Sounding the alarm

I took the dogs jogging again today, and we passed the alpaca's pasture. First I had Dottie with me and the alpacas stayed back when usually when they see me they walk towards the fence. But they did that the other day when I jogged with the dogs. Then I jogged with Bailey. For some reason they did not like Bailey. I heard this odd shrill sound, sort of like a bird, but I could tell it was coming from the alpacas. I couldn't tell who was making the sound as none of their mouths moved. Emma happened to be in the barn playing with the cats and said Snowstorm was making the sound, she knew because she could see his lungs moving. On my second lap they still were making that sound at us so I took Bailey home and finished my jog on my own. Snowstorm did it again when it was just me, even after I spoke to let him know it was me. I guess jogging with the dogs is too scary for them.