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Cited by 235Primate Behavior and EcologyNeuroendocrine regulation and behaviorAnimal Behavior and Reproduction

Food sharing is linked to urinary oxytocin levels and bonding in related and unrelated wild chimpanzees

Open access
Wittig, Roman M., Crockford, Catherine, Deschner, Tobias, Langergraber, Kevin E., Ziegler, Toni E., Zuberbühler, Klaus·2014·Proceedings of the Royal Society B: Biological Sciences
DOI 10.1098/rspb.2013.3096PMC PMC3906952
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Abstract

Humans excel in cooperative exchanges between unrelated individuals. Although this trait is fundamental to the success of our species, its evolution and mechanisms are poorly understood. Other social mammals also build long-term cooperative relationships between non-kin, and recent evidence shows that oxytocin, a hormone involved in parent–offspring bonding, is likely to facilitate non-kin as well as kin bonds. In a population of wild chimpanzees, we measured urinary oxytocin levels following a rare cooperative event—food sharing. Subjects showed higher urinary oxytocin levels after single food-sharing events compared with other types of social feeding, irrespective of previous social bond levels. Also, urinary oxytocin levels following food sharing were higher than following grooming, another cooperative behaviour. Therefore, food sharing in chimpanzees may play a key role in social bonding under the influence of oxytocin. We propose that food-sharing events co-opt neurobiological mechanisms evolved to support mother–infant bonding during lactation bouts, and may act as facilitators of bonding and cooperation between unrelated individuals via the oxytocinergic system across social mammals.

Verified 2026-10-09 · 1 reference not checked yet

AI snapshot

Written from the paper’s full text.

TL;DR

In wild chimpanzees, urinary oxytocin was higher after food-sharing events than after social feeding without sharing, and higher after food sharing than after grooming. The authors propose that food sharing co-opts lactation-related oxytocin mechanisms to support bonding and cooperation among kin and non-kin.

Key findings

  • Urinary oxytocin after food sharing was significantly higher than after non-sharing social feeding: mean log10 OT 1.407 ± 0.102 versus 0.884 ± 0.066 pg mg⁻¹ crea; F₁,₇₉ = 9.623, p = 0.003.
  • Food sharing was associated with higher urinary oxytocin than grooming: mean log10 OT 1.41 ± 0.10 versus 0.99 ± 0.05 pg mg⁻¹ crea; F₁ = 16.496, p < 0.001; a within-subject subset also showed this difference (n = 9, Wilcoxon exact p = 0.035).
  • Within food-sharing samples, oxytocin did not differ significantly by kin/non-kin, bond/non-bond, giving/receiving, meat/other food, or sex combination; models 2a and 2b did not explain variance better than null models. Food sharing with bond partners had the highest levels (1.42 ± 0.11 pg mg⁻¹ crea), significantly higher than grooming with bond partners (1.13 ± 0.07), but not significantly higher than food sharing with non-bond partners (1.36 ± 0.23).
  • The study observed 42 food-sharing events in 2009; urine samples were obtained after 33 food-sharing and 46 social feeding events. Shared foods were meat (46%), fruit (30%), rotten wood pith (18%), and honey (6%).

Methods

  • Observational field study of the Sonso community, Budongo Forest, Uganda, January 2009–July 2010; 79 urine samples from 26 chimpanzees (10 adult females, 3 subadult females, 6 adult males, 7 subadult males; mean 3.0 ± 1.97 samples per chimpanzee).
  • Urine was collected 15–60 min after single food-sharing events or after 1 h of social feeding without sharing; oxytocin was measured by enzyme immunoassay and expressed as pg mg⁻¹ creatinine.
  • Relationship quality was assessed with the Composite Relationship Index from focal/all-occurrence sampling; kinship was determined from faecal DNA; dominance was based on pant-grunts. Five generalized linear mixed models tested log10-transformed urinary oxytocin with subject, partner, and/or dyad identity as random factors.

Limitations

  • Stated: models 2a and 2b had small sample sizes (n = 33), which may have reduced power and caused instability; there were relatively few food-sharing samples between non-bond partners; the relationship between central and peripheral oxytocin release remains unclear; and whether food sharing has a stronger bonding effect than grooming remains to be tested.
  • Evident from the design: the study is correlational and observational, so it cannot establish causality between food sharing and oxytocin release; oxytocin was measured after events without baseline samples; and results come from one wild chimpanzee community, limiting generalization.

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

Integrity signals

Registry

Crossref · 10.1098/rspb.2013.3096

Cites

87 of 89 references verified0 citation errors · 1 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 89 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    In wild chimpanzees, urinary oxytocin levels were higher after food-sharing events than after social feeding without food sharing.

    “Subjects showed higher urinary oxytocin levels after single food-sharing events compared with other types of social feeding, irrespective of previous social bond levels.”
    • Also stated in: § (b) Link between food sharing and urinary oxytocin levels · plain
      “Urinary oxytocin concentrations after social feeding events were significantly higher with food sharing than without (F 1,79 ¼ 9.623, p ¼ 0.003, table 3 and figure 1; mean log 10 OT share + s.e.¼ 1.407 + 0.102 pg mg 21 crea versus mean log 10 OT non-share + s.e.¼ 0.884 + 0.066 pg mg 21 crea).”
    • Also stated in: § 4. Discussion · boosted
      “Our results provide empirical evidence that food-sharing events in chimpanzees are associated with significantly higher urinary oxytocin levels than non-sharing social feeding events.”
    Quote in the paperSubstantial claim
  • Findingown data

    In wild chimpanzees, urinary oxytocin levels following food sharing were higher than following grooming.

    “Also, urinary oxytocin levels following food sharing were higher than following grooming, another cooperative behaviour.”
    • Also stated in: § (c) Comparison of urinary oxytocin levels following either food-sharing or grooming events · plain
      “Urinary oxytocin levels following food-sharing events (mean log 10 OT + s.e.¼ 1.41 + 0.10 pg mg 21 crea) were significantly higher than following grooming events (mean log 10 OT + s.e.¼ 0.99 + 0.05 pg mg 21 crea; table 5a and figure 2a).”
    Quote in the paperSubstantial claim
  • Findingown data

    Following sharing events, there were no significant differences in urinary oxytocin levels between bond and non-bond partners.

    “bond or non-bond partners (bond: mean log 10 OT + s.e.¼ 1.42 + 0.11 pg mg 21 crea; nonbond: mean log 10 OT + s.e.¼ 1.36 + 0.23 pg mg 21 crea)”
    Quote in the paperNot a substantial claim
  • Findingown data

    Among non-kin food-sharing partners, three quarters of all donors were dominant.

    “Among non-kin food-sharing partners, three quarters of all donors were dominant.”
    Quote in the paperNot a substantial claim
  • Findingown data

    Less than 10% of the events sampled involved sharing between non-kin males and females in a possible meat-for-sex exchange context.

    “Less than 10% of the events sampled involved sharing between non-kin males and females in a possible meat-for-sex exchange context (table 2).”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim. 32
  • May combine two claims. 29
  • The quote only partly states this claim. 2

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

    Findingown data

    All food-sharing events sampled included begging behaviour by the receiver before receiving food from the donor.

    “All food-sharing events sampled included begging behaviour by the receiver before receiving food from the donor.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Neither model 2a nor model 2b explained the variation better than the null model.

    “Neither models 2a or 2b explained the variation better than the null model (likelihood ratio test model 2a: x 2 ¼ 0.08, d.f.¼ 3, n.s.; model 2b: x 2 ¼ 6.24, d.f.¼ 5, n.s.).”
    Quote in the paperNot a substantial claim

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

    Findingown data

    Males showed an average sharing rate of 0.00187 h−1 and females 0.00176 h−1.

    “Controlling for the overall observation time per male or female, respectively, males showed an average sharing rate of 0.00187 h 21 and females showed an average sharing rate of 0.00176 h 21 .”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Sex, age of subjects, and monopolizability of the food did not explain a significant amount of the variance in urinary oxytocin levels.

    “Potentially confounding variables, such as the sex or age of the subjects, or the monopolizability of the food, did not explain a significant amount of the variance in the urinary oxytocin levels (table 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    None of the predictor variables tested in the univariate models reached significance, showing that the lack of significance in models 2a and 2b was unlikely to be due to power issues.

    “None of the predictor variables tested in the univariate models reached significance (bond type: F 1,33 ¼ 0.074, p ¼ 0.787; CRI: F 1,33 ¼ 0.277, p ¼ 0.602; kin relationship: F 1,33 ¼ 0.020, p ¼ 0.888; sharing direction: F 1,33 ¼ 0.008, p ¼ 0.931; food category: F 1,33 ¼ 1.289, p ¼ 0.264; sex combination: F 2,33 ¼ 1.200, p ¼ 0.314), which showed that the lack of significance in models 2a and 2b was”
    Quote in the paperSubstantial claim

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

    Findingown data

    In 25% of the cases, food sharing was sampled between unrelated males.

    “In 25% of the cases, we sampled food sharing between unrelated males.”
    Quote in the paperNot a substantial claim

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

    Findingown data

    In 2009, 42 food-sharing events were observed in the Sonso community.

    “In 2009, we observed 42 food-sharing events (without overt aggression occuring during the begging event) in the Sonso community.”
    Quote in the paperNot a substantial claim

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

    Findingown data

    Food items shared were meat (46%), fruit (30%), rotten wood pith (18%) and honey (6%).

    “Food items shared were meat (46%), fruit (30%), rotten wood pith (18%) and honey (6%; electronic supplementary material, table S1).”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    Following sharing events, there were no significant differences in urinary oxytocin levels between food shared between females, males, or both sexes.

    “and food was shared between females, males or between both sexes (F-F: mean log 10 OT + s.e.¼ 1.36 + 0.11 pg mg 21 crea; M-F: mean log 10 OT + s.e.¼ 1.57 + 0.17 pg mg 21 crea; M-M: mean log 10 OT + s.e.¼ 1.21 + 0.17 pg mg 21 crea).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In Budongo, only low harassment levels were observed, not high harassment levels.

    “Also, it should be noted that in contrast to the Gombe field site (Tanzania) where the harassment avoidance hypothesis was examined [55], in Budongo we only observed low and not high harassment levels.”
    Quote in the paperSubstantial claim0 of 1 sources checked
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  • Classified as probably not a substantial claim.

    Findingown data

    Urine samples were obtained after 33 food-sharing and 46 social feeding events.

    “Urine samples were obtained after 33 food-sharing and 46 social feeding events.”
    Quote in the paperSubstantial claim

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

    Findingown data

    The highest level of harassment, the receiver placing his hand over the mouth of the donor, was never observed.

    “While the lower level of harassment did occur often, the highest level of harassment, the receiver placing his hand over the mouth of the donor, was never observed.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Food sharing significantly predicted urinary oxytocin concentrations in model 1 (p=0.003), whereas sex, age, and monopolizability of food did not.

    “food share 1 9.623 0.003 share 0.427 3.102 0.003”
    • Also stated in: § 4. Discussion · plain
      “sex of subject 1 0.127 0.725 male 20.043 20.357 0.725 age of subject 1 ,0.000 0.989 adult 20.002 20.014 0.989 monopolizability of food 1 1.522 0.221 high 0.171 1.234 0.221”
    Quote in the paperSubstantial claim

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    Both receivers and donors of food had higher urinary oxytocin levels after food-sharing compared with non-sharing events.

    “food share 1 9.623 0.003 share 0.427 3.102 0.003”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In food-sharing samples only, bond type, kin relationship, sharing direction, food category, and sex combination did not significantly influence urinary oxytocin concentrations.

    “Likelihood ratio test: x 2 ¼ 0.08, d.f.¼ 3, n.s.. (b) Model 2b-predictor variables and parameters entered in the model: food category (meat, not meat), sharing direction (subject: receiving, not receiving) sex combination (female-female, male -female, male -male).Likelihood ratio test: x 2 ¼ 6.24, d.f.¼ 5, n.s.; n ¼ 33 samples, 18 subjects.”
    Quote in the paperSubstantial claim

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

    Premisecitation

    Oxytocin acts in the brain by reducing anxiety and fear, enhancing social memory, and activating neural reward circuits.

    “Physiologically, oxytocin acts in the brain by reducing anxiety and fear [19,20], enhancing social memory [16][17][18]21] and activating neural reward circuits [21].”
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    Premisecitation

    In chimpanzees, grooming among bonding partners is associated with higher urinary oxytocin concentration than grooming between non-bonding partners.

    “Such a link is also evident in chimpanzees, where grooming among bonding partners is associated with higher urinary oxytocin concentration than grooming between non-bonding partners [15].”
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    Interpretationreasoning

    Food-sharing events co-opt neurobiological mechanisms evolved to support mother-infant bonding during lactation bouts, and may act as facilitators of bonding and cooperation between unrelated individuals via the oxytocinergic system across social mammals.

    “We propose that food-sharing events co-opt neurobiological mechanisms evolved to support mother-infant bonding during lactation bouts, and may act as facilitators of bonding and cooperation between unrelated individuals via the oxytocinergic system across social mammals.”
    Quote in the paperSubstantial claim

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

    Premisecitation

    When centrally administered, oxytocin enhances both affiliation with bonding partners and aversion to strangers in unrelated female voles.

    “When centrally administered, oxytocin enhances both affiliation with bonding partners and aversion to strangers in unrelated female voles [14].”
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    Premisecitation

    In humans, exogenously administered oxytocin enhances the encoding of social memory, both of positive and negative events, suggesting that higher oxytocin levels improve memorization of social interactions.

    “Additionally, in humans, exogenously administered oxytocin enhances the encoding of social memory, both of positive [30] and negative [31] events, suggesting that higher oxytocin levels improve memorization of social interactions.”
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    Premisecitation

    In humans and other social mammals, oxytocin plays a central role in facilitating bonding between mother and offspring, and between mating partners.

    “In humans and other social mammals, the hormone oxytocin plays a central role in facilitating bonding between mother and offspring, and between mating partners [16][17][18].”
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    Premisecitation

    Other social mammals form cooperative relationships between unrelated adults that can last over months or years.

    “Recent studies show that, in addition to humans, other social mammals form cooperative relationships between unrelated adults, which can last over months or years (chimpanzees [7], baboons [8,9] and feral horses [10]).”
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    Premisecitation

    Exogenously administered oxytocin enhances cooperative behaviour between related animals, and behaviours associated with trust and generosity between unrelated humans.

    “If exogenously administered, oxytocin enhances cooperative behaviour [22,23] between related animals, and behaviours associated with trust [24][25][26] and generosity [27] between unrelated humans.”
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    Premisecitation

    In humans, plasma oxytocin concentration is related to perceived closeness to or support received by a partner, suggesting a relation between higher oxytocin levels and stronger social bonding.

    “In humans, the concentration of plasma oxytocin is related to the perceived closeness to [28] or support received by [29] a partner, suggesting a relation between higher oxytocin levels and stronger social bonding.”
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    Study design and conductnone given

    Urine samples were collected only if subjects had engaged in no affiliative behaviours other than the target behaviour in the hour prior to urination.

    “We collected urine samples if subjects had engaged in no affiliative behaviours (e.g.grooming or copulation) other than the target behaviour in the hour prior to urination.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S1 (asserted).

    Interpretationreasoning

    Food sharing may be a key behaviour for social bonding in chimpanzees.

    “We therefore hypothesize that food sharing may be a key behaviour for social bonding in chimpanzees.”
    Quote in the paperNot a substantial claim

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

    Premisecitation

    In chimpanzees, food sharing is not restricted to meat but has also been reported with non-meat foods, for example honey or large fruits such as Carica papaya or Treculia africana.

    “Food sharing in chimpanzees, however, is not restricted to meat but has also been reported with non-meat foods, for example honey [52], or large fruits such as Carica papaya [57] or Treculia africana [52].”
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    Study design and conductreasoning

    To compensate for variation in urine concentration, creatinine levels were measured in each sample and all oxytocin values were expressed as pg mg−1 crea.

    “To compensate for variation in urine concentration, we measured creatinine (crea) levels in each sample [66] and expressed all oxytocin values as pg mg 21 crea.”
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    Study design and conductcitation

    Samples were not collected if grooming or copulation also occurred within 60 min prior to urination, as both behaviours are likely to independently increase urinary oxytocin levels.

    “In both conditions, samples were not collected if grooming or copulation also occurred within 60 min prior to urination, as both of these behaviours are likely to independently increase urinary oxytocin levels [39].”
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    Study design and conductcitation

    Variables did not exhibit problems of collinearity.

    “Variables did not exhibit problems of collinearity [68] (Kendall's t and Spearman's r , 0.7 in all cases).”
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    Premisecitation

    Peripheral measures of oxytocin from plasma or urine correlate positively with psychological and behavioural patterns, indicating that peripheral oxytocin levels reflect central processing of oxytocin.

    “Significantly, peripheral measures of oxytocin from plasma or urine correlate positively with psychological and behavioural patterns, such as aversion reduction in male mice [19], social contact in marmosets [40], lactation in rhesus macaques [41], rates of affiliative behaviours in pair-bonded tamarins [42] and grooming in closely bonded chimpanzees [15], indicating that peripheral oxytocin level”
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    Interpretationcitation

    As in some species, low testosterone is linked to nurturance and high oxytocin is linked to social bonding, and together these results suggest that food sharing might provide the optimal conditions for social bonding.

    “As in some species, low testosterone is linked to nurturance (i.e.behaviours that involve gentle warm contact with others) [70] and high oxytocin is linked to social bonding [70], and together these results suggest that food sharing might provide the optimal conditions for social bonding (see [70]).”
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    Study design and conductreasoning

    Reduced power in models 2a and 2b may have led to false negatives, as well as some risk of instability in derived estimates.

    “As models 2a and 2b investigated many predictor variables relative to the number of cases (n ¼ 33, d.f.¼ 3 or d.f.¼ 5), reduced power may have led to false negatives (i.e.erroneously non-significant effects), as well as some risk of instability in the derived estimates.”
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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Food sharing between unrelated individuals outside the mating context is rare but has been reported for humans, vampire bats, chimpanzees and bonobos.

    “Food sharing between unrelated individuals outside the mating context is rare but has been reported for humans, vampire bats, chimpanzees and bonobos [13,46,48,49,52].”
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    Premisecitation

    In most species, food sharing occurs between kin, such as parents provisioning offspring, or between mating partners.

    “In most species, food sharing occurs between kin, such as parents provisioning their offspring (birds [44], mammals [45,47,49]), or between mating partners (insects [44], birds [43], mammals [45,47,50], humans [51]).”
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    Study design and conductown data

    Five outliers (more than 2 s.d.) were excluded from the food-sharing dataset to ensure they were not driving main effects.

    “Five outliers (more than 2 s.d.) were excluded from the foodsharing dataset (three non-sharing and two sharing samples) to be sure that they were not driving any main effects.”
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    Premisecitation

    In chimpanzees and vampire bats, food sharing typically occurs between individuals that also engage in other cooperative behaviours at higher rates, such as grooming and providing coalitionary support.

    “In chimpanzees and vampire bats, food sharing typically occurs between individuals that also engage in other cooperative behaviours at higher rates, such as grooming and providing coalitionary support [13,49,[52][53][54].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
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  • May combine two claims.

    Interpretationcitation

    Higher oxytocin concentrations may be related to better cooperation via stronger bonding and better social memory.

    “In sum, higher oxytocin concentrations may be related to better cooperation via stronger bonding and better social memory.”
    Quote in the paperSubstantial claim

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    Premisecitation

    Oxytocin is released into the peripheral circulation before being excreted in urine, although the exact nature of the relationship between central and peripheral releases has yet to be clarified.

    “Methodologically important is the fact that oxytocin not only acts within the brain, but is also released into the peripheral circulation before being excreted in urine, although the exact nature of the relationship between central and peripheral releases have yet to be clarified [34][35][36][37][38][39].”
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    Premisecitation

    Food sharing may serve several functions in chimpanzees.

    “Indeed, the possibility that food sharing may serve several functions in chimpanzees seems supported by several studies [61,72].”
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    Interpretationreasoning

    Sharers may experience a mutual increase in positive attitude, resulting in the promotion of stronger social bonds and longer-term benefits of more frequent cooperation.

    “Also, as oxytocin is thought to act on positive feedback circuits [16,17,21], sharers may experience a mutual increase in positive attitude [15,79,80], resulting in the promotion of stronger social bonds and longer-term benefits of more frequent cooperation [23,26,80].”
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    Premisecitation

    Positive feedback circuitry involving oxytocin is a key mechanism for bond formation between mother and infant.

    “This positive feedback circuitry is considered a key mechanism for bond formation between mother and infant [34,75].”
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    Premisecitation

    In some mammals, maternal care and provisioning of food aids infant survival beyond the age of lactation.

    “In some mammals, maternal care and provisioning of food, however, aids infant survival beyond the age of lactation [75].”
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    Premisecitation

    Links between food sharing and long-term benefits have been described on a behavioural level for chimpanzees reciprocally sharing meat, exchanging meat for sex, or exchanging meat for agonistic support.

    “Such links between food sharing and long-term benefits have been described on a behavioural level for chimpanzees reciprocally sharing meat [7,78], and exchanging meat for sex [50] or agonistic support [54].”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [7] source

      Not checked in the free run.

    • cites [78] source

      Not checked in the free run.

    • cites [50] source

      Not checked in the free run.

    • cites [54] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    Both receivers and donors perceived the food-sharing interaction positively.

    “suggesting that both perceived the interaction positively [70].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [70] source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    The interface between oxytocin and the dopaminergic reward system may contribute to the success of mother-infant and pair-bonding processes.

    “It is thought that the interface between oxytocin and the dopaminergic reward system may contribute to the success of mother-infant and pair-bonding processes [18,[75][76][77].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [18] source

      Not checked in the free run.

    • cites [75] source

      Not checked in the free run.

    • cites [76] source

      Not checked in the free run.

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

    Interpretationcitation

    The link between food sharing and oxytocin found in chimpanzees may also be relevant for humans.

    “This link between food sharing and oxytocin found in chimpanzees may also be relevant for humans [70], where pro-social behaviour has often been linked to food sharing and provisioning [46,81,82].”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [70] source

      Not checked in the free run.

    • cites [46] source

      Not checked in the free run.

    • cites [81] source

      Not checked in the free run.

    • cites [82] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Food sharing may act as a trigger and predictor of cooperative relationships.

    “Food sharing may, in effect, act as a trigger and predictor of cooperative relationships.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Lactation is connected to peripheral and central oxytocin release in mammals.

    “and is well known to be connected to peripheral and central oxytocin release in mammals [34,74].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [34] source

      Not checked in the free run.

    • cites [74] source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    In mammals, lactation is the primary form of food sharing.

    “In mammals, lactation has been described as the primary form of food sharing [73]”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [73] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Food sharing in chimpanzees occurs between kin, in sexual contexts, and also between non-kin adults in non-sexual contexts, which is unusual in the animal kingdom.

    “What makes food sharing in chimpanzees unusual in the animal kingdom is that, as well as occurring between kin [52] and in sexual contexts [50], food sharing also occurs between non-kin adults in non-sexual contexts [13,15,52,53].”
    Quote in the paperSubstantial claim0 of 5 sources checked
    • cites [52] source

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    • cites [50] source

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    • cites [13] source

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    • cites [15] source

      Not checked in the free run.

    • cites [53] source

      Not checked in the free run.

51 of 51

  • The paper relies on this without support.

    Baseline urinary oxytocin levels before food-sharing events do not differ systematically from those before non-sharing social feeding events.

    “Our target behaviours were single food-sharing events or 1 h of feeding in the presence of chimpanzees without sharing food.”

  • The paper relies on this without support.

    Unmeasured factors do not confound the association between food sharing and urinary oxytocin levels.

    “Thus, our results suggest a direct link between food-sharing events and urinary oxytocin levels.”

  • The paper relies on this without support.

    The food-sharing events observed in the Sonso community are representative of food sharing in wild chimpanzees.

    “We therefore hypothesize that food sharing may be a key behaviour for social bonding in chimpanzees.”
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?

  • The oxytocinergic system in chimpanzees is involved in prosocial and cooperative behavior between both kin and nonkin group members, such as grooming and food sharing.

    “Also similar to humans, the oxytocinergic system in chimpanzees is involved in prosocial and cooperative behavior between both kin and nonkin group members, such as grooming (19) and food sharing (20), suggesting parallels in oxytocinergic system involvement between humans and chimpanzees.”

    From Oxytocin reactivity during intergroup conflict in wild chimpanzees (2017) · cites this paper as [20]

  • All samples relating to a target context were collected within the time window of oxytocin excretion into urine at least 15 min after the start and up to 60 min after the end of interactions.

    “All samples relating to a target context were collected within the time window of oxytocin excretion into urine at least 15 min after the start and up to 60 min after the end of interactions (19, 20).”

    From Oxytocin reactivity during intergroup conflict in wild chimpanzees (2017) · cites this paper as [20]

  • Oxytocin concentration of urine samples was measured using an established method to sample specific events.

    “We conducted focal animal sampling (23) for 20 adult male and female chimpanzees of two neighboring groups, and measured the oxytocin concentration of urine samples from all individuals using an established method to sample specific events (19, 20).”

    From Oxytocin reactivity during intergroup conflict in wild chimpanzees (2017) · cites this paper as [20]

  • The clearance of oxytocin into urine in chimpanzees was taken to be 15 to 60 min after secretion, adapted from a human clearance study.

    “We took the clearance of oxytocin into urine in chimpanzees to be 15 to 60 min after secretion (19, 20), adapted from a human clearance study (43).”

    From Oxytocin reactivity during intergroup conflict in wild chimpanzees (2017) · cites this paper as [20]

  • Urinary oxytocin measures show biobehaviorally relevant levels following target behaviors or social interactions that occur within the 15 to 60 min time window.

    “Urinary oxytocin measures show biobehaviorally relevant levels following target behaviors or social interactions that occur within this time window (19, 20).”

    From Oxytocin reactivity during intergroup conflict in wild chimpanzees (2017) · cites this paper as [20]

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.

  • Model 3b behavioural-context test has conflicting degrees of freedom

    Minor

    The results report F with 1 numerator degree of freedom for the five-context comparison, whereas Table 5b reports 4 degrees of freedom for the same behavioural-context test with F = 9.821.

  • Model 2a predictors differ between the table caption and results

    Minor

    The Table 4 caption lists sex combination as a Model 2a predictor, but the Model 2a results list sharing direction instead. The reported three predictor degrees of freedom correspond to the three variables in the results, not to both variables.

2 of 2

Cites

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Related

Authors
Wittig, R. M., Crockford, C., Deschner, T., Langergraber, K. E., Ziegler, T. E., & Zuberbühler, K.
Affiliations
  • Max Planck Society (DE)
  • Boston University (US)
  • University of Wisconsin–Madison (US)
  • University of St Andrews (GB)
Corresponding author
  • Wittig, Roman M.
  • Crockford, Catherine
ORCID
Venue
Proceedings of the Royal Society B: Biological Sciences
Publisher
The Royal Society
Published
2014-03-07
Volume
281
Issue
1778
Pages
20133096
ISSN
  • 0080-4649 (ISSN-L)
  • 0962-8452
  • 1471-2954
DOI
10.1098/rspb.2013.3096
PMC
PMC3906952
OpenAlex
W2123761254
Cited by
235
References
87
Citations by year
2026: 4 · 2025: 13 · 2024: 20 · 2023: 11 · 2022: 20 · 2021: 14 · 2020: 17 · 2019: 29 · 2018: 16 · 2017: 28 · 2016: 33 · 2015: 19 · 2014: 8 · 2013: 2
FWCI
43.40
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)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • Max Planck Digital Library (submittedVersion)
  • MPG.PuRe (Max Planck Society) (submittedVersion)
Funders
  • Wenner-Gren Foundation
  • Royal Zoological Society of Scotland
  • Leverhulme Trust
  • British Academy
  • Max-Planck-Institut für Evolutionäre Anthropologie
  • National Institutes of Health (P51OD011106)
  • U.S. Public Health Service (NCRR000167)
  • National Center for Research Resources
Topics
  • Social Sciences › Psychology › Social Psychology › Primate Behavior and Ecology
  • Social Sciences › Psychology › Social Psychology › Neuroendocrine regulation and behavior
  • Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Animal Behavior and Reproduction
Keywords
food sharing, social bonding, chimpanzees, non-kin cooperation, grooming, oxytocinergic system, social evolution, cooperative behavior
MeSH terms
Animals, Pan troglodytes, Cooperative Behavior, Feeding Behavior, Female, Grooming, Male, Object Attachment, Oxytocin

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.

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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