Migration in the Anthropocene: how collective navigation, environmental system and taxonomy shape the vulnerability of migratory species

Abstract

Recent increases in human disturbance pose significant threats to migratory species using collective movement strategies. Key threats to migrants may differ depending on behavioural traits (e.g. collective navigation), taxonomy and the environmental system (i.e. freshwater, marine or terrestrial) associated with migration. We quantitatively assess how collective navigation, taxonomic membership and environmental system impact species' vulnerability by (i) evaluating population change in migratory and non-migratory bird, mammal and fish species using the Living Planet Database (LPD), (ii) analysing the role of collective navigation and environmental system on migrant extinction risk using International Union for Conservation of Nature (IUCN) classifications and (iii) compiling literature on geographical range change of migratory species. Likelihood of population decrease differed by taxonomic group: migratory birds were more likely to experience annual declines than non-migrants, while mammals displayed the opposite pattern. Within migratory species in IUCN, we observed that collective navigation and environmental system were important predictors of extinction risk for fishes and birds, but not for mammals, which had overall higher extinction risk than other taxa. We found high phylogenetic relatedness among collectively navigating species, which could have obscured its importance in determining extinction risk. Overall, outputs from these analyses can help guide strategic interventions to conserve the most vulnerable migrations.This article is part of the theme issue 'Collective movement ecology'.

Collective animal navigation and migratory culture: from theoretical models to empirical evidence

“…This predicted collapse is due to an Allee effect, whereby positive feedback between reduced population size and reduced benefits from collective navigation (regardless of mechanism) leads to further reductions in the population size. Indeed, sudden population collapse has been observed in many group migrating species [ 100 ]. Further, migratory distance in wildebeest may be linked to population size [ 101 , 102 ] and in the case of caribou, migrations have stopped altogether when population sizes became low, only to recover when the number of animals increased [ 103 ].…”

An analysis of threats and factors that predict trends in Canadian vertebrates designated as at-risk

“…Broad-scale quantitative assessments on the impact of threats on population trends are rare. Recently, several studies have investigated large-scale relationships between predictor variables and vertebrate population trends, many of which rely on data from the Living Planet Index (LPI) Data Portal (Craigie et al 2010;Collen et al 2011; Barnes et al 2016;Leung et al 2017;Daskalova et al 2018;Hardesty-Moore et al 2018;Spooner et al 2018). For those that incorporated biodiversity threats, only a subset of threat categories was included.…”

Long‐term effects of land‐use change on bird communities depend on spatial scale and land‐use type

“…As mobile organisms that can move freely between habitats with a diverse suite of body size, feeding, and behavioral traits, bird community structure and composition can quickly change in response to environmental perturbations on short-time scales (Thorn et al 2018). As long-lived vertebrates that may or may not adapt to changing conditions, population responses of individual species may not be consistent over longer time scales (Hardesty-Moore et al 2018). Birds also perform a wide range of important ecosystem processes including pollination (Zanata et al 2017), seed dispersal (Sekercioglu et al 2004), and can also be important topdown controls on lower trophic levels (Gruner 2004).…”