Combining semantic symbols is behavior we have evidence of in other species, but without evidence of structure impacting the relationships between the meanings we still don't have sytax. That seems like a good candidate for where we might find syntax given the apparent semantic richness, but we still have a lot of work to do deciphering prairie dog communication before we can make a scientific claim one way or the other about if it is language.
https://www.nytimes.com/2017/05/12/magazine/can-prairie-dogs...