Devote your entire existence to them!

Well, clearly we’re not all ready to be parents – or we are and we’re exhausted – because this was a very unpopular option. Just 25% of my audience chose to be the kind of parent that devoted everything to their offspring. So, let’s meet an animal that takes parental care to an extreme (and extremely dark) place…

Japanese foliage spiders (Chiracanthium japonicum)

These spiders have a pretty gnarly way of starting life. They show matriphagy, an unusual and extreme behaviour where the newly hatched spiderlings turn on and eat their mother – while she’s still alive!

The poor spider mother who gets eaten by her spiderlings
Kids can be so demanding. In the Japanese foliage spider, spiderlings will eat their mother while she’s still alive. Photo via kumomushi.web.fc2.com

This seems bizarre, but there are benefits to performing matriphagy. Researchers compared two groups of foliage spiderlings – the first group were allowed to eat Mum (as they do naturally) whilst the second group had their Mum whisked away before they could get their fangs in her.

What the researchers found was that eating Mum had three key benefits: firstly, it helped the spiderlings to grow bigger and secondly it gave them enough energy to moult into a more developed form – making them both fitter and better hunters come time to leave their nest. Finally, it also helped to reduce sib-cannibilism (where the spiderlings eat each other). They do this less when they’re eating their Mum so more spiderlings survive. Thanks Mum!

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A dead lace weaver mother (Amaurobius similis), another spider species that performs matriphagy. Photo: Flickr/Tone Killick

Finally, matriphagy is often thought to have evolved when mothers have little to no chance of reproducing again. By this logic, it makes sense to put absolutely everything into your first and only reproductive attempt (literally everything… like your whole bod) to give them the best possible chance at survival.

Back to the questions!
What you didn’t choose: Chuck ’em out into the big wide world

Screen Shot 2016-07-17 at 6.26.54 pmReference

Toyama, M. (2001). Adaptive advantages of matriphagy in the foliage spider, Chiracanthium japonicum (Araneae: Clubionidae). Journal of Ethology19(2), 69-74.