Are there any poisonous mammals?

[Whack-a-Mole]

The thread title pretty much says it all but let me clarify a bit:

For the purposes of this thread I mean 'poisonous' to include anything from venom used in hunting to poison spines (not that I can think of any mammals with a spine off of the top of my head) to having poisonous body chemistry such that if something eats them it will get sick and die (like a puffer fish has a highly poisonous gland such that eating one, assuming you get around the spines, will kill you unless the gland is carefully avoided). If you really want to stretch the definition of poisonous is there anything like the Komodo Dragon that while not actually poisonous has a bite so laden with bacterial nastiness as to have a similar effect?

Personally I can't think of any mammals with poison at their disposal. As such I wonder if anyone can speculate on why this is so? Certainly poison has shown itself to be highly useful as a survival mechanism to thousands of other creatures (insects, fish, reptiles, bacteria, plants). Some mammals, such as the skunk, do have chemical warfare methods at their disposal so clearly a mammal can come up with at least noxious substances if not outright poisonous ones. I also think some mammals can have resistances to some poisons such as some weasels being resistant to snake venom so they can successfully hunt poisonous snakes suggesting that mammalian bio-chemistry might be able to manage poisons.

It just seems odd that something so widely used by so many creatures on this planet is almost completely overlooked by an entire branch of organisms and I'm curious if there is a reson why or it just 'is'.

_{Thinking about reptiles on the list are there any poisonous birds? I can't think of one there either but birds evolved out of reptiles and reptiles have poison at their disposal making me wonder why birds would drop this useful weapon?}

[Whack-a-Mole]

Originally posted by Whack-a-Mole
For the purposes of this thread I mean 'poisonous' to include anything from venom used in hunting to poison spines (not that I can think of any mammals with a spine off of the top of my head)...

Before anyone pokes fun at me for this I realize that all mammals have a spine (as in backbone). I'm talking about pointy spikes protruding from the body as a defensive measure (in case that wasn't clear).

[troub]

The platypus has venomous feet, and is a mammal although a strange one.

[sunstone]

Male platypus have spurs capable of injecting poison from glands (I can't remember if the glands are located in the rear legs or in the posterior abdomen)

[Pleonast]

As troub mentioned, the platypus has poisonous spurs. But only the males. From http://home.mira.net/~areadman/plat.htm:

The male Platypus has a sharp, hollow, horny spur about 15 millimetres long on the inside of both hind leg ankles. This is connected to a venom gland which produces a very strong toxin. The spur can be used in defence against predators (the venom can cause excruciating pain in humans and is strong enough to kill a dog.) but the fact that it is restricted to the male - and that the gland reaches its greatest development in the mating season - suggests that it is normally employed in aggressive encounters between males.

[Bibliovore]

Damn, you beat me to it. Yes, I was going to say that a platypus has a poisonous spur, but I'm not entirely sure if they count as mammals. Yes, they have fur, but they also lay eggs, so I'm not sure if monotremes (like the platypus and the Echidna) are also classified as Mammals. I thought that mammals had to have mammary glands and wombs and give birth to live young...

Anyway, the platypus is the only one I can think of, but i have no idea why poison never really caught on among mammals when it seems like such a useful evolutionary tool.

[Polycarp]

The duckbilled platypus, which seems to have made a career out of breaking every rule about what you're supposed to do as a mammal, is the exception here as well. Platypus venom.

Intriguingly, contrary to the assertion in the platypus cite (and several other sites describing the platypus as the only venomous mammal), several species of shrew have evolved venom in their saliva. The Short-Tailed Shrew sometimes secretes a venom similar to that of a cobra. This site adds the European Water Shrew and several other Insectivora:

Platypus (_Ornithorhynchus anatinus_) - poisonous spur
Echidna (_Tachyglossus aculeatus) - poisonous spur
European Water Shrew (_Neomys fodiens_) - delivered by a groove formed by the lower incisors; shrew venom has different components, one of which affects cold-blooded prey, and another "warm-blooded"
Short-tailed Shrew (_Blarina brevicauda_) - same delivery mechanism; "about three times more venomous than the European Water Shrew"
Hedgehogs (various species) - anoint their spines with poisonous secretions of other animals, e.g. toads. "Young hedgehogs lick toxins from their mother's spines and self-anoint themselves (sic) even before their eyes are open"
Madagascan Tenrecs (various species) - some anoint their spines with the venom of other animals

Note that these are derived from the 1989 edition of a Golden nature guide; the accuracy of the information would need some research to validate.

[everton]

The Northern Short-Tailed Shrew (Blarina brevicauda) also has a venomous bite.

The Hooded Pitohui, Variable Pitohui and Brown Pitohui are poisonous birds found in Papua New Guinea.

[Earl Snake-Hips Tucker]

The solenodon is venomous.

[Pleonast]

Yes, Bibliovore, platypuses and echidnas are mammals. See the Tree of Life website for a handy reference. I believe the exact relationship between monotremes, marsupials and Eutheria is still somewhat in question. But they are definitely all considered mammals. All mammals produce milk, although I'm not sure if that is the defining characteristic.

[Polycarp]

"The Venomous Solenodons "= band name?

[troub]

Originally posted by Bibliovore
Damn, you beat me to it. Yes, I was going to say that a platypus has a poisonous spur, but I'm not entirely sure if they count as mammals. Yes, they have fur, but they also lay eggs, so I'm not sure if monotremes (like the platypus and the Echidna) are also classified as Mammals. I thought that mammals had to have mammary glands and wombs and give birth to live young...

The platypus does produce milk for its egg-hatched children. Production of milk, as far as I know, is the main requirement to be a mammal.

[Colibri]

Originally posted by troub
The platypus does produce milk for its egg-hatched children. Production of milk, as far as I know, is the main requirement to be a mammal.

In fossil forms, the conventional dividing line for mammals is the possession of a jaw articulation formed by the squamosal and dentary bones, rather than between the quadrate and articular as in more primitive forms. As a corollary, mammals have a lower jaw composed of a dentary bone only (rather than multiple bones) and 3 middle ear ossicles (rather than one). By these characteristics, monotremes are definitely mammals.

[curly chick]

Taking this question in a slightly different direction, more in the direction of the Kimodo dragon which you mentioned in your OP.

Some animals have commensal bacteria and viral populations which do the host mammal no damage at all, but if that host mammal bites a different species, then the bite can result in the death of the new mammal species.

For instance, a bite from a bat can give you or me rabies, but the bat isn't affected.

I know it isn't a venom, but it is a biological poison, at the disposal of the bat.

[Whack-a-Mole]

Can anyone here speculate on why so few mammals seem to have a poisonous capacity?

I am just speculating here but it seems that most 'older' branches of life possess poison capacity in many of the creatures. Bacteria, plants, fish and reptiles all have plenty of examples of poisonous members. The 'newer' branches of life, birds and mammals, seem to largely be devoid of poison. Indeed, the platypus is a perfect example. An animal that can perhaps be considered the least advanced of all mammals...almost a bridge to something earlier. From this it seems to me that birds and mammals (for the most part) actually discarded the capacity for poison/venom. As such is there a downside to being poisonous? I know venom takes some effort for the animal to produce (effort in a biological sense that it takes resources) but so many animals do use it it would seem to be a worthwhile tradeoff. Why not a poisonous biochemistry so other animals won't eat you?

In short, I wonder why something found in such abundance among other creatures and shown to be useful to so many of those creatures would be almost completely absent from one (or two including most birds) major branch of life on earth?

[CarnalK]

curly chick I don't think bats are immune to rabies. From a NS provincial government PDF File FAQ:

What are the clinical signs of rabies in bats?

Rabies in bats, like other animals, cannot be diagnosed reliably by an evaluation ofbehavior or clinical signs alone. Laboratory testing is essential. However, any bat thatis active by day, is found in a place where bats are not usually seen (i.e. in your roomor on your lawn), or is unable to fly, is far more likely to be ill, and may possibly berabid. Such bats are often the most easily approached

Whack-a-mole said:

am just speculating here but it seems that most 'older' branches of life possess poison capacity in many of the creatures. Bacteria, plants, fish and reptiles all have plenty of examples of poisonous members. The 'newer' branches of life, birds and mammals, seem to largely be devoid of poison.

Well I believe there are a lot more types of insects and reptiles than mammals. I'm not quite sure percentage-wise the poisonous members stack up.

Remember also that all mammals have a bacterial level poison system- from our skin acidity to our active immune system.

[Colibri]

Originally posted by Whack-a-Mole
In short, I wonder why something found in such abundance among other creatures and shown to be useful to so many of those creatures would be almost completely absent from one (or two including most birds) major branch of life on earth?

Note that birds and mammals are the two mostly endothermic ("warm-blooded") groups among animals.

I would speculate that a poisonous/venomous strategy, being essentially passive, is most advantageous for organisms that are slow-moving or sedentary, or which can be incapacitated by low temperatures. Even if a snake has been made sluggish due to cold, it can still bite, even if not so quickly.

Poison/venom requires an energetic investment to make. Endotherms may generally be better off relying on active fight-or-flight mechanisms to deter predators, since these only have to be used when the animal is actually under threat. The energetic cost of toxicity is constant, regardless if the animal needs it at that particular time.

[percypercy]

Originally posted by everton
The Northern Short-Tailed Shrew (Blarina brevicauda) also has a venomous bite.

The Southern Short-tailed Shrew Blarina carolinensis is also venomous. (I knew there was a reason I took Mammology) ::grin:: I can wax on for hours about shrews if you'd care to hear about it.
-Lil

[Brad Amundsen]

The human mouth is capabale spewing more venom than any other mammal.

[Matchka]

I think the opossum is immune/resistant to lots of snake venom. At least that's what the park lady told us when we visited Okee Fenokee (sp?) in GA.

Interesting speculation byColibri , but spiders move DAMN fast when they're hunting--which is when they are most likely to invenomate (I stole that word from Steve Irwin). I agree that, like a tail or a big brain, venom is probably a pretty expensive compound for a critter to produce so it will only evolve it if it is the best option available.

What gets invenomated? Predators of things like toads, pladypusses and blowfish (smallish, clumsy things that I guess have evolved poison as opposed to enhanced senses & speedier forms of motility). And prey of things like spideys and snakes (little bugs & little vertibrates). Notice that the bigger snakes have opted for constriction? I wonder if the amount of venom required to kill, say, a goat would be too toxic or too expensive to produce? And some of the bigger spideys hunt without venom (I think). And from previous posts it seems that any poisonous mammals are teeney.

All that spewed, how about: Little things need to cheat, big things (and relatively speaking, the majority of mammals are bigger than the majority of birds, arthropods and fishies) can overpower/motate themselves away from prey/predators. They don't NEED venom because of their behavior: Monkeys cruise the trees anyway, humans carry handguns anyway, carnivores are quadrupedal endotherms & therefore pretty quick anyway, ruminants are pretty big & have horns anyway. But shrews, well, they need help.