I am not aware of any sounds they make but im an sure they make some kind of sound. I think it would be some type of bark almost, similar to an axis deer.But I really would not worry about it. I have never heard of anyone hunting nilgai with calls. Just try and spot some and stalk them.The pig situation is out of controlin some parts of texas. We are pretty much overrun with hogs, so you have a pretty good chance getting some. I killed9 of them last deer season and3 more in the spring. Ive only gotten one this summer cuz no animalsmove around much when its 107 degrees and they visit the tanks(waterholes) at night. They are a real nuisance to ranchers and farmers.If i am correct on the location of the area youll be hunting there may also be some javelina. If you are not familiar with javelina they look likea small pig, but arent really relatedto pigs at all.Look up a few pics of javelinas and youll easily tell the difference betweenthem and a hog.They are pretty much considered varmints and they dont taste to good, but they are fun to shoot.