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Cited by 25Animal Behavior and ReproductionPhysiological and biochemical adaptationsAvian ecology and behavior

The peacock train does not handicap cursorial locomotor performance

Open access
Thavarajah, Nathan K., Tickle, Peter G., Nudds, Robert L., Codd, Jonathan R.·2016·Scientific Reports
DOI 10.1038/srep36512PMC PMC5090354
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Abstract

Exaggerated traits, like the peacock train, are recognized as classic examples of sexual selection. The evolution of sexual traits is often considered paradoxical as, although they enhance reproductive success, they are widely presumed to hinder movement and survival. Many exaggerated traits represent an additional mechanical load that must be carried by the animal and therefore may influence the metabolic cost of locomotion and constrain locomotor performance. Here we conducted respirometry experiments on peacocks and demonstrate that the exaggerated sexually selected train does not compromise locomotor performance in terms of the metabolic cost of locomotion and its kinematics. Indeed, peacocks with trains had a lower absolute and mass specific metabolic cost of locomotion. Our findings suggest that adaptations that mitigate any costs associated with exaggerated morphology are central in the evolution of sexually selected traits.

AI snapshot

Written from the paper’s full text.

TL;DR

In peacocks, carrying the fully grown sexually selected train did not impair terrestrial locomotion; absolute and mass-specific metabolic cost of locomotion were lower during the breeding season than with rudimentary trains, with no kinematic differences. The authors suggest co-adaptations mitigate locomotor costs of exaggerated traits.

Key findings

  • During the breeding season with full trains, peacocks had lower absolute and mass-specific metabolic power consumption during walking than outside the breeding season, and net cost of transport was lower overall with the minimum occurring at a higher speed.
  • Kinematics were unaffected by season: duty factor, stance time, and swing time decreased with speed, while stride length and stride frequency increased with speed, but there were no differences between full-train and rudimentary-train conditions.
  • Resting metabolic rate did not differ significantly between seasons: absolute resting Pmet was 12.44 ± 0.58 W vs. 13.49 ± 0.59 W (t = 1.26, df = 17, P = 0.22), and mass-specific resting Pmet was 2.62 ± 0.12 W vs. 2.94 ± 0.12 W (t = 1.96, df = 17, P = 0.07).
  • RER values were close to 1 in both seasons (breeding: 1.01 ± 0.01; non-breeding: 0.95 ± 0.15), and the U-shaped cost-of-transport curve indicated a minimum at 0.75 m s⁻¹.

Methods

  • Adult peacocks were tested with open-flow indirect calorimetry on a treadmill during the breeding season (May; n = 10, Mb 4.76 ± 0.10 kg, full 1.5 m train) and non-breeding season (November; n = 9, Mb 4.58 ± 0.09 kg, rudimentary train), at speeds of 0.5, 0.64, 0.75, 0.88, and 1 m s⁻¹.
  • Kinematics were filmed in lateral view at 25 Hz (≤0.75 m s⁻¹) or 100 Hz (≥0.75 m s⁻¹), tracking the left foot to quantify duty factor, stride frequency, stride length, stance time, and swing time.
  • Energetics were analyzed with quadratic GLMs, kinematics with ANCOVA, residuals checked with Shapiro–Wilk tests, and resting metabolic rate and body mass compared with t-tests.

Limitations

  • The paper states that the results focus entirely on costs associated with locomotion; other costs of sexual selection may lie in trait development and display rather than in moving with the trait.
  • The paper states that after molt the birds were stressed and reluctant to move, so walking data could not be collected until the train was in rudimentary regrowth not extending beyond the body; different sample sizes resulted from one male damaging his leg and being unavailable for non-breeding trials.
  • Evident from the text: the sample was small (n = 10 and n = 9), only male peacocks were studied, the treadmill speed range was limited, and the authors note it would be interesting to know whether wild preferred speeds correspond to the minimum cost of transport.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/srep36512

Cites

50 of 50 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

9 of 35 cited sources checked · 6 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    Askew found that the train did not reduce take off flight performance in peacocks.

    “Recently, Askew19 found that the train did not reduce take off flight performance”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [19] Askew, G. N. The elaborate plumage in peacocks is not such a drag. J Exp Biol. 217, 3237–3241 (2014). source
  • Interpretationcitation

    The lower cost of transport (CoT) when the train is fully expressed is an adaptation that enables peacocks to balance energy requirements during periods of high-energy use and low food acquisition such as territorial behavior and displays used to attract mates.

    “Therefore, we suggest that the lower CoT when the train is fully expressed is an adaptation that enables peacocks to balance energy requirements during periods of high-energy use and low food acquisition such as territorial behavior and displays used to attract mates33.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [33] Harikrishnan, S., Vasudevan, K. & Sivakma, K. Behaviour of indian Peafowl Pavo cristatus Linn. 1758 During the Mating Perio in a Natural Population. The Open Ornithology Journal. 3, 13–19 (2010). source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • Rests on an assumption: The metabolic costs associated with locomotion are a key component of the daily energy expenditure of many species of bird such as the peacock.
  • Premisecitation

    Economical load carriage was also documented in other species that produce exaggerated sexually selected traits.

    “economical load carriage was also documented in other species that produce exaggerated sexually selected traits25”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [25] McCullough, E. L. & Tobalske, B. W. Elaborate horns in a giant rhinoceros beetle incur negligible aerodynamic costs. P Roy Soc B-Biol Sci. 280, doi: Artn 20130197.10.1098/Rspb.2013.0197 (2013). source
  • Premisecitation

    There is a surprising lack of evidence to support the idea that locomotion in peacocks is in some way affected by sexually selected traits.

    “However, there is a surprising lack of evidence to support the idea that locomotion in peacocks is in some way affected by sexually selected traits19.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [19] Askew, G. N. The elaborate plumage in peacocks is not such a drag. J Exp Biol. 217, 3237–3241 (2014). source
  • Interpretationcitation

    Economical load carriage may be a more widespread phenomenon in Galliformes.

    “indicating that economical load carriage may be a more widespread phenomenon in Galliformes24”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [24] Marsh, R. L., Ellerby, D. J., Henry, H. T. & Rubenson, J. The energetic costs of trunk and distal-limb loading during walking and running in guinea fowl Numida meleagris I. Organismal metabolism and biomechanics. J Exp Biol. 209, 2050–2063, doi: 10.1242/jeb.02226 (2006). source

      The 'Economy of carrying loads on the trunk' section reports economical load carriage in guinea fowl: net metabolic rate rose 17% with a 23% increase in body mass. The paper does not report load-carriage results for other Galliformes, so it supports the guinea-fowl example but not the suggested wider distribution within the group. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
  • Classified as probably not a substantial claim. 23
  • May combine two claims. 16
  • The quote only partly states this claim. 1

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In other Galliformes, testosterone levels are related to the onset of sexually selected ornamental and behavioural displays.

    “In other Galliformes, testosterone levels are related to the onset of sexually selected ornamental and behavioural displays2627.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [26] Lindsay, W. R., Webster, M. S. & Schwabl, H. Sexually Selected Male Plumage Color Is Testosterone Dependent in a Tropical Passerine Bird, the Red-Backed Fairy-Wren (Malurus melanocephalus). Plos One 6, doi: ARTN e26067.10.1371/journal.pone.0026067 (2011). source

      The Results (Molt and Plumage Color; page unavailable) report that testosterone treatment stimulated earlier molt, and the Discussion links testosterone to breeding plumage in red-backed fairy-wrens. The cited paper studies a passerine, not Galliformes, and these passages do not establish the onset of behavioural displays in Galliformes. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • cites [27] Fusani, L. Testosterone control of male courtship in birds. Horm Behav. 54, 227–233, doi: 10.1016/J.Yhbeh.2008.04.004 (2008). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Previous studies in birds have tended to focus on the influence of sexually selected traits during flight rather than terrestrial locomotion.

    “Previous studies in birds have tended to focus on the influence of sexually selected traits during flight rather than terrestrial locomotion51516171819.”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [5] Evans, M. R. & Thomas, A. L. R. The Aerodynamic and Mechanical Effects of Elongated Tails in the Scarlet-Tufted Malachite Sunbird - Measuring the Cost of a Handicap. Anim Behav. 43, 337–347, doi: 10.1016/S0003-3472(05)80229-5 (1992). source
    • cites [15] Barbosa, A. & Moller, A. P. Aerodynamic costs of long tails in male barn swallows Hirundo rustica and the evolution of sexual size dimorphism. Behav Ecol. 10, 128–135, doi: 10.1093/Beheco/10.2.128 (1999). source
    • cites [16] Buchanan, K. L. & Evans, M. R. The effect of tail streamer length on aerodynamic performance in the barn swallow. Behav Ecol. 11, 228–238, doi: 10.1093/Beheco/11.2.228 (2000). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Several studies have made inferences about the costs of carrying exaggerated traits by either removing or artificially exaggerating them further.

    “Several studies have made inferences about the costs of carrying exaggerated traits by either removing or artificially exaggerating them further51516171819.”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [5] Evans, M. R. & Thomas, A. L. R. The Aerodynamic and Mechanical Effects of Elongated Tails in the Scarlet-Tufted Malachite Sunbird - Measuring the Cost of a Handicap. Anim Behav. 43, 337–347, doi: 10.1016/S0003-3472(05)80229-5 (1992). source
    • cites [15] Barbosa, A. & Moller, A. P. Aerodynamic costs of long tails in male barn swallows Hirundo rustica and the evolution of sexual size dimorphism. Behav Ecol. 10, 128–135, doi: 10.1093/Beheco/10.2.128 (1999). source
    • cites [16] Buchanan, K. L. & Evans, M. R. The effect of tail streamer length on aerodynamic performance in the barn swallow. Behav Ecol. 11, 228–238, doi: 10.1093/Beheco/11.2.228 (2000). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    All kinematics parameters were influenced by speed (U).

    “All of the kinematics parameters were influenced by U.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The relationship between net cost of transport (CoTnet) and speed (U) was U-shaped and changed with U at a similar rate in both seasons.

    “The relationship between net cost of transport (CoTnet) and U was U-shaped and changed with U at a similar rate in both seasons.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Stride length (lstride) and stride frequency (fstride) increased with increasing speed (U).

    “lstride and fstride increased with increasing U”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Duty factor (DF), stance time (tstance) and swing time (tswing) all decreased with increasing speed (U).

    “DF, tstance and tswing all decreased with increasing U”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Absolute Pmet increased with increasing body mass (Mb).

    “Absolute Pmet also increased with increasing Mb”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    CoTnet was lower overall when the peacocks had their full trains, with the minimum CoTnet occurring at a higher speed (U) than when the trains were in a rudimentary state.

    “CoTnet was lower overall when the peacocks had their full trains, with the minimum CoTnet occurring at a higher U, than when the trains were in a rudimentary state”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    RER values for all walking trials during both seasons were close to 1.

    “RER values for all walking trials during both seasons were close to 1”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Territorial behaviour is a key component of mating success in peacocks and during this time intra-sexual agonistic behaviour is frequent among the birds.

    “Territorial behaviour is a key component of mating success in peacocks and during this time intra-sexual agonistic behaviour is frequent among the birds21.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [21] Loyau, A., Jalme, M. S. & Sorci, G. Intra-and intersexual selection for multiple traits in the peacock (Pavo cristatus). Ethology 111, 810–820, doi: 10.1111/J.1439-0310.2005.01091.X (2005). source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    The respirometry box was designed so that the rear panel was sloping to both minimize the volume of the box and to ensure that the train did not touch the box itself at any point.

    “The box was designed so that the rear panel was sloping to both minimize the volume of the box and to ensure that the train did not touch the box itself at any point.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationcitation

    Our results focus entirely on the costs associated with locomotion; numerous other costs related to sexual selection may be incurred, and for peacocks these may lie in the development of the trait and in its display rather than the inherent cost of moving around with the trait.

    “It is important to stress that our results focus entirely on the costs associated with locomotion, there are of course numerous other costs related to sexual selection that may be incurred, indeed for peacocks these may lie in the development of the trait and in its display4344 rather than the inherent cost of moving around with the trait.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [43] Emlen, D. J., Warren, I. A., Johns, A., Dworkin, I. & Lavine, L. C. A Mechanism of Extreme Growth and Reliable Signaling in Sexually Selected Ornaments and Weapons. Science 337, 860–864, doi: 10.1126/Science.1224286 (2012). source
    • cites [44] Ros, A. F. H., Correia, M., Wingfield, J. C. & Oliveira, R. F. Mounting an immune response correlates with decreased androgen levels in male peafowl, Pavo cristatus. J Ethol. 27, 209–214, doi: 10.1007/S10164-008-0105-0 (2009). source

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    The experimental time periods were chosen to allow for natural comparison of the effects of carrying the train (i.e. in birds with and without their trains).

    “The experimental time periods were chosen to allow for natural comparison of the effects of carrying the train (i.e. in birds with and without their trains).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Females prefer to mate with peacocks that exhibit the most elaborate train.

    “Females prefer to mate with peacocks that exhibit the most elaborate train10.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [10] Petrie, M., Halliday, T. & Sanders, C. Peahens Prefer Peacocks with Elaborate Trains. Anim Behav. 41, 323–331, doi: 10.1016/S0003-3472(05)80484-1 (1991). source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    A U-shaped curve during walking locomotion has also been observed in another large cursorial bird, the emu (Dromaius novaehollandiae), and field observations revealed that the self-selected speeds preferred by emu were tightly clustered around the lowest point of the curve in line with predictions they chose this speed to minimize the CoT.

    “A U-shaped curve during walking locomotion has also been observed in another large cursorial bird, the emu (Dromaius novaehollandiae), and field observations revealed that the self-selected speeds preferred by emu were tightly clustered around the lowest point of the curve in line with predictions they chose this speed to minimize the CoT34.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [34] Watson, R. R. et al. Gait-specific energetics contributes to economical walking and running in emus and ostriches. P Roy Soc B-Biol Sci. 278, 2040–2046, doi: 10.1098/Rspb.2010.2022 (2011). source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    The different sample sizes are a result of one male damaging his leg at the farm, and this bird was therefore unavailable during the non-breeding season trials.

    “The different sample sizes are a result of one male damaging his leg at the farm, where the peacocks were housed between the experimental time periods, and this bird was therefore unavailable during the non-breeding season trials.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Shapiro-Wilk tests were performed on the standardised residuals generated by each statistical model to ensure that the data conformed to a normal distribution.

    “Shapiro–Wilk tests were performed on the standardised residuals generated by each statistical model to ensure that the data conformed to a normal distribution.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    The accuracy of the respirometry system (±4%) was validated by N2 dilution tests.

    “The accuracy of the system (± 4%) was validated by N2 dilution tests45.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [45] Fedak, M. A., Rome, L. & Seeherman, H. J. One-Step N2-Dilution Technique for Calibrating Open-Circuit Vo2 Measuring Systems. J Appl Physiol 51, 772–776 (1981). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    When traits are exhibited that appear cumbersome, natural selection may select for co-adaptations for the mitigation of any additional costs.

    “when traits are exhibited that appear cumbersome, natural selection may select for co-adaptations for the mitigation of any additional costs4142.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [41] Moller, A. P. The cost of secondary sexual characters and the evolution of cost-reducing traits. Ibis. 138, 112–119 (1996). source
    • cites [42] Husak, J. F. & Swallow, J. G. Compensatory traits and the evolution of male ornaments. Behaviour. 148, 1–29, doi: 10.1163/000579510x541265 (2011). source
    • Rests on an assumption: There will be a trade off between natural and sexual selection of traits: sexual selection may act to enhance trait size while natural selection will minimize the effect of this on for example predation risk.

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    RERs were monitored for all trials to ensure that the birds were locomoting aerobically.

    “RER’s were monitored for all trials to ensure that the birds were locomoting aerobically39.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [39] Taylor, C. R., Heglund, N. C. & Maloiy, G. M. O. Energetics and Mechanics of Terrestrial Locomotion.1. Metabolic Energy-Consumption as a Function of Speed and Body Size in Birds and Mammals. J Exp Biol. 97, 1–21 (1982). source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims. The quote only partly states this claim.

    Premisecitation

    The curvilinear relationship between metabolic power consumption (Pmet) and speed (U) during walking in peacocks is also seen in other animals including some species of large bird, but deviates from the more common linear relationship found in many species.

    “the relationship between metabolic power consumption (Pmet) and speed (U) for walking during both experimental periods was curvilinear, which is also seen in other animals including some species of large bird”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [34] Watson, R. R. et al. Gait-specific energetics contributes to economical walking and running in emus and ostriches. P Roy Soc B-Biol Sci. 278, 2040–2046, doi: 10.1098/Rspb.2010.2022 (2011). source
    • cites [39] Taylor, C. R., Heglund, N. C. & Maloiy, G. M. O. Energetics and Mechanics of Terrestrial Locomotion.1. Metabolic Energy-Consumption as a Function of Speed and Body Size in Birds and Mammals. J Exp Biol. 97, 1–21 (1982). source
    • cites [40] Kram, R. & Taylor, C. R. Energetics of Running - a New Perspective. Nature 346, 265–267, doi: 10.1038/346265a0 (1990). source

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    At the very least, exaggerated traits will add extra mass to a terrestrially locomoting animal which should require extra energy expenditure, as energy is needed to produce forces proportional to body mass (Mb).

    “Yet, at the very least, exaggerated traits will add extra mass to a terrestrially locomoting animal which should require extra energy expenditure, as energy is needed to produce forces proportional to body mass (Mb)20.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [20] Taylor, C. R., Heglund, N. C., Mcmahon, T. A. & Looney, T. R. Energetic Cost of Generating Muscular Force during Running - a Comparison of Large and Small Animals. J Exp Biol. 86, 9–18 (1980). source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductcitation

    After feather molt, birds are often very stressed meaning the peacocks were reluctant to move on the treadmill once the train was completely molted; consequently, walking data could not be collected until the train was in a state of rudimentary regrowth not extending beyond the body of the bird.

    “However, after feather molt, birds are often very stressed32 meaning the peacocks were reluctant to move on the treadmill once the train was completely molted. Consequently, walking data could not be collected until the train was in a state of rudimentary regrowth not extending beyond the body of the bird.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [32] Husak, J. F. & Fox, S. F. Sexual selection on locomotor performance. Evol Ecol Res. 10, 213–228 (2008).

  • May combine two claims.

    Interpretationcitation

    Combined with our results, neither terrestrial nor volant locomotion are negatively impacted by the exaggerated sexually selected train of peacocks.

    “which combined with our results, indicates that neither terrestrial or volant locomotion are negatively impacted by the exaggerated sexually selected train of peacocks.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationcitation

    An increase in testosterone could stimulate muscle growth in peacocks, which could in turn influence seasonal differences in locomotion.

    “An increase in testosterone could stimulate muscle growth in peacocks2829, which could in turn influence seasonal differences in locomotion303132.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [28] Tobin, C. & Joubert, Y. Testosterone-Induced Development of the Rat Levator Ani Muscle. Dev Biol. 146, 131–138, doi: 10.1016/0012-1606(91)90453-A (1991). source
    • cites [29] Hikim, I. S. et al. Testosterone-induced increase in muscle size in healthy young men is associated with muscle fiber hypertrophy. Am J Physiol-Endoc M. 283, E154–E164, doi: 10.1152/Ajpendo.00502.2001 (2002). source
    • cites [30] Sinervo, B., Miles, D. B., Frankino, W. A., Klukowski, M. & DeNardo, D. F. Testosterone, endurance, and darwinian fitness: Natural and sexual selection on the physiological bases of alternative male behaviors in side-blotched lizards. Horm Behav. 38, 222–233, doi: 10.1006/hbeh.2000.1622 (2000). source

  • Classified as probably not a substantial claim.

    Premisecitation

    Sexually selected traits often appear cumbersome or conspicuous and are presumed to handicap the possessor in a number of ways, including their locomotor performance.

    “Sexually selected traits, however, often appear cumbersome or conspicuous and are presumed to handicap the possessor in a number of ways, including their locomotor performance13.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [13] Zahavi, A. Mate Selection - Selection for a Handicap. J Theor Biol. 53, 205–214, doi: 10.1016/0022-5193(75)90111-3 (1975). source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    During the breeding season, male peacocks establish and defend territories on the lek.

    “During the breeding season, males establish and defend territories on the lek21.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [21] Loyau, A., Jalme, M. S. & Sorci, G. Intra-and intersexual selection for multiple traits in the peacock (Pavo cristatus). Ethology 111, 810–820, doi: 10.1111/J.1439-0310.2005.01091.X (2005). source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    Manipulating sexually selected traits by artificially removing them will produce clearly defined experimental testing of the role of the train, but it means any changes in general body condition, hormone levels, plumage quality or the influence of diurnal rhythms is not taken into account in the animals being investigated.

    “However, while manipulating sexually selected traits by artificially removing them will produce clearly defined experimental testing of the role of the train it does mean any changes in general body condition, hormone levels, plumage quality or the influence of diurnal rhythms is not taken into account in the animals being investigated.”
    Quote in the paperNot a substantial claim
29 of 29

  • The paper relies on this without support.

    Many exaggerated traits represent an additional mechanical load that must be carried by the animal and therefore may influence the metabolic cost of locomotion and constrain locomotor performance.

    “Many exaggerated traits represent an additional mechanical load that must be carried by the animal and therefore may influence the metabolic cost of locomotion and constrain locomotor performance.”

  • The paper relies on this without support.

    The evolution of sexual traits is often considered paradoxical as, although they enhance reproductive success, they are widely presumed to hinder movement and survival.

    “The evolution of sexual traits is often considered paradoxical as, although they enhance reproductive success, they are widely presumed to hinder movement and survival.”

  • The paper relies on this without support.

    The metabolic costs associated with locomotion are a key component of the daily energy expenditure of many species of bird such as the peacock.

    “The metabolic costs associated with locomotion are a key component of the daily energy expenditure of many species of bird such as the peacock.”

  • The paper relies on this without support.

    There will be a trade off between natural and sexual selection of traits: sexual selection may act to enhance trait size while natural selection will minimize the effect of this on for example predation risk.

    “As is to be expected there will be a trade off between natural and sexual selection of traits. While sexual selection may act to enhance trait size natural selection will minimize the effect of this on for example predation risk.”
4 of 4

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Non-breeding trials list 0.75 m/s twice and omit 0.88 m/s

    Minor

    The methods say the birds were exercised at five specified speeds, but the non-breeding trial counts list only four distinct speeds: 0.75 m/s appears twice and 0.88 m/s is absent.

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Authors
Thavarajah, N. K., Tickle, P. G., Nudds, R. L., & Codd, J. R.
Affiliations
  • University of Manchester (GB)
  • University of Leeds (GB)
ORCID
Venue
Scientific Reports
Publisher
Springer Science and Business Media LLC
Published
2016-11-02
Volume
6
Issue
1
Pages
36512-36512
ISSN
2045-2322 (ISSN-L)
DOI
10.1038/srep36512
PMC
PMC5090354
OpenAlex
W2546433475
Cited by
25
References
50
Citations by year
2025: 4 · 2024: 1 · 2023: 7 · 2022: 2 · 2021: 5 · 2020: 1 · 2019: 2 · 2018: 1 · 2017: 2
FWCI
1.81
Type
journal article
Language
en
Open access
Licence
Locations
  • Scientific Reports (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • White Rose Research Online (University of Leeds, The University of Sheffield, University of York) (acceptedVersion)
  • PubMed Central (submittedVersion, cc-by)
  • Research Explorer (The University of Manchester) (submittedVersion, cc-by)
Funders
  • Leverhulme Trust (RPG-2012-759)
  • University of Manchester
  • Biotechnology and Biological Sciences Research Council (BB/I021116/1, 1627355, BB/L021116/1)
Topics
  • Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Animal Behavior and Reproduction
  • Physical Sciences › Environmental Science › Ecology › Physiological and biochemical adaptations
  • Physical Sciences › Environmental Science › Ecology › Avian ecology and behavior
Keywords
sexual selection, locomotor performance, metabolic cost of locomotion, cursorial locomotion, respirometry, peacock, locomotion kinematics, mechanical loading
MeSH terms
Adaptation, Physiological, Animals, Female, Locomotion, Male, Galliformes

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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