Surgery is primarily taught through mentoring, where an expert mentor supervises a mentee performing surgery, taking over when necessary. Telementoring systems aim to provide mentees with access to remote mentors, but the physical distance between mentors and mentees poses unique challenges to surgical training. We investigate the underlying needs leading to takeovers in onsite mentoring and assess mentors’ ability to fulfill address these needs remotely using existing telestration tools, namely pointers and drawings on shared views. Through interviews and workshops with expert surgeons, we find that (1) mentors take over to convey gestures related to instrument placement, tissue displacement, force, and movement, (2) mentors gather information about location of tissue, equipment, and instruments, as well as gesture constraints, and (3) surgeons judge telestration insufficient for these needs. Based on this gap between onsite mentoring practices and telementoring tools, we discuss novel tools to address these needs and their evaluation.