A multicenter, prospective, phase II trial of second-line aflibercept plus FOLFIRI in patients with metastatic colorectal cancer refractory to an anti-EGFR antibody: HGCSG1801.

Aflibercept (AFL) plus FOLFIRI prolongs overall survival (OS) in patients with metastatic colorectal cancer (mCRC). However, there is limited evidence on the efficacy and safety of AFL plus FOLFIRI previously treated with anti-epidermal growth factor receptor (EGFR) agents. Therefore, we conducted a prospective open-label phase II trial evaluating the efficacy and safety of AFL plus FOLFIRI in Japanese patients with mCRC failing a prior oxaliplatin-based chemotherapy plus an anti-EGFR agent. AFL (4 mg/kg iv) followed by FOLFIRI (irinotecan 180 mg/m2, leucovorin 200 mg/m2 iv, bolus 5-fluorouracil [5-FU] 400 mg/m2, and infusional 5-FU 2400 mg/m2/46 h) was given every 2 weeks until progression or unacceptable toxicities. The primary endpoint was progression-free survival (PFS) rate at 6 months. Forty three patients were enrolled between November 2019 and October 2022. The primary endpoint was met: 6-month PFS rate was 58.8% (90% confidence interval [CI], 45.7%-72.0%). Median PFS and OS were 7.3 months (95% CI, 5.5-11.0 months) and 18.8 months (95% CI, 12.9-26.6 months), respectively. The overall response rate was 20.9% (95% CI, 10.0-36.0%) and disease control rate was 88.4% (95% CI, 74.9-96.1%). The main grade ≥3 adverse events included hypertension (62.8%), neutropenia (55.8%), leukopenia (25.6%), febrile neutropenia (11.6%), fatigue (9.3%), anorexia (9.3%), proteinuria (9.3%), and diarrhea (7.0%). No deaths and no new safety signals with a causal relation to the study treatment were observed. This study suggests that AFL plus FOLFIRI shows a high response rate and a manageable safety profile in Japanese patients with mCRC who failed prior oxaliplatin-based chemotherapy plus an anti-EGFR agent.

Utility of a Passive Bending Colonoscope for Endoscopic Retrograde Cholangiopancreatography in Patients with Surgically Altered Anatomy.

BACKGROUND AND AIM: The utility of a passive bending colonoscope (PBCS) in ERCP for patients with surgically altered anatomy has not been established. This study compared the outcome of PBCS-ERCP and balloon-assisted enteroscope (BAE)-ERCP. METHODS: This multicenter observational study included 343 patients with surgically altered anatomy who underwent ERCP. Among these, 110 underwent PBCS-ERCP and 233 underwent BAE-ERCP. Propensity score matching was applied, and a final cohort of 210 (105 in each group) with well-balanced backgrounds was analyzed. The primary outcome was the success rate of reaching anastomosis or ampulla of Vater. Secondary endpoints included the cannulation success rate, completion rate, procedure time (to reach, cannulate, complete), and adverse events. RESULTS: The success rate for reaching the target was 91.4% (96/105) with PBCS and 90.5% (95/105) with BAE (odds ratio [95% CI] 1.12, [0.44-2.89], P = 0.809). The mean time required to reach the target was significantly shorter in PBCS: 10.04 min (SD, 9.62) with PBCS versus 18.77 min (SD, 13.21) with BAE (P < 0.001). There were no differences in the success of cannulation or procedure completion, although the required times for cannulation and procedure completion were significantly shorter in PBCS. The incidence of adverse events was significantly higher in BAE (19.0%) than in PBCS (4.8%; P < 0.001). CONCLUSIONS: In patients with surgically altered anatomy, PBCS-ERCP showed promising results with shorter time to reach, cannulate, and a lower incidence of adverse events compared with BAE-ERCP. The success rate of reaching was favorable through PBCS compared with BAE. CLINICAL TRIAL REGISTRATION: UMIN000045546.

Outcome of surgical parathyroidectomy for tertiary hyperparathyroidism in kidney transplant recipients: tertiary hyperparathyroidism should not be ignored, for the sake of precious allografts.

Tertiary hyperparathyroidism is a complication of kidney transplantation. This complicated condition carries over from the dialysis period and varies according to the function of the transplanted allograft. Treatments include pharmacotherapy (mainly using calcimimetics) and parathyroidectomy, but calcimimetics are currently not covered by the national insurance system in Japan. Two types of parathyroidectomy can be performed: subtotal parathyroidectomy; and total parathyroidectomy with partial autograft. Both types can be expected to improve hypercalcemia. Concerns about the postoperative deterioration of allograft function are influenced by preoperative allograft function, which is even more likely to be affected by early surgery after kidney transplantation. In general, transient deterioration of allograft function after surgery is not expected to affect graft survival rate in the medium to long term. Tertiary hyperparathyroidism in kidney transplant recipients negatively impacts allograft and patient survival rates, and parathyroidectomy can be expected to improve prognosis in both kidney recipients and dialysis patients. However, studies offering high levels of evidence remain lacking.

The risk of weekend biopsy: Impact of specimen source and fixation status on HER2 assessment in the treatment of advanced gastric cancer (The HER_WEEKEND study).

Accurate evaluation of human epidermal growth factor receptor type 2 (HER2) expression is crucial for determining chemotherapy regimens in gastric cancer. However, formalin fixation status has been identified as an important factor affecting HER2 assessment reliability. This retrospective cohort study aimed to investigate the correlation between sample collection day (weekday vs. weekend) and source (biopsy vs. surgical specimens) in assessing HER2 expression in patients with unresectable advanced/recurrent gastric cancer. Data were collected from gastric cancer patients who received chemotherapy at a single public hospital in Japan from 2008 to 2021. The analysis included 177 patients (109 men, 68 women) with a median age of 68.0 (21-88) years, and the primary outcome was the HER2 positivity rate. The overall HER2 positivity rate was 18.1%, with higher rates on weekdays (20.0%) compared to weekends (12.8%). Biopsies had higher positivity rates on weekdays (23.9%) but lower rates on weekends (11.1%) than surgical specimens. Significant differences were observed in formalin fixation times between weekdays and weekends for both biopsies and surgical samples. The study findings suggest that longer formalin fixation times on weekends may lead to underestimating HER2 expression, particularly in biopsies. Therefore, it is crucial to be cautious of excessive formalin fixation when collecting samples, especially during weekend biopsies.

Development and nationwide validation of kidney graft injury markers using urinary exosomes and microvesicles (complete English translation of the Japanese version).

BACKGROUND: Non-invasive, prompt, and proper detection tools for kidney graft injuries (KGIs) are awaited to ensure graft longevity. We screened diagnostic biomarkers for KGIs following kidney transplantation using extracellular vesicles (EVs; exosomes and microvesicles) from the urine samples of patients. METHODS: One hundred and twenty-seven kidney recipients at 11 Japanese institutions were enrolled in this study; urine samples were obtained prior to protocol/episode biopsies. EVs were isolated from urine samples, and EV RNA markers were assayed using quantitative reverse transcription polymerase chain reaction. Diagnostic performance of EV RNA markers and diagnostic formulas comprising these markers were evaluated by comparison with the corresponding pathological diagnoses. RESULTS: EV CXCL9, CXCL10, and UMOD were elevated in T-cell-mediated rejection samples compared with other KGI samples, while SPNS2 was elevated in chronic antibody-mediated rejection (cABMR) samples. A diagnostic formula developed through Sparse Logistic Regression analysis using EV RNA markers allowed us to accurately (with an area under the receiver operator characteristic curve [AUC] of 0.875) distinguish cABMR from other KGI samples. EV B4GALT1 and SPNS2 were also elevated in cABMR, and a diagnostic formula using these markers was able to distinguish between cABMR and chronic calcineurin toxicity accurately (AUC 0.886). In interstitial fibrosis and tubular atrophy (IFTA) urine samples and those with high Banff chronicity score sums (BChS), POTEM levels may reflect disease severity, and diagnostic formulas using POTEM detected IFTA (AUC 0.830) and high BChS (AUC 0.850). CONCLUSIONS: KGIs could be diagnosed with urinary EV mRNA analysis with relatively high accuracy.

Mitochondrial stress and glycoxidation increase with decreased kidney function.

Mitochondrial stress increases the production of fumarate, an intermediate of the Krebs cycle. Fumarate non-enzymatically reacts with the thiol group of cysteine, leading to the production of S-(2-succinyl)cysteine. Here, we quantified the concentration of fumarate, the free form of S-(2-succinyl)cysteine, and advanced glycation end-products, including N ε-(carboxymethyl)lysine and N δ-(5-hydro-5-methyl-4-imidazolone-2-yl)-ornithine, in the serum of chronic kidney disease patients, using liquid chromatography-tandem mass spectrometry and an enzymatic assay. In a cross-sectional study, we evaluated the difference in metabolite concentration between healthy individuals (n = 22) and kidney transplant patients (n = 93). Additionally, we evaluated the metabolite concentration of end-stage renal disease patients (n = 17) before and 1, 3, 6, and 12 months after transplantation, in a longitudinal study. While the S-(2-succinyl)cysteine and AGEs levels were significantly increased in accordance with the rising chronic kidney disease severity, they were significantly decreased after transplantation. However, fumarate levels were only significantly different in end-stage renal disease patients. The S-(2-succinyl)cysteine levels correlated with the pre-existing kidney function marker. This study demonstrates that mitochondrial metabolic disorders contribute to impaired kidney function, and that measuring blood S-(2-succinyl)cysteine levels may be a minimally invasive way to evaluate the metabolic change in chronic kidney disease.

Phase II Study of Continued Trastuzumab Plus Irinotecan in Patients with HER2-positive Gastric Cancer Previously Treated with Trastuzumab (HGCSG 1201).

BACKGROUND: The efficacy of irinotecan plus continuous trastuzumab beyond progression in patients with gastric cancer previously treated with trastuzumab plus standard first-line chemotherapy has not been reported. METHODS: Patients with human epidermal growth factor receptor 2 (HER2)-positive advanced gastric cancer who were previously treated with trastuzumab received trastuzumab every 3 weeks and irinotecan every 2 weeks. The primary endpoint was the overall response rate (ORR), and the secondary endpoints included progression-free survival (PFS), 6-month survival rates, safety, and subgroup analysis by HER2 status. RESULTS: Sixteen patients were enrolled in a 3-year pre-planned registration period. This study was prematurely closed due to poor patient accrual. The ORR and disease control rate were 6.7% (95% CI, 0.2-32.0) and 53.3% (95% CI, 26.6-78.7). The median PFS and overall survival (OS) were 2.4 months (95% CI, 0.0-5.2) and 9.7 months (95% CI, 8.2-11.2), respectively. The most frequently reported grades 3-4 adverse events were neutropenia (40%), anemia (27%), anorexia (33%), and fatigue (33%). CONCLUSION: With only 16 patients enrolled, the present study has very low power to detect any clinical benefit of trastuzumab plus irinotecan beyond disease progression in patients with HER2-positive advanced gastric cancer who previously received trastuzumab.Trial Identifier: UMIN000007636.

Phase II Study of Ramucirumab Plus Irinotecan Combination Therapy as Second-Line Treatment in Patients with Advanced Gastric Cancer: HGCSG1603.

BACKGROUND: Ramucirumab is a human IgG1 monoclonal vascular endothelial growth factor receptor-2 antibody that inhibits tumor cell growth and affects the tumor cell microenvironment. We assessed the efficacy and safety of ramucirumab plus irinotecan combination therapy as second-line treatment in patients with previously treated advanced gastric cancer. MATERIALS AND METHODS: Patients with advanced gastric cancer refractory or intolerant to primary chemotherapy were included. Ramucirumab 8 mg/kg plus irinotecan 150 mg/m2 combination therapy was administered every 2 weeks. The primary endpoint was progression-free survival rate at 6 months and secondary endpoints were overall survival, progression-free survival, response rate, safety, and dose intensity for each drug. RESULTS: Thirty-five patients were enrolled between January 2018 and September 2019. The progression-free survival rate at 6 months was 26.5% [95%CI, 13.2%-41.8%, P = .1353)]. Median progression-free and overall survivals were 4.2 months (95%CI, 2.5-5.4 months) and 9.6 months (95%CI, 6.4-16.6 months), respectively. The overall response rate was 25.9% (95%CI, 11.1-36.3%) and disease control rate was 85.2% (95%CI, 66.3-95.8%). Grade ≥3 adverse events that occurred in >10% of patients included neutropenia, leucopenia, anemia, anorexia, and febrile neutropenia. No death or new safety signals with a causal relation to the study treatment were observed. CONCLUSION: Although the primary endpoint was not achieved statistically, combination therapy of ramucirumab plus irinotecan showed anticancer activity and a manageable safety profile for second-line treatment of patients with advanced gastric cancer.

Decision making for anti-VEGF inhibitor continuation: dip stick? or urine protein/creatinine ratio? (VERSiON UP study).

BACKGROUND: Monitoring proteinuria is important for the management of patients with cancer treated with anti-vascular endothelial growth factor (VEGF) or anti-VEGF receptor (VEGFR) inhibitors (VEGF/Ri). Here we investigated the difference between the urine protein/creatinine ratio (UPCR) and a qualitative value test (QV) on the decision making of treatment continuation and the usefulness of UPCR testing in patients with gastrointestinal cancer treated with anti-VEGF/Ri. METHODS: From January 2017 to December 2018, a survey was conducted based on the medical records of patients with gastrointestinal cancer with a QV of ≥2+ during the use of anti-VEGF/Ri at seven Japanese institutions participating in the Onco-nephrology Consortium. The primary endpoint was the ratio of the worst UPCR < 2.0 (low UPCR) in cases with a QV2+ at the point of the first proteinuria onset. The secondary endpoints were a comparison of low UPCR and worst UPCR ≥2.0 (high UPCR), the concordance rate between UPCR and QV in the Common Terminology Criteria for Adverse Events (CTCAE) grading, and the differences in the decision making for anti-VEGF/Ri continuation. RESULTS: Among the 71 patients enrolled, the proportion of low UPCR in onset QV2+ (n = 53) was 66% (n = 35). In a comparison between low (n = 36) and high UPCR cases (n = 24), body weight (P = 0.036), onset QV status (P = 0.0134), and worst QV status (P < 0.0001) were significantly associated with UPCR levels. The concordance rate for CTCAE Grade 2 of both the QV and UPCR was 83%. Regarding the judgment of anti-VEGF/Ri continuation, treatment was continued in 42.4% of cases when the QV became 3+, whereas only 25% continued treatment when the UPCR value became high. CONCLUSION: Urine dipstick test results may overestimate proteinuria, and the UPCR result tended to be more critical than the QV when deciding the treatment policy. TRIAL REGISTRATION: This study is a multiple institutional retrospectively registered observational trial. CLINICAL TRIAL NUMBER: University Hospital Medical Information Network (UMIN) Clinical Trials Registry (protocol ID UMIN000042545 ).

Feasibility of edoxaban for asymptomatic cancer-associated thrombosis in Japanese patients with gastrointestinal cancer: ExCAVE study.

BACKGROUND: Although initial therapy with a parenteral anticoagulant is required before edoxaban, this strategy is frequently avoided in actual clinical practice because of its complexity. This study assessed the feasibility of edoxaban without initial heparin usage for asymptomatic cancer-associated thrombosis (CAT) in Japanese patients with gastrointestinal cancer (GIC) at high risk of bleeding. METHODS: In this multicenter prospective feasibility study conducted at 10 Japanese institutions, patients with active GIC who developed accidental asymptomatic CAT during chemotherapy were recruited. Edoxaban was orally administered once daily without initial parenteral anticoagulant therapy within 3 days after detecting asymptomatic CAT. The primary outcome was the incidence of major bleeding (MB) or clinically relevant non-major bleeding (CRNMB) during the first 3 months of edoxaban administration. RESULTS: Of the 54 patients enrolled from October 2017 to September 2020, one was excluded because of a misdiagnosis of CAT. In the remaining 53 patients, the primary outcome occurred in six patients (11.3%). MB occurred in four patients (7.5%), including gastrointestinal bleeding in three patients and intracranial hemorrhage in one patient. CRNMB occurred in two patients (3.8%), including bleeding from the stoma site and genital bleeding in one patient each. There were no deaths attributable to bleeding, and all patients who experienced MB or CRNMB recovered. CONCLUSIONS: The risk of bleeding after edoxaban without heparin pretreatment was acceptable, demonstrating new treatment options for asymptomatic CAT in patients with GIC.

Greetings among female chimpanzees in Mahale, Tanzania.

Greeting behaviors have been reported in several primate species, although their forms and context may vary across species. Chimpanzees (Pan troglodytes) greet each other in various ways when they meet; however, many recent studies of greetings in chimpanzees have mostly focused on pant grunt vocalizations, which are often viewed as equivalent to submissive signals. As most greetings in chimpanzees are directed toward adult males, either from other males or females, relatively few studies have focused on female-female greetings. Thus, the primary aim of this study was to describe the greetings (not limited to pant grunts) between chimpanzee females in the Mahale Mountains National Park based on long-term observational data. I observed 405 female-female greeting events (10.9 instances per 100 observation hours [obsn. h]) between 1994 and 2018, of which 242 were pant grunts (6.5 instances per 100 obsn. h); 42.3% of greetings were nonaudible, such as tactile or gestural greetings. Most pant grunts were directed toward older females; females under 20 years of age were generally responsible for this trend, as they were the most frequent greeters among females and tended to perform pant grunts toward older females. Nonetheless, among females 20 years of age or older, pant grunts from an older to a younger female were not rare (37%). Compared to previous studies in Mahale, pant grunts between females were an order of magnitude less than those directed toward males. There may also be a large difference in the frequencies of female-female pant grunts across study sites, which may be attributed to differences in female gregariousness.

REVIVE study: a prospective observational study in chemotherapy after nivolumab therapy for advanced gastric cancer.

Nivolumab is an increasingly used standard care treatment for heavily pretreated patients with advanced gastric cancer, with increasing clinical use in Japan. Data from retrospective studies on various tumors have shown the objective response rate to cytotoxic chemotherapy potentially improves after an exposure to immune checkpoint inhibitors. Based on these data, we conducted the multicenter observational REVIVE study to evaluate the efficacy and safety of cytotoxic chemotherapy in nivolumab-refractory or nivolumab-intolerant patients with advanced gastric cancer. Patients who are refractory or intolerant to nivolumab and scheduled to receive irinotecan monotherapy, oxaliplatin combination treatment or oral trifluridine/tipiracil hydrochloride therapy will be included. The primary end point is overall survival of nivolumab-pretreated patients with advanced gastric cancer after the cytotoxic chemotherapy. Clinical trial registration: UMIN000032182 (umin.ac.jp).

Post-kidney transplant soluble Klotho levels are determined by pretransplant soluble Klotho levels in both living donors and recipients.

BACKGROUND: Soluble Klotho (sKl), the free form of membrane-bound Klotho predominantly expressed in the kidney, is detectable in serum and may have multiple pleiotropic effects. Patients with end-stage kidney disease are possibly sKl deficient, and kidney transplantation is the treatment of choice in these patients; however, little is known about changes in posttransplant sKl level and the factors influencing these changes. METHODS: We conducted a prospective longitudinal study to examine changes in posttransplant sKl level in recipients for 12 months after living-donor kidney transplantation and analyzed correlations between posttransplant changes in sKl levels and various influencing factors in both recipients and donors. RESULTS: 29 kidney transplant recipients and their living donors were included for analysis. The results showed that sKl levels transiently decreased at 1 week posttransplant but progressively increased thereafter for 12 months. Multivariable linear regression analysis showed that body surface area-adjusted donor sKl levels were associated with posttransplant increases in recipient sKl levels at 12 months. In addition, pretransplant recipient sKl levels and body surface area-adjusted donor sKl levels were identified as an independent predictor of 12-month posttransplant sKl levels. CONCLUSION: Pretransplant sKl levels in both kidney recipients and living donors are a strong determinant of sKl levels after kidney transplantation.

Skeletal and mineral metabolic effects of risedronate in a rat model of high-turnover renal osteodystrophy.

INTRODUCTION: High-turnover bone disease is a major consequence of SHPT and may explain the high risk for fracture in patients with advanced chronic kidney disease (CKD). Bisphosphonates suppress bone turnover and improve bone strength, but their effects have not been fully characterized in advanced CKD with severe SHPT. Bisphosphonates also increase 1,25-dihydroxyvitamin D levels in normal and uremic rats, but the underlying mechanism remains to be determined. MATERIALS AND METHODS: We investigated the skeletal and mineral metabolic effects of RIS, a pyridinyl bisphosphonate, in rats with severe SHPT induced by 5/6 nephrectomy plus a high phosphate diet. RESULTS: Nephrectomized rats developed severe SHPT, along with hyperphosphatemia, low 1,25-dihydroxyvitamin D, and markedly increased FGF23. Moreover, these rats exhibited characteristic features of high-turnover renal osteodystrophy, including increased indices of trabecular bone turnover, decreased cortical bone thickness, inferior cortical biomechanical properties, and a prominent increase in peritrabecular fibrosis. RIS treatment increased bone volume and partially attenuated trabecular bone remodeling, cortical bone loss, and mechanical properties, whereas it produced a marked improvement in peritrabecular fibrosis along with a corresponding decrease in osteogenic gene markers. RIS treatment also suppressed the elevation of FGF23, which was associated with increased 1,25-dihydroxyvitamin D. CONCLUSIONS: In a rat model of severe SHPT, treatment with RIS partially attenuated histological manifestations of high-turnover bone disease. RIS treatment also suppressed the elevation of FGF23, which may explain the increased 1,25-dihydroxyvitamin D production during the treatment.

Lethal aggression in Pan is better explained by adaptive strategies than human impacts.

Observations of chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) provide valuable comparative data for understanding the significance of conspecific killing. Two kinds of hypothesis have been proposed. Lethal violence is sometimes concluded to be the result of adaptive strategies, such that killers ultimately gain fitness benefits by increasing their access to resources such as food or mates. Alternatively, it could be a non-adaptive result of human impacts, such as habitat change or food provisioning. To discriminate between these hypotheses we compiled information from 18 chimpanzee communities and 4 bonobo communities studied over five decades. Our data include 152 killings (n = 58 observed, 41 inferred, and 53 suspected killings) by chimpanzees in 15 communities and one suspected killing by bonobos. We found that males were the most frequent attackers (92% of participants) and victims (73%); most killings (66%) involved intercommunity attacks; and attackers greatly outnumbered their victims (median 8:1 ratio). Variation in killing rates was unrelated to measures of human impacts. Our results are compatible with previously proposed adaptive explanations for killing by chimpanzees, whereas the human impact hypothesis is not supported.

Correction to: Preventive effect of early introduction of everolimus and reduced­exposure tacrolimus on renal interstitial fibrosis in de novo living­donor renal transplant recipients.

In the Original publication of the article, the co-author name has been misspelled as "Yousuke Nakagawa".

Preventive effect of early introduction of everolimus and reduced-exposure tacrolimus on renal interstitial fibrosis in de novo living-donor renal transplant recipients.

BACKGROUND: To improve the long-term outcomes following renal transplantation, prevention of renal-allograft interstitial fibrosis (IF), mainly due to calcineurin inhibitors, is an important therapeutic target. Everolimus (EVR) was reported to have antifibrotic effects. We aimed to investigate the safety, efficacy, and IF of our modified immunosuppressive regimen, which includes early introduction of EVR and reduced-exposure tacrolimus (Tac) (EVR group), and compare it with the standard-exposure tacrolimus-based regimen (Tac group) in de novo living-donor renal recipients. METHODS: In this retrospective, single-center cohort study, we compared the 2-year clinical courses between the two groups according to intention to treat. Additionally, in patients in whom biopsies were obtained at 1 h, 3 months, and 12 months post-transplant, we compared IF between the groups using imaging analysis. RESULTS: Overall, 47 patients were included (EVR group, n = 22; Tac group, n = 25). There were no significant differences in renal function and incidences of rejection and viral infections between the groups at the 2-year post-transplant follow-up. However, pathologic imaging analysis (n = 34) revealed chronological progression of IF in the Tac group during the first year post-transplant and no changes in the EVR group (fibrosis rate at 3 months: 20.8 vs. 13.6%, p < 0.001; at 12 months: 24.7 vs. 14.7%, p < 0.001, respectively). CONCLUSION: Our modified immunosuppressive regimen may have an antifibrotic effect on transplanted kidneys without loss of safety and efficacy.

Wild chimpanzees deprived a leopard of its kill: Implications for the origin of hominin confrontational scavenging.

This study reports the first observed case of wild chimpanzees (Pan troglodytes) obtaining animal prey freshly killed by a sympatric leopard (Panthera pardus) and scavenging it with the leopard still nearby. This observation has important implications for the emergence of confrontational scavenging, which may have played a significant role in human evolution. Many scholars agree that eating meat became important during human evolution, and hominins first obtained meat by scavenging. However, it is debatable whether scavenging behavior was "passive" or "confrontational (power)." The latter is more dangerous, as it requires facing the original predator, and it is thus considered to have been important for the evolution of several human traits, including cooperation and language. Chimpanzees do scavenge meat, although rarely, but no previous evidence of confrontational scavenging has hitherto emerged. Thus, it was assumed that they are averse to confrontation with even leopard-sized predators. However, in the observed case the chimpanzees frequently emitted waa barks, which indicated that they were aware of the leopard's presence but they nevertheless continued to eat the scavenged meat. In addition, we compiled and reviewed 49 cases of chimpanzee encounters with animal carcasses in the Mahale Mountains of Tanzania in 1980-2017. Chimpanzees scavenged meat in 36.7% of these cases, and tended to eat the meat when it was fresh or if the animal species was usually hunted by chimpanzees. However, no evidence indicated that carcasses were avoided when leopard involvement was likely. These results suggest that chimpanzee-sized hominins could potentially confront and deprive leopard-size carnivores of meat.

A newborn infant chimpanzee snatched and cannibalized immediately after birth: Implications for "maternity leave" in wild chimpanzee.

OBJECTIVES: This study reports on the first observed case of a wild chimpanzee infant being snatched immediately after delivery and consequently cannibalized by an adult male in the Mahale Mountains, Tanzania. We demonstrate "maternity leave" from long-term data from the Mahale M group and suggest that it functions as a possible counterstrategy of mother chimpanzees against the risk of infanticide soon after delivery. MATERIALS AND METHODS: The subjects of this study were the M group chimpanzees at Mahale Mountains, Tanzania. The case of cannibalism was observed on December 2, 2014. We used the long-term daily attendance record of the M group chimpanzees between 1990 and 2010 to calculate the lengths of "maternity leave," a perinatal period during which a mother chimpanzee tends to hide herself and gives birth alone. RESULTS: We observed a very rare case of delivery in a wild chimpanzee group. A female chimpanzee gave birth in front of other members, and an adult male snatched and cannibalized the newborn infant immediately after birth. Using the long-term data, we demonstrate that the length of "maternity leave" is longer than that of nonmaternity leave among adult and adolescent female chimpanzees. DISCUSSION: We argue that this cannibalism event immediately after birth occurred due to the complete lack of "maternity leave" of the mother chimpanzee of the victim, who might lack enough experience of delivery. We suggest that "maternity leave" taken by expecting mothers may function as a possible counterstrategy against infanticide soon after delivery.