Most snakes, including desert snakes, are afraid of people.
The aliens tried to avoid human contact.
Snakes avoid human contact if possible, and will try to escape. Snakes are more interested in hunting smaller prey (rats, mice, etc) than humans. If walking in an area known for snakes, then walk noisily. The vibrations will warn of your approach and give the snake time to slither away. The only poisonous snake in the UK, is the Adder. In other countries, some species of snake are more deadly, so it is sensible to avoid such snakes. But, in any case, there is no need to kill snakes.
Yes, rattlesnakes can be found in cities, especially in neighborhoods that are on the fringes of the city and close to the snake's habitat. I live in El Paso, Texas, and rattlesnakes are frequently found within the city limits.
Koalas are not vicious. They will avoid human contact wherever possible.
No. Platypuses avoid contact with humans as much as possible.
Chickens prefer a social group (flock) but will do well as long as they have human contact.
Not at all - snakes feed on vermin (rats, mice, voles, rabbits etc) which keeps their numbers controlled. The only reason they get a bad press, is because the human race keeps encroaching on their natural habitat - bringing them into closer contact with snakes !
Snakes help the human race by helping women in labor.
It's likely, but in most cases prefer to leave humans alone and avoid them rather than go out and kill them.
snakes can be 2x the age in human years than they are in snake years.
No, snakes are not cannibals. There are snakes that eat other snakes, but cannibals are humans who eat human flesh.
Go and live in a cave or on a dessert island with no human contact. I.e. the mere act of living and coming into contact with others brings moral problems.