Egg-laying mammal suffers in a warming climate

On my recent trip to Australia, I saw many of the country’s wonderfully weird animals. Unfortunately, albeit not for lack of trying, I did not manage to see the species I was most curious about: the platypus. Now, it seems it may soon be even harder to spot one of these interesting animals.

New research shows that, as with many other species, the platypus habitat is being impacted by climate change, specifically the animals are suffering from the warming of the Australian continent.

Platypus-sketch.jpg

A colour print of platypuses from 1863. Author: John Gould. Source: Wikimedia Commons.

The platypus is truly remarkable: it is one of the few species of mammals that lay eggs.
It is also peculiar in that there is no other animal with similar looks.

In fact, the first European scientist to describe the platypus, the British naturalist George Shaw in 1799, initially thought the specimen he was examining to be an elaborate hoax. According to the Australian Platypus Conservancy website, “he even took a pair of scissors to the pelt, expecting to find stitches attaching the bill to the skin.” He thought someone had sewn a duck’s beak onto the body of a creature similar to a beaver.

Platypuses are semi-aquatic animals with mammalian fur and broad, flat tails like those of beavers, but they have duck’s beaks and lay eggs. Their reptilian gait, the ability to sense electric fields through electroreceptors in their bills, and the fact that the males are capable of delivering venom (a rarity among mammals), only add to the bizarreness of the species.

Who wouldn’t want to catch a glimpse of such an animal? Unfortunately, even if you travel to their native habitat in eastern Australia and Tasmania, you’ll have a hard time finding one in the wild.

The easiest places to spot a platypus are large rivers and small streams as the animals spend much of their time in the water foraging for food, and hide in burrows when outside. However, they are typically visible only when they resurface for 10 to 20 seconds in-between dives and are hard to identify in a fast-flowing stream. They are also alarmed by noise and sudden movements so keep their distance from the less-quiet observer.

According to a new study, lead by Professor Jenny Davis (Monash University, Australia) and published in the journal Global Change Biology, the love of water of this species is precisely why it is vulnerable to climate change.

The reason for this is the animal’s fur. On one hand, this fur coat keeps the platypus insulated for up to 10 hours a day in water with temperatures that can go down to zero degrees Centigrade. But in warmer waters it will make it harder for the animal to cool down. (Thermal infrared images show that the platypus only loses body-heat from its eyes, which are closed under water.)

“The highly insulating fur is an asset for surviving in cooler climates but becomes a liability in warmer conditions,” Prof. Davis told the BBC.

One of the platypus cooling strategies is remaining in its burrow. However, the animal needs to eat about 20% of its body weight each day, meaning that it spends many hours looking for food. And the water is where the shrimps, crayfish and insects that make up its diet are. The platypus can’t stay in its burrow for too long or it will starve.

To find out exactly how vulnerable the species is to the warming of the Australian continent, the team started by examining the known distribution of the platypus. They found out that both temperature and rainfall are factors that determine where the species is present.

They then set out to determined what factor was more important. This was done by analyzing historical records of the distribution of platypus over the past two centuries.

Surprisingly, researchers found that rainfall was the determining factor until about the 1960’s. But since then, the temperature has been having a bigger influence on the distribution of platypus on the Australian continent.

As explained in the article, “this correlates directly with the change in the annual maximum temperature anomaly from cooler to warmer conditions in southeastern Australia.” In other words, the warmer temperatures drove the platypus out of regions in south Australia that the species previously inhabited.

As the climate continues its warming tendency, both higher water temperatures and drying water streams will have an effect on the platypus way of life. The new research suggests that “there is real cause for concern over the future status of this species,” the authors write.

At present, the animal is not in danger of extinction. Moreover, if current average temperatures continue to rise, the species will probably adapt, as it did in the past, by moving to cooler parts of Australia such as Tasmania and other islands.

However, because they are so hard to spot, there are very few accurate estimates of platypus numbers. This means that it could take a while before someone notices they are disappearing from places where they were once abundant.

It seems one more species may fall prey to climate change. And as BBC’s Matt Walker writes, “not just any easy-to-ignore species, but an evolutionary icon, and an animal symbolic of the wildlife on an entire continent.”

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6 thoughts on “Egg-laying mammal suffers in a warming climate

  1. Laura Wheeler

    What a quirky little story about George Shaw… thinking the “specimen” he was examining was an elaborate hoax and that someone had sewn a duck’s beak onto a beaver! Hehe! I guess a platypus does look a bit like a duck/beaver breed! They are usually described as a “hodgepodge” of familiar species.
    So many new things i have learnt from your post, that the platypus can sense electric fields, the males are capable of delivering venom and they must eat 20% of their body weight everyday!
    To add another fact to the bill, Platypuses do not have teeth, so they scoop up bits of gravel to help them to “chew” their meal! Wow it makes me wonder why I have not been more interested in them before. But it also makes me very sad that climate change is damaging their habitats.

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  2. Barbara Ferreira

    Hi Laura, I’m glad you liked the post. I was really pleased when found out about this paper on the BBC website. By writing a blog post about it, I got to report recent scientific research and, at the same time, write about the platypus. I really wanted to see one when I went to Australia — they are such interesting creatures!
    Thanks for that extra fact: if I remember right from the research I did for this post, platypuses do have teeth when they are born but end up losing them before adulthood!

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  3. Laura Wheeler

    Sadly I didn’t see one when I was travelling through Auz either!
    That is strange that they are born with teeth yet lose them before adulthood. I wonder what evolutionary reasoning is behind that? As they clearly need teeth…..?

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  4. Barbara Ferreira

    I’m not sure what the evolutionary reason is. All I found about it was a one-line sentence on wikipedia:
    "A platypus is born with teeth, but these drop out at a very early age, leaving the horny plates with which it grinds its food."
    Maybe it needs teeth when its young because the "horny plates" aren’t strong enough to grind food?

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  5. Mike Fowler

    Hmmm, they suckle milk when they’re very young, so it’d be nice to know exactly when they lose them. Wikipedia states that they drop out quickly, but they suckle for 3-4 months.
    It’s possibly an ancestral hangover, that evolution has done its best to get rid of (after hatching), but hasn’t quite got round to doing anything about the embryonic stages yet, possibly due to overlap with other developmental pathways. That’s all speculation though.
    Platypuses are incredibly cool though, as are all the monotremes!

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  6. Laura Wheeler

    Hi Mike,
     
    They are cool indeed!! And clearly they prefer the cool too 🙂
     
    Thanks for your thoughts, it seems like it is possibly an ancestral hangover… if anyone knows, do speak up!? 

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