>>I have only one 'hot' being a cobra, but I have a few questions regarding them as a whole.
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>>I have read they do not inject poison in defense most of the time, so I was wondering exactly how that worked?
Venom is injected by the action of muscles surrounding the venom glands which are under conscious control of the snake. So, they can decide whther or not to inject venom and how much. They CAN decide not to bite in self defemse, but obviously they don't do this all the time, or there would be virtually no snake bites of humans.
>>Is it the temperment of the snake or species itself that determines if they poison you when they bite, or the level of threat percieved by them?
All of the above.
>>Also if you were to 'milk' a snake or the snake was to inject something with venom, would that reduce the chance of a envemonating bite the next bite? How long would that last then?
Since they can control the amount injected with each bite, if they feel like it, they can inject venom several times within a few seconds. Milking them probably does a better job of getting rid of MOST of the venom, BUT 1) They really hate being milked, so if there is any venom left they will be much more likely to use it if they get the chance. 2) Milking a hot snake is one of the most dangerous things you can do wih them, and certainly not something a novice should be trying.
Summary: Assume that a cobra is always prepared to kill you.
Before everyone lines up to tear you a new one, may I suggest that these are fairly basic questions that you really should have gotten answers to LONG BEFORE you started keeping any hot, let alone a cobra. You Really should consider getting rid of this snake until you've learned a lot more, gotten some training and worked with some less dangerous snakes for a while...