Friday, April 16, 2010

Movement Matters

You think "movement" matters in a working terrier? Well it does! Only it's not the dog's movement that counts -- it's the human who has to move off the sofa, and move out of the driveway, and move into the field with a shovel in hand and a terrier at his or her side.

That said, I will say this about movement: two legs on a dog is probably not enough. A dog can certainly work with three legs and one eye. But two legs seems to me to to be a bit short on leg. That said, I am willing to make an allowance that there may be exceptions and I will not hold fast to my prejudices for reasons soon to be revealed.

No, the dog below is not a terrier, but if a terrier like this ever does show up, I will be happy to take it into the field, where I have little doubt it will do quite well.

This is a repost from November 2007.


Anonymous said...

That is so adorable I'm going to start breeding them that way. In a teacup size.

Johann The Dog said...

Faith is amazing, thanks for sharing her story! Woofs, Johann

Anonymous said...

Well, bipedality with strongly reduced forelimbs worked for the Tyrannosaurid dinosaurs, so why not in canids? Actually the recent discovery in China of a fossil of an early tyrannosaurid proved a bit of an upset for paleontologists, because it showed that a meat-eating dinosaur with strongly reduced forelimbs worked even at a relatively small size (no more than 3 metres long).

The hypothesis was that T. rex was strongly biased towards scavenging. Its teeth are not those of a pure predator; they're much more robust and less blade-like than those of presumed pure predators like Deinonychids, plus the reduction of forelimbs in favour of a very big skull and enormous bite strength tends to argue against T. rex being an active predator (though evidence on hadrosaurs of what can only be healed T. rex bite marks argues that T. rex wasn't at all averse to killing).

A big scavenger or kill-stealer only really works when the animal is big enough to intimidate smaller pack-predators off a kill. T. rex was easily big enough to do that, and looks to have been an extremely efficient walker (upper and lower leg bones the same lenght, same as us) but not a good runner, so it probably only ever got into a run on rare occasions.

The ancestor, by contrast, was a better runner and much more agile, but had similar reduced forelimbs and increased head, which seems to disprove the hypothesis that forelimbs are needed for an animal to be a good killer.

The one thing to note though is that all dinosaurs had bird-like lungs, four-chambered hearts and active, homeothermic warm-blooded metabolisms, plus air sacs, pneumatic bones and highly efficient breathing. This is why Tyrannosaurids look like they shouldn't be able to balance; the tail was a lot heavier than those of mammals, and the head, neck and torso a lot lighter than those of a mammal. The one thing we mammals score on where dinos didn't is brains; pretty much all dinosaurs had reptile-sized brains so weren't what you'd call smart.