DOI: 10.5061/dryad.dv41ns1v3
title: Rethinking megafauna

description: Concern for megafauna is increasing among scientists and non-scientists.
 Many studies have emphasized that megafauna play prominent ecological
 roles and provide important ecosystem services to humanity. But, what
 precisely are “megafauna”? Here we critically assess the concept of
 megafauna and propose a goal-oriented framework for megafaunal research.
 First, we review definitions of megafauna and analyze associated
 terminology in the scientific literature. Second, we conduct a survey
 among ecologists and paleontologists to assess the species traits used to
 identify and define megafauna. Our review indicates that definitions are
 highly dependent on the study ecosystem and research question, and
 primarily rely on ad hoc size-related criteria. Our survey suggests that
 body size is crucial, but not necessarily sufficient, for addressing the
 different applications of the term megafauna. Thus, after discussing the
 pros and cons of existing definitions, we propose an additional approach
 by defining two function-oriented megafaunal concepts: “keystone
 megafauna” and “functional megafauna”, with its variant “apex megafauna”.
 Assessing megafauna from a functional perspective could challenge the
 perception that there may not be a unifying definition of megafauna that
 can be applied to all eco-evolutionary narratives. In addition, using
 functional definitions of megafauna could be especially conducive to
 cross-disciplinary understanding and cooperation, improvement of
 conservation policy and practice, and strengthening of public perception.
 As megafaunal research advances, we encourage scientists to unambiguously
 define how they use the term “megafauna” and to present the logic
 underpinning their definition.
description: We surveyed
 researchers working on megafauna to get a better understanding of how they
 understand the concept when using it. For this purpose, we
 designed a questionnaire to investigate the megafauna concept among
 researchers. The questionnaire was divided in three parts: Part 1 was
 devoted to researchers’ personal and expertise data; Part 2 showed
 pictures of 120 species (15 mammals, 15 birds, 15 reptiles, 15 amphibians,
 15 fishes, 15 terrestrial invertebrates, 15 marine invertebrates and 15
 freshwater invertebrates, spanning the whole body size range of each
 group; habitat refers to the main habitat
 during the whole life, being also the main habitat for
 adults); and Part 3 formulated questions regarding different
 definitions of megafauna. We used foreground color pictures
 of animals without human-related scale references. All photographs avoided
 backlighting, represented the entire body of the animal, had less than 10%
 visible sky and pictured adult individuals. Among the list of pictures, we
 asked respondents to indicate the species that fell into their concept of
 megafauna. We selected the respondents in
 several steps following Sutherland et al. (2013) and Hays et
 al. (2016). First, we identified leading
 experts in the ecology and conservation of megafauna (particularly,
 human-wildlife conflicts and ecosystem services associated with
 megafauna), as well as in paleontology (mainly, vertebrate paleontology
 and paleoecology), based on their publication record and
 extent of work in these fields. These experts were invited to
 participate in a workshop organized in the Doñana Biological Station-CSIC
 (EBD; Seville, Spain, November 9-11 2016;
 http://www.ebd.csic.es/web/megafauna-workshop/home) to discuss on
 megafauna and their benefits and detriments to humans. Before the meeting,
 experts were asked to fill in the questionnaire on-line. Second, the same
 questionnaires were distributed to researchers who attended the first
 workshop session, which was open to all EBD researchers. These EBD
 researchers were asked to fill in the questionnaires at the beginning of
 the session, i.e. before hearing invited researchers and participating in
 discussions. Third, experts attending the workshop
 (<i>n</i>=20) were asked to contact and distribute the
 questionnaires to other researchers of their fields with the aim of
 obtaining a minimum of ten researchers belonging to the 12 broad fields
 resulted from all combinations of ecosystem of expertise (terrestrial,
 marine and freshwater), period of expertise (prehistorical and historical)
 and taxonomic expertise (vertebrates and invertebrates). We obtained a
 total of 93 questionnaires (note that one researcher can be expert in more
 than one combination of ecosystem, period and taxonomic
 expertise). To represent species traits and
 other relevant characteristics that may determine the probability of a
 species to be classified as megafauna, we compiled information on the
 taxonomy, biology, ecology, behavior, conservation status and popularity
 among the general public of the species included in the questionnaires.
 Also, we recorded respondents’ characteristics that might have an
 influence on the questionnaires’ results (personal details, and research
 experience and expertise).