Dear colleagues, On-behalf of my co-authors I am pleased to share our new publication in Scientific Reports: Nutritional status and prey energy density govern reproductive success in a small cetacean. Authors: Lonneke L. IJsseldijk, Sanne Hessing, Amy Mairo, Mariel T. I. ten Doeschate, Jelle Treep, Jan van den Broek, Guido O. Keijl, Ursula Siebert, Hans Heesterbeek, Andrea Gröne & Mardik F. Leopold Abstract: A variety of mammals suppress reproduction when they experience poor physical condition or environmental harshness. In many marine mammal species, reproductive impairment has been correlated to polychlorinated biphenyls (PCBs), the most frequently measured chemical pollutants, while the relative importance of other factors remains understudied. We investigate whether reproductively active females abandon investment in their foetus when conditions are poor, exemplified using an extensively studied cetacean species; the harbour porpoise (Phocoena phocoena). Data on disease, fat and muscle mass and diet obtained from necropsies in The Netherlands were used as proxies of health and nutritional status and related to pregnancy and foetal growth. This was combined with published life history parameters for 16 other areas to correlate to parameters reflecting environmental condition: mean energy density of prey constituting diets (MEDD), cumulative human impact and PCB contamination. Maternal nutritional status had significant effects on foetal size and females in poor health had lower probabilities of being pregnant and generally did not sustain pregnancy throughout gestation. Pregnancy rates across the Northern Hemisphere were best explained by MEDD. We demonstrate the importance of having undisturbed access to prey with high energy densities in determining reproductive success and ultimately population size for small cetaceans. It is open access so a PDF of the article can be downloaded freely at: https://www.nature.com/articles/s41598-021-98629-x With kind regards, Lonneke IJsseldijk Lonneke L. IJsseldijk<https://www.uu.nl/medewerkers/LLIJsseldijk> | Project Manager Cetacean Research | Utrecht University | Veterinary<https://www.uu.nl/organisatie/faculteit-diergeneeskunde> Medicine | Biomolecular Health Sciences | Pathology | Yalelaan 1, 3584 CL Utrecht | room O.170 | (+3130) 253 5312 | (+316) 244 556 98 | l.l.ijsseldijk@uu.nl<mailto:l.l.ijsseldijk@uu.nl>| Follow us @ | Instagram<https://www.instagram.com/strandingresearch> | LinkedIn<https://www.linkedin.com/in/lonneke-ijsseldijk-64014226/> | Online<http://www.uu.nl/strandingsonderzoek> [cid:image001.png@01D7D168.D2025090]