DOI: 10.5061/dryad.djh9w0vws
title: “Chancing on a spectacle:” co-occurring animal migrations and interspecific interactions

description: Migrations of diverse wildlife species often converge in space and time,
 with their journeys shaped by similar forces (i.e., geographic barriers
 and seasonal resources and conditions); we term this “co-migration.”
 Supporting this, recent studies have elucidated co-migrations and seasonal
 patterns that govern the location and timing of multiple species’
 journeys. Beyond their significance as natural wonders, species with
 overlapping migrations may interact ecologically, with potential effects
 on population and community dynamics. Direct and indirect ecological
 interactions including predation and competition between migrant species
 remain poorly understood, in part because migration is the least-studied
 phase of animals’ annual cycles. To address this gap, we conducted a
 literature review to examine whether animal migration studies incorporate
 multiple species and to what extent they investigate interspecific
 interactions between co-migrants. Following a key word search, we read all
 migration research papers in 23 relevant peer-reviewed journals during
 2008-2017. Thirty percent of animal migration papers reported two or more
 species with coinciding migrations, suggesting that co-migrations are
 common, although few studies investigated or discussed these mixed-species
 migrations further. Synthesizing those that did explore this phenomenon,
 we present examples and describe five types of ecological interactions
 between migrating species, including predator-prey, host-parasite, and
 commensal relationships. Deepening ecological knowledge of interspecific
 interactions among migratory animal communities will enhance understanding
 of the drivers of migration and could improve predictions about wildlife
 responses to global change. Further research focused on multi-species
 migrations could also inform conservation efforts for migratory animal
 populations, many of which are declining or shifting, with unexplored
 consequences for other co-migratory species.
description: We used the keyword “migration” to identify animal migration
 research papers published during a 10-year period (2008-2017). We selected
 23 journals to capture a diversity of animal migration studies, including
 two journals focused broadly on biology (<i>Proceedings of the Royal
 Society Biological Sciences</i>, <i>Global Change
 Biology</i>); nine on ecology (<i>Ecography</i>,
 <i>Ecological Applications</i>, <i>Ecology</i>,
 <i>Ecology Letters</i>, <i>Journal of Ecology</i>,
 <i>Journal of Animal Ecology</i>,
 <i>Oecologia</i>, <i>Oikos</i>, <i>Marine
 Ecology Progress Series</i>); three on behavior (<i>Animal
 Behavior</i>, <i>Behavioral Ecology</i>,
 <i>Behavioral Ecology and Sociobiology</i>); three on
 conservation and management (<i>Biological Conservation</i>,
 <i>Conservation Biology</i>, <i>Journal of Wildlife
 Management</i>); two on movement (<i>Animal
 Migration</i>, <i>Movement Ecology</i>); and four that
 are taxa-specific, for birds (<i>The Auk: Ornithological
 Advances</i>), insects (<i>Annual Review of
 Entomology</i>), mammals (<i>Journal of Mammalogy</i>),
 and fishes (<i>Fisheries and Oceanography</i>). We read the
 introductions of all papers from the keyword search to verify their focus
 on the migratory phases of animal annual cycles, inclusive of staging and
 stopover sites. Next, we read the entirety of each identified paper and
 recorded geographic and taxonomic focus. Publications incorporating two or
 more species with co-occurring migrations were classified as “co-migration
 studies” either if a potential interaction between species was the focus
 of research or if the possibility of an interaction was discussed in the
 paper. For the purposes of the literature review, we did not include
 interactions among migratory species during stationary or resident phases
 (e.g., breeding or overwintering seasons). Our intention was to focus on
 species with overlapping spatiotemporal patterns in their migratory
 journeys and how they interact. We excluded review papers but included
 meta-analysis and modeling papers. We categorized co-migrant interactions
 by type.