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Cited by 40Physiological and biochemical adaptationsEvolution and Paleontology StudiesComparative Animal Anatomy Studies

Mammalian intestinal allometry, phylogeny, trophic level and climate

Open access
Duque-Correa, María J., Codron, Daryl, Meloro, Carlo, McGrosky, Amanda, Schiffmann, Christian, Edwards, Mark S., Clauss, Marcus·2021·Proceedings of the Royal Society B: Biological Sciences
DOI 10.1098/rspb.2020.2888PMC PMC7893215
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Abstract

An often-stated ecomorphological assumption that has the status of ‘textbook knowledge’ is that the dimensions of the digestive tract correlate with diet, where herbivores—consuming diets of lower digestibility—have longer intestinal tracts than faunivores—consuming diets of higher digestibility. However, statistical approaches have so far failed to demonstrate this link. Here, we collated data on the length of intestinal sections and body mass of 519 mammal species, and test for various relationships with trophic, climatic and other biological characteristics. All models showed a strong phylogenetic signal. Scaling relationships with body mass showed positive allometry at exponents greater than 0.33, except for the caecum, which is particularly large in smaller species. Body mass was more tightly linked to small intestine than to large intestine length. Adding a diet proxy to the relationships increased model fit for all intestinal sections, except for the small intestine when accounting for phylogeny. Thus, the diet has a main effect on the components of the large intestine, with longer measures in herbivores. Additionally, measures of habitat aridity had a positive relationship with large intestine length. The small intestine was longer in species from colder habitats at higher latitudes, possibly facilitating the processing of peak intake rates during the growing season. This study corroborates intuitive expectations on digestive tract anatomy, while the dependence of significant results on large sample sizes and inclusion of specific taxonomic groups indicates that the relationships cannot be considered fixed biological laws.

AI snapshot

Written from the paper’s full text.

TL;DR

The study compiles intestinal length and body mass data for 519 mammal species and tests allometry, phylogeny, diet, and climate. It finds strong phylogenetic signal and positive allometry for most intestinal sections, with diet mainly affecting large-intestine sections and climate/latitude linked to small and large intestine length.

Key findings

  • Strong phylogenetic signal was present: Pagel’s λ 0.97–0.99 and Blomberg’s K 0.58–0.76; PGLS λ > 0.9. All intestinal lengths scaled positive allometrically (exponents > 0.33) except the caecum, which scaled negative allometrically. Body mass was more tightly linked to small intestine than large intestine length (ΔAICc GLS = 357, PGLS = 135 versus large intestine; caecum/colon ΔAICc GLS > 308, PGLS > 178).
  • Adding a diet proxy increased model fit for all intestinal sections in GLS; in PGLS it improved large intestine fit (ΔAICc 15–25) but not small intestine fit (ΔAICc = 1.7 less supported, trophic proxy not significant). %faunivory was negatively related to length. Diet effects varied by taxon: no effect in Primates, Eulipotyphla, Carnivora, and Artiodactyla; effects occurred in Marsupialia and Afrotheria (total and large intestine), Chiroptera (total intestine), and Rodentia (large intestine).
  • Higher precipitation or actual evapotranspiration was linked to shorter large intestine/colon lengths, while small intestine length increased at higher absolute latitude and colder temperatures. For total intestine, the best GLS model included diet and latitude, and the best PGLS model included diet and temperature. Volant mammals had shorter total intestines in GLS and PGLS; being marine was not significant individually; forestomach presence was positive in GLS but not PGLS.

Methods

  • Literature compilation plus unpublished post-mortem data; final database included total intestine for 519 species, small intestine 397, large intestine 387, caecum 352, and colon/rectum 370. Body mass and intestinal section lengths were recorded, with weighted means correcting for sample size.
  • Biological traits included diet from EltonTraits, classified by %faunivory and 70%/90% cutoffs, plus volant, marine, and forestomach status; climate variables from PanTHERIA included latitude, precipitation, temperature, and actual evapotranspiration. A phylogenetic tree was pruned to the 519 species with data.
  • Analyses used linear regressions on log-transformed data with GLS and PGLS, λ estimated by maximum likelihood, and AICc model comparison with ΔAICc > 2. Phylogenetic signal was estimated with Blomberg’s K and Pagel’s λ.

Limitations

  • Stated: typical constraints of large literature compilations apply; the authors could not account for diet actually ingested in the months before measurement or during ontogeny, and intestinal flexibility varies among species. The data are recommended for broad patterns across many species, not for comparing a specific pair of species. The functional units of the colon cannot be separated, so colon/rectum length may reflect adaptations to both herbivory and arid environments.
  • Stated: absolute statements are cautioned against. Based on 519 species, the PGLS model relating total intestinal length to body mass and diet had better support than body mass alone (ΔAIC = 3), but in reduced datasets of 387 or 351 species both models were equally supported (ΔAIC = 1.9 and 0). Diet effects depend on taxonomic level and sample composition, and defining “diet” consistently across taxa is problematic.
  • Evident: the study is observational and correlational, with no experimental manipulation; sample sizes and taxonomic coverage are uneven across intestinal sections (e.g., limited bat data for small intestine); diet data sometimes came from the closest taxonomic relative when species data were missing; climate variables came from a database; and GLS/PGLS discrepancies indicate results depend on accounting for phylogeny.

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

Integrity signals

Registry

Crossref · 10.1098/rspb.2020.2888

Cites

84 of 84 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

7 of 55 cited sources checked · 4 supported · 0 flagged · accuracy not yet measured

  • Premisecitation
    § Background · p. 4

    Large-scale studies that accounted for phylogeny did not confirm an association between diet and intestinal length.

    “By contrast, large-scale studies that accounted for phylogeny did not confirm an association between diet and intestinal length [15-19] or GIT complexity [20].”
    Quote in the paperSubstantial claim1 of 5 sources checked
    • cites [15] 15. Lavin S.R., Karasov W.H., Ives A.R., Middleton K.M., Garland T. 2008 Morphometrics of the avian small intestine compared with that of nonflying mammals: a phylogenetic approach. Physiol Biochem Zool 81 , 526-550. source
    • cites [16] 16. McGrosky A., Codron D., Müller D.W.H., Navarrete A., Isler K., Hofmann R.R., Clauss M. 2019 Gross intestinal morphometry and allometry in ruminants. J Morphol 280 , 1254-1266.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [17] 17. McGrosky A., Meloro C., Navarrete A., Heldstab S.A., Kitchener A.C., Isler K., Clauss M. 2019 Gross intestinal morphometry and allometry in primates. Am J Primatol 81 , e23035.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [18] 18. Lovegrove B.G. 2010 The allometry of rodent intestines. J Comp Physiol B 180 , 741-755. source
    • cites [19] 19. Smith H.F., Parker W., Kotzé S.H., Laurin M. 2017 Morphological evolution of the mammalian cecum and cecal appendix. Comptes Rendus Palevol 16 , 39-57. source
  • Findingcitation
    § Discussion · p. 16

    Volant mammals had shorter total intestines than terrestrial mammals.

    “Similar to previous findings, volant mammals had shorter total intestines than terrestrial mammals [15, 21, 22]”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [15] 15. Lavin S.R., Karasov W.H., Ives A.R., Middleton K.M., Garland T. 2008 Morphometrics of the avian small intestine compared with that of nonflying mammals: a phylogenetic approach. Physiol Biochem Zool 81 , 526-550. source
    • cites [21] 21. Price E.R., Brun A., Caviedes-Vidal E., Karasov W.H. 2015 Digestive adaptations of aerial lifestyles. Physiology 30 , 69-78. source
    • cites [22] 22. Caviedes-Vidal E., McWhorter T.J., Lavin S.R., Chediack J.G., Tracy C.R., Karasov W.H. 2007 The digestive adaptation of flying vertebrates: high intestinal paracellular absorption compensates for smaller guts. PNAS 104 , 19132-19137. source

      The Results and Discussion report that bats had significantly shorter intestines than comparably sized nonflying mammals. The paper specifies its finding as shorter small intestines, however, and does not establish that bats had shorter total intestinal length. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
  • Premisecitation
    § Discussion · p. 15

    Available data does not suggest a difference in digestive processes for protein and fat between herbivores, omnivores or carnivores.

    “Available data does not suggest a difference in digestive processes for protein and fat between herbivores, omnivores or carnivores [68]”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [68] 68. Richard O.K., Codron D., Hagen K.B., Südekum K.-H., Clauss M. 2017 Little differences in digestive efficiency for protein and fat in mammals of different trophic guilds and digestive strategies: source
  • Premisecitation
    § Discussion · p. 16

    Increased paracellular absorption compared to other mammals compensates for shorter intestines.

    “Additionally, increased paracellular absorption compared to other mammals compensates for shorter intestines [22].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [22] 22. Caviedes-Vidal E., McWhorter T.J., Lavin S.R., Chediack J.G., Tracy C.R., Karasov W.H. 2007 The digestive adaptation of flying vertebrates: high intestinal paracellular absorption compensates for smaller guts. PNAS 104 , 19132-19137. source

      The Results and Discussion report higher paracellular absorption in small birds and bats than in nonflying mammals. The paper also finds shorter small intestines in those flying vertebrates, but describes compensation as a hypothesis consistent with the data, rather than an established effect. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
  • Findingown data
    § Abstract · p. 2

    The small intestine was longer in species from colder habitats at higher latitudes.

    “The small intestine was longer in species from colder habitats at higher latitudes, possibly facilitating the processing of peak intake rates during the growing season.”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim. 23
  • May combine two claims. 36
  • The quote only partly states this claim. 10

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

    Premisecitation
    § Background · p. 4

    Special adaptations to a volant lifestyle are thought to influence GIT anatomy.

    “Other factors than diet thought to influence GIT anatomy include special adaptations to a volant [15, 21, 22] or a marine [23-25] lifestyle, or the aridity of the habitat [16, 26, 27].”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [15] 15. Lavin S.R., Karasov W.H., Ives A.R., Middleton K.M., Garland T. 2008 Morphometrics of the avian small intestine compared with that of nonflying mammals: a phylogenetic approach. Physiol Biochem Zool 81 , 526-550. source
    • cites [21] 21. Price E.R., Brun A., Caviedes-Vidal E., Karasov W.H. 2015 Digestive adaptations of aerial lifestyles. Physiology 30 , 69-78. source
    • cites [22] 22. Caviedes-Vidal E., McWhorter T.J., Lavin S.R., Chediack J.G., Tracy C.R., Karasov W.H. 2007 The digestive adaptation of flying vertebrates: high intestinal paracellular absorption compensates for smaller guts. PNAS 104 , 19132-19137. source

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

    Premisecitation
    § Background · p. 3

    Ecomorphological diversity is considered the main driver of species diversity, and diet is considered as one of the most important components of an animal's niche.

    “Ecomorphological diversity is considered the main driver of species diversity, and diet is considered as one of the most important components of an animal's niche [1].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [1] 1. Sahney S., Benton M.J., Ferry P.A. 2010 Links between global taxonomic diversity, ecological diversity and the expansion of vertebrates on land. Biol Lett 6 , 544-547. source

      The Results and Discussion link ecological diversity closely with tetrapod family diversity, and Methods includes diet among the variables defining ecological modes. But the Discussion identifies expansion into available ecospace—not ecomorphological diversity itself—as the main driver of tetrapod diversification. The paper does not rank diet as one of the most important components of an animal’s niche. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S2 (checkable).

    Premisecitation
    § Methods · p. 7

    Comparative analyses need to consider the phylogenetic structure of the datasets that are analyzed.

    “Comparative analyses need to consider the phylogenetic structure of the datasets that are analyzed [41-43].”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [41] 41. Garland T., Bennett A.F., Rezende E.L. 2005 Phylogenetic approaches in comparative physiology. J Exp Biol 208 , 3015-3035. source
    • cites [42] 42. Rezende R.P., Diniz-Filho J. 2012 Phylogenetic analyses: comparing species to infer adaptations and physiological mechanisms. Comprehensive Physiology 2 , 645-674. source
    • cites [43] 43. Clauss M., Dittmann M.T., Müller D.W.H., Zerbe P., Codron D. 2014 Low scaling of a life history variable: analysing eutherian gestation periods with and without phylogeny-informed statistics. Mamm Biol 79 , 9-16. source

  • May combine two claims.

    Findingown data
    § Results · p. 8

    In all PGLS analyses, there was a strong phylogenetic signal (λ > 0.9), indicating significant phylogenetic structure in all datasets.

    “In all PGLS analyses, there was a strong phylogenetic signal (λ > 0.9), indicating significant phylogenetic structure in all datasets (Tables S2-S12).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 7

    Generally, the small intestine represented the longest intestinal section, followed by the colon/rectum, and the caecum.

    “Generally, the small intestine represented the longest intestinal section, followed by the colon/rectum, and the caecum (Fig. S1).”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data
    § Table S2 Summary statistics for allometric scaling as log(y) = a + b log(body mass), or y = (10 a ) BM b (significant parameters in bold ) · p. 31

    In GLS models of total intestine length across 519 mammal species, the Trophic90 herbivore category has a positive coefficient of 0.27 (95% CI 0.23 to 0.32) relative to faunivores, controlling for body mass.

    “| Trophic90 | -182.3 | 8.1 | 90Herbivore | 0.27 (0.23 to 0.32) | 0.92 (0.87 to 0.95) | -479.1 | 3.3 | 0.07 (0.00 to 0.14) |”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data
    § Table S2 Summary statistics for allometric scaling as log(y) = a + b log(body mass), or y = (10 a ) BM b (significant parameters in bold ) · p. 31

    In GLS models of total intestine length across 519 mammal species, the Trophic70 herbivore category has a positive coefficient of 0.24 (95% CI 0.20 to 0.28) relative to faunivores, controlling for body mass.

    “| Trophic70 | -181.9 | 8.5 | 70Herbivore | 0.24 (0.20 to 0.28) | 0.92 (0.86 to 0.95) | -482.4 | 0.0 | 0.08 (0.01 to 0.14) |”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 9

    Having a forestomach had a positive relationship with total intestine length in GLS but not in PGLS.

    “When assessed individually with body mass, being volant had a negative relationship with total intestine length in both GLS and PGLS (Fig. S5A); being marine was not a significant factor; and having a forestomach had a positive relationship with total intestine length in GLS but not in PGLS (Fig. S5B; Table S6).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 9

    In GLS, a model that included diet and all three factors (volant, marine, forestomach) was the best-supported, with all factors being significant (here, being marine had a positive effect on length).

    “In GLS, a model that included diet and all three factors (volant, marine, forestomach) was the bestsupported (ΔAIC c to the next-best model = 9), with all factors being significant (here, being marine had a positive effect on length).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Discussion · p. 12

    In the reduced datasets of 387 or 351 species, both models (body mass alone vs body mass and diet) were equally supported (ΔAIC=1.9 and 0, respectively).

    “However, in the reduced datasets of 387 or 351 species, both models were equally supported (ΔAIC=1.9 and 0, respectively, Table S3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Conclusions · p. 18

    Trophic differentiation of the small intestine follows mammalian phylogeny and yields no significant signal when accounting for phylogeny.

    “whereas a trophic differentiation of the small intestine follows mammalian phylogeny, and yields no significant signal when accounting for phylogeny.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 10

    In PGLS, the best models included diet and either AET or temperature for the large intestine, but only diet and AET for the colon/rectum.

    “In PGLS, the best models included diet and either AET or temperature for the large intestine (ΔAIC c < 2; ΔAIC c to precipitation = 2, to other models > 4), but only diet and AET for the colon/rectum (ΔAIC c to other models > 2) (Tables S10 and S11).”
    Quote in the paperSubstantial claim

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

    Findingcitation
    § References · p. 28

    In the Chivers and Hladik dataset, the overlap between diet groups is substantial.

    “In that dataset, the overlap between diet groups is substantial - a fact typically not mentioned when it is cited.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [5]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Findingown data
    § Discussion · p. 12

    A comparatively large dataset (351 species) did not indicate an effect of trophic level on total intestinal length, whereas a yet distinctively larger dataset (519 species) did.

    “Thus, a comparatively large dataset (351 species) did not indicate an effect of trophic level on total intestinal length, whereas a yet distinctively larger dataset (519 species) did.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 9

    Clear diet effects for the total and large intestine were evident in the samples of Marsupialia and Afrotheria, and for the total intestine only in Chiroptera.

    “Clear diet effects for the total and large intestine were evident in the samples of Marsupialia and Afrotheria, and for the total intestine only (as large intestine data were lacking for this group) in Chiroptera.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 8

    Any trophic proxy increased the data fit for the total intestine, with %faunivory showing the best fit.

    “Any trophic proxy increased the data fit for the total intestine, with %faunivory showing the best fit (Table S3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 9

    In PGLS, the model including diet and all three factors had similar support as other models that included diet and being volant; neither being marine nor having a forestomach was significant.

    “In PGLS, this model had similar support as other models that included diet and being volant (ΔAIC c < 2); neither being marine nor having a forestomach was significant in these or other PGLS models (Table S6).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 10

    For the small intestine, models including diet, being marine and having a forestomach were the best-supported in GLS; both factors were positively related to length.

    “For the small intestine, for which hardly any data for bats existed, models including diet, being marine and having a forestomach were the best-supported in GLS (ΔAIC c to nextbest model = 8); both factors were positively related to length.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingreasoning
    § Discussion · p. 13

    Whereas in GLS, having a forestomach was a significant factor for a longer small intestine, this was not significant in PGLS.

    “Whereas in GLS, having a forestomach was a significant factor for a longer small intestine, this was not significant in PGLS, most likely because the presence of a forestomach is not evenly distributed across taxa but represents a hallmark of specific taxa [34, 59].”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation
    § Discussion · p. 14

    This positive allometry applied to the small intestine, the colon/rectum, and the summative measures large and total intestine.

    “This applied to the small intestine, the colon/rectum, and the summative measures large and total intestine.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data
    § Table S2 Summary statistics for allometric scaling as log(y) = a + b log(body mass), or y = (10 a ) BM b (significant parameters in bold ) · p. 31

    In PGLS models of total intestine length across 519 mammal species, the Trophic90 herbivore category has a positive coefficient of 0.07 (95% CI 0.00 to 0.14) relative to faunivores, controlling for body mass.

    “| Trophic90 | -182.3 | 8.1 | 90Herbivore | 0.27 (0.23 to 0.32) | 0.92 (0.87 to 0.95) | -479.1 | 3.3 | 0.07 (0.00 to 0.14) |”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § References · p. 28

    The proportion of readily digestible plant parts or less digestible plant parts did not yield a better data fit and only had a significant effect in GLS but not PGLS.

    “The proportion of more readily digestible plant parts (fruits, nectar, seeds), or of the less digestible plant parts (leaves and stems) did not yield a better data fit, and only had a significant effect in GLS but not PGLS (Table S3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 8

    When using only species for which all respective data were available, the small intestine-body mass relationship achieved lower AICc than the large intestine-body mass relationship, or than the caecum-body mass and colon/rectum-body mass relationships.

    “When using only species for which all respective data were available, the small intestine-body mass relationship achieved lower AIC c than the large intestine-body mass relationsip (ΔAIC c GLS=357, PGLS =135), or than the caecum-body mass and colon/rectum-body mass relationships (ΔAIC c GLS>308, PGLS>178), suggesting that the large intestine is more subjected to additional influence factors (Table”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 9

    No effect for the total intestine but an effect on the large intestine was observed in Rodentia.

    “No effect for the total intestine but an effect on the large intestine was observed in Rodentia.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Discussion · p. 12

    The fact that there is a diet effect on the total intestinal tract length across all mammals, or within Chiroptera, contrasts with the absence of such an effect in Primates, Carnivora or Artiodactyla.

    “The fact that there is a diet effect on the total intestinal tract length across all mammals, or within Chiroptera, contrasts with the absence of such an effect in Primates, Carnivora or Artiodactyla (Table S4).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Discussion · p. 13

    Whereas in GLS, all diet descriptors were significantly related to total intestine length, this was not the case for several of them in PGLS.

    “Whereas in GLS, all diet descriptors were significantly related to total intestine length, this was not the case for several of them in PGLS (Table S2), suggesting phylogenetic specialization on either easily digestible or less easily-digestible plant parts.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 10

    Latitude was positively related to intestine length, and temperature negatively.

    “Latitude was positively related to intestine length (Fig. 3A), and temperature negatively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results · p. 8

    The addition of %faunivory yielded a far better data fit (ΔAICc 19-316) for all intestinal sections in GLS; the difference from the model without trophic proxy was least for the small intestine.

    “The addition of %faunivory yielded a far better data fit (ΔAIC c 19-316) for all intestinal sections in GLS; the difference from the model without trophic proxy was least for the small intestine (Table S4).”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data
    § Table S2 Summary statistics for allometric scaling as log(y) = a + b log(body mass), or y = (10 a ) BM b (significant parameters in bold ) · p. 31

    In GLS models of total intestine length across 519 mammal species, the Trophic90 omnivore category has a positive coefficient of 0.15 (95% CI 0.10 to 0.19) relative to faunivores, controlling for body mass.

    “| Trophic90 | -182.3 | 8.1 | 90Omnivore | 0.15 (0.10 to 0.19) | 0.92 (0.87 to 0.95) | -479.1 | 3.3 | 0.04 (-0.02 to 0.10) |”
    Quote in the paperNot a substantial claim

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

    Findingown data
    § 760 761 · p. 51

    Most data points in the analysis of small intestinal length and body mass for marine and nonmarine mammals refer to Carnivora.

    “Most data points refer to Carnivora”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data
    § 724 725 726 · p. 37

    In Artiodactyla, the diet proxy (%faunivory) is not significantly associated with large intestinal length in GLS models (c = -0.31, 95% CI -0.94 to 0.31).

    “| Artiodactyla | Total intest. | BM + %faunivory | 81 | -79.0 | 1.4 | c | -0.31 (-0.94 to 0.31) | 0.38 (NA to NA) | -94.0 | 2.0 | 0.02 (-0.85 to 0.89) |”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data
    § Table S2 Summary statistics for allometric scaling as log(y) = a + b log(body mass), or y = (10 a ) BM b (significant parameters in bold ) · p. 32

    In PGLS models of caecum length across 352 mammal species, %faunivory has a negative coefficient of -0.32 (95% CI -0.46 to -0.18), controlling for body mass.

    “| | | | | | | b c -0.69 | 0.43 (0.41 to 0.45) (-0.76 to -0.62) | | | | | -0.32 (-0.46 to -0.18) |”
    Quote in the paperSubstantial claim

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

    Findingnone given
    § 760 761 · p. 51

    One phocid had a surprisingly short small intestine.

    “where one phocid had a surprisingly short small intestine”
    Quote in the paperNot a substantial claim

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

    Findingown data
    § Table S2 Summary statistics for allometric scaling as log(y) = a + b log(body mass), or y = (10 a ) BM b (significant parameters in bold ) · p. 31

    Among PGLS models of total intestine length with different diet proxies, the Trophic70 model has the lowest AICc (ΔAIC = 0.0).

    “| Trophic70 | -181.9 | 8.5 | a | 2.11 (2.08 to 2.15) | 0.92 (0.86 to 0.95) | -482.4 | 0.0 | 2.15 (1.84 to 2.46) |”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data
    § Table S2 Summary statistics for allometric scaling as log(y) = a + b log(body mass), or y = (10 a ) BM b (significant parameters in bold ) · p. 32

    In GLS models of caecum length across 352 mammal species, %faunivory has a negative coefficient of -0.69 (95% CI -0.76 to -0.62), controlling for body mass.

    “| | | | | | | b c -0.69 | 0.43 (0.41 to 0.45) (-0.76 to -0.62) | | | | | -0.32 (-0.46 to -0.18) |”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data
    § 724 725 726 · p. 35

    In Eutheria, the diet proxy (%faunivory) has a significant negative association with large intestinal length in GLS models (c = -0.70, 95% CI -0.76 to -0.64).

    “| Marsupials | Large intest. | BM + %faunivory | 352 | -72.8 | 0.0 | c | -0.70 (-0.76 to -0.64) | 0.89 (0.80 to 0.94) | -266.2 | 0.0 | -0.31 (-0.43 to -0.20) |”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given
    § 760 761 · p. 51

    The two largest species are baleen whales, which have, compared to other Cetartiodactyla, rather short small intestines.

    “the two largest species are baleen whales, which have, compared to other Cetartiodactyla, rather short small intestines”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data
    § 724 725 726 · p. 35

    In Boroeutheria, the diet proxy (%faunivory) has a significant negative association with large intestinal length in GLS models (c = -0.73, 95% CI -0.80 to -0.66).

    “| Boroeutheria | Total intest. | BM + %faunivory | 453 | -206.2 | 0.0 | | -0.73 (-0.80 to | 0.82 (0.73 to 0.89) | -516.0 | 0.0 | |”
    Quote in the paperSubstantial claim

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

    Findingown data
    § 760 761 · p. 51

    Another short small intestine is from the afrotherian dugong (Dugong dugon).

    “another short small intestine is from the afrotherian dugong ( Dugong dugon )”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data
    § 724 725 726 · p. 35

    In Eutheria, the diet proxy (%faunivory) has a significant negative association with total intestinal length in GLS models (c = -0.27, 95% CI -0.31 to -0.22).

    “| Marsupials | Total intest. | BM + %faunivory | | -196.0 | 0.0 | c | -0.27 (-0.31 to -0.22) | 0.91 (0.86 to 0.94) | -525.2 | 0.0 | -0.07 (-0.14 to 0.00) |”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § Background · p. 4

    The aridity of the habitat is thought to influence GIT anatomy.

    “Other factors than diet thought to influence GIT anatomy include special adaptations to a volant [15, 21, 22] or a marine [23-25] lifestyle, or the aridity of the habitat [16, 26, 27].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [16] 16. McGrosky A., Codron D., Müller D.W.H., Navarrete A., Isler K., Hofmann R.R., Clauss M. 2019 Gross intestinal morphometry and allometry in ruminants. J Morphol 280 , 1254-1266.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [26] 26. Woodall P.F., Skinner J.D. 1993 Dimensions of the intestine, diet and faecal water loss in some African antelope. J Zool 229 , 457-471. source
    • cites [27] 27. Cain J.W., Krausman P.R., Rosenstock S.S., Turner J.C. 2006 Mechanisms of thermoregulation and water balance in desert ungulates. Wildl Soc Bull 34 , 570-581. source

  • Classified as probably not a substantial claim.

    Premisecitation
    § Background · p. 3

    Mammals consuming highly digestible diets, such as faunivores, do not need complex or long GITs.

    “Mammals consuming highly digestible diets, such as faunivores (carnivores, insectivores) do not need complex or long GITs; mammals that feed mainly on vegetable matter, especially on the leaves and stems of grass or browse, require large fermentation chambers to digest plant fibre [5].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

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

    Premisecitation
    § Background · p. 4

    Special adaptations to a marine lifestyle are thought to influence GIT anatomy.

    “Other factors than diet thought to influence GIT anatomy include special adaptations to a volant [15, 21, 22] or a marine [23-25] lifestyle, or the aridity of the habitat [16, 26, 27].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [23] 23. McGrosky A., Navarrete A., Isler K., Langer P., Clauss M. 2016 Gross intestinal morphometry and allometry in Carnivora. Eur J Wildl Res 62 , 395-405. source
    • cites [24] 24. Mårtensson P.E., Nordoy E.S., Messelt E.B., Blix A.S. 1998 Gut length, food transit time and diving habit in phocid seals. Polar Biology 20 , 213-217. 494 495 496 497 498 499 500 501 502 source
    • cites [25] 25. Krockenberger M.B., Bryden M.M. 1994 Rate of passage of digesta through the alimentary tract of southern elephant seals ( Mirounga leonina ). J Zool 234 , 229-237. source

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationown data
    § Abstract · p. 2

    This study corroborates intuitive expectations on digestive tract anatomy.

    “This study corroborates intuitive expectations on digestive tract anatomy, while the dependence of significant results on large sample sizes and inclusion of specific taxonomic groups indicates that the relationships cannot be considered fixed biological laws.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § Background · p. 3

    Mammals that feed mainly on vegetable matter, especially on the leaves and stems of grass or browse, require large fermentation chambers to digest plant fibre.

    “Mammals consuming highly digestible diets, such as faunivores (carnivores, insectivores) do not need complex or long GITs; mammals that feed mainly on vegetable matter, especially on the leaves and stems of grass or browse, require large fermentation chambers to digest plant fibre [5].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation
    § Discussion · p. 16

    Forestomachs occur in large mammalian herbivores of various taxa and in muroid rodents.

    “Forestomachs do not only occur in large mammalian herbivores of various taxa [59], but also in muroid rodents [34, 69, 70].”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [59] 59. Langer P. 1988 The mammalian herbivore stomach . Stuttgart/New York, Gustav Fischer Verlag. 578 579
    • cites [34] 34. Langer P. 2017 Comparative anatomy of the gastrointestinal tract in Eutheria: Taxonomy, biogeography and food. Vol I: Afrotheria, Xenarthra and Euarchontoglires. Vol II: Laurasiatheria, general discussion . Berlin, De Gruyter. source
    • cites [69] 69. Vorontsov N.N. 1967/1969 Evolution of the alimentary system in rodents . Novosibirsk,

      Not checked in the free run.

    • cites [70]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationreasoning
    § Discussion · p. 16

    The presence of a forestomach follows clear phylogenetic boundaries, explaining the absence of a significant signal in PGLS.

    “The presence of a forestomach follows clear phylogenetic boundaries, which explains the absence of a significant signal in PGLS.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The presence of a forestomach follows clear phylogenetic boundaries.

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

    Interpretationown data
    § Discussion · p. 11

    The present study provides a comprehensive data collection on mammalian intestinal length, which corroborates previously stated concepts on intestinal allometric scaling, and intuitive concepts about the relationships between digestive tract anatomy, diet, and environmental aridity.

    “The present study provides a comprehensive data collection on mammalian intestinal length, which corroborates previously stated concepts on intestinal allometric scaling, and intuitive concepts about the relationships between digestive tract anatomy, diet, and environmental aridity.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

    Interpretationown data
    § Discussion · p. 11

    While macroevolutionary trends can be stated, they should not be considered fixed biological laws, and results may depend to a large extent on the size and composition of the investigated sample.

    “The scatter evident from plots recommend that while macroevolutionary trends can be stated, they should not be considered fixed biological laws, and that results may depend to a large extent on the size and composition of the investigated sample.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data
    § Results · p. 9

    Taxa within Eutheria, Boroeutheria, Euarchontoglires and Laurasiatheria differ systematically by total intestine length and diet.

    “For the total intestine, the large groups of Eutheria, Boroeutheria, Euarchontoglires and Laurasiatheria showed significant effects of diet in GLS but not PGLS, indicating that taxa within these groups differ systematically by total intestine length and diet.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S2 (checkable), S3 (load-bearing).

    Interpretationown data
    § Discussion · p. 12

    One might question how generalizable a result is that requires such immense sample sizes.

    “Although the result of the model using the larger sample size corresponds to our expectations, one might question how generalizable a result is that requires such immense sample sizes.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing). May combine two claims.

    Study design and conductown data
    § Results · p. 10

    The pattern for the small intestine does not appear convincing at visual inspection, being based on rather few species.

    “The pattern, however, does not appear convincing at visual inspection, being based on rather few species (Fig. S6).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion · p. 15

    Our results suggest the hypothesis that major constant differences in dietary or humidity niches are mainly reflected in the length of the caecum and colon, whereas differences in the constancy in intake and digestion are reflected in the length of the small intestine.

    “Our results suggest the hypothesis that major constant differences in dietary or humidity niches are mainly reflected in the length of the caecum and colon, whereas differences in the constancy in intake and digestion are reflected in the length of the small intestine.”
    Quote in the paperSubstantial claim

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

    Interpretationcitation
    § Discussion · p. 16

    The negative relationship between precipitation/AET and colon length may not be consistent within specific mammal groups.

    “even though this pattern may not be consistent within specific mammal groups [18].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [18] 18. Lovegrove B.G. 2010 The allometry of rodent intestines. J Comp Physiol B 180 , 741-755. source

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

    Interpretationcitation
    § References · p. 28

    Various details of Chivers and Hladik's work suggest the methods are not robust.

    “Various details of this work might lead to the conclusion that the methods are not robust:”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [5]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationreasoning
    § Discussion · p. 13

    A factor that contributes significantly to variation in GLS, but does not do so in PGLS, is likely distributed unequally across the phylogeny; phylogenetic diversification then reflects the diversity in this factor.

    “A factor that contributes significantly to variation in GLS, but does not do so in PGLS, is likely distributed unequally across the phylogeny; phylogenetic diversification then reflects the diversity in this factor.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data
    § Discussion · p. 11

    Additional, existing concepts on the effect of being a volant or marine species are also supported, and some new findings on associations are provided with having a forestomach, and with the mid-latitude of the species current geographic range.

    “Additional, existing concepts on the effect of being a volant or marine species are also supported, and some new findings on associations are provided with having a forestomach, and with the mid-latitude of the species current geographic range.”
    Quote in the paperSubstantial claim

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

    Premisecitation
    § Discussion · p. 16

    In birds, the relationship between volant lifestyle and shorter intestines does not necessarily apply to the caecum.

    “In birds, this does not necessarily apply to the caecum [72].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [72]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationown data
    § Discussion · p. 12

    It is important to reference the taxonomic level on which a statement is based.

    “Our results also indicate that it is important to reference the taxonomic level on which a statement is based.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data
    § Discussion · p. 15

    It is plausible that in animals that consume higher proportions of plant material, the caecum and proximal colon are generally longer, as documented in the present study, and more complex.

    “Therefore, it is plausible that in animals that consume higher proportions of plant material, these sections are generally longer, as documented in the present study, and more complex [20].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [20] 20. Langer P., Clauss M. 2018 Morphological adaptation of the eutherian gastrointestinal tract to diet. Vertebr Zool 68 , 237-252.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationreasoning
    § Discussion · p. 13

    The presence of a forestomach is not evenly distributed across taxa but represents a hallmark of specific taxa, which explains why it was not significant in PGLS.

    “Whereas in GLS, having a forestomach was a significant factor for a longer small intestine, this was not significant in PGLS, most likely because the presence of a forestomach is not evenly distributed across taxa but represents a hallmark of specific taxa [34, 59].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [34] 34. Langer P. 2017 Comparative anatomy of the gastrointestinal tract in Eutheria: Taxonomy, biogeography and food. Vol I: Afrotheria, Xenarthra and Euarchontoglires. Vol II: Laurasiatheria, general discussion . Berlin, De Gruyter. source
    • cites [59] 59. Langer P. 1988 The mammalian herbivore stomach . Stuttgart/New York, Gustav Fischer Verlag. 578 579

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

    Interpretationreasoning
    § Discussion · p. 13

    A relationship that is significant in GLS but not in PGLS shows no convergence across taxa; however, the functional association between the variables should not be discarded based on the PGLS result alone.

    “A relationship that is significant in GLS but not in PGLS shows no convergence across taxa; however, the functional association between the variables should not be discarded based on the PGLS result alone.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Discussion · p. 17

    In seasonal environments, many mammals incur costs of reproduction in the growing season and build up body reserves used in the dormant season.

    “In seasonal environments, many mammals have to incur the costs of reproduction in the growing season and also build up body reserves, which are then used in the dormant season [75].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [75]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

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

    Premisecitation
    § 760 761 · p. 52

    The koala (Phascolarctos cinereus) is known to use caecum contents for feeding its young.

    “a species that is known to use caecum contents for feeding its young [80]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [80]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

64 of 64

  • The paper relies on this without support.

    The diet of the closest taxonomic relative is a valid proxy for a species' diet when species-specific diet data are missing.

    “If a species was not included in that dataset, the diet of the closest taxonomic relative was used.”

  • The paper relies on this without support.

    The digestive action in the small intestine is not related to fibre fermentation but to auto-enzymatic digestion of proteins, fats, and easily digested carbohydrates.

    “By contrast, the digestive action in the small intestine is not related to fibre fermentation, but to auto-enzymatic digestion of proteins, fats, and easily digested carbohydrates.”

  • The paper relies on this without support.

    The presence of a forestomach follows clear phylogenetic boundaries.

    “The presence of a forestomach follows clear phylogenetic boundaries, which explains the absence of a significant signal in PGLS.”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Across mammalian taxa, differences in intestinal length can be explained by diet.

    “Across mammalian taxa, differences in intestinal length can be explained by diet.Species that consume higher proportions of plant matter have longer intestines, especially large intestines (Duque-Correa et al. 2021).”

    From Digestive anatomy and diet of free-ranging maned wolf (Chrysocyon brachyurus) (2025) · cites this paper as Duque-Correa et al. 2021

  • Within mammalian taxa, intestinal length is a phylogenetically conserved feature.

    “Within mammalian taxa, intestinal length is a phylogenetically conserved feature (Duque-Correa et al. 2021).”

    From Digestive anatomy and diet of free-ranging maned wolf (Chrysocyon brachyurus) (2025) · cites this paper as Duque-Correa et al. 2021

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.

  • Simulation count differs between supplement text and code

    Minor

    The Table S1 note says the phylogenetic-signal analyses used 9999 simulations per analysis, while the supplied calls for both K and λ set nsim to 999.

  • Figure S5 is cited for volant status but captioned for marine status

    Minor

    The results cite Figure S5A for the volant relationship, but the supplementary caption describes Figure S5 as a small-intestine comparison of marine and nonmarine mammals.

  • Not all PGLS models have λ above 0.9

    Minor

    The blanket statement conflicts with several models in Table S5, including a Carnivora large-intestine model with λ = 0.22.

  • Reported Blomberg's K range excludes the caecum

    Minor

    The results give a K range of 0.58-0.76, but Table S1 reports a caecum-length K of 0.34. The subsequent sentence acknowledges that caecum K is lower, so the stated overall range is incomplete.

  • Figure 3 is cited for climate but captioned for biological factors

    Minor

    The results cite Figure 3A for a latitude relationship, whereas the Figure 3 caption identifies panel A as a comparison of nonvolant and volant mammals.

  • Figure S6 is cited for the marine pattern but captioned for caecum length

    Minor

    The discussion of the marine small-intestine pattern points to Figure S6. Its supplementary caption instead describes caecum length and coprophagy groups.

6 of 6

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. Orr RT, 1976, Vertebrate biology
  2. Vorontsov NN, 1967, /1969 evolution of the alimentary system in rodents

Cited by

Sorted by citations

Related

Authors
Duque-Correa, M. J., Codron, D., Meloro, C., McGrosky, A., Schiffmann, C., Edwards, M. S., & Clauss, M.
Affiliations
  • Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Winterthurerstr. 260, 8057 Zurich, Switzerland
  • University of the Free State (ZA)
  • Liverpool John Moores University (GB)
  • Arizona State University (US)
  • University of Zurich (CH)
  • California Polytechnic State University (US)
Corresponding author
Clauss, Marcus
ORCID
Venue
Proceedings of the Royal Society B: Biological Sciences
Publisher
The Royal Society
Published
2021-02-10
Volume
288
Issue
1944
Pages
20202888
ISSN
  • 0080-4649 (ISSN-L)
  • 0962-8452
  • 1471-2954
DOI
10.1098/rspb.2020.2888
PMC
PMC7893215
OpenAlex
W3126478460
Cited by
40
References
76
Citations by year
2026: 8 · 2025: 10 · 2024: 7 · 2023: 8 · 2022: 4 · 2021: 2
FWCI
2.86
Type
journal article
Language
en
Open access
Licence
royalsociety.org/journals/ethics-policies/data-sharing-mining/ (tdm)
Locations
  • Proceedings of the Royal Society B Biological Sciences (publishedVersion)
  • PubMed (publishedVersion)
  • Liverpool John Moores University (acceptedVersion)
  • PubMed Central (submittedVersion)
  • Zurich Open Repository and Archive (University of Zurich) (submittedVersion)
  • Zenodo (CERN European Organization for Nuclear Research) (submittedVersion, public-domain)
  • DRYAD (public-domain)
Funders
Schweizerischer Nationalfonds zur F&#x00F6;rderung der Wissenschaftlichen Forschung (CRSII5_189970 / 1)
Topics
  • Physical Sciences › Environmental Science › Ecology › Physiological and biochemical adaptations
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
  • Health Sciences › Medicine › Urology › Comparative Animal Anatomy Studies
Keywords
allometry, phylogenetic signal, trophic levels, herbivory, diet digestibility, climate, latitude, small intestine
MeSH terms
Animals, Diet, Digestion, Intestines, Mammals, Phylogeny, Gastrointestinal Tract

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 2026-10-26.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-26.

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.

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