Dear colleagues, We are pleased to announce the publication of the paper: Haro D., Riccialdelli L., Blank O., Matus R., Sabat P. 2019. Estimating the isotopic niche of males and females of false killer whales (*Pseudorca crassidens*) from Magellan Strait, Chile. Marine Mammal Science https://onlinelibrary.wiley.com/doi/10.1111/mms.12564 Summary 1. To understand the trophic habits of both sexes better, this study aims to assess and compare the isotopic niche of adult male and adult female false killer whales over different time scales, using carbon (δ13C) and nitrogen (δ15N) stable isotope ratios in bone collagen and skin from two independent stranding events. 2. The events occurred in nearby areas, in the eastern zone of the Magellan Strait, Chile. Bone samples were obtained from 34 adults from the first stranding (1989) and skin samples were obtained from 15 adult specimens from the second stranding (2013). Isotopes values from both bone collagen and skin samples were examined from males and females. The isotopic niche was estimated by Bayesian Ellipse Analysis based on δ13C and δ15N values. Layman metrics were calculated to complement the evaluation of the isotopic niche. 3. In multivariate tests, no significant differences were found between sexes for the isotope values of δ13C or δ15N of bone collagen (MANOVA, Wilks λ = 0.92, P = 0.26), and δ13C and δ15N from skin (MANOVA, Wilks λ = 0.63, P = 0.06). However, in the univariate analysis, the δ15N values were significantly higher in the skin of females (W = 8, P = 0.02). Male individuals stranded in 1989 had a larger isotopic niche area than females (Pr(M|D) = 0.93). Likewise, males had higher values than females in all estimated Layman metrics. By contrast, skin samples showed that female individuals had a larger isotopic niche area than males (Pr(M|D) = 0.85). In this stranded group, females had higher values than males for all Layman metrics. 4. Our results from isotopic niche metrics constructed from bone collagen revealed that male false killer whales had a wider isotopic niche and major degree of individual specialization than females. In addition, results from skin suggest that females were feeding on higher trophic level prey than males over a short temporal scale (days/months). This result could be related to their lactation period. Lactating females have an increased energy requirement to provide good quality milk to their offspring, which would lead to the consumption of prey with higher energy value (e.g., fish), and with different values of δ13C and δ15N. Please contact me at <daniela.haro.diaz@gmail.com> for a PDF copy or questions. -- Dra. Daniela Haro Díaz