West Indian Manatees Use Partial Migration to Expand Their Geographic Range Into the Northern Gulf of Mexico

Abstract

Partial migration provides a mechanism for species to shift their geographic ranges into new, environmentally favorable regions but has been poorly studied as a means to alleviate effects of climate change. Populations at the edge of their geographic range are ideal to investigate how migratory behaviors may enable range expansion as adjacent areas become more climatically favorable. We determined the contribution of partial migration to the range expansion of West Indian manatees (Trichechus manatus) using GPS data from tagged individuals that migrated between the northern Gulf of Mexico (nGoM) and primary habitat in peninsular Florida. Most of these manatees migrated to the nGoM annually and exhibited high site fidelity among years. Many individuals spent cumulatively more time in the nGoM than in peninsular Florida, indicating the nGoM is a regular part of their geographic range, and they returned to peninsular Florida to meet temperature-related physiological needs for survival. Autumn migrations most frequently terminated at Crystal River, Florida, and manatees that commenced migration late in the season stopped less frequently and had more directed movements. Spring migrations most frequently terminated at Mobile Bay, Alabama, and several manatees quickly and directly migrated from Florida to nGoM stopover sites. Migrations ranged from 10 to 133 days in length, and variation in duration was primarily driven by use of stopover sites and directedness of travel. These data confirm partial migration as an important component of manatee migratory behavior that has already enabled range shifts for manatees on the U.S.A. Gulf of Mexico coast and has potential to facilitate future responses to climate change. As the most common type of migration across the animal kingdom, partial migration may provide a global mechanism for a diverse variety of species to resist the range limiting effects of climate change.

Ecological roles and importance of sea cows (Order: Sirenia): a review and prospectus

“…Today, ongoing climate change has the potential to shape ecological roles of sirenians -notably by altering their access to macrophytes, trophic impacts, and movements (e.g. Cloyed et al 2021).…”

Thermal microrefugia and changing climate affect migratory phenology of a thermally constrained marine mammal

“…In the United States (USA), the West Indian manatee (Trichechus manatus; hereafter manatee) is a vulnerable marine mammal species that is thought to comprise a single population of individuals employing various strategies of residency and movement. The species is known to use partial migration, including seasonal short and long-distance movements, making it an ideal study species to examine variation in migratory phenology under changing climate conditions (Deutsch et al, 2008;Cloyed et al, 2021). Manatee distribution within the USA is limited by physiological intolerance to sustained water temperatures < 20°C, traditionally restricting the species' winter range to peninsular Florida (Irvine, 1983;Bossart et al, 2003).…”

“…Types of thermal microrefugia typically used by manatees in peninsular Florida include warm water discharges created by industrial facilities, primarily power plants, or natural springs and passive thermal basins that retain heat without a constant inflow of warm water (Laist and Reynolds, 2005a, b;Laist et al, 2013;Valade et al, 2020). During warmer months, manatees disperse from winter refuge sites to access food and other resources throughout their range (Deutsch et al, 2003;Cummings et al, 2014;Hieb et al, 2017;Cloyed et al, 2021).…”

“…These microrefugia allowed for stepping-stone movements to previously unused sites at more northern latitudes (Laist and Reynolds, 2005a). Correspondingly, sightings of manatees in northern Florida and states west and north of Florida also increased (Fertl et al, 2005;Cummings et al, 2014;Hieb et al, 2017), and manatees are now documented as regular seasonal visitors to these areas (Hieb et al, 2017;Cloyed et al, 2021). Few studies, however, have examined migration and habitat selection in these regions (Deutsch et al, 2003;Cloyed et al, 2021;Cloyed et al, 2022).…”

“…Correspondingly, sightings of manatees in northern Florida and states west and north of Florida also increased (Fertl et al, 2005;Cummings et al, 2014;Hieb et al, 2017), and manatees are now documented as regular seasonal visitors to these areas (Hieb et al, 2017;Cloyed et al, 2021). Few studies, however, have examined migration and habitat selection in these regions (Deutsch et al, 2003;Cloyed et al, 2021;Cloyed et al, 2022). In particular, no studies have attempted to identify thermal microrefugia outside of Florida that may affect the phenology of seasonal manatee migrations.…”