I was riding the same path a couple of years ago, 23km into a 50km ride, just about as far from home as I could get. I saw a snake across the left hand side of the path.
I saw it well enough to know that the bitey end was off the left hand side of the path and there was plenty of room to scoot around on the right. I stop pedaling and I think the ratchet noise of the free hub startled the serpent and it decided that it was no longer safe to be on the path. Unfortunately instead of going straight off the path, it did a 180 and came back towards where I was planning to pass by it.
If you believe Darwin et al, our evolutionary instinct to avoid snakes dates back perhaps millions of years, but we have only been riding bikes some 150 years. My body (brain obviously offline), pulled the cleat on the left side where the snake was coming from (all ok so far), and lifted it as far from the snake as possible (still ok), and then jammed my foot in the spokes in front of the fork (it gets bad now).
All that forward momentum had to exert its energy somehow and my back wheel and backside overtook my head as I exited the vehicle over the handlebars. It is at this moment (mid fall) I noticed a black shape move out in front of me out of the corner of my eye. I had plenty of time to think it could only be the snake, as physics was pretty much governing what would happen next and my mind was therefore free to consider other things.
The next thing I remember is standing up looking left and right to see where the snake had gone. Thankfully nowhere to be seen, only my black water bottle that had also decided to abandon ship. Oh well at least that was the black shape I saw as I fell.
Now it was time to assess the damage. Collarbones intact, and no claret to be seen. Checked the knees, nothing. Back moved ok. My left big toe was sore though, couldn't figure that out at the time.
I then picked up my bike and saw a small rip in the seat. But nothing else that was obvious. I went to get back on and found that after half a revolution the front wheel had jammed. I hopped off and looked at the front wheel and it was jammed on the brake blocks. I release the brakes and the wheel then jammed on the fork!
It was then I noticed that the three of the blade spokes had been ripped out of the hub. Ah, that's why my toe hurts. Later the bruise across my toes would show exactly where the spoke had hit the foot. My advice, always wear sturdy shoes.
So then I have to call my wife and get her to pick me up from the nearest freeway exit and I had to walk my bike back in a wheely.
That slippery serpent resulted in a $400 repair bill, that thankfully the insurance company paid $300 of it.
To this day I still don't know how I went over the handlebars at 30kmh without even getting a scratch!
YES, look out for snakes on the southern bike path. But even with snakes (and kangaroos) it is still not as dangerous as the northern bike path!
Hell is riding home into the Perth south wester