Obituary: Mark A. Elgar (1957 – 2025)

Matthew R. E. Symonds^1*Theresa M Jones²Raoul Mulder²Christopher B. Freelance³

• ¹Deakin University School of Life and Environmental Sciences, Burwood, Australia
• ²The University of Melbourne School of BioSciences, Parkville, Australia
• ³The University of Melbourne School of Biomedical Sciences, Parkville, Australia

The pragmatic decision to work more locally proved an excellent one, allowing him to collect a large amount of "field" data on the roof of the Zoology Department in Cambridge. It resulted in several important publications on vigilance, including his most highly cited paper (Elgar 1989), which to this day remains the go-to reference on the topic.Following his PhD, Mark commenced a post-doc at the University of Oxford, under the mentorship of Prof. Paul Harvey, where he was one of the early adopters and advocates for 'The Comparative Method' in evolutionary biology -the need to consider phylogenetic relationships in the analysis of cross-species patterns -applying this to foundational studies of the evolution of metabolic rates and sleep in mammals (Elgar & Harvey 1987;Elgar et al 1988).A return to Australia, in the late 1980s, saw Mark hold a fellowship at the University of New South Wales, before obtaining a permanent tenured position at the University of Melbourne in 1991, notionally as a vertebrate zoologist but with interests that were much better described as evolutionary ecology. He devoted much of his subsequent career to his core love of spiders, with a particular focus on sexual cannibalism -the subject of his most major book volume (Elgar & Crespi, 1992) and key reviews (e.g. Elgar & Schneider, 2004) -and also web structure and characteristics (Herberstein et al. 2000). His work on spiders provoked another key research theme, on sexual selection and sperm competition (Elgar 1998), which expanded into other invertebrate taxa (Jones & Elgar 2004).Spiders were also the starting point for a major focus in the latter half of his career -chemical communication. Starting with the observation that spiders can eavesdrop on ant alarm signals (Allan et al., 1996) and that salticid spiders employ chemical mimicry to prey on ants (Allan et al., 2002), Mark expanded his interests to examine the evolution of pheromones and other chemical cues more generally across a wide range of taxa (including ants, beetles, flies and moths) and in particular focussing on the ecological factors that drive diversity in these signals (Symonds & Elgar, 2008;Henneken et al., 2017).Having focussed on the evolution of the signal, it was perhaps a natural progression that Mark subsequently became equally interested in the receiver component of the communication system. His work in this late stage of his career concerned how environmental and behavioural factors can shape the evolution of insect antennal morphology (Elgar et al. 2018;Elgar et al. 2019;Elgar & Freelance, 2025), and the interplay between anthropogenic stressors, antennal function and insect declines. With potential applications for biodiversity and threatened species conservation (Freelance et al. 2022;Wang et al. 2023), Mark would sometimes describe his later projects, with characteristic selfdeprecation, as his "last desperate attempt at doing something useful." Yet he was fully aware of the enduring worth of blue-sky research -work he considered himself deeply fortunate to have undertaken.Mark himself was always brimming with ideas and theories, which came to him like (to quote Camille Saint-Saens) like "an apple tree produces apples". He enjoyed applying those ideas to topics that might seem remote from his core research -such as his work on human leadership (Elgar, 2016).In the final years of his career, Mark renewed his interest in nature as a source of inspiration for design to solve problems, both co-chairing a bio-inspired design initiative at The University of Melbourne and advocating for greater interest in the field from biologists (Ng et al., 2021;Stuart-Fox et al., 2023).In addition to his own research, Mark played for many years a significant role in the field through his service as editor-in-chief of three journals -Behavioral Ecology, Australian Journal of Zoology and, in more recent times, Frontiers in Ecology and Evolution. He was also a long-serving member of the board of Behavioral Ecology and Sociobiology. He took his roles as an editor seriously, with a great desire to improve the review process for authors, even helping to coordinate the editors-in-chief of most of the major journals in evolution, ecology and behaviour into producing an aspirational manifesto on how reviewers should behave (McPeek et al., 2009). Many of his ex-students have gone on to hold editorial roles themselves, citing Mark's collaborative and uplifting mindset as the yardstick against which they compare themselves. His concern for improving scientific culture also extended into issues of sex and gender, both in terms of how pejoratively gendered language was used in descriptions of animal sexual behaviour (Elgar et al. 2013), to debunking the myths around gender (Fine and Elgar 2017) and calling for a more equitable assessment of the publication records of women scientists (Symonds et al. 2006). His service to university governance was equally exemplary. He served two terms on the council of the University of Melbourne, and contributed to almost every senior university committee imaginable, leading reform on subjects ranging from teaching and learning quality to research integrity and publications.Mark was a passionate and innovative teacher, known for his generosity and commitment to student learning. He coordinated and developed numerous undergraduate and graduate subjects, and taught a Massively Open Online Course on Animal Behaviour that reached over 100,000 learners globally.Here too he was a tireless advocate for equity, particularly for students from rural and disadvantaged backgrounds.Mark was genuinely fascinated by and convinced of the excellence of the work everyone did under his guidance. As one ex-PhD student put it "he always made you feel that your research was more interesting than it actually was." Although he was not a seasoned field biologist, he was convinced that careful observation of nature was the key to generating ideas, and he was not at all prescriptive about what might emerge. He famously encouraged his students to go out and observe until they saw something interesting, an approach one described as "both a privilege and terrifying". In this way, he entrusted his students with an exceptional degree of ownership of their ideas and confidence in their own capacity to test those ideas.It would be wrong, though, to create the impression that his students were left to sink or swim. His intellectual and emotional support for them was powerful. He cared deeply for his students and took their setbacks to heart. A rejected paper would almost always spark instant indignation, swiftly followed by calm, strategic resolve. With his editor's instinct for tone and argument, he helped turn disappointments into opportunities for sharper thinking and stronger writing.While obviously enjoying seeing his students achieve highly, Mark developed a strong reputation for taking on PhD students who were enthusiastic and talented but perhaps lacked confidence or, like himself, were not inclined to perform well on recall-based written examinations in their undergraduate studies. There was no hierarchy within his group -the ideas and perspectives of all members from the Honours student on their first day through to himself were afforded equal consideration and respect, and all were encouraged to be extremely open and collaborative with their research. Many an Elgar lab Christmas party was held in Mark's backyard fully at his own expense, and this epitomises his commitment to fostering a sense of genuine camaraderie and belonging amongst his students. His kindness and collegiality are the first things many of his ex-students recall when reminiscing about their time working with him.Mark was a talented raconteur, who loved nothing better than holding court in a lab meeting or the tearoom, often punctuating his opinions with entertaining insouciance. It's a cliché to say that his door was always open, but in his case it was literally true, and he never seemed unhappy for students and colleagues to drop in for a chat. In the second half of his career, when Mark became a father, his dedication to his family was also transparent every single day -serving as a role-model and reminding younger academics that it was possible to prioritise family commitments and yet still have a successful academic career.As Mark dealt with his cancer, in the last few years, he was more inclined to reflect on his own career, and so it was a pleasure for many of his former colleagues, post-docs, and students to be able to celebrate that career with him at his retirement function in June 2025. It gave him the opportunity to hear the appreciation for the huge and positive influence he had on those of us whose careers he had shaped, guided and championed.