Three Francois' langurs (Trachypithecus francoisi) were found dead, without previous clinical signs, over a 48-hour period at a zoological institution after transfer to a new exhibit. A hybrid yew shrub (Taxus baccata × T. cuspidata) was found in close proximity to the exhibit perimeter fence. Despite clinical suspicion of yew intoxication, thin-layer chromatography performed on gastric contents was negative. However, microscopic examination of gastric contents revealed multiple yew fragments, and taxine alkaloids were detected by gas chromatography and mass spectrometry of the gastric contents to confirm yew intoxication. Acute death of the animals prevented treatment. The fourth langur in the collection survived, most likely because of its low rank in the troop's hierarchy, with a suspected small amount or none of the plant ingested. To the authors' knowledge, this case report is the first yew intoxication documented in a nonhuman primate species. Taxus spp. intoxication is an often fatal condition reported in domestic animals and humans. In comparison with these species, mortality appeared delayed in the Francois' langurs, most likely because of their unique gastrointestinal anatomy, with both foregut and colonic fermentation. Plant intoxication should be a differential diagnosis when multiple acute deaths are observed after recent introduction to a new enclosure.
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