Young et al. (2004) tested the hypothesis that the length of the spikes on the fringe around the head of the horned lizard (Phrynosoma mcallii) helps prevent predation by the loggerhead shrike (Lanius ludovicianus). They measured the longest spike length on two groups of horned lizards: living individuals (n = 15) and dead individuals that had been impaled on thorns or barbed wire (n = 15). The latter group represents those killed by loggerhead shrikes, which impale prey for later consumption. Living individuals had a mean spike length of 24.28 mm, with a standard deviation of 2.63. Dead individuals had a mean spike length of 21.99 mm, with a standard deviation of 2.71 (5 pts) Young et al. (2004) tested the hypothesis that the length of the spikes on the fringe around the head of the horned lizard (Phrynosoma mcallii) helps prevent predation by the loggerhead shrike (Lanius ludovicianus). They measured the longest spike length on two groups of horned lizards: living individuals (n=15) and dead individuals that had been impaled on thorns or barbed wire (n=15). The latter group represents those killed by loggerhead shrikes, which impale prey for later consumption. Living individuals had a mean spike length of 24.28mm, with a standard deviation of 2.63 . Dead individuals had a mean spike length of 21.99mm, with a standard deviation of 2.71 ..