18/02/2020

(AU) Mammal That Mates Itself To Death Will Struggle Under Climate Change, Scientists Say

Newsweek - 



A small Australian mammal that mates itself to death will struggle under climate change, scientist have said.
For a study published in the journal Frontiers in Physiology, a team of researchers investigated how climate change may affect the yellow-footed antechinus, or Antechinus flavipes—a marsupial that has a rare and unusual mating behavior known as "male semelparity." This is where a whole generation of males die in their first mating season.
In the case of the yellow-footed antechinus, the mating season may last two to three weeks and takes place in the Australian winter and spring months, depending on where in the country a given population is located. In this time the males succumb to stress and exhaustion after having copulated with so many female partners.In the latest paper, the scientists found that if this marsupial experiences warmer temperatures during the early stages of its life, it may be less capable of adapting to and surviving the winter. The marsupials are born between September and November and so they spend their first months in the Australian summer and autumn, which are expected to become hotter under climate change. This could mean that many males will be unable to survive the winter in future, so would be incapable of mating.
The scientists, led by Clare Stawski from the University of New England and the Norwegian University of Science and Technology, exposed captive-bred juveniles to either "cold" or "warm" temperatures—17 and 25 degrees Celsius (63 to 77 degrees Fahrenheit.) The mammals were about 100 days old at the beginning of this experiment, and had just finished being weaned by their mothers.
Stawski and colleagues then monitored various factors such as body mass and the activity levels of the animals.
Once the juveniles had reached adult size, at around 220 days of age, the scientists conducted a series of temperature tests and measured the basal metabolic rate—the number of calories required to keep the body functioning at the most basic level while it is resting—of the animals.
In one test, the mammals were placed in a chamber where the temperature was 18 degrees Celsius. This was then increased by 4 degree Celsius increments every two hours, until the temperature reached 30 degrees.
In the second test, the initial temperature in the chamber began at 14 degrees Celsius and was reduced to 10 degrees after three hours.
The results showed that temperatures experienced by juvenile yellow-footed antechinuses during development can impact the behavior and physiology of the animal.
Juveniles placed in the "cold" group just after being weaned were able to adapt their metabolic rate as the temperature around them changed. But the metabolic rate of those juveniles that had initially been placed in the warm group did not change when exposed to colder temperatures.
Stock photo: A yellow-footed antechinus. iStock
According to the researchers, this indicates that the juveniles raised in warm conditions may have less "phenotypic plasticity"—the ability of an organism to adapt to environmental influences.
This has significant implications for the yellow-footed antechinus given temperatures in Australia are expected to rise with climate change, according to the Commonwealth Scientific and Industrial Research Organisation (CSIRO)—an Australian government agency.
"We hypothesize that as individuals raised in warm conditions appear to have less phenotypic flexibility, they may not be able to respond effectively to prolonged increases in temperature and therefore struggle throughout winter," Stawski told ABC News.
This lack of phenotypic plasticity in juveniles raised in warm conditions does not bode well for a species that is dependent on a single breeding event and experiences "a complete population turnover," the authors wrote in the study.
This makes the species particularly vulnerable to potentially deadly environmental events, such as heatwaves, which are expected to become more common under climate change, according to CSIRO.
If these events occur in the periods when there are no males, and only pregnant or lactating females, there is a chance that significant numbers of females could die, meaning fewer offspring, leading to a subsequent reduction in the population.
While the latest study focused only on the yellow-footed antechinus, which has a relatively wide distribution across Australia, other species in the same genus (group of species) with smaller ranges may be even more severely affected by climate change, Andrew Baker from the Queensland University of Technology, Australia, who was not involved in the paper, told ABC.
Scientists only know about a handful of species that display male semelparity. Most of these are invertebrates, or animals without a backbone, making Antechinus an unusual case.
The Frontiers in Physiology paper is not the only recent piece of research to highlight the plight of animals in Australia under climate change.
One study published in the journal Biological Conservation found that populations of the iconic platypus were at risk in the face of increasingly dry conditions. The researchers found that under current climate projections, platypus numbers could decline by up to 73 percent by 2070.

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