Suppose I want to say
After ELL was launched it took a bite in the traffic of ELU's traffic.
Here by took a bite I want to convey that ELL has snatched some of the traffic of ELU. So what is the common ideal expression to convey the same meaning?
To say that it took away some of EL&U's traffic, took a bite could be appropriate. However, it would be used with out of, not in.
After ELL was launched, it took a bite out of EL&U's traffic.
Additional reference: http://idioms.thefreedictionary.com/take+a+bite+out+of
You could also say
After ELL was launched, it diverted some of EL&U's traffic.
After ELL was launched, it stole some of EL&U's traffic.