diff --git a/src/shaders/antsCompute.frag b/src/shaders/antsCompute.frag
index 1567fd6..e52b3c0 100644
--- a/src/shaders/antsCompute.frag
+++ b/src/shaders/antsCompute.frag
@@ -91,7 +91,19 @@ void main()	{
 
     bool movementProcessed = false;
 
+    // calculate this ant's index from its UV position in the texture
+    ivec2 texSize = textureSize(tLastState, 0);
+    int antIndex = int(vUv.y * float(texSize.y)) * texSize.x + int(vUv.x * float(texSize.x));
+
     if (pos == vec2(0)) { // init new ant
+        // only activate ants within the start count
+        if (antIndex >= ANTS_START_COUNT) {
+            // dormant ant — output zeros and skip everything
+            FragColor = vec4(0);
+            FragColorExt = vec4(0);
+            return;
+        }
+
         #if VIEW_MODE_SIDE
         // spawn on sand surface: random X, scan down from top to find first non-air cell
         float spawnX = rand(vUv * 10000.);