Dear colleagues, My coauthors and I are pleased to share news of the following publication: Keen, E.M., Wren, J., O’Mahony, É., Wray, J. catRlog: a photo-identification project management system based in R. Mamm Biol (2021). https://doi.org/10.1007/s42991-021-00158-7 Abstract Photo-identification (photo-ID) databases can comprise versatile troves of information for well-studied animal populations and, when organized well and curated carefully, can be readily applied to a wide range of research questions, such as population abundance estimates, meta-population connectivity and social network structure. To bring the potential impact of photo-ID data within reach of a greater number of research groups, we introduce an R-based photo-ID project management system, named catRlog. As a computer directory with custom apps embedded throughout, catRlog serves as a workflow organizer that simplifies, streamlines, and improves the quality of photo-ID data processing. The system can be utilized by research teams in a number of ways, ranging from automated formatting and printing of a photo-ID catalog, to photo-ID matching, thereby creating and expanding a historical catalog, to processing of identification data to generate datasets necessary for site fidelity, mark–recapture, and social association analyses. As an R-based tool, the apps are open-source, cross-platform, readily customizable, and easily updated. catRlog has been tested using photo-ID databases of humpback whales (Megaptera novaeangliae) and fin whales (Balaenoptera physalus) within a mainland fjord system of Pacific Canada, but is a generalized system useful for almost any photo-ID project of any species in any habitat. A detailed user’s manual and example dataset are provided. This article is a contribution to the special issue of Mammalian Biology on “Individual Identification and Photographic Techniques in Mammalian Ecological and Behavioural Research: Methods, Applications and Concepts”—Editors: Leszek Karczmarski, Stephen C.Y. Chan, Daniel I. Rubenstein, Scott Y.S. Chui and Elissa Z. Cameron. The paper and catRlog manual may be viewed here: https://rdcu.be/csdPC The catRlog code lives here: https://github.com/ericmkeen/catRlog Please contact me with any questions (ericmkeen@gmail.com) Best wishes, Eric Keen