Like this?
library(dplyr)
data.plot2 <- data.plot %.%
group_by(trick) %.%
mutate(success_rel = success / sum(success) * 100)
ggplot(data.plot2,aes(y=success_rel,x=trick,fill=animal))+geom_bar(stat="identity") + theme(axis.text.x = element_text(angle=90))