. Oikos 105, 79-88.
5.
Clark, R.G., Meger, D. E. & Ignatiuk, J. B. 1995 Removing American crows and
duck nesting success. Can. J. Zool. 73, 518-522.
6.
Desy, E. & Batzli, G. O. 1989 Effects of food availability and predation on prairie
vole demography: a field experiment. Ecology 70, 411-421.
7.
Dion, N., Hobson, K. A. & Lariviere, S. 1999 Effects of removing duck-nest
predators on nesting success of grassland songbirds. Can. J. Zool. 77, 1801-1806.
8.
Garrettson, P. R. & Rohwer, F. C. 2001 Effects of mammalian predator removal on
production of upland-nesting ducks in North Dakota. J. Wildl. Manage. 65, 398-405.
9.
Garretson, P. R., Rohwer, F. C., Zimmer, J. M., Mense, B. J. & Dion, N. 1996 Effects
of mammalian predator removal on waterfowl and non-game birds in North Dakota.
Trans. 61st. No. Am. Wildl. and Natur. Resour. Conf. 61, 94-101.
3
10. Graham, I. M. & Lambin, X. 2002 The impact of weasel predation on cyclic fieldvole survival: the specialist predator hypothesis contradicted. J. Anim. Ecol. 71, 946956.
11. Greenwood, R. J. 1986 Influence of Striped Skunk removal on upland duck nest
success in North Dakota. Wildl. Soc. Bull. 14, 6-11.
12. Greenwood, R. J., Arnold, P. M. & McGuire, B. G. 1990 Protecting duck nests from
mammalian predators with fences, traps, and a toxicant. Wildl. Soc. Bull. 18, 75-82.
13. Hambäck, P. A., Oksanen, L., Ekerholm, P., Lindgren, Å., Oksanen, T. & Schneider,
M. 2004 Predators indirectly protect tundra plants by reducing herbivore abundance.
Oikos 106, 85-92.
14. Henke, S. E. and Bryant, F. C. 1999 Effects of coyote removal on the faunal
community in Western Texas. J. Wildl. Manage. 63, 1066-1081.
15. Huitu, O., Koivula, M., Korpimäki, E., Klemola, T. & Norrdahl, K. 2003 Winter food
supply limits growth of northern vole populations in the absence of predation.
Ecology 84, 2108-2118.
16. Huitu, O., Laaksonen, J., Norrdahl, K. & Korpimäki, E. 2005 Spatial synchrony in
vole population fluctuations – a field experiment. Oikos 109, 583-593.
17. Jackson, D.B. 2001 Experimental removal of introduced hedgehogs improves wader
nest success in the Western Isles, Scotland. J. Appl. Ecol. 38, 802-812.
18. Kinnear, J. E., Onus, M. L. & Summer, N. R. 1998 Fox control and rock-wallaby
population dynamics - II. An update. Wildl. Res. 25, 81-88.
4
19. Klemola, T., Koivula, M., Korpimäki, E. & Norrdahl, K. 1997 Small mustelid
predation slows population growth of Microtus voles: A predator reduction
experiment. J. Anim. Ecol. 66, 607-614.
20. Klemola, T., Koivula, M., Korpimäki, E. & Norrdahl, K. 2000 Experimental tests of
predation and food hypotheses for population cycles of voles. Proc. R. Soc. B 267,
351-356.
21. Korpimäki, E. & Norrdahl, K. 1998 Experimental reduction of predators reverses the
crash phase of small-rodent cycles. Ecology 79, 2448-2455.
22. Korpimäki, E., Norrdahl, K., Huitu, O. & Klemola, T. 2005 Predation induced
synchrony in population oscillations of co-existing small mammal species. Proc. R.
Soc. B 272, 193-202.
23. Korpimäki, E., Norrdahl, K., Klemola, T., Pettersen, T. & Stenseth, N. C. 2002
Dynamic effects of predators on cyclic voles: field experimentation and model
extrapolation. Proc. R. Soc. B 269, 991-997.
24. Lokemoen, J. T. & Woodward, R. O. 1993 An assessment of predator barriers and
predator control to enhance duck nest success on peninsulas. Wildl. Soc. Bull. 21,
275-282.
25. Lokemoen, J. T., Doty, H. A., Sharp, D. E. & Neaville, J. E. 1982 Electric fences to
reduce mammalian predation on waterfowl nests. Wildl. Soc. Bull. 10, 318-323.
26.
Lomolino, M. 1984 Immigrant selection, predation and the distributions of Microtus
pennsylvanicus and Blarina brevicauda on islands. Am. Nat. 123, 468-483.
5
27. Marcström, V., Keith, L. B., Engren, E. & Cary, J. R. 1989 Demographic responses of
arctic hares (Lepus timidus) to experimental reductions of red foxes (Vulpes vulpes)
and martens (Martes martes). Can. J. Zool. 67, 658-668.
28. Marcström, V., Kenward, R. E. & Engren, E. 1988 The impact of predation on boreal
tetraonids during vole cycles: An experimental study. J. Anim. Ecol. 57, 859-873.
29. Mayer, P. M. & Ryan, M. R. 1991 Electric fences reduce mammalian predation on
Piping Plover nests and chicks. Wildl. Soc. Bull. 19, 59-63.
30. Meserve, P. L., Gutiérrez, J. R., Yunger, J. A., Contreras, L. C. & Jaksic, F. M. 1996
Role of biotic interactions in a small mammal assemblage in semiarid Chile. Ecology
77, 133-148.
Meserve, P. L., Gutiérrez, J. R. & Jaksic, F. M. 1993 Effects of vertebrate predation
on a caviomorph rodent, the degu (Octodon degus), in a semiarid thorn scrub
community in Chile. Oecologia 94, 153-158.
Experiment started by Meserve et al. (1993), results taken from Meserve et al. (1996).
31. Moorhouse, R., Greene, T., Dilks, P., Powlesland, R., Moran, L., Taylor, G., Jones,
A., Knegtmans, J., Wills, D., Pryde, M., Fraser, I., August, A. & August, C. 2003
Control of introduced mammalian predators improves kaka Nestor meridionalis
breeding success: reversing the decline of a threatened New Zealand parrot. Biol.
Cons. 110, 33-44.
6
32. Nie, H. & Liu, J. 2005 Regulation of root vole population dynamics by food supply
and predation: a two-factor experiment. Oikos 109, 387-395.
33. Nordström, M., Högmander, J., Laine, J., Nummelin, J., Laanetu, N. & Korpimäki, E.
2003 Effects of feral mink removal on seabirds, waders and passerines on small
islands in the Baltic Sea. Biol. Cons. 109, 359-368.
34. Nordström, M., Högmander, J., Nummelin, J., Laine, J., Laanetu, N. & Korpimäki, E.
2002 Variable responses of waterfowl breeding populations to long-term removal of
introduced American mink. Ecography 25, 385-394.
35. Norrdahl, K. & Korpimäki, E. 1995 Effects of predator removal on vertebrate prey
populations: Birds of prey and small mammals. Oecologia 103, 241-248.
36. Norrdahl, K. & Korpimäki, E. 1996 Do nomadic avian predators synchronize
population fluctuations of small mammals? A field experiment. Oecologia 107, 478483.
37. Norrdahl, K., Heinilä, H., Klemola, T. & Korpimäki, E. 2004 Predator-induced
changes in population structure and individual quality of Microtus voles: a large scale
field experiment. Oikos 105, 312-324.
38. Pearse, A. T. & Ratti, J. T. 2004 Effects of Predator Removal on Mallard Duckling
Survival. J. Wildl. Manage. 68, 342-350.
39. Sargeant, A. B., Sovada, M. A. and Shaffer, T. L. 1995 Seasonal predator removal
relative to hatch rate of duck nests in waterfowl production areas. Wildl. Soc. Bull. 23,
507-513.
40. Sundell, J. 2003 Population dynamics of microtine rodents: an experimental test of
the predation hypothesis. Oikos 101, 416-427.
7
41. Tapper, S. C., Potts, G. R. & Brockless, M. H. 1996 The effect of an experimental
reduction in predation pressure on the breeding success and population density of
grey partridges Perdix perdix. J. Appl. Ecol. 33, 965-978.
42. Vibe-Petersen, S., Leirs, H. & de Bruyn, L. 2006 Effects of predation and dispersal on
Mastomys natalensis population dynamics in Tanzanian maize fields. J. Anim. Ecol.
75: 213-220.
43. Wolff, J. O., Fox, T., Skillen, R. R. & Wang, G. 1999 The effects of supplemental
perch sites on avian predation and demography of vole populations. Can. J. Zool. 77,
535-541.
44. Ylönen, H., Viitala, J. & Mappes, T. 1991 How much do avian predators influence
cyclic bank vole populations? An experiment during a peak year. Ann. Zool. Fennici
28, 1-6.
45. Yunger, J.A. 2004 Movement and spatial organisation of small mammals following
vertebrate predator exclusion. Oecologia 139, 647-654.
Unreplicated studies
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Bartmann, R. M., White, G. C. & Carpenter, L. H. 1992 Compensatory mortality in a
Colorado mule deer population. Wildl. Monogr. 121, 1-39.
2.
Beasom, S. L. 1974 Relationships between predator removal and white-tailed deer net
productivity. J. Wildl. Manage. 38, 854-859.
8
3.
Boonstra, R., Boutin, S., Byrom, A., Karels, T., Hubbs, A., Stuart-Smith, K., Blower,
M. & Antpoehler, S. 2001 The Role of Red Squirrels and Arctic Ground Squirrels. In
Ecosystem Dynamics of the Boreal Forest - The Kluane Project (eds. C. J. Krebs, S.
Boutin & R. Boonstra), pp. 179-214. New York: Oxford University Press.
4.
Boonstra, R., Krebs, C. J., Gilbert, S. & Schweiger, S. (2001). Voles and Mice. In
Ecosystem Dynamics of the Boreal Forest - The Kluane Project (eds. C. J. Krebs, S.
Boutin & R. Boonstra), pp. 215-239. New York: Oxford University Press.
5.
Byrom, A. E., Karels, T. J., Krebs, C. J. & Boonstra, R. 2000 Experimental
manipulation of predation and food supply of arctic ground squirrels in the boreal
forest. Can. J. Zool. 78, 1309-1319.
Hubbs, A.H. & Boonstra, R. 1997 Population limitation in Arctic ground squirrels:
Effects of food and predation. J. Anim. Ecol. 66, 527-541.
Karels, T. J., Byrom, A. E., Boonstra, R. & Krebs, C. J. 2000 The interactive effects
of food and predators on reproduction and overwinter survival of arctic ground
squirrels. J. Anim. Ecol. 69, 235-247.
The experiment was started by Hubbs & Boonstra (1997); results from Byrom et al.
(2000) and Karels et al. (2000) were combined into one study.
6.
Cuthbert, R. 2002 The role of introduced mammals and inverse density-dependent
predation in the conservation of Hutton´s shearwater. Biol. Cons. 108, 69-78.
9
7.
Dilks, P. 1999 Recovery of a Mohua (Mohoua ochrocephala) population following
predator control in the Eglinton Valley, Fiordland, New Zealand. Notornis 46, 323332.
O’Donnell, C. F. J., Dilks, P. J. & Elliott, G. P. 1996 Control of a stoat (Mustela
erminea) population irruption to enhance mohua (yellowhead) (Mohoua
ochrocephala) breeding success in New Zealand. N. Z. J. Zool. 23, 279-286.
The experiment was started by O’Donnell et al. (1996), final results were taken from
Dilks (1999).
8.
Duebbert, H. F. & Kantrud, H. A. 1974 Upland duck nesting related to land use and
predator reduction. J. Wildl. Manage. 38, 257-265.
Duebbert, H. F. & Lokemoen, J. T. 1980 High duck nesting success in a predatorreduced environment. J. Wildl. Manage. 44, 428-437.
These were combined into one study, because Duebbert & Lokemoen (1980) report
results from the whole time span of the experiment, whereas Duebbert & Kantrud
(1974) only report results from one year.
9.
Edminster, F. C. 1939 The effect of predator control on ruffed grouse populations in
New York. J. Wildl. Manage. 3, 345-352.
10
10. Erlinge, S. 1987 Predation and noncyclicity in a microtine population in southern
Sweden. Oikos 50, 347-352.
11. Harris, M. P. & Wanless, S. 1997 The effect of removing large numbers of gulls
Larus spp. on an island population of oystercatchers Haematopus ostralegus:
implications for management. Biol. Cons. 82, 167-171.
12. Hatter, I. W. & Janz, D. W. 1994 Apparent demographic changes in black-tailed deer
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rabbits on Whale Island, and effects of rat and rabbit eradication. N. Z. J. Ecol. 24,
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exotic predator turned biocontrol agent. Biol. Cons. 108, 335-359.
This article consists of six individual predator removals, which have been considered
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16. Krebs, C. J., Boutin, S., Boonstra, R., Sinclair, A. R. E., Smith, J. N. M., Dale, M. R.
T., Martin, K. & Turkington, R. 1995 Impact of food and predation on the snowshoe
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11
17. LaGrange, T. G., Hansen, J. L., Andrews, R. D., Hancock, A. W. & Kienzler, J.
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12
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populations during a population cycle. Oikos 87, 382-398.
13