Will spiders bite my dog?

I field a lot of questions about spider bites, and I have argued that spider bites are exceedingly rare (for humans). But what about our pets? Do our furry friends get bitten by spiders? If they get bitten, how do they react? Let’s look at this, move beyond anecdotes, and see what science has to say on the topic!

Can spiders bite my dog or cat?

The short answer to this is: YES. Some spiders are physically capable of biting mammals, including dogs and cats.


This is my dog, Abby. Should she be scared of spiders?

The longer answer is that we really don’t know about this for the vast majority of spider-pet interactions, and even if spiders can bite mammals, I would argue that such events are relatively uncommon. Spiders certainly don’t hunt dogs or cats, and when bites do occur, they are likely quite accidental. Your puppy Ralph can be quite energetic and rambunctious, and stick his snout into a dark corner which may be home to an arachnid. I’ve certainly seen my cat “play” with insects and spiders, and ping-pong an arthropod across the kitchen floor. However, we certainly have to get a little lucky to see an actual spider-pet interaction, and dogs and cats can’t tell us whether they have been bitten by a spider. Proper verification of any bite requires evidence.

In some cases, the evidence isn’t in dispute, such as the paper by O’Hagan and colleagues who state quite clearly in their peer-reviewed paper:

Two 9-week-old Chihuahua pus weighing 960 grams and 760 grams were seen to be attacked and bitten by a large black spider. The spider was killed” (O’Hagan et al. 2006).

Right: the puppies were seen to have been bitten by a spider, and presumably the pet-owners know what a spider looks like. Also, that paper was co-authored by a well-known Arachnologist, Dr. Raven – having an arachnologist involved in these studies is important, and gives credibility to the incident. This is a good example of a verifiable interaction between dogs and spiders.

There’s another detailed paper by Isbister et al., outlining spider bites (in the family Theraphosidae, a family of Tarantula spiders) in humans and dogs: their evidence isn’t in dispute either, and in two cases, the human was bitten just after the dog was bitten. That’s pretty clear!

Without clear evidence, however, it becomes tricky: there’s a case report of a Brittany spaniel being brought to a hospital, with “swelling on its muzzle, left of the midline” (Taylor & Greve 1985). This became a ‘suspected’ case of loxoscelism, and assumed by the authors to be caused by the brown recluse spider. However, diagnosis of loxoscelism is very difficult, and other more probably causal agents could be investigated. Stated another way: it may not be the spider. Don’t blame the spider without adequate evidence. As Rick Vetter states on his excellent website:

There are many different causative agents of necrotic wounds, for example: mites, bedbugs, a secondary Staphylococcus or Streptococcus bacterial infection. Three different tick-inflicted maladies have been misdiagnosed as brown recluse bite…” (Rick Vetter, accessed Feb 9 2015)

It’s also very tricky to look at a ‘wound’ on a pet and determine whether or not a spider was involved. I would suggest if there are multiple wounds, or lacerations, multiple bumps and bruises, it is unlikely to have been caused by a spider, and other more likely causal agents should be investigated (e.g., punctures, skin reaction to something, or perhaps an insect sting, or fleas).

So, bottom line: although I think direct interactions between spiders and our pets are relatively rare, spiders are certainly capable of biting our dogs or cats.


Do cats and spiders mix?

What happens if my pet is bitten by a spider?

If there is clear evidence that a spider bit your pet, there are really only two outcomes: nothing will happen (or your pet may exhibit mild reactions that may not be immediately obvious), or there will be clear, definable symptoms, and these may lead to more serious consequences.

I think the first scenario is more common than the latter, largely because we just don’t have a good way of tracking the frequency of spider-pet interactions, and as is the case with humans, the vast majority of spiders probably aren’t venomous to our pets. Our pets certainly get ‘mildly’ sick all the time – I think of the times that my dog got an upset stomach, and I always assume she tracked down some ‘snacks’ when on an off-leash run (I think she is quite fond of rabbit droppings…).

Science does provide us some data about more serious reactions when our pets do get bitten by certain spiders. The paper by Isbister et al., from 2003, is quite detailed, and gives case studies of a number of verified bites by spiders on humans and canines in Australia. Here’s the alarming part:

There were seven bites in dogs, and in two of these the owner was bitten after the dog. In all seven cases the dog died. In one case… the Alsatian died within 2 h of the bite. In two cases small or juvenile dogs died in less than an hour…” (Isbister et al.)

In this paper, the effects on humans were relatively minor, but this was not the case for our furry friends – reactions were severe and fast and resulted in death. The poor little Chihuahua pups mentioned earlier were equally unlucky, as reported by O’Hagan et al. Although both of these studies were from Australia, and involved only one family of spiders, it’s certainly scientifically interesting that canines were affected so strongly, and their reactions provide opportunities to further research the components of spider venom (e.g., see Hardy et al 2014).

There is also some evidence that cats may be affected by spider venom: research reported by Gwaltney-Brant et al, and Hardy et al, stated that toxicity studies result in fatalities of our feline friends:

Cats are very sensitive to the effects of widow venom. In one study, 20 of 22 cats died after widow-spider bites, with an average survival time of 115 h. Paralysis occurs early in the course; severe pain is evidenced by howling and other vocalizations…” (Gwaltney-Brant et al.*)

That’s pretty grim. Interestingly, this case reports on envenomation by widow spiders in the genus Latrodectus (e.g., the genus that includes all the black widow spiders that occur in North America) – these spiders are relatively common in some habitats, and can certainly live in proximity to humans. Looking at Australia again, Hardy et al. state that cats are seemingly unaffected when bitten by female funnel-web spiders in Australia. So,  effects of spider venom on cats and dogs differs depending on the type of spider, and even our pets aren’t likely to respond the same way to different kinds of spiders. Clearly, it is difficult to generalize about any of this!


Black widow spider – bad for cats? (photo by Sean McCann)

In sum, I have presented some details about spiders and how they might interact with our beloved pets. It’s fair to say that our pets certainly may get bitten by spiders, but overall I would argue such interactions are relatively rare. However, dogs and cats are certainly not immune to spider venom, and there is evidence to suggest they might have strong negative reactions to spider bites.

Despite this, I don’t see this as reason to panic or start stomping on any arachnid that wanders across your living room floor. The evidence we have is still relatively limited, and we just don’t have much information about effects of venom on pets, for those spiders that commonly inhabit our homes. I also think the lack of evidence is important to mention: if our pets were getting bitten by spiders on a regular basis, there would be more papers on the topic, and certainly more cases where anecdotes made the transition to evidence.

I think it’s possible to love your pets AND be an arachnophile. That’s certainly how I live my life.

[A BIG thanks to Maggie Hardy, Daniel Llavaneras and Catherine Scott, for helping point me to literature on this topic]


Hardy, M.C., J. Cochrane and R.E. Allavena (2014). Venomous and Poisonous Australian Animals of Veterinary Importance: A Rich Source of Novel Therapeutics. Biomed Res. Intl. doi: 10.1155/2014/671041

Isbister, G.K. J.E. Seymour, M.R. Gray, R.J. Raven (2003). Bites by spiders of the family Theraphosidae in humans and canines. Toxin doi:10.1016/S0041-0101(02)00395-1

Gwaltney-Brant, S.M., E.K. Dunayer and H.Y. Youssef. (2007) Terrestrial Zootoxins. Ch. 64 in Veterinary Toxicology (Edited by R. C. Gupta).

O’Hagan, B.J., R.J. Raven, and K.M. McCormick (2006) Death of two pups from spider evenomation. Aust. Vet. J. 84: 291

Taylor, S.P. and J.H. Greve. (1985) “Suspected Case of Loxoscelism (Spider-bite) in a Dog,” Iowa State University Veterinarian: Vol. 47: Iss. 2, Article 1.


*I was not able to access or read the original paper upon which this statement is based (Peterson and McNalley 2006 Spider evenomation: black widow, in Small Animal Toxicology, 2nd edition)

© C.M. Buddle (2016)

Spiderday (#24) – January

It’s SPIDERDAY! As promised, this feature on the blog will be a monthly occurrence, so here’s the round-up of the best Arachnid-themed links and stories from the past few weeks.

To start off, here’s a lovely image of a wolf spider, by Christy Pitto:

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Frozen spiders

Winter has arrived here in the Montreal area. Brrrrrr. Last night was below -25C, there’s a bitter wind, and about a foot of snow on the ground. I found my warm mitts and down jacket, but our arthropod friends don’t have this luxury! This time of year really gets me thinking about how spiders are handling the weather….

What do spiders do in the winter?

Some spiders don’t overwinter at all, and instead die at the end of the Fall, with their hardy egg cases doing the overwintering. Many other spiders, however,  do remain active under the snow, in a little zone called the ‘subnivean zone‘ – between the snow and the ground. Others hunker down, nestled in leaf litter, under bark, or in otherwise concealed locations. On slightly warmer winter days, spiders can also become quite active on the snow surface. But all of this is generally not enough to guarantee survival, because even subnivean zones and hidey-holes can get very cold.

Maybe they freeze, and come back to life after it warms up? You may be inclined to think so – it certainly happens with a lot of insects. And, check out this photo that popped up on Twitter a week or so ago, by Nash Turley. It shows a fishing spider under a layer of thin ice, and it was still alive after Nash helped it out of its icy tomb. What the heck?


A fishing spider, under ice.

Did this spider  ‘flash freeze’, and like a good science fiction movie, pop back to life once it warmed up?

Probably not… I think ‘flash frozen’ spiders probably won’t survive. The literature generally suggests that spiders are not freeze tolerant. In other words, their tissues cannot survive the process of freezing, and ice will cause irreparable damage. Instead, I suspect Nash’s spider was already prepared or preparing for winter, and got trapped under the ice, but hadn’t yet frozen. It’s physiological adaptations involve some nifty and super-cool tricks.

Spiders are generally thought to be freeze avoidant* (e.g. here’s a paper on this), and through the process of accumulating glycols in their blood (i.e., antifreeze), are able to supercool. This means their tissues remain unfrozen at temperatures well below freezing, because they have physiologically adapted via the production of special antifreeze compounds that stops them from turning into ice. It’s a neat trick, and one that is relatively common in the invertebrate world. Of course, supercooling alone doesn’t ensure survival at extremely cold temperatures, and that’s where other adaptations come into play. Spiders will therefore find their way to the relatively insulated subnivean zone, or deep down in soil or leaf-litter. These behavioural adaptations (i.e., selecting overwintering sites), combined with supercooling superpowers, helps them get through the cold seasons. 

For me, I’ll stick to my down jacket, and enjoy how Hydro Quebec helps keep our buildings warm!

* actually, we don’t know nearly enough about spiders and their overwintering physiology. I should state that I assume most spiders are freeze avoidant, based on the current literature on the topic – there’s a LOT more species to study, though!

Spiderday (#23) – Happy Holidays

SPIDERDAY is finally back – it’s been a few weeks, but the end of the term has been hectic. However, it’s time to catch up on some great Arachnid-themed links from the last little while.

This will also be my last post of 2015, so I’ll also take this opportunity to THANK YOU for reading and commenting on this blog. I also wish everyone a Happy Holidays! Arthropod Ecology will certainly keep on truckin’ in 2016.

Here's looking at you... A close up of an Araneidae, from Insects Unlocked.

Here’s looking at you… A close up of an Araneidae, from Insects Unlocked.

Collectors cards, Arachnid style.

Collectors cards, Arachnid style.

Heating, cooling, and trying to drown Arctic pseudoscorpions

The Beringian Arctic pseudoscorpion is a charming Arachnid, living under rocks near sub-arctic rivers and streams, in primarily unglaciated parts of the Yukon. It has captured my fascinating for years, and the story of its natural history is starting to unfold. However, some fundamentals about the biology of Wyochernes asiaticus remain unknown: as the most northern pseudoscorpion in North America, how does it survive in such cold climates? How is it adapted to frequent flooding that occurs in its primary habitat, next to streams and rivers?

The Arctic pseudoscorpion, Wyochernes asiaticus

The Arctic pseudoscorpion, Wyochernes asiaticus

Science is a collaborative process, and I teamed up with two thermal biologists to start to answer some of these physiological questions. PhD student Susan Anthony and Prof. Brent Sinclair*, both from Western University in Ontario, came to the Yukon with us last summer, and together we collected pseudoscorpions at Sheep Creek, just north of the Arctic Circle. Part of Susan’s PhD research is about the thermal biology of Arachnids, so Susan and Brent wanted to see what we could learn about Arctic pseudoscorpions. They brought the wee arachnids back to Ontario, and Susan ran a series of experiments, resulting in a recent publication (in Polar Biology).

Susan Anthony and Brent Sinclair, both from Western University.

Susan Anthony and Brent Sinclair, both from Western University.

The experiments may sound a little cruel, but they are the standard approach when studying some of the cold tolerance, thermal biology and physiology of arthropods. Susan heated up and cooled down the critters, and discovered that they can survive up to about 38 degrees Celsius, and down to about -7 degrees Celsius. The upper threshold is relatively low compared to other arthropods, which makes sense since W. asiaticus lives at high latitudes. Because the specimens didn’t survive freezing, we know it’s ‘freeze avoidant’ rather than ‘freeze tolerant’. This is aligns with what we know from many other northern (or southern! i.e, in the Antarctic) arthropods. Presumably the pseudoscorpions adapt to the north by being able to supercool, or perhaps by cryoprotective dehydration,. However, its lower threshold isn’t that low, given the extreme cold winter temperatures in the Yukon. But since our collections were in the mid-summer, this might mean it’s not yet started to adapt, physiologically, for the colder winter conditions.

The next experiments involved immersing the pseudoscorpions in water and seeing how long they survive. This was done because we were very curious to know how these tiny animals might live in habitats that flood frequently. Amazingly, 50 percent of the arachnids survived under water for up to 17 days (!), and after testing with de-oxygenated water, Susan had a similar result: they certainly weren’t relying on oxygen in the water for breathing. Susan did notice, however, that they appeared to have a silvery bubble or ‘film’ around their bodies when immersed so we assume they used this air bubble for breathing during the immersion period, something known from other arachnids.

Sheep Creek, Yukon - a habitat that frequently floods: now we know how the tiny Arachnids survive the flooding!

Sheep Creek, Yukon – a habitat that frequently floods: now we know how the tiny Arachnids survive the flooding!

Putting this in the context of the pseudoscorpion’s habitat in the Yukon: it seems that the sub-arctic rivers in the Yukon typically flood for periods up to 10 days, in the spring. Our little arachnid likely just hunkers down in their habitats under rocks, breathing from air trapped around its body, waiting for floodwaters to recede.

I’m very excited about this paper, in part because of what we have learned that links the ecology of the species to its physiology. I’m also excited because this work represents a major advancement in the fundamental knowledge about Arachnids. Our work is the first to uncover any basic biology related to the physiological adaptations of pseudoscorpions to cold/heat and to immersion tolerance.

This is kind of stunning: the Pseudoscorpiones are an entire Order of Arachnids, yet nobody has ever worked to figure out how they adapt, physiologically, to extreme environmental conditions. AN ENTIRE ORDER! And it’s 2015! An analogy would be figuring out that some butterflies (Order Lepidoptera) bask in the sun, to thermoregulate. Or, like figuring out how ducks (Order: Anseriformes) don’t freeze their feet when standing on ice. These are ‘textbook’ examples of thermal biology and physiology – such facts could be considered common knowledge. Yet looking to the Arachnids, the story of the thermal biology of pseudoscorpions has only just begun. One paper at a time, we will continue to make progress.

The Arctic pseudoscorpion: it has stories to tell. Photo by C. Ernst, reproduced here with permission.

The Arctic pseudoscorpion: it has stories to tell. Photo by C. Ernst, reproduced here with permission.

As Tschinkel & Wilson state, every species has an epic tale to tell. Even tiny arachnids that live under rocks above the Arctic circle are proving interesting for many scientific disciplines: each chapter of its story is starting to unfold, and I’m quite sure there are a lot of very interesting chapters still to come.


Anthony, S.E., C.M. Buddle and B.J. Sinclair. 2015. Thermal biology and immersion tolerance of the Beringian pseudoscorpion Wyochernes asiaticus. Polar Biology.


*A sincere thanks to Brent and Susan for including me on this paper, and for being willing to come to the Yukon with our team, to do collaborative research. I’ve learned a great deal in the process, and am delighted that partnerships between ecologists and physiologists can work out so well.

Questions and answers about spiders

Spiders, spiders, everywhere. I get asked a LOT of questions about spiders – from students, friends, neighbors, over twitter, and from journalists. I recently spent some time talking to a journalist in my hometown about spiders in Quebec*, and thought to share the details here! Here’s a copy of some of the Q&A with the journalist:

A beautiful dock spider (photo by Sean McCann)

A beautiful dock spider (photo by Sean McCann)

Q1) Why your obvious fascination with spiders?

Spiders are fascinating because they have remarkable biology and life history, and are certainly as beautiful as all other animals. They are the top predators in their own world, feeding on insects that may cause economic damage to our crops, or catching mosquitoes that seek us out for a blood meal. They build stunning webs, have remarkable diversity of body types and the live almost everywhere on the planet (all terrestrial parts, except the Antarctic). As babies the ‘balloon’ up into the air, and are among the best dispersers in the world – better than many flying insects. They are among the most common animals in ecosystems – we have recorded, for example, that wolf spiders occur in densities of over 1 spider per square m in parts of the Arctic tundra. What’s not to love?

Q2) How long have you been interested in them and why do you think they have a bad rap with so many people ?

I became interested in spiders when I was doing my undergraduate degree at the University of Guelph. A botany Professor there was working on the old cedar trees growing off the cliff faces of the Niagara escarpment, and during one summer he hired me to help with that work. While hanging off cliff faces, I couldn’t help but notice SO MANY SPIDERS and this piqued my curiosity, Professor Larson then allowed me to do a research project in the lab, and I did that project on spiders. Like to many things … a little knowledge is a dangerous thing. As I learned more, I became more and more fascinated by Arachnids, and continued on to do another undergraduate research project on spiders, and it just continued and continued until this day. I have been working with spiders now for over 20 years of my life.

Arachnophobia is real and serious for many people, but in many cases, people are not necessary arachnophobic, but rather have a general (unfounded) loathing for spiders and I believe this is largely because they have not explored their incredible biology and natural history. With education, I find people can shift from fear to curiosity and amazement. There have been studies done that illustrate that the ways that spiders move, and their extra legs, may contribute to a general fear of spiders – in other words, they can surprise us and are so “Leggy” that it causes a startle reaction and this perhaps leads to fear. This is very common in our society, and this feeds a cycle of fear, as our children learn fears from us. There may be some genetic basis to being afraid of spiders, also, and this probably relates to the fact that some spiders are indeed venomous to humans. In this part of the world, however, there are very few spiders of medical importance, and spider bites are exceedingly rare. Although everyone has a story about a spider bite, most of these are not verified, and other more likely causes should be investigated. Misdiagnosis is common in the medical field, also.

Q3) Why are they beneficial in the garden? And, even in moderation I assume, in the home ?

Spiders are beneficial because they eat many insects that themselves can be harmful to our gardens. In our homes they also feed on other insects that live in our homes. Without spiders, we would certainly have more other critters in our house and garden.

A cellar spider, with prey (c) A. Bradford

A cellar spider, with prey (c) A. Bradford

Q4) How many types of spiders do you think we have in this region and what would you estimate their total population to be?

There are over 40,000 different species of spiders in the world, over 3,000 species known in Canada, and over 600 species known from Quebec. That is a LOT of different kinds of spiders! There are certainly more species of spiders in the world than there are mammals or birds. I estimate an average yard in any small town in southern parts of Canada harbour easily 20-30 different species, and our local forests certainly can have over 100 different species.

It’s difficult to estimate population (i.e., how many of each kind of spider), but it’s fair to say that the old saying that you are always within three feet of spider is likely quite accurate, at least when you are in natural environments. The sheer biomass and density of spiders in some parts of the world is truly astounding.

Q5) What are some of the most common kinds of spiders?  What do they do during the winter?

Common spiders in our homes include things like the “Zebra jumper” Salticus scenicus it’s the little black and white jumping spider that is common in our window sills or on the walls of our houses, especially on warm summer days. Many of us have the Cellar spiders Pholcus phalangioides in our houses (they have long, gangly legs, but are not to be confused with “Daddy long legs – aka Harvestmenpersons – they are cousins to spiders, but not actually spiders!). In our gardens in the late summer, we see many individuals of the black-and yellow garden spider Argiope aurantia – it’s very large, with black and yellow striping on its abdomen, stringing up its huge webs in our gardens. Another very common orb-weaving spider, that also matures in the late summer, is Neoscona crucifera. We often see funnel-web or grass spiders (Agelenopsis) on dewy mornings: they can build their sheet-webs (with a funnel retreat at one end) on shrubs or on our lawns, in very high densities – obvious with a heavy layer of dew. We also find Canada’s largest spider in southern Quebec – an impressive animal!

The cute Zebra jumper (By Alex Wild)

The cute and common Zebra jumper (By Alex Wild)

Spiders do various things in the winter – in some cases the egg cases overwinter, and in other cases the spiders overwinter. Most spiders are “freeze avoidant”, meaning that they cannot freeze without dying, so they often adapt by ‘supercooling’ which essentially means they produce antifreeze in their bodies so they will survive below freezing temperatures. Spiders generally find places to hide in the winter, whether it’s in leaf-litter, under rocks, or finding a way into our warm basements.

Q6) Do you have a personal favourite spider?  If so, why, and what is it called?

I really like the ant-mimicking jumping spiders such as Peckhamia pictata  – it occurs in Quebec, and is a marvellous mimic of ants – most people don’t notice it because it fools us by its shape and behaviour – and so very easy to mistake as an ant instead of a spider. There are, in the world, about 300 different species of jumping spiders that mimic ants – a behaviour that is more common in the tropics, but also happens with some species here in the north.

Q7) How long have spiders been around on Earth and how long do spiders, on average, live?

Spiders have been around for perhaps 400 million years, which is a very, very long time. They have been on this planet far longer than us!

In this part of the world, spiders typically live one year, although some larger species may take more than one year to reach adulthood. In captivity spiders can live a very long time – I have a Tarantula named Harriet, in my lab at McGill, and she is approaching 20 years old.

© C.M. Buddle (2015)

*indeed, this Q &A was Quebec-focused, so may not be generalizable to all parts of the world!

Spiderday (#22)

It’s been a couple of weeks, but nevertheless, here is another edition of SPIDERDAY! All the best Arachnid-themed links, pulled from the web in the last little while.

Just look at this Jumping spider keeping an eye on her babies! Photo by Nick Porch (reproduced here with permission)

Just look at this Jumping spider keeping an eye on her babies! Photo by Nick Porch (reproduced here with permission)

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