The majority of science learning occurs in informal environments such as museums or aquaria, but also in online spaces such as forums or social media (Falk & Storksdieck, 2010). In a design-based effort, we report here on the examination of the behavioral engagement of a community of followers with social media messages that were systematically produced by researchers on XXXX, an NSF-funded project focused on building knowledge and relationships that center on paleontology (i.e. the study of fossils). Focusing Twitter and Facebook, we investigated the following research question: what messaging elements lead to increased behavioral engagement? In this presentation, we concentrate specifically on quantifying behavioral engagement with social media messaging and refining Falk and Dierking’s (2013) Contextual Model of Learning (CMoL) as it applies to the social media landscape. We find that community engagement varies dependent on platform, messaging elements such as hashtags, URLs, mentions, and post type. In particular, the use of hashtags without the inclusion of other messaging elements on Twitter showed significantly lower engagement than when used on Facebook. While these findings are significant in and of themselves, we argue that our study provides empirical evidence for use of CMoL with social media.