Does it do anything besides keep the female from leaveing before the jobs done

The purpose of the tie is not fully understood, it could be also to help prevent other males from mating with the female.

The knot is also usefull for making sure nothing comes out of the vagina during mating to help insure that it takes. ^_^

technically speaking, the duration of the tie is supposed to guarantee a greater percentage chance of the dog being the father of the bitch's pups. the longer the female is prevented from being bred by another dog, the more head-start the dog's sperm has in continuing his line (which is, of course, the whole reason for sex).

it also keeps the sperm from just sliding out of the bitch's vagina, since the first few inches are a 45 degree drop from the main vaginal canal to the actual vaginal lips. It helps with the whelping... but not so much for the effective breeding sans knot! :lol:

in dog-on-bitch mating, the female actually 'holds' the tie. because the bitch HAS to be bigger than the dog (to carry the pups to term and whelp successfully) she will not hold or tolerate the knot of a larger male. (and if he's WAY too big, she won't even allow him to mount her). The strong muscles just before the cervix clamp down on the knot (like a lock and key mechanism) and keep the dog inside her, so his slower sperm have a chance to make it up her tubes and fertilize the eggs.

all rather technical... i much prefer 'because it's a freakin awesome feeling to be tied!' :inlove:

right!

However I'm not sure about what you said about the female has to be bigger than the male. If that's the case, why are in many breeds the males are huge compared to females? Basset hounds for example (because its a breed I'm most familiar with), the males are huge! The females are rather petite compared to the guys.

that's a breed standard, and breed-in-breed there's no problem. the dam and sire (bitch and dog) share the same brackets on size... a bitch of the same breed had to pass the breeding male initially, after all! :)

but you get into a lot of trouble if you're breeding, say... a female pomeranian and a male border collie. The BC pups will be HUGE for the uterine horn, let alone to actually pass through the birth canal. Chances are the bitch will either suffer massive complications or simply self-abort the litter if she allows the dog to tie her at all. Imagine a poor corgi trying to carry a litter of corgi-dane mixes! OUCH!

But you're totally right about mating within the breed. Most of that gender size difference comes with growth, most pups are only a few ounces different when they're born.
Bassets are a great example of breeds that have very specific 'density' standards for males and females. Shepherds also have that requirement (although it doesn't automatically constitute a fault or serious fault in showing), males must look masculine and females must look feminine. im sure other breeds do as well, but I'm not as familiar with other standards.

yay, breeding! *does a dance*