▁system ▁exc itation ▁that ▁gets ▁released ▁in ▁the ▁form ▁of ▁tail ▁movements . ▁Ca ud al ▁l uring ▁is ▁not ▁merely ▁tail ▁und ulations , ▁but ▁must ▁specifically ▁be ▁attract ive ▁to ▁pre y . ▁Ca ud al ▁dist raction ▁is ▁another ▁behavior ▁used ▁by ▁sn akes , ▁and ▁the ▁tail ▁mot ions ▁are ▁similar ▁to ▁ca ud al ▁l uring . ▁The ▁difference ▁is ▁in ▁the ▁s nake ' s ▁post ure ▁and ▁especially ▁in ▁the ▁nature ▁and ▁outcome ▁of ▁the ▁behavior ▁in ▁reference ▁to ▁the ▁encounter ▁with ▁pre y . ▁Other ▁ca ud al ▁l uring - like ▁movements ▁occur ▁as ▁warning ▁signals ▁and ▁are ▁induced ▁by ▁stress ful ▁circumstances . ▁ ▁References ▁▁ ▁Category : E th ology ▁Category : M im ic ry <0x0A> </s> ▁Bra in ▁posit ron ▁emission ▁tom ography ▁is ▁a ▁form ▁of ▁posit ron ▁emission ▁tom ography ▁( P ET ) ▁that ▁is ▁used ▁to ▁measure ▁brain ▁met abol ism ▁and ▁the ▁distribution ▁of ▁ex ogen ous ▁radi ol abeled ▁chemical ▁agents ▁throughout ▁the ▁brain . ▁P ET ▁measures ▁em issions ▁from ▁radio act ively ▁l abeled ▁met abol ically ▁active ▁chemical s ▁that ▁have ▁been ▁inject ed ▁into ▁the ▁blood stream . ▁The ▁emission ▁data ▁from ▁brain ▁P ET ▁are ▁computer - process ed ▁to ▁produce ▁multi - dimensional ▁images ▁of ▁the ▁distribution ▁of ▁the ▁chemical s ▁throughout ▁the ▁brain . ▁ ▁Process ▁The ▁posit ron ▁em itting ▁radio is ot op es ▁used ▁are ▁usually ▁produced ▁by ▁a ▁cycl ot ron , ▁and