With temperatures changing so dramatically around the world, wildlife is often forced to relocate to find suitable habitat – and scientists are working hard to understand how many species struggle when trying to find new homes .
Animals that go to higher elevations face two problems: cooler temperatures and thinner, less oxygen-rich air (hence, breathing is more difficult). In a new study, a group of Anna’s hummingbirds (Kaleb Anna) on a flight at an altitude of 1,200 meters (4,000 ft) above their natural habitat.
Curiously, the hummingbirds’ metabolic rate actually decreased while they were flying. They also fly shorter periods of time with less efficiency, most likely due to lack of oxygen.
While temperatures may be warmer in the future, cooler altitudes will have a chilling effect on a hummingbird’s sleep patterns. When the birds slept, they went into a kind of mini-hibernation more often, which also reduced their metabolism by an average of 37 percent.
The team behind the study say getting to higher ground will be a major challenge, at least in the case of hummingbirds.
In their report, the researchers write, “Our results suggest that low oxygen availability and low barometric pressure can pose difficult challenges for hummingbirds moving from top to bottom due to rising temperatures, especially when there is little long-term acclimation.” published paper.
These birds are already being forced to move their homes in response to rising temperatures, and they can currently be found at altitudes between 10 and 2,800 meters (33-9186 ft). This covers a distance and a range of temperatures, but the research team was interested to see if there was an upper limit.
In this study, 26 hummingbirds were flown from across the current altitude range, and all struggled equally to adapt. However, the study found that people from higher elevations tended to have larger hearts to improve oxygen distribution throughout the body.
The researchers used a variety of methods to measure sleep levels and metabolic rate in hummingbirds, including using a funnel filled with syrup to encourage the birds to eat while also monitoring their oxygen consumption.
Production of carbon dioxide during sleep, another indicator of metabolic rate, was also recorded. Hummingbirds spent at least 87.5 percent of the night in a small, energy-efficient hibernation, compared to 70 percent normally. Again, this was consistent no matter what height the hummingbirds were photographed from.
“This means that even if they come from a warm or cold place, they hibernate when it’s very cold, and it’s cold.” Ecologist Austin Spence says: von der University of Connecticut.
Hummingbirds, in this case, make great study subjects due to their high-energy lifestyle. They are able to cope with a wide range of weather conditions, but it seems that traveling to higher ground might be too far for them – unless they do it slowly enough for their bodies to adjust.
However, species don’t necessarily need to fly to higher altitudes to find cooler temperatures, as they can also change latitudes – and researchers think these hummingbirds may need to venture north at some point.
The study authors also suggest that future studies and models should not simply look at temperature as a trigger for species to change location. Other factors, including water and oxygen availability, must also be considered.
“To fully understand a species’ ability to change in response to global warming, it is necessary to assess its physiological performance within its current range and to compare it to performance beyond its current range,” researchers write.
The search was published in Journal of Experimental Biology.