A university student has been cautioned after sending an e-mail containing a picture of a dead cat to an animal rights group behind protests in Oxford.
Students supporting animal experiments marching in Oxford
The man sent the e-mail to the website of SPEAK - leading protests against animal testing at Oxford University's new £18m biomedical research centre.
In it, the unnamed 20-year-old had threatened to kill a cat for every new posting on the website.
The student was arrested on suspicion of malicious communication in February.
The message also claimed the man had then put the pictured animal in a cage used for "torturing hamsters" and thrown it around and he threatened to post dead cats to the activist group.
Referring to last month's scheduled march by the student movement, Pro-test - in favour of the Oxford laboratory - the message ended: "See you on Saturday."
It is thought the police do not believe the student actually carried out the attack but cautioned him for sending the e-mail.
A Thames Valley police spokesman said: "This individual acted in a way which was utterly insensitive and deliberately provocative.
"He may have seen his actions simply as a joke, but he caused a great deal of distress to people visiting the website."
SPEAK said the email "illustrated the type of individuals that support vivisection".