• Question: I have a tricky question, do you know why crabs stand to the waves of the see? Or you know What are the changes in emotional behavior in koalas when they're alone or in a group? If you don't know them don't worry they're questions people never answered me:)

    Asked by Clara E to Carrie, Cedric, Ellen, Ines, Rupert on 7 Mar 2017.
    • Photo: Carrie Ijichi

      Carrie Ijichi answered on 7 Mar 2017:

      I’m guessing that some crabs stand at the waves of the sea because there is something there they really want. That might be a food source, being safe from predators or keeping the right moisture balance. It’ll probably depend on the species of crab though because they can be quite different.
      I don’t know very much about Koalas but I know social contact is important for them. We can’t tell exactly how an animal feels, but if they were isolated from other koalas they’d probably have negative feelings and feel more positive when they’re with familiar koalas.

    • Photo: Ellen Williams

      Ellen Williams answered on 7 Mar 2017:

      I don’t know about emotional behaviour in koala’s but I always understood koala’s in the wild to be solitary animals that come together only for mating (I watched a really interesting program once where a group of scientists were tracking koala’s to make sure they weren’t getting too close to the highways – apparently that is one of the greatest causes of mortality). That isn’t to say that koala’s in captivity should never have social partners – orangutans for example are solitary animals in the wild but are housed (reasonably) successfully in groups in zoos. Forcing any animal into an unnatural social group though can be detrimental to their welfare and may lead to increased aggression.

      I have no idea about the crabs, sorry! I can have a look on Dr Google if none of the other guys can help though. I do think crabs are very cute. I have done lots of sea swimming and in clear waters it is great fun watching the crabs race around underneath you!

    • Photo: Rupert Marshall

      Rupert Marshall answered on 7 Mar 2017:

      That is a tricky question. And I’m afraid I’m not an expert on crabs or koalas, I’m very sorry.
      But here’s a couple of interesting facts: shore crabs, the sort you get in rockpools, have blue blood because of all the iron – like they’re royalty or something. And fiddler crabs do stand up but it’s to wave their giant claw at females to try to attract them. In fact the males tend to wave their crabs in unison, like a Mexican wave. So there you have it: crabs stand up in waves to attract females 🙂

    • Photo: Ines Goncalves

      Ines Goncalves answered on 9 Mar 2017:

      Some species of crabs (maybe even all, I’m not sure) have pretty complex eyes. Fiddler crabs for example, are know not only for their one giant claw, but also for the fact that they have their eyes up on stalks (https://www.google.co.uk/search?q=fiddler+crab&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjonriDxcrSAhVDWxQKHakcA2cQ_AUIBigB&biw=1254&bih=630)
      This is because the cells in the stalks and in their eyes are arraigned in layers in different directs which allows them to expand or contract to let light in or keep it off if it too bright. This allows crabs to filter the light and especially polarisation (light rays that flow in the same direction) and helps them see better. For example, when we go to the beach and we stare at the water when the sun is shining it looks really bright so that when we then look away to the sand it may seem very dark. Fiddler crabs (and I think also other crabs) have ways to filter these differences in light so that they don’t get temporarily blind, which would make them vulnerable to predators.

      As for koalas… I’m afraid I don’t know much about them other than that a friend of mine told me they smell. :/

    • Photo: Cedric Tan

      Cedric Tan answered on 15 Mar 2017:

      Apologies for the delayed reply, these are great and challenging questions and I have had to think about them.

      I have seen crabs withstanding the waves of the sea in many of the rocky shores I have visited in Singapore, Croatia and Portugal. Importantly, I have noticed that they seem undisturbed by the waves and are actually feeding on the algae of the rocks. It is probably a good time to do it as the strong waves deter predators such as birds. This video might be related, from minute 1:00

      On your second question regarding Koalas. We have not been able to understand fully the emotional changes in koalas and in animals in general, that’s because they are unable to communicate with us to tell us how we feel. Interestingly, Koalas like being on their own (solitary) and only in group when they are young and with their mothers or when they want to mate. So I supposed they are ‘happier’ on their own most of the times.

      http://koalainfo.com/koalas-are-solitary-animals

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