Wild boars. Bears. Wolves. Poisonous snakes. Northern Spain has all those, but honestly you are more in danger of slipping on loose rocks and getting injured, or getting struck by a vehicle or even getting struck by lightning than you are of being attacked by wildlife.
I wouldn't even give it a thought.
I'm from a bunch of islands at the opposite end of the earth to Spain where anything remotely dangerous with 0, 2, 4, 6 or 8 legs(excepting the Katipo spider) had ancestors that came or hitched a ride on a seagoing vessel of some kind and currently resides in a prohibitively expensive commercial habitat. So I too was very interested in things that might bite and what to do if they did.
I had a link with all the snakes for identification purposes. Over 7 weeks on the Salvador and Primitivo we saw quite a few dead snakes and pencil -thin tiny live snakes. It became amusing to photograph tiny snakes and giant slugs. A few times we'd see a snake whizzing out of our way in the long grass in the daytime. However we became a little complacent and on our last evening of walking on the grass verge into Negriera, we startled a sleepy Lataste viper which was too cool to whizz away and did a very impressive aggressive display - but didn't actually bite us. Avoid complacency - especially at dusk and dawn.
Our first night in Leon my phone alarm rang in Kiwi time and I dashed out to the toilet to try to silence it and met a peregrina with a tick behind her knee who instructed me in how to remove a tick correctly. We wore long sleeves and leggings in pasture and never got a tick.
We never had bedbugs.
We never saw or heard a wolf.
We walked through many boar-hunting preserves and saw a few hunters and their dogs, but never a boar. Maybe they didn't see any either...
Most of the dogs minded their own business. As a precautionary measure I swung a Pacer pole in front of and behind me and walked between dogs and daughter to protect both of our legs. All except one small dog took the hint and that one was retrieved by its human after a display of fangs and growl.
We thought there were 8 re-introduced bears in Asturias, but we were wrong. There are really over 120 and there are groves of nuts and fruit being planted for the mama and baby bears rather than peregrinos - but we saw neither bears nor sign thereof.
I'd read that people had had alarming encounters with cattle, and had been prodded by inquisitive steers when walking at home so I read up on how to keep cows and steers happy, and avoid bulls. The Spanish cows and steers were all pretty happy and the bulls well-fenced so no worries there.
I researched those vultures too. Apparently they can tell if you're dead, so are no threat while you're alive and could save freight costs of shipping your remains home should said remains be weighed. So I felt quite relaxed about them.
Back home we drive on the left. I got talking to an old lady from Pola de Lena who advised me to always walk izquierda or else the traffic would get me from behind like El Torro.
So 2 legs and 4 wheels were the most hazardous and we survived and thrived unscathed.
