The silver rice rat, an endangered species unique to the Florida Keys, prefers to live along the water's edge for easy access to its low-tide marine species diet.
The study was publihed in Biodiversity and Conservation.
This proximity to the ocean inspired a team of scientists at the University of Florida to investigate the rats' movements in connection to historical tidal data collected over a 17-year period. Between 2004 and 2021, the sea level increased 0.142 metres, and the rats relocated to higher land, according to the study. The rats really relocated at a somewhat faster rate than the apparent change in sea level.
“We expected them to shift upslope, but it was surprising that the elevational range shift was so clear and more than we expected from the rise in sea level,” said Paul Taillie, the lead author, who completed the study as a postdoctoral researcher in the lab of Robert McCleery, UF/IFAS professor of wildlife ecology. “Part of this could be because sea level rise changes year to year. But there was also Hurricane Irma in 2017, which facilitated an upward push of coastal species.”
Taillie, who is currently an associate professor of geography at the University of North Carolina at Chapel Hill, noted that he and McCleery began studying on rice rats in 2019 when the USFWS became worried about the endangered species' fate following Hurricane Irma.
“We still don’t know where the rats go during hurricanes, but we do know that they were around after Hurricane Irma,” Taillie said. “They might climb up trees and wait for the storm surge to subside, and then come back down and rebuild their nests. They can swim, too.”
Taillie and McCleery collaborated with the USFWS, which had previously gathered data on rice rat migrations on one Keys island, to better understand how the rice rat responded to changes in sea level rise.
The rats in that study were captured and equipped with telemetry collars, allowing researchers to watch their travels. Taillie and McCleery revisited this data in 2021, using a similar technique to follow rats on three of the islands. They then compared the elevation of each data set to the sea level at the time the data was gathered.
“Telemetry is very tricky. You first have to catch the animals and get the collars on them, and even when you do that, you may get some malfunction,” Taillie said. “They may fall off, or the rats like to chew off the antenna, and they will eventually gnaw off the collar.”
Fortunately for the researchers, silver rice rats keep to a fairly predictable routine. They nest under bushes or shrubs at very low elevation, taking advantage of low tide to reach their below-sea-level prey, which include small crabs and snails.
“The rice rat will come out of the nest when the tide is out, an elevational migration of just a few centimeters,” Taillie said. “Originally, we thought that, because this is a coastal species occurring at the very lowest elevations, we might see them benefit from sea level rise, but they’re very restricted in terms of their diet and the environment, living in a very narrow band of the coastal zone. They’re sensitive to these changes.”
McCleery added that the study showed that while animals can adapt to sea level rise, there are limits to their resilience.
“Projecting trends into the future, we found dramatic declines in the amount of habitat that would be available for rats in the coming decades if no actions are taken,” McCleery said. “This highlights the vulnerability of Florida’s unique coastal wildlife to sea level rise in the years to come.”
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