Squirrel S-quarrels - Reds Dead With No Redemption?

So, now it's time to get down to some nitty-gritty stuff on invasive species. But first, here's my topic deciding thought process:

*Hmm what do people like? Cute things? Hmm.. what's cute? Unicorns! Damn they're not real... Teddy bears? Crap, not actually alive...*

Sorry Charlie, this blog just isn't for you...

Things were looking bleak, but luckily I came across  this video and thought a piece on the ongoing squirrel saga would be a good theme.

I'm sure most of us are aware of the UK's red squirrel decline, so I'm going to cover some things you may not be aware of. Ladies and gentleman, fasten your seat belts... we're taking a trip to Italy!

The red squirrel: endearing but endangered.

But before we jet off, consider this:

Imagine you're about to race Usain Bolt... let's say, for a succulent acorn 100m away. Given that you have the same transport resources (just yourself), who will win? Probably him right? You'll just have to get your food somewhere else...

BUT it turns out there are thousands of Mr Bolts and they are EVERYWHERE you used to get your acorns.

AND, even worse, you've now got the ruddy flu. That acorn is looking more and more unattainable... before you know it what was your territory now belongs to the Usains and then, the ruddy flu finishes you off. Damn...

It's hard to compete when you're up against someone more athletic.

That was a depressing scenario right? But that's (kind of) a metaphor for what the red squirrel has to deal with when in the same environment as greys. I mean, if you're not empathetic right now, you're probably heartless.

The grey squirrel, originally North American, arrived in Britain in 1876 and has had an Italian presence since 1948 (Bertolino, 2008). The spread is a concern as greys can have negative impacts on biodiversity, forestry and crops (Bertolino et al., 2013). 

In Piedmont, NW Italy, Bertolino et al (2013) confirm replacement of native reds by the invasive greys. In 1970 reds were 'widely distributed' and greys restricted. However, by 2010, reds were extinct in 120 out of 194 2 x 2 km² sites. Overall the red is no longer present in 1689 km² of area where it was previously. The significance of these changes is confirmed by statistical testing. 

A clear shift: Occupancy area of grey and red squirrels from 1970 to 2010 and fitted regression curves

So, why this trend? Time to step away from the metaphor to the real ecological goings on...

Native replacement is due to competitive exclusion that reds are unable to avoid (Wauters et al., 2002). The two species use the same food and space resources (Bertolino, 2008). The grey is bigger, faster and more aggressive (must be something about the Grey's Anatomy...), essentially meaning it gets dibs on crucial resources. This reduces juvenile body growth and breeding success of reds, both positive feedbacks accelerating their decline.

Scrat: Even the movies know that the greys get the acorns.

Ecologically speaking, niche partitioning is required for related species to co-exist in the same environment (Wauters et al., 2002). This means that they require different resources or have different methods of utilising the same resource. In this case, there is no niche partitioning and the red squirrel is, sadly, out-competed.

And, to top it all off, grey squirrels carry a squirrel parapoxvirus that does not affect them but causes high mortality in reds (Rushton et al., 2006). How nutty is that? 

Pox problem: Symptoms include death.

If the greys spread across the Italian border then the long term survival of the native red in Europe is under serious threat (Bertolino et al., 2013).

Luckily for red squirrels, schemes are in place to save it, including in East Anglia and, as we saw before, the Isles of Scilly. In my opinion, programs like these are essential if we want to preserve biodiversity in the face of threats such as invasive species and Italy should attempt similar projects to save the red squirrel and prevent the grey's further spread. Especially as the greys are only present in Europe because us humans introduced them.

If action is taken, the reds may yet have their redemption.

Over and out

The Invader Inspector