The Hidden Threat of Processionary Caterpillars to Dogs in Portugal

At the risk of sounding dramatic, if you’re traveling to Portugal with a dog, there’s an increasing threat you need to be aware of – one that’s lurking on hiking trails and even beachside paths across the country.

Processionary caterpillars are becoming a growing danger in Portugal, but don’t worry – we’ve got you covered. Here’s everything you need to know to keep you and your furry companion safe while exploring.

What Are Processionary Caterpillars?

Processionary caterpillars, especially the pine and oak species, are the larvae of moths that are common in Southern Europe, particularly Spain & Portugal.

They are easily recognisable by the way they move in formation in one long, trailing line – a behaviour that gives them their name. While these caterpillars are fascinating to observe, they’re also a potential danger: each caterpillar is covered in tiny, hair-like toxic spines.

These hairs can cause severe allergic reactions in humans and animals, ranging from skin rashes to respiratory issues if inhaled.

What Do Processionary Caterpillars Do?

Aside from being a risk to dogs, small children and even adults in some cases – which we’ll get onto shortly – the main goal in a processionary caterpillar’s life is to fatten up and get ready to pupate into a harmless processionary moth ( thaumetopoea pityocampa ). We’ve all read the hungry hungry caterpillar book, right?

They do this by gauging on pines & oak trees before descending to the forest floor and marching to their chosen spot to pupate underground.

They then emerge some time later as a silk moth and the cycle starts again, with the moths laying their eggs on nearby trees.

How Dangerous Are Portugal’s Processionary Caterpillars?

To understand how dangerous they are, we first need to look at where the danger comes from: their toxic hairs… but how can these tiny hairy caterpillars be any risk at all to things as big as a human or dog?

When they’re in the marching phase, if they feel threatened at all, they will shoot those tiny hairs out in all directions for several feet in the hope of making the danger go away. Those tiny hairs are packed with a toxin that is extremely irritating if they get caught in your eyes, nose or mouth, and they’ve even been known to cause severe allergic reactions for those more sensitive to bites and stings.

Of course, it’s during this phase that they’re most likely to come into contact with humans and dogs which is why they’re a danger that you need to be aware of when out and about.

It’s less likely for a human to have a severe reaction, but the Processionary Caterpillars rash and irritation can last for days so your best bet really is to avoid disturbing them.

If you do come into contact with them you can rinse the area and use anti-Inflammatory creams or antihistamines to ease the discomfort, but if symptoms are severe or on your face you’ll need to seek medical attention.

Processionary Caterpillars And Dogs

Now, as adults we can keep a better eye out when walking and jump over them if we see them.

Dogs, however? Have a tendency to go sniffing around in bushes, pine needles and leaves unaware of the risks carried by the Processionary Caterpillars in Portugal.

Which is where things can get really scary. Dogs who have come into contact with the toxic hairs have gone on to lose parts of their tongue and/or nose, if not their life from the reactions they’ve had.

They don’t have to come into direct contact either. Simply stepping on stray hairs can cause discomfort, which can cause a dog to lick their paws and get the hairs in their mouth and airways.

How To Know If Your Dog Came Into Contact With A Caterpillar

If your dog has been off lead and you’re not sure what they came into contact with, these are some of the signs to look out for:

• Drooling
• Panting
• Vomiting
• Itching their face
• Swelling 

If you spot any of these, or know your dog got near the killer caterpillars you need to go to a vet urgently.

There are a few rumoured processionary caterpillars treatment ideas that you can do at home but honestly? It’s best to just rush to the vets rather than waste precious time trying to fix it yourself.

National Emergency Number – 112

Poison Information Centre – (00351) 800 250 250

National Health Service (SNS24) – (00351) 808 24 24 24

Where Do Processionary Caterpillars Live?

Processionary Caterpillars live mostly in Pine Forests all around the country – as well as other countries in Southern Europe – but are more prominent the further south you go.

Once you reach the Leiria District and head down towards the Algarve, you’ll notice more and more of the candyfloss-like Processionary Caterpillar nests in the pine trees.

When Are Marching Caterpillars A Risk?

This is where things get a bit tricky.

There used to be predictable seasons for when the processionary caterpillars in Portugal would leave their nest but now that weather patterns are changing and winters are more mild, in some areas it seems they are almost all year round.

I’ll outline the processionary caterpillar seasons below but please be aware of nests regardless of when you’re travelling Portugal.

Processionary caterpillars nests are built through December, January and February. They’re easy to spot in pine trees because they almost look like balls of cotton wool or candyfloss. If you’re travelling Portugal and spot these, the nests themselves are harmless but you’ll want to be cautious about the ground around them.

The traditional caterpillar season in Portugal is January through to April but they’re leaving earlier and earlier each year and we actually stumbled across some in OCTOBER in our local woodlands.

For Leiria District specifically, which is where we live, it seems there are now two seasons. The first is between March and June and the other is Aug to October. However, all it takes is for this season to start earlier, and last longer and we’re going to have caterpillars all year around. 

It’s also worth noting that they can march for 3 -5 km. So you need to be on alert in towns and streets that are near pines too.

How Do You Get Rid Of Hairy Processionary Caterpillars?

If you live in Portugal and have pine trees on your property, you’ll need to have a plan on how to get rid of them.

They’re considered one of the most destructive invasive species in Portugal because of how quickly they can eat through the trees, so aside from reporting an infestation to your local council here are a few quick tips to help keep them at bay:

• Remove Nests. This should be outsourced to someone who knows how to do this safely, but at very least you need to wear protective clothing and eyewear.
• Put a sticky trap around the trunk of the tree to stop them reaching the floor once they start marching. This might need to be replaced frequently (with protective clothing) because they can crawl over dead caterpillars once the trap starts to fill up.
• Attract local bird life to act as natural pest control. Bats and wasps do the trick too.
• Remove pine trees. Honestly? This was our plan when we were looking for houses in Portugal. It’s easier than dealing with the nests each year, and of course just because you don’t have them one year doesn’t mean the moths won’t lay eggs the next year.